Due Date Calculator: weeks pregnant and due date by period, ovulation or IVF

Updated on 14 October 2026 · Fertilio Editorial Team

You calculate your due date from the first day of your last period: you add 280 days, which is 40 weeks. If your cycle is longer or shorter than 28 days, the due date shifts by the difference. If you know the day of ovulation or conception, it is 266 days from that day. A last period on Monday, 2 November 2026, gives Monday, 9 August 2027, with a 28-day cycle, and 13 August 2027 with a 32-day cycle. After IVF, ICSI, or frozen embryo transfer, you calculate from the transfer day, and the rules are in the section Due date after IVF.

How the calculator works

The calculator has four starting points. All of them lead to the same reference day, the calculated first day of the last period. The weeks of pregnancy are counted from that day, as the German maternity guidelines (Mutterschafts-Richtlinien) require.

The classic Naegele’s rule is: first day of the last period plus 7 days, minus 3 months, plus 1 year. Because months differ in length, it gives 280 to 283 days depending on the starting month (our own recalculation for 2026). The calculator therefore counts days, not months. The rule assumes a 28-day cycle with ovulation on day 14 (ACOG). With a longer cycle, ovulation comes later, so the extended Naegele’s rule adds the difference: 4 days more for a 32-day cycle, 3 days fewer for a 25-day cycle. The German-language guideline on induction of labor also names the first day of the last period and the cycle length as the basis for the due date (AWMF 015-088).

A cycle of 24 to 38 days is considered normal (FIGO 2018). The calculator accepts 20 to 45 days. If your cycle is very irregular, the due date based on your period is only a rough estimate. In that case, the measurement at the first ultrasound is what counts.

What week 12+3 means

Week 12+3 means 12 completed weeks and 3 days since the first day of the last period. You are then in the 13th week of pregnancy. Accordingly, the information for insured persons in the maternity guidelines describes the period from 8+0 to 11+6 as the 9th to 12th week of pregnancy. Because counting starts with the period, the baby is about two weeks younger than the week of pregnancy suggests: at the end of the 12th week of pregnancy, only about ten weeks have passed since fertilization (familienplanung.de).

How accurate is the calculated date?

Only a few babies are born on the calculated day itself. In an Australian analysis of 18,708 singleton births with spontaneous onset of labor, it was 5%, and about two thirds were born within 7 days of the due date (Khambalia 2013). In a US study in which ovulation was determined from hormone levels in urine, 4% of babies were born on day 280. Even with a known ovulation date, the length of pregnancy there varied by up to five weeks (Jukic 2013).

That is why your gynecologist’s office checks the due date at the first ultrasound. In Germany, this scan takes place between 8+0 and 11+6 weeks of pregnancy and serves, among other things, to determine gestational age precisely (maternity guidelines). What is measured is the crown-rump length of the embryo. If it differs by 7 days or more from the calculation based on the period, the due date is corrected according to the guideline on induction of labor, in Switzerland from as little as 5 days (AWMF 015-088). After IVF, by contrast, the day of fertilization is the reference (AWMF 085-002). If your practice has changed the due date, choose “Due date” in the calculator and enter the new date.

Weeks of pregnancy, trimesters, and prenatal care

This section applies to Germany, Austria, and Switzerland.

The table shows the most important stages of pregnancy in Germany. The calculator’s timeline converts the same weeks into calendar dates.

In Austria, a new examination program in the Parent-Child Pass (Eltern-Kind-Pass) has been in effect since 1 October 2026, with four ultrasound examinations in the 8th to 16th, 18th to 22nd, 30th to 34th, and 35th to 38th week of pregnancy. The glucose test there falls between the 24th and 28th week of pregnancy (Federal Law Gazette, BGBl. II No. 241/2026). In Switzerland, basic health insurance covers ultrasound examinations in the 12th to 14th and the 20th to 23rd week of pregnancy (Health Care Benefits Ordinance, KLV Art. 13).

When was conception?

Counting back from the due date, conception was, by calculation, 266 days earlier, so for a due date on 9 August 2027, it was on 16 November 2026. That is the day of ovulation, not necessarily the day of intercourse. Pregnancy is possible on six days: the five days before ovulation and the day of ovulation itself (Wilcox 1995). The calculator therefore shows the fertile days before the day of conception as well. Conception cannot be pinned down more precisely from the due date, because ovulation varies from cycle to cycle. If you are still trying to get pregnant, the Ovulation Calculator shows your fertile days.

Maternity protection

The calculator shows you when maternity protection begins: in Germany 6 weeks before the calculated due date (week 34+0), in Austria 8 weeks before (week 32+0). What counts is the expected day of delivery according to a medical certificate, in Germany also according to a midwife’s certificate. In Switzerland, there is no fixed protection period before the birth, and maternity leave begins with the birth.

How long maternity protection lasts after a premature, multiple, or cesarean birth, and how much maternity allowance (Mutterschaftsgeld) or maternity benefit (Wochengeld) you get, is worked out by the Maternity Leave Calculator. The link below the result carries over your due date. Since 1 June 2025, a protection period has also applied in Germany after a miscarriage from the 13th week of pregnancy (MuSchG § 3), and the periods are listed in the section When does maternity protection begin?

Due date after IVF, ICSI, and frozen embryo transfer

You calculate your due date after ICSI or IVF from the day of transfer: with a day 5 blastocyst, it falls 261 days after the transfer, and with a day 3 embryo, 263 days after. This rule comes from Committee Opinion 700 of the US medical societies for obstetrics and gynecology (ACOG), ultrasound (AIUM), and maternal-fetal medicine (SMFM). It speaks of assisted reproduction in general and therefore applies to IVF and ICSI alike. A transfer on 2 November 2026 gives 21 July 2027 (day 5) or 23 July 2027 (day 3).

The formula for IVF and ICSI

The basis is ACOG Committee Opinion 700 from 2017, which was reaffirmed in 2025. For a day 5 blastocyst, the text reads, word for word, “the EDD would be 261 days from the embryo replacement date.” EDD stands for estimated due date. For a day 3 embryo, the same passage gives 263 days. According to ACOG, after assisted reproduction the due date should be determined from the age of the embryo and the transfer date.

The numbers can be derived. By convention, the due date is 280 days after the first day of the last period, and ACOG assumes ovulation on cycle day 14. From ovulation to the due date, that leaves 266 days. In IVF, egg retrieval takes the role of ovulation: studies on dating after IVF set the gestational age as retrieval day plus 14 days (Tunón 2000, Sladkevicius 2005). A day 5 blastocyst is already 5 days old on transfer day, and 266 minus 5 gives 261 days.

For embryos on day 2, day 4, and day 6, ACOG gives no figure of its own. The calculator applies the same rule, which is our own derivation: 264, 262, and 260 days to the due date. The calculation for frozen embryo transfer and egg donation is derived in the same way, and the details are further below. For insemination there is no documented formula. The calculator sets the day of insemination equal to ovulation, which is an estimate without supporting evidence.

Why you are already in week 2+5 of pregnancy on transfer day

Weeks of pregnancy are counted from the first day of the last period, which is called post menstruationem (p. m.). The German maternity guidelines (Mutterschafts-Richtlinien) expressly require this way of counting. After IVF, the calculator sets the last period, by calculation, 14 days before egg retrieval. On the day a day 5 blastocyst is transferred, you are therefore, by calculation, in week 2+5 of pregnancy: two completed weeks and five days, so in the third week of pregnancy. With a day 3 embryo, it is 2+3 on transfer day, and the values for all embryo ages are in the table above.

Maternity record and guideline: the IVF day counts

The German maternity record (Mutterpass) in the version of 28 September 2023 has the fields Date of conception (if certain), Calculated due date, and Due date (corrected after the course of pregnancy, if applicable). After IVF, the date of conception is known: the day of egg retrieval or, for a frozen embryo transfer, the transfer day minus the embryo age. The calculator shows you both reference dates: the day of egg retrieval as the calculated conception date (for a frozen embryo transfer, the corresponding day) and the calculated last period 14 days before that.

The German-language guideline on first-trimester diagnostics is AWMF 085-002. DEGUM is the lead society, with professional societies from Germany, Austria, and Switzerland taking part. The guideline states that for IVF pregnancies, the time of conception should be used to determine gestational age, not the crown-rump length on ultrasound. ACOG sees it the same way. After IVF, the IVF date is therefore the reference according to guidelines.

How accurate is the due date after IVF?

In a Norwegian study of 208 IVF singletons, ultrasound dating differed on average by only 0.9 days from dating based on egg retrieval; crown-rump length was measured. A difference of more than 7 days occurred in only 3 cases (Tunón 2000). When babies are actually born varies after IVF much as it does after natural conception, see How accurate is the calculated date?

For twins, the calculation gives the same due date, because it depends only on transfer day and embryo age (our own derivation). For multiple births, longer protection periods after birth apply in Germany and Austria, and the Maternity Leave Calculator works out the periods.

Which week of pregnancy are you in after transfer?

The table shows which week of pregnancy you are in how many days after transfer. It applies equally to fresh and frozen embryo transfer.

An example for the common question “How many weeks pregnant am I 2 weeks after transfer?”: with a day 5 blastocyst, you are then in week 4+5, and with a day 3 embryo, in week 4+3. Nine days after the transfer of a day 5 blastocyst, week 4+0 begins, and 16 days after, week 5+0. With a day 6 blastocyst, you are one day further along in each case.

When to test after transfer?

No professional society names a fixed test day. The European society ESHRE only writes that progesterone should be given at least until the day of the pregnancy test. The UK regulator HFEA advises against testing too early because the result may be wrong. The US society ASRM names no day in its patient booklet. According to a study from Linz, hCG is usually measured for the first time 9 to 17 days after transfer. Accordingly, there is no recommendation for a specific day to date (Trautner 2024).

Clinics count from the transfer or from egg retrieval. We converted the information from eight centers into days after transfer: days after retrieval minus the age of the embryo. The selection is not representative; it shows the range. How the transfer itself works is explained in the article on the IVF process.

Studies measure on similar days. In Amsterdam, measurements were taken on day 14, 15, or 16 after retrieval (Lambers 2006), in a US study on day 16 after retrieval with a repeat on day 18 (Noorhasan 2015). In Linz, the measurement was taken 14 days after the transfer of a day 5 blastocyst (Trautner 2024).

Why the calculator shows day 14 to 19 after egg retrieval

For the blood test, the calculator shows a window from day 14 to day 19 after retrieval and converts it into days after transfer. For a day 5 blastocyst, that is day 9 to day 14 after transfer, for a day 6 blastocyst day 8 to day 13, and for a day 3 embryo day 11 to day 16. The start is the day from which the Kinderwunsch-Zentrum Hannover calls the blood test reliable. For a day 5 blastocyst, the end corresponds to the statement “2 weeks after transfer” that five of the eight centers make. The Linz study, too, measured on day 19 after retrieval for fresh transfer.

For frozen embryo transfer, there is no egg retrieval. The calculator then uses the transfer day minus the embryo age as the starting point. This fits studies in which the blastocyst was transferred 5 days after ovulation or after the start of progesterone (Li 2022, Kidera 2025, Trautner 2024). In a large randomized trial from China with 4,376 women, the transfer was also done 5 days after ovulation or after the start of progesterone (Wei 2026). In the natural cycle with a trigger shot, transfers 6 or 7 days after the shot were similarly successful, with live birth rates of 33.8% and 33.0% (Saupstad 2026, 602 women). How the cycle variants of frozen embryo transfer work is explained in the article on frozen embryo transfer.

The timeline shows implantation 8 to 10 days after retrieval. For a day 5 blastocyst, that is day 3 to day 5 after transfer, for a day 3 embryo day 5 to day 7. The basis is a study of natural conception with 141 pregnancies that lasted at least until six weeks after the last period. In 84% of them, the embryo implanted 8 to 10 days after ovulation (Wilcox 1999). For IVF, this is an analogy, not a measurement.

Blood test or urine test?

In blood, according to the guideline on early pregnancy loss (AWMF 015-076), an hCG value above 5 IU/l indicates a pregnancy. Modern lab tests already detect values below 1 IU/l. Urine tests, by contrast, have a detection limit of about 20 to 50 IU/l, and faintly positive tests may be misread as negative.

The calculator therefore shows the urine test as meaningful only from day 16 after retrieval. For a day 5 blastocyst, that is day 11 after transfer, for a day 3 embryo day 13. This is our own derivation: Hannover states that a reliable result with urine comes about 2 days after the reliable blood test. We did not find a study that checks urine tests after IVF day by day.

Your clinic’s test day takes priority. The calculator shows a typical time window, not an appointment. Your clinic knows your protocol and your medications.

Test series after transfer and trigger shot

A test series means taking a urine test every day, starting from the trigger shot or from the transfer, and laying the test strips side by side. The idea: the line from the hCG in the shot first gets weaker, and if it then gets stronger again, the hCG is supposed to come from the embryo. According to our research, no study has checked whether this can be read reliably after IVF. The individual building blocks are backed by evidence.

The trigger shot can make the test positive for up to 10 days. The product information for choriogonadotropin alfa 250 micrograms (recombinant hCG, about 6,500 IU) and for human chorionic gonadotropin 5,000 IU (from urine) both state up to 10 days. For that long, hCG measurement in blood and urine may be affected. According to both, the half-life is about 30 hours. In an older study of 34 IVF patients, injected hCG was detectable with a lab test for up to 14 days (Damewood 1989).

In terms of timing, that means, by our calculation: egg retrieval usually takes place 34 to 36 hours after the trigger (ASRM). With a day 5 blastocyst, day 10 after the trigger therefore falls on about day 3 to 4 after transfer. The calculator asks about the trigger shot and sets it one day before retrieval. For “Yes” or “Not sure,” it shows until when a urine test can be positive because of the shot, for a day 5 blastocyst until day 4 after transfer.

Further hCG doses extend the time. Some clinics support the second half of the cycle with hCG injections, as the Kinderwunschzentrum Ludwigsburg describes, for example. In Linz, women with fewer than 10 eggs additionally received 1,500 to 3,000 IU of hCG (Trautner 2024). According to the product information for the urine-derived hCG preparation, hCG can accumulate in the blood with repeated injections. The calculator also points out that further hCG injections extend the time window. The 2025 ESHRE guideline now advises against, with a strong recommendation, giving additional standard-dose hCG (1,500 IU) after an hCG trigger shot to support the second half of the cycle (luteal phase).

Not every trigger contains hCG. With a trigger using only a GnRH agonist, you get no hCG. In the so-called dual trigger, GnRH agonist and hCG are combined (ESHRE 2025), and then the time window of the hCG products applies. Which shot you received is in your treatment plan.

Progesterone is not named as a source of interference. The product information for a vaginal progesterone preparation (micronized progesterone 200 mg) does not mention any influence on pregnancy tests. The guideline AWMF 015-076 names other factors as sources of interference, such as heterophilic antibodies. However, progesterone can delay a period, as the fertility clinic novum points out, for example. The absence of bleeding is therefore not a reliable sign on its own.

Tests that are too early can be false negative. Shortly after implantation, the hCG value may still be below the detection limit of a urine test. On day 7 after frozen embryo transfer of a blastocyst, the mean value in women who later had a baby was 61.1 IU/l. The range was 1.3 to 210.2 IU/l (Ueno 2014, 7,342 live births). A urine test that only responds from 20 to 50 IU/l can miss such values.

hCG levels after blastocyst transfer

hCG is the pregnancy hormone that blood and urine tests measure. The table collects published blood values after the transfer of a blastocyst, separated into fresh and frozen embryo transfer. The rows show women who later gave birth. Exceptions are Zhu 2019, with pregnancies lasting beyond 13 weeks, and Shibli Abu Raya 2023, with pregnancies in which a heartbeat was visible 6 weeks after transfer. The numbers describe groups and are not a norm. Fertilio does not evaluate individual lab values. Whether your value fits your course is for your clinic to judge.

IU/l equals mIU/ml. Median: half of the women were below this value, half above. Middle half: 25 to 75% of the measured values. Weeks of pregnancy are given for a day 5 blastocyst, one day later for day 6. The studies used different lab tests, and their results differ. The table is not a norm: Values far below the median also occur in intact pregnancies. Your clinic decides how to interpret your value.

Why the values vary so widely

Frozen embryo transfer: In Linz, the median 14 days after transfer for later births was 1,416 IU/l after frozen embryo transfer and 932 IU/l after fresh transfer (Trautner 2024). An Australian analysis of 869 singleton births after single embryo transfer found, with an equally long second half of the cycle, a median of 844.5 IU/l after frozen versus 369 IU/l after fresh transfer (Keane 2016). In Maribor, by contrast, the means were close together at 989 IU/l (fresh) and 920 IU/l (frozen) (Reljič 2013). Values after fresh and frozen transfer therefore cannot be compared directly.

Twins: In Maribor, twin pregnancies had a mean of 1,456 IU/l (fresh) and 1,534 IU/l (frozen) 13 days after transfer, singletons 989 and 920 IU/l (Reljič 2013). In Finland, the median 12 days after transfer was 115 IU/l for singletons and 201 IU/l for multiples; the study does not state the embryo age (Poikkeus 2002). The ranges overlap, and only an ultrasound shows whether it is twins.

Body weight: In Chicago, measurements were taken on, among other days, day 15 after retrieval; for a day 5 blastocyst, that is day 10 after transfer. For later births, the median was 303 IU/l at a BMI under 25 and 223 IU/l at a BMI of 30 or above (Hughes 2022).

Lab test: In a comparison of 80 samples on 7 measurement systems, 71% of the system pairs differed significantly. That applied, however, to the higher range of 1,500 to 3,500 IU/l (Desai 2014). The guideline AWMF 015-076 advises doing follow-up measurements in the same lab with the same test.

What a single value tells you

A meta-analysis of 12 studies on single embryo transfer examined how well a single hCG value predicts a live birth. It found a sensitivity of 0.87 and a specificity of 0.70 (Wen 2026). Put in numbers, that means: about 13% of the later births were below the respective cutoff, and 30% of the pregnancies without a birth were above it. The cutoffs of the individual studies ranged from 117 to 1,621 mIU/ml, and the authors do not recommend a universally valid value.

A low value is not a definitive verdict either. In Istanbul, about half of the women below the cutoff calculated there still had a baby (Ozer 2023). In Toronto, the first value in 483 pregnancies with a known outcome was at most 50 mIU/ml, and 12% of these ended in a birth. The lowest first value with a later birth was 6 mIU/ml. With such low starting values, the further rise predicted the outcome much better than with higher ones (DiMarco 2026). Several study protocols provide for a second measurement after two days (Ozer 2023, Shibli Abu Raya 2023, Noorhasan 2015).

Values after day 3 transfer

On transfer day, a day 3 embryo is two days younger than a day 5 blastocyst. The values therefore only become comparable when you count in days after retrieval. Day X after a day 5 transfer corresponds to day X+5 after retrieval, and day X after a day 3 transfer corresponds to day X+3. Even then, the values are not necessarily the same. At the same interval from fertilization, studies found lower values after blastocyst transfer (Zhang 2003), higher values (Oron 2015), and equal values (Dahiya 2017).

How fast does hCG rise?

The rule of thumb “hCG doubles every 48 to 72 hours” is too rough. A US study examined 287 women who came in because of pain or bleeding and later had an intact pregnancy in the uterus. In these women, hCG rose by a median of 124% in two days, so faster than a doubling. As the slowest rise that is still normal, the study gives 53% in two days; about 99% of intact pregnancies were above that (Barnhart 2004). The guideline AWMF 015-076 adopts this value. Later, the same research group showed that the minimum rise depends on the starting value: 49% in two days below 1,500 mIU/ml, 40% between 1,500 and 3,000, 33% above 3,000 (Barnhart 2016). Both studies come from women with symptoms, not from IVF groups.

After IVF, it looks similar. In 391 IVF pregnancies with a later birth, hCG also rose by a mean of 124% in two days (Chung 2006). In twins and triplets, the values were higher, but the rate of rise was not. Another US study found a mean rise in two days of 129% in singletons and 125% in twins. In a so-called vanishing twin, when only one of two gestational sacs that formed continues to develop, it was 114%. An unusual course, even an initial drop, did not rule out a later birth there either (Brady 2013).

The British guideline NICE NG126 recommends, when the location of the pregnancy is unclear, two measurements exactly 48 hours apart where possible. A rise of more than 63% there points to a developing pregnancy in the uterus. It does not rule out an ectopic pregnancy, however, so an ultrasound follows. This is not a routine scheme after IVF, but it shows the principle: the course matters more than a single number. Your clinic assesses it, and Fertilio deliberately offers no calculator for this.

When you should not wait for the next appointment: In case of bleeding or pain in the lower abdomen, call your fertility clinic or your gynecologist’s office. Outside office hours, contact the on-call medical service or the emergency room. When the location is unclear, NICE gives more weight to symptoms than to individual hCG values.

After the positive test

After the positive blood test comes the ultrasound. The timing for typical findings comes mostly from studies of natural early pregnancies.

For a day 5 blastocyst, 5+0 is day 16 after transfer and 6+0 is day 23 (our own calculation). The calculator’s timeline also shows these typical times according to Doubilet: the gestational sac at week 5+0 and the heartbeat at week 6+0. In the calendar export, it enters the period in between if you wish. After IVF, the earliest heartbeat did not depend on the transfer day or on the cleavage stage of the embryo (Schats 1990).

The discriminatory zone is the point from which a gestational sac should be visible. Bree 1989 named 1,000 mIU/ml, measured against an older reference standard. The guideline AWMF 015-076 gives an hCG value of 1,500 IU/l, below which nothing is usually visible yet. Other studies place the threshold as high as 3,500 IU/l, and the guideline lists this range as well.

When the first ultrasound takes place is set by your clinic. The Kinderwunschzentrum Döbling in Vienna schedules it five weeks after transfer, which for a day 5 blastocyst is week 7+5. Ludwigsburg examines about three weeks after the positive test, and the Cantonal Hospital of the Grisons in Chur about 14 days after the blood test. In these three examples, the first ultrasound is therefore 2 to 3 weeks after the blood test. After that, care passes to your gynecologist; the Kinderwunsch Institut Dr. Schenk in Dobl, for example, hands over from the seventh week. Bring the day of egg retrieval with you; for a frozen embryo transfer, bring the transfer day and the embryo age.

In Germany, the maternity guidelines provide for three basic ultrasound examinations, one per trimester. The first falls between 8+0 and 11+6 weeks of pregnancy and serves, among other things, to determine gestational age precisely. In Austria, a new examination program in the Parent-Child Pass (Eltern-Kind-Pass) with four ultrasound examinations has been in effect since 1 October 2026. The first falls between the 8th and 16th week of pregnancy, and the expected due date is also calculated at that time. The first trimester ends at 13+6 weeks of pregnancy (ACOG), and the calculator’s timeline shows this date as well.

Frozen embryo transfer, egg donation, and insemination

Frozen embryo transfer: What counts is the age of the embryo, not the storage time. ACOG speaks only of embryo age and transfer date and does not distinguish between a fresh and a thawed embryo. We therefore apply the formula unchanged (our own derivation): a day 5 blastocyst that was stored for two years has its due date 261 days after the transfer. The rule provides no correction day for thawing. A Danish study likewise set the day of conception for frozen embryo transfer as transfer day minus 3 or minus 5 days, respectively (Brockmeier 2024). If the embryo was cultured further after thawing, its age on transfer day counts.

Day 6 blastocysts are transferred sometimes on day 5, sometimes on day 6 of progesterone administration. In a Danish study of 746 frozen cycles, the live birth rate did not differ (Celicanin 2025). The calculator uses the embryo age you enter, so for a day 6 blastocyst, 6 days.

Egg donation: For egg donation, the same calculation applies as for IVF, which is also our own derivation. The recipient’s last period does not matter; what counts is embryo age and transfer day.

Insemination: For insemination, the day of ovulation is not known exactly, and there is no formula from a guideline. The US health agency CDC does not count IUI as assisted reproduction, and the ACOG rule refers to assisted reproduction such as IVF. The calculator sets the day of insemination equal to ovulation and calculates 266 days. On the day of insemination, you are thus, by calculation, in week 2+0. This is an estimate without support from a guideline. A Danish study likewise equated the day of conception with the day of insemination (Brockmeier 2024).

According to the product information for the urine-derived hCG preparation (5,000 IU), the trigger shot with hCG triggers ovulation about 36 hours after administration. The Kinderwunsch-Zentrum Hannover names day 14 after insemination as the earliest time for the pregnancy test. For IUI, the calculator counts from the day of insemination as it otherwise does from retrieval: blood test window from day 14 to day 19, urine test from day 16 after insemination. This is our own derivation.

Because ovulation is only estimated, the calculator points out for IUI that the ultrasound will set the due date later. According to ACOG, in pregnancies without IVF the due date is changed if the ultrasound before 14+0 weeks of pregnancy differs by more than 7 days from the dating based on the period. Before 9+0 weeks, a difference of more than 5 days is already enough. The German-language guideline on induction of labor gave 7 days as the threshold, and 5 days for Switzerland (AWMF 015-088, as of 2020, a revision is under way).

If it did not work this time

A negative test after weeks full of hope hurts. Give yourself time before thinking about the next step. Sometimes the test is positive at first, and then the value falls again. After IVF, this affects roughly 5% to 20% of positive tests, depending on the study and definition (Zeadna 2015, Muñoz 2024, DiMarco 2026). What such a biochemical pregnancy means is explained in a separate article. When you are ready: the IVF Calculator shows how the chances develop over several attempts. The cost calculator works out what out-of-pocket cost remains for another attempt in Germany, Austria, or Switzerland. Some couples want a second opinion or are considering switching clinics. The Fertility Clinic Finder shows you suitable fertility clinics for that.

Frequently asked questions

How do I calculate my due date?

Add 280 days to the first day of your last period. If your cycle differs from 28 days, add or subtract the difference (extended Naegele’s rule). If you know the day of ovulation, it is 266 days from that day. The calculator above does both and also shows which week of pregnancy you are in today.

What is Naegele’s rule?

A rule of thumb for the due date: first day of the last period plus 7 days, minus 3 months, plus 1 year. It goes back to the Heidelberg obstetrician Franz Carl Naegele in the 19th century and assumes a 28-day cycle. Because months differ in length, it gives 280 to 283 days. Counting 280 days is more precise.

How accurate is the calculated due date?

Only about 4% to 5% of babies are born exactly on the calculated day (Jukic 2013, Khambalia 2013). Around two thirds are born within 7 days of the due date. The due date is a reference point for prenatal care and maternity protection, not a birthday.

Which week of pregnancy am I in?

Count the full weeks since the first day of your last period. Week 12+3 means 12 completed weeks and 3 days, so you are in the 13th week of pregnancy. The calculator shows you today’s week of pregnancy as soon as you enter a date.

Why is pregnancy counted from the last period?

Because the first day of the period is usually known, but the day of fertilization is not. That is why the weeks are counted from the period, as the maternity guidelines require. In the first two weeks, you already count as pregnant by calculation, even though ovulation is still to come.

Can the due date still change?

Yes, at the first ultrasound. If the size of the embryo differs by 7 days or more from the calculation based on the period, your practice sets a new due date, in Switzerland from as little as 5 days (AWMF 015-088). After IVF, the due date from the transfer applies.

How do I calculate the due date with an irregular cycle?

Enter the average length of your last cycles in the calculator. If your cycle varies a lot, the due date based on your period is only a rough estimate. If you know the day of ovulation, for example from ovulation tests, it is better to calculate from that day. The first ultrasound sets the definitive due date.

When does maternity protection begin?

In Germany 6 weeks before the calculated due date (MuSchG § 3), in Austria 8 weeks before (MSchG § 3). That corresponds to week 34+0 and week 32+0, and the calculator shows both dates. After IVF, the same applies as after natural conception. Switzerland has no fixed period before the birth, and afterward an employment ban of 8 weeks applies (ArG Art. 35a). The Maternity Leave Calculator works out the end date and the maternity allowance.

How do I calculate the due date after ICSI?

Exactly as after IVF, because the fertilization method changes nothing about the age of the embryo. You add 261 days to the transfer day if a day 5 blastocyst was transferred, or 263 days for a day 3 embryo (ACOG Committee Opinion 700). More about the procedure is on the page about ICSI.

How do I calculate the week of pregnancy after a blastocyst transfer?

On the day a day 5 blastocyst is transferred, you are, by calculation, in week 2+5 of pregnancy, that is 19 days after the calculated last period. Every day after the transfer is added: 9 days after the transfer, week 4+0 begins, and 14 days after, you are in week 4+5. With a day 6 blastocyst, you are one day further along in each case.

How do I calculate the due date after a frozen embryo transfer?

As with a fresh transfer: transfer day plus 266 days minus the age of the embryo. For a day 5 blastocyst, that is 261 days, for a day 3 embryo 263 days. The time on ice does not count. Applying the ACOG rule to frozen embryo transfer is our own derivation.

Does the day of retrieval or the day of transfer count in IVF?

Both lead to the same due date: from retrieval 266 days, from transfer 266 days minus the embryo age. With a frozen embryo transfer, there is no retrieval in the transfer cycle, so you calculate from the transfer day.

When can I take a pregnancy test after transfer at the earliest?

No professional society names a fixed day. According to a study from Linz, hCG is usually measured for the first time 9 to 17 days after transfer (Trautner 2024). The Kinderwunsch-Zentrum Hannover gives 7 days after a blastocyst transfer as the earliest time. The blood test is reliable there from day 14 after retrieval, so for a day 5 blastocyst from day 9 after transfer. Your clinic sets the day for you.

From when is a urine test after the transfer of a blastocyst meaningful?

The calculator shows the urine test from day 16 after retrieval, so for a day 5 blastocyst from day 11 after transfer. Urine tests only respond from about 20 to 50 IU/l, while in blood a value above 5 IU/l already indicates a pregnancy (AWMF 015-076). An early negative urine test is therefore not yet a final result. The blood test at your clinic is the reliable one.

Can the trigger shot make the test positive?

Yes, if it contains hCG. According to the product information for choriogonadotropin alfa and for urine-derived hCG (5,000 IU), it can affect hCG measurement in blood and urine for up to 10 days. Further hCG injections extend this time. For a day 5 blastocyst, the time window ends, by our calculation, at about day 3 to 4 after transfer. A trigger using only a GnRH agonist contains no hCG.

Is it normal to test positive only late?

A urine test turning positive only late can be due to its detection limit: it only responds from about 20 to 50 IU/l (AWMF 015-076). Values vary widely early on. Seven days after a frozen embryo transfer of a blastocyst, they ranged from 1.3 to 210.2 IU/l in women with a later birth (Ueno 2014). How the pregnancy is progressing is shown by the blood test and ultrasound, not by the day of the first line.

How high is hCG 14 days after blastocyst transfer?

In Linz, the measurement took place 14 days after the transfer of a day 5 blastocyst. In women with a later birth, the median was 932 IU/l after fresh transfer and 1,416 IU/l after frozen embryo transfer (Trautner 2024). The individual values ranged from 149 to 2,870 IU/l (fresh) and from 100 to 8,298 IU/l (frozen). In a Turkish study, the medians were 888 and 1,000 IU/l (Elmas 2025). How a single value should be assessed is decided by your clinic.

Does a high hCG value mean twins?

Not necessarily. In twins, the values are higher on average: in Maribor, they were a mean of 1,456 IU/l 13 days after fresh transfer, compared with 989 IU/l in singletons (Reljič 2013). The ranges overlap, though. How many embryos have implanted is shown only by ultrasound.

Are IVF babies born earlier?

A Dutch study found a small difference. It compared 307 IVF singletons with 307 comparable singletons without IVF. With spontaneous onset of labor, the IVF children were born after 275 instead of 278 days, so 3 days earlier (Koudstaal 2000). The difference was at the border of statistical significance. The calculated due date remains the reference point for prenatal care and maternity protection.

Sources

Guidelines, agencies, and laws

• Committee Opinion No. 700: Methods for Estimating the Due Date, Obstet Gynecol 2017;129(5):e150-e154, ACOG with AIUM and SMFM, 2017, reaffirmed 2025
• S2e guideline on first-trimester diagnostics and therapy at 11 to 13+6 weeks of pregnancy, AWMF 085-002, short version 1.3, DEGUM with DGGG, OEGUM, SGUMGG, and OEGGG, 2025
• S2k guideline on early pregnancy loss in the first trimester, AWMF 015-076, version 1.2, DGGG, OEGGG, and SGGG, January 2025
• S2k guideline on induction of labor, AWMF 015-088, version 1.1, DGGG, OEGGG, and SGGG, as of December 2020, valid until 1 December 2025, revision registered
• ESHRE Guideline Ovarian Stimulation for IVF/ICSI, Update 2025, Hum Reprod 2026;41(4):498-514, ESHRE, 2025
• NICE guideline NG126: Ectopic pregnancy and miscarriage, recommendations 1.6 and 1.8, NICE, last updated 17 June 2026
• Maternity guidelines (Mutterschafts-Richtlinien), version of 21 September 2023, last amended 16 July 2026, Federal Joint Committee (Gemeinsamer Bundesausschuss, G-BA), 2026
• Maternity record (Mutterpass), version of 28 September 2023, Federal Joint Committee (G-BA), 2023
• Examinations during pregnancy, Parent-Child Pass, Austrian public health portal, as of 1 October 2026
• Counting weeks of pregnancy, familienplanung.de, Bundesinstitut für Öffentliche Gesundheit (Federal Institute for Public Health), accessed October 2026
• Eltern-Kind-Pass-Untersuchungsprogramm-Verordnung (Austrian ordinance on the Parent-Child Pass examination program), Federal Law Gazette, BGBl. II No. 241/2026, Federal Legal Information System, 2026
• Krankenpflege-Leistungsverordnung (KLV, Swiss Health Care Benefits Ordinance), Art. 13, Fedlex, as of 1 August 2026
• Preterm birth, fact sheet, World Health Organization, accessed October 2026
• In vitro fertilisation (IVF), Human Fertilisation and Embryology Authority, accessed October 2026
• Assisted Reproductive Technologies, patient booklet, American Society for Reproductive Medicine, revised 2018
• Assisted Reproductive Technology Surveillance, United States 2016, MMWR Surveill Summ 2019;68(4), CDC, 2019
• § 3 Maternity Protection Act (MuSchG), Federal Ministry of Justice (Bundesministerium der Justiz), last amended 22 December 2025
• § 3 Austrian Maternity Protection Act 1979 (MSchG), Federal Legal Information System, version as of 5 July 2024
• Labor Act (ArG), Art. 35a, Fedlex, version of 1 September 2023

Studies

• Tunón K et al.: Gestational age in pregnancies conceived after in vitro fertilization, Ultrasound Obstet Gynecol 2000;15(1):41-46
• Sladkevicius P et al.: Ultrasound dating at 12-14 weeks of gestation in in-vitro fertilized pregnancies, Ultrasound Obstet Gynecol 2005;26(5):504-511
• Khambalia AZ et al.: Predicting date of birth and examining the best time to date a pregnancy, Int J Gynaecol Obstet 2013;123(2):105-109
• Jukic AM et al.: Length of human pregnancy and contributors to its natural variation, Hum Reprod 2013;28(10):2848-2855
• Wilcox AJ et al.: Timing of sexual intercourse in relation to ovulation, N Engl J Med 1995;333(23):1517-1521
• Munro MG et al.: The two FIGO systems for normal and abnormal uterine bleeding symptoms and classification of causes of abnormal uterine bleeding in the reproductive years: 2018 revisions, Int J Gynaecol Obstet 2018;143(3):393-408
• Koudstaal J et al.: Obstetric outcome of singleton pregnancies after IVF: a matched control study in four Dutch university hospitals, Hum Reprod 2000;15(8):1819-1825
• Wilcox AJ et al.: Time of implantation of the conceptus and loss of pregnancy, N Engl J Med 1999;340(23):1796-1799
• Lambers MJ et al.: Optimizing hCG cut-off values: a single determination on day 14 or 15 is sufficient for a reliable prediction of pregnancy outcome, Eur J Obstet Gynecol Reprod Biol 2006;127(1):94-98
• Noorhasan DJ et al.: Serum hCG Levels following the Ovulatory Injection: Associations with Patient Weight and Implantation Time, Obstet Gynecol Int 2015:520714
• Trautner PS et al.: Single day 14 serum hCG values allow prediction of viable pregnancy and are significantly higher in frozen as compared to fresh single blastocyst transfer, J Assist Reprod Genet 2024;41(8):2193-2200
• Damewood MD et al.: Disappearance of exogenously administered human chorionic gonadotropin, Fertil Steril 1989;52(3):398-400
• Brockmeier C et al.: Association between the length of in vitro embryo culture, mode of ART, and the initial endogenous hCG rise in ongoing singleton pregnancies, Hum Reprod 2024
• Celicanin MM et al.: Day 6 vitrified blastocyst transfer on day 5 vs. day 6 of progesterone shows similar outcomes in HRT-FET cycles, Sci Rep 2025;15:32792
• Kidera N et al.: Serum human chorionic gonadotropin can predict live birth 7 days after frozen-thawed blastocyst transfer, F S Rep 2025;6(4):455-461
• Bree RL et al.: Transvaginal sonography in the evaluation of normal early pregnancy: correlation with HCG level, AJR Am J Roentgenol 1989;153(1):75-79
• Schats R et al.: Embryonic heart activity: appearance and development in early human pregnancy, Br J Obstet Gynaecol 1990;97(11):989-994
• Doubilet PM: Sonographic Evaluation of Early Pregnancy Loss, handout, American Institute of Ultrasound in Medicine, accessed October 2026
• Ueno S et al.: Maternal age and initial β-hCG levels predict pregnancy outcome after single vitrified-warmed blastocyst transfer, J Assist Reprod Genet 2014;31(9):1175-1181
• Hughes LM et al.: Early β-hCG levels predict live birth after single embryo transfer, J Assist Reprod Genet 2022;39(10):2355-2364
• Ozer G: Initial β-hCG levels and 2-day-later increase rates effectively predict pregnancy outcomes in single blastocyst transfer in frozen-thawed or fresh cycles, Medicine (Baltimore) 2023;102(42):e35605
• Zhu W et al.: Maternal β-HCG concentrations in early IVF pregnancy: association with the embryo development stage of blastocysts, Reprod Biomed Online 2019;38(5):683-690
• Xiong F et al.: Initial serum HCG levels are higher in pregnant women with a male fetus after fresh or frozen single blastocyst transfer, Taiwan J Obstet Gynecol 2019;58(6):833-839
• Elmas B et al.: Can Serum β-hCG Values Measured after Embryo Transfer Predict Live Birth in Both Fresh and Frozen Transfers?, J Coll Physicians Surg Pak 2025;35(10):1335-1339
• Li Y et al.: Trophectoderm Biopsy Differentially Influences the Level of Serum β-Human Chorionic Gonadotropin With Different Embryonic Trophectoderm Scores in Early Pregnancy From 7847 Single-Blastocyst Transfer, Front Endocrinol 2022;13:794720
• Reljič M et al.: Human chorionic gonadotropin levels are equally predictive for pregnancy outcome after fresh and vitrified-warmed blastocyst transfer, J Assist Reprod Genet 2013;30(11):1459-1463
• Shibli Abu Raya Y et al.: High initial β-hCG predicts IVF outcomes accurately and precludes the need for repeated measurements, Endocr Connect 2023;12(11):e230189
• Keane KN et al.: Higher β-HCG concentrations and higher birthweights ensue from single vitrified embryo transfers, Reprod Biomed Online 2016;33(2):149-160
• Poikkeus P et al.: Serum HCG 12 days after embryo transfer in predicting pregnancy outcome, Hum Reprod 2002;17(7):1901-1905
• Desai D et al.: Human chorionic gonadotropin discriminatory zone in ectopic pregnancy: does assay harmonization matter?, Fertil Steril 2014;101(6):1671-1674
• Wen Q et al.: Diagnostic accuracy of initial serum β-hCG in predicting pregnancy outcomes post-SET in IVF/ICSI cycles: a systematic review and meta-analysis, Front Endocrinol 2026;17:1636981
• DiMarco S et al.: Live births after low initial β-hCG in IVF cycles: a retrospective cohort study, BMC Pregnancy Childbirth 2026;26:463
• Zeadna A et al.: A comparison of biochemical pregnancy rates between women who underwent IVF and fertile controls who conceived spontaneously, Hum Reprod 2015
• Muñoz E et al.: Is biochemical pregnancy loss associated with embryo or endometrium? A retrospective cohort study in frozen single embryo transfer of own and donated oocytes, Hum Reprod 2024
• Wei D et al.: Natural ovulation versus programmed regimens before frozen embryo transfer in ovulatory women: multicentre, randomised clinical trial, BMJ 2026
• Saupstad M et al.: Optimizing the protocol for modified natural cycle frozen embryo transfer (mNC-FET): a multicentre, single-blinded randomized controlled trial, Hum Reprod Open 2026(1):hoag003
• Zhang X et al.: Delay of embryo transfer to day 5 results in decreased initial serum beta-human chorionic gonadotropin levels, Fertil Steril 2003;80(6):1359-1363
• Oron G et al.: Predictive value of maternal serum human chorionic gonadotropin levels in pregnancies achieved by in vitro fertilization with single cleavage and single blastocyst embryo transfers, Fertil Steril 2015;103(6):1526-1531
• Dahiya M et al.: Embryo transfer day does not affect the initial maternal serum β-hCG levels, Eur J Obstet Gynecol Reprod Biol 2017;212:75-79
• Tanbo TG et al.: Maternal concentrations of human chorionic gonadotrophin in very early IVF pregnancies and duration of pregnancy, Reprod Biomed Online 2018;37(2):208-215
• Barnhart KT et al.: Symptomatic patients with an early viable intrauterine pregnancy: HCG curves redefined, Obstet Gynecol 2004;104(1):50-55
• Barnhart KT et al.: Differences in Serum Human Chorionic Gonadotropin Rise in Early Pregnancy by Race and Value at Presentation, Obstet Gynecol 2016;128(3):504-511
• Chung K et al.: Defining the rise of serum HCG in viable pregnancies achieved through use of IVF, Hum Reprod 2006;21(3):823-828
• Brady PC et al.: Early β-human chorionic gonadotropin trends in vanishing twin pregnancies, Fertil Steril 2013;100(1):116-121

Product information

• Choriogonadotropin alfa 250 micrograms, product information (summary of product characteristics), European Medicines Agency, accessed October 2026
• Human chorionic gonadotropin 5,000 IU from urine, product information, as of February 2024
• Micronized progesterone 200 mg, soft capsules for vaginal use, product information, as of February 2026

Examples from fertility clinics (all accessed October 2026)

• Rest phase after transfer, Kinderwunschzentrum am Universitätsklinikum Frankfurt
• 7 steps, patient booklet, KITZ Regensburg, 2019
• Frequently asked questions about fertility treatment, Kinderwunsch-Zentrum Hannover
• Frequently asked questions, novum - Zentrum für Reproduktionsmedizin, Essen/Duisburg
• Treatment roadmap, Kinderwunschzentrum Ludwigsburg
• IVF in 10 steps, Kinderwunsch Institut Feichtinger, Vienna
• After IVF treatment, Kinderwunschzentrum Döbling, Vienna
• Information for physicians, Female Health Clinic, Zurich
• Tips for the days after embryo transfer, fertility center at the Cantonal Hospital of the Grisons, 2023
• Kinderwunsch Institut Dr. Schenk, Dobl