Infertility: causes and when to see a doctor

Hope every month, then your period again. At some point everything revolves around one question: Why am I not getting pregnant? You are not alone. About one in six people are affected by infertility at some point in their lives (Cox 2022).

This guide explains when it is called infertility, when you should get checked, and what causes there are in women and men. It is based on the guidelines of the German, Austrian, and Swiss societies for gynecology and obstetrics (DGGG, OEGGG, SGGG; 2026, called the “DACH guideline” here), the WHO (2025), NICE (2026), ESHRE, and ASRM. Where they disagree, we tell you. This guide is no substitute for a conversation with a doctor.

When is it called infertility?

Infertility is defined as the absence of a clinical pregnancy after 12 months of regular, unprotected sexual intercourse. This is how the international ICMART glossary (2025), the WHO, and the DACH guideline define it. Evaluation and treatment may also begin earlier, depending on age, medical history, and findings. Infertility does not mean that pregnancy is impossible. Permanent infertility is called sterility.

According to NICE, more than 80% of couples in the general population get pregnant within one year if the woman is under 40 and they have regular unprotected intercourse. Of the remaining couples, about half get pregnant in the second year.

Cumulative share of couples with a clinical pregnancy when having intercourse twice a week. Source: NICE NG257, Table 1.

A meta-analysis for the WHO shows how common infertility is: Lifetime prevalence worldwide was 17.5% (95% CI 15.0 to 20.3) and 16.5% in Europe. The worldwide figure is based on surveys of women; for men it was 12.4% (Cox 2022). This means at least one period of 12 months of trying without getting pregnant. In Germany in 2012/13, among respondents born in 1971 to 1973 and 1981 to 1983, 7.5% of women and 6.5% of men were affected at the time of the survey, meaning they had been unsuccessful for more than 12 months or considered themselves infertile (Passet-Wittig 2016).

When to get evaluated

The DACH guideline sets different timelines by age because a woman’s fertility declines after age 35.

At exactly 35, you already belong to the 6-month group according to ASRM. With PMOS (formerly PCOS) and cycles longer than 38 days, the German PCOS guideline already refers to infertility after 3 to 6 months without pregnancy. If you had a miscarriage or an ectopic pregnancy during the waiting period, NICE says the time frame does not start over (1.16.7).

Both partners should be evaluated at the same time (ASRM 2021; EAU 2026, strong recommendation).

Which tests are included?

For women, the DACH guideline includes: a conversation with both partners, a transvaginal ultrasound that counts the small follicles (antral follicles), hormone levels on cycle days 2 to 5 (LH, FSH, TSH, prolactin, total testosterone, DHEAS, SHBG, estradiol, AMH; recommendation 3.7.E32), progesterone about 7 days after the presumed ovulation, and a check of the fallopian tubes (3.4.E14).

For men, the semen analysis is central. An abnormal result is repeated after 11 weeks at the earliest; a normal one is not (WHO 2025).

Not every guideline considers every test necessary:

The AMH Chart shows how AMH levels are distributed by age in studies.

In-depth article

Fertility test for women in Germany, Austria & Switzerland

Home test, gynecologist or fertility clinic: what a fertility test for women shows and what it costs. Insurance rules for Germany, Austria, Switzerland.

What does health insurance pay for?

This section applies to Germany, Austria, and Switzerland.

In Germany, the statutory health insurance funds (gesetzliche Krankenversicherung, GKV) pay in full for tests to find the cause (familienplanung.de, as of January 7, 2026; Section 27 of Social Code Book V, Sozialgesetzbuch V, SGB V). There are exceptions for AMH testing without a medical reason and, according to information from practices, for HyCoSy; details are in the fertility test guide. Hormonal stimulation on its own also counts as ordinary medical treatment (Directive on Assisted Reproduction, No. 1). Restrictions apply only to assisted reproduction: a 50% subsidy under Section 27a of Social Code Book V, only for married couples using their own eggs and sperm, both at least 25, woman under 40, man under 50.

In Austria, the IVF Fund (IVF-Fonds) pays 70% of an IVF or ICSI treatment, among other things when there is a statutory indication, the woman is under 40, and the man is under 50. In Switzerland, basic health insurance (Grundversicherung) pays for at most three inseminations per pregnancy, but not for IVF (Annex 1 of the Health Care Benefits Ordinance, Krankenpflege-Leistungsverordnung, KLV). More in the cost calculator.

How are the causes distributed?

“Is it me or is it him?” That can rarely be answered in one word. In a WHO study of 8,500 couples from 25 countries, collected in the 1980s, the cause lay with the woman alone in 30.6%, with the man alone in 18.7%, and with both in 26.3%. In 10.8%, no cause was found (WHO 2025). The WHO itself describes these data as relatively old.

The German IVF Registry (Deutsches IVF-Register, D.I.R.) shows only couples in IVF or ICSI treatment. Of 62,533 treatments in 2024, 37.5% had a male indication, 24.3% a female indication, and 26.2% a mixed indication; in 7.4%, the cause remained unexplained (our own calculation). For female indications, multiple entries are possible, so the values are shares of all entries:

Source: German IVF Registry, Yearbook 2024, p. 41; 23,168 entries for IVF, 53,861 for ICSI.

Ovulation disorders and PMOS

According to ASRM, ovulation disorders are found in about 15% of all couples with infertility and account for up to 40% of causes in women. Causes include PMOS, obesity, weight fluctuations, very heavy exercise, thyroid disorders, elevated prolactin, and the beginning of the menopausal transition (ASRM 2021).

According to the WHO, the most common cause of absent ovulation is PMOS, previously called polycystic ovary syndrome (PCOS). Since May 2026, it has been called polyendocrine metabolic ovarian syndrome internationally: It is not about abnormal cysts but about many immature follicles, and both hormones and metabolism are affected (Lancet 2026). Depending on the criteria, PMOS affects 10 to 13% of women of reproductive age (international guideline 2023). In a long-term Swedish study, 86.7% of women with PCOS who wanted to become pregnant had at least one child, compared with 91.6% in the comparison group (Hudecova 2009).

If ovulation does not occur, the international guideline, the WHO, and the German PCOS guideline recommend letrozole as the first choice and clomiphene or gonadotropins only as a second choice (AWMF 089-004). The DACH guideline names letrozole or clomiphene. In Germany, letrozole is approved only for breast cancer after menopause, and the prescribing information even lists a premenopausal hormonal status as a contraindication. When trying to conceive, using it is off-label and requires a doctor to inform you beforehand; a pregnancy must be ruled out first. Clomiphene is approved for inducing ovulation in women who do not ovulate, for a maximum of 6 cycles. In a US study of 750 women with PCOS (mean BMI 35), within up to five cycles, 27.5% with letrozole and 19.1% with clomiphene had a baby (Legro 2014).

Metformin alone is less effective and is not approved for PMOS when trying to conceive (off-label). In cases of overweight, the German PCOS guideline recommends a weight loss of 5 to 10% before pregnancy. There is no special diet with a proven benefit, and the data are insufficient for inositol. Letrozole, clomiphene, and metformin are prescription-only under the German Prescription Drug Ordinance (Arzneimittelverschreibungsverordnung, AMVV), Annex 1.

In-depth article

Getting pregnant with PCOS: letrozole, metformin, IVF

Getting pregnant with PCOS: letrozole (off-label), metformin (off-label), gonadotropins, IVF. Guidelines, insurance in Germany, Austria & Switzerland.

Elevated prolactin

A persistently elevated prolactin level can disrupt ovulation (NICE). A single elevated value is not enough for a diagnosis: Stress during the blood draw, some psychiatric medications, an underactive thyroid, or so-called macroprolactin can be behind it. The DACH guideline therefore recommends repeat testing. If the elevation is confirmed and comes with symptoms, a dopamine agonist should be used; the first choice is cabergoline (3.7.E41; NICE; WHO). Cabergoline is approved for this and is prescription-only (Prescription Drug Ordinance, Annex 1). According to the prescribing information, it is stopped as a precaution one month before the planned conception once the cycle is regular again.

Thyroid and Hashimoto’s

In subclinical hypothyroidism, only the TSH level is elevated; in overt hypothyroidism, free T4 is also low. Hashimoto’s usually shows up in lab tests as TPO antibodies, often with normal thyroid function. About 8 to 11% of women with infertility or a previous miscarriage have such antibodies, about as many as other women of childbearing age (ATA 2026). According to the ATA, they are associated with a somewhat higher risk of miscarriage, about 2 to 8 percentage points in absolute terms. ASRM considers the data on this to be conflicting.

Overt hypothyroidism or hyperthyroidism should be treated before pregnancy (DACH guideline, 3.7.E48). For a mildly elevated TSH and for antibodies without a functional disorder, the recommendations differ:

The ATA guideline, supported by ESHRE and the European Thyroid Association, is based on large studies. In the TABLET trial, 952 women with TPO antibodies, normal thyroid function, and a history of miscarriage or infertility received 50 µg of levothyroxine or a placebo. The live birth rate (birth from the 34th week of pregnancy) was 37.4% and 37.9% (RR 0.97; 0.83 to 1.14; Dhillon-Smith 2019). T4LIFE, with 187 women after at least two miscarriages, and an IVF trial with 600 women also found no difference in live births (50% vs. 48% and 31.7% vs. 32.3%). The DACH guideline itself states that the threshold of 2.5 mU/l lacks scientific evidence. Its “may” recommendation is a consensus.

If you already take levothyroxine, your TSH should be between 0.5 and 2.5 mU/l before pregnancy (ATA 2026). Levothyroxine is approved for treating an underactive thyroid and is prescription-only (Prescription Drug Ordinance, Annex 1). You do not need to avoid iodine with Hashimoto’s, but you should check with a doctor before taking iodine tablets (Healthy Start network, Gesund ins Leben, 2026). Evidence for selenium is lacking (ATA 2026).

Fallopian tubes

The DACH guideline gives fallopian tube damage as the cause in up to 35%. If a blockage is not suspected, it recommends a contrast ultrasound (HyCoSy) first. If it is normal, the tubes are very likely open (negative predictive value 99.5%). If endometriosis is suspected, or after infections or an ectopic pregnancy, a laparoscopy follows. The WHO recommends HyCoSy or the X-ray method hysterosalpingography (HSG), and ESHRE considers both comparable.

In the H2Oil trial of 1,119 women with infertility, an HSG with oil-based contrast led to a live birth from a pregnancy in the following six months in 38.8%, compared with 28.1% with water-based contrast (Dreyer 2017). ESHRE therefore prefers oil-based agents in unexplained infertility. The DACH guideline and NICE recommend removing or blocking a fluid-filled fallopian tube (hydrosalpinx) before IVF.

Uterus: fibroids, polyps, septum

In a practice-based study of 600 women undergoing a fertility evaluation, an ultrasound with saline solution found abnormalities in the uterine cavity in 16.2%, mostly polyps (13.0%) (Tur-Kaspa 2006).

With fibroids, location matters. Fibroids that protrude into the cavity (submucosal) lower the pregnancy rate, and removing them seems to help. Fibroids on the outer surface (subserosal) do not affect fertility. Fibroids within the muscle wall also seem to lower fertility, but whether removing them helps is unclear (Pritts 2009). The DACH guideline recommends removing submucosal fibroids (FIGO type 0 and 1) by hysteroscopy before fertility treatment (3.4.E16), and the same for polyps (3.4.E17). In a randomized trial of 215 women before insemination, there were 64 pregnancies after polyp removal and 29 without removal (RR 2.1; Pérez-Medina 2005).

Whether a uterine septum (dividing wall) should be operated on is controversial. In the TRUST trial of 80 women with a septum, 31% after surgery and 35% without surgery had a baby within 12 months (Rikken 2021). The WHO advises against surgery in women trying to conceive who have not had recurrent miscarriages, the DACH guideline allows surgery as an option, and ASRM recommends shared decision-making (2024).

Endometriosis and adenomyosis

In endometriosis, tissue similar to the uterine lining grows outside the uterus. The WHO estimates that about 10% of women of reproductive age and 25 to 50% of women with infertility are affected (WHO 2025). The German endometriosis guideline considers a precise estimate impossible and counts infertility among the leading symptoms.

ESHRE, NICE, and the German guideline agree: Hormone therapies that suppress endometriosis are not recommended when you are currently trying to conceive (NICE NG73, 1.10.4). They suppress ovulation and cost time. A Cochrane analysis did find somewhat higher pregnancy rates after surgery followed by hormone therapy than after surgery alone (RR 1.22; 11 studies). However, the studies did not record the time to pregnancy (Chen 2020; AWMF 015-045). In mild endometriosis, removing the lesions by laparoscopy can help. In a randomized trial of 341 women, within 36 weeks 30.7% with removal and 17.7% without removal had a pregnancy that lasted at least 20 weeks (Marcoux 1997). For deep endometriosis, ESHRE sees no convincing fertility benefit of surgery; the German guideline is more optimistic. Cysts on the ovary (endometriomas) should not be operated on routinely before IVF because this may lower ovarian reserve (ESHRE). After IVF or ICSI, the live birth rate overall is similar to that without endometriosis (OR 0.94) and lower in severe endometriosis (Hamdan 2015).

In adenomyosis, tissue similar to the uterine lining lies within the muscle wall of the uterus. It is detected first by ultrasound; MRI is the second step (AWMF 015-045). After IVF or ICSI, the live birth rate was lower in a meta-analysis (OR 0.59; Cozzolino 2022) and the risk of miscarriage was about twice as high (RR 2.12; Vercellini 2014). In women with endometriosis who want to conceive, adenomyosis should also be looked for (AWMF 015-045).

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Endometriosis and fertility: chances, surgery or IVF

Endometriosis and fertility: chances without treatment, the EFI, surgery or IVF, endometrioma and AMH, adenomyosis and pregnancy according to guidelines.

Age

According to ASRM, a woman’s age is the single most important factor for fertility. By age 40, fertility is about half as high as in the late 20s or early 30s (ASRM 2022). In IVF, the live birth rate per embryo transfer in the German IVF Registry was 30.9% at ages 30 to 34 and 9.3% at ages 41 to 44 (IVF, data from 2019 to 2023). AMH does not predict a spontaneous pregnancy (NICE). The IVF Calculator shows how IVF chances develop over several attempts.

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Getting pregnant at 40, 42, 45: chances by age

Chances, miscarriage risk, IVF live birth rates, and insurance rules for ages 35 to 45, with German IVF Registry data. For Germany, Austria & Switzerland.

Weight, smoking, and lifestyle

Weight: It probably takes longer with a BMI of 30 or higher, according to NICE. Men with a BMI of 30 or higher have an increased risk of reduced fertility. In couples undergoing a fertility evaluation (woman with ovulation and an open fallopian tube, normal semen analysis), the chance of a spontaneous pregnancy fell by about 4% in relative terms per BMI point above a BMI of 29 (van der Steeg 2008, 3,029 couples).

Smoking: According to older observational studies, women who smoke are more often infertile (odds ratio 1.6), reach menopause 1 to 4 years earlier, and need almost twice as many attempts with IVF (ASRM 2024). According to the DACH guideline, the effects are reversible based on observational studies.

Alcohol and caffeine: At the time of conception, the DACH guideline recommends abstaining from alcohol. Less than 200 mg of caffeine per day, about two cups of coffee, does not seem to impair fertility, whereas more than 500 mg lowers it (DACH guideline 2026; ASRM 2022). NICE finds no consistent association.

Folic acid: For everyone trying to conceive, the Healthy Start network recommends 400 µg of folic acid daily, from the time you start trying to conceive until the end of the 12th week of pregnancy. For those who start less than 4 weeks before conception, the network recommends 800 µg daily, also until the end of the 12th week (Healthy Start network 2026).

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Causes in men

A male factor is involved in about half of couples, and in about one in five it is the sole factor (EAU 2026). In 30% of men with a fertility disorder, the cause remains unclear. Common findings are a varicose vein at the testicle (varicocele, 14.8%), absence of sperm in the ejaculate (azoospermia, 11.2%), and a hormone deficiency (10.1%). A semen analysis alone cannot reliably separate fertile from infertile men, the EAU emphasizes. More in the guide Male fertility and on semen analysis values.

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Male infertility: causes and treatment in 2026

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Unexplained infertility

Sometimes everything looks normal. In up to three in ten couples, the usual evaluation finds no clear cause (ESHRE 2023; familienplanung.de 2026). That is exhausting, but there are paths forward.

ESHRE (2023) recommends insemination with hormonal stimulation as the first treatment, a strong recommendation based on very low-quality evidence; the timing depends on age and duration. The WHO (2025) advises expectant management with counseling first (3 to 6 months in studies), then stimulated insemination with clomiphene or letrozole, then IVF. NICE recommends trying for a total of 2 years and then offering up to 4 inseminations with gonadotropins or IVF. In the German IVF Registry, the clinical pregnancy rate per insemination with partner sperm from 2020 to 2024 ranged from 8.0% (clomiphene) to 14.5% (recombinant FSH), depending on stimulation, across all indications.

Letrozole is off-label for this. According to the prescribing information, clomiphene is approved for women who do not ovulate, but in unexplained infertility ovulation does occur. ESHRE recommends against endometrial scratching and probably does not recommend antioxidants, inositol, or acupuncture. Psychological support should be offered.

Luteal phase deficiency

This refers to a second half of the cycle that lasts 10 days or less. According to ASRM and SREI (2026), there is no reliable test for it and no progesterone level that defines a normal luteal phase. It has not been proven that luteal phase deficiency is an independent cause of infertility or recurrent miscarriage.

The guidelines differ on measuring progesterone. NICE offers it to everyone; the DACH guideline provides for it about 7 days after ovulation to confirm ovulation. ESHRE (2023) and the German-language guideline on recurrent miscarriage (2026) advise against routine testing with regular cycles. Progesterone is released in pulses and, according to ASRM, can change up to eightfold within 90 minutes.

There is no evidence of benefit for progesterone in a natural cycle (ASRM 2026). After IVF or ICSI, however, it is standard (ESHRE 2025, strong recommendation). Progesterone requires a prescription. In a study of 284 women aged 30 to 44 with no known fertility disorder, the chance of conceiving in the next cycle was somewhat lower after a cycle with a short second half (defined there as 11 days or less, counting the day of ovulation). After 12 months, there was no statistically significant difference (Crawford 2017).

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Luteal phase defect: low progesterone and fertility

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Miscarriage and biochemical pregnancy

Some couples get pregnant and then lose the pregnancy. This is painful and more common than many people think: At least 10 to 15% of clinically recognized pregnancies end in miscarriage, about 80% of them in the first trimester (AWMF 015-076). In a US study with daily urine tests, 22% of 198 pregnancies ended before they were clinically recognized (Wilcox 1988). Such a biochemical pregnancy can be detected only through the hormone hCG and ends before it can be seen on an ultrasound (ICMART 2025).

The risk increases with age. In Norway (pregnancies recorded in registries from 2009 to 2013), it was 9.8% at ages 25 to 29 and 32.2% at ages 40 to 44. After exactly one previous miscarriage, the next pregnancy ended the same way again in 19.8%, compared with 11.6% in women with no previous pregnancy (Magnus 2019). So about four in five pregnancies after a miscarriage did not end in another miscarriage.

According to the German-language guideline, no waiting period is needed afterward if there is no reason against it (AWMF 015-076). In 2007, the WHO recommended waiting at least 6 months after a miscarriage or an abortion. This recommendation is based on a single study from Latin America that could not separate miscarriages from induced abortions. A meta-analysis of 16 studies even found fewer repeat miscarriages with an interval of less than 6 months than with a longer interval (RR 0.82; Kangatharan 2017). The guideline on recurrent miscarriage recommends an evaluation after three consecutive miscarriages, and in justified cases already after two (AWMF 015-050). ESHRE and ASRM already speak of recurrent miscarriage after two losses. In a Danish specialty clinic, 66.7% of women with recurrent miscarriage had a baby within 5 years (Lund 2012). If you have pain or heavy bleeding in early pregnancy, get examined by a doctor immediately, also because of a possible ectopic pregnancy (AWMF 015-076).

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Chemical pregnancy: signs, causes and chances

Chemical pregnancy explained: definition, signs, how common it is naturally and after IVF, hCG levels, waiting time and chances at the next attempt.

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Pregnant after miscarriage: waiting time and hCG

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Next steps

You do not have to sort this out alone. Here is how you can proceed:

1. Check the timing: The table above shows when an evaluation is recommended. You should both go together.
2. Find a clinic: In the clinic directory, you can compare clinics. Our Fertility Clinic Finder suggests suitable clinics after a few questions.
3. Clarify the costs: What the health insurance fund covers for a treatment can be found under insurance coverage and in the guide Fertility treatment cost.
4. Take care of yourself: According to the DACH guideline, emotional strain is a common reason for stopping treatment. Get support if it becomes too much.

The guide Assisted reproduction explains the treatment paths. If embryos are frozen during IVF, a frozen embryo transfer can follow later. According to the German IVF Registry, after one fresh and two frozen embryo transfers from one egg retrieval, about half of couples had a baby when embryos could be frozen and used (all indications).

In-depth article

Frozen embryo transfer in Germany, Austria & Switzerland

Frozen embryo transfer day by day: natural or artificial cycle, 2026 evidence, success rates by age, and costs in Germany, Austria, and Switzerland.

Frequently asked questions

Why am I not getting pregnant even though everything is normal?

In up to three in ten couples, the evaluation finds no clear cause (ESHRE 2023). Depending on age and duration, guidelines then recommend expectant management with counseling or insemination with hormonal stimulation (ESHRE 2023, WHO 2025).

When should I get evaluated?

Under 35: after 12 months. Age 35 or older: after 6 months (ASRM 2023). Over 40: no waiting period, straight to a fertility clinic (DACH guideline 2026). With irregular cycles or known pre-existing conditions, also no waiting period (ASRM 2021; NICE 2026).

Is it more often the woman or the man?

In a WHO study of 8,500 couples from the 1980s, the cause lay with the woman alone in 30.6%, with the man alone in 18.7%, and with both in 26.3% (WHO 2025). A male factor is involved in about half of couples (EAU 2026).

What does health insurance pay for in cases of infertility?

In Germany, the statutory health insurance funds pay in full for tests to find the cause (familienplanung.de 2026; Section 27 of Social Code Book V). According to information from practices, some centers bill HyCoSy privately, and an AMH test without a medical reason is self-pay. Marriage and age limits and the 50% subsidy apply only to assisted reproduction (Section 27a of Social Code Book V).

Can Hashimoto’s affect fertility?

TPO antibodies are associated with a somewhat higher risk of miscarriage (ATA 2026). With normal thyroid function, however, levothyroxine does not improve the chance of having a baby (TABLET trial: 37.4% vs. 37.9% live births). A true underactive thyroid is treated before pregnancy (DACH guideline 2026).

Can you get pregnant with PMOS (formerly PCOS)?

Yes. In a long-term Swedish study, 86.7% of women with PCOS who wanted to become pregnant had at least one child (Hudecova 2009). If ovulation does not occur, letrozole (off-label) is the first choice according to the international, WHO, and German PCOS guidelines (AWMF 089-004). The 2026 DACH guideline names letrozole or clomiphene (AWMF 015-085).

Does stress cause infertility?

There is no clear evidence, and the studies contradict each other (DACH guideline 2026). In a meta-analysis of 3,583 women in fertility treatment, anxiety or depressed mood before treatment had no effect on the outcome (Boivin 2011).

Does the waiting period start over after a miscarriage?

No. A miscarriage or ectopic pregnancy during the waiting period does not reset the time frame until evaluation (NICE NG257, 1.16.7). According to the German-language guideline, no waiting period is needed before trying again if there is no reason against it (AWMF 015-076). In 2007, the WHO recommended at least 6 months, based on a single study. A meta-analysis even found fewer repeat miscarriages with a shorter interval (Kangatharan 2017).

Sources

Guidelines and position statements

• AWMF 015-085, Diagnosis and treatment before assisted reproduction, DGGG, OEGGG, SGGG, version 2.0, 2026
• AWMF 015-050, Recurrent miscarriage, version 2.0, 2026
• AWMF 015-076, Early pregnancy loss, version 1.2, 2025
• AWMF 015-045, Endometriosis, version 5.1, 2025
• AWMF 089-004, Polycystic ovary syndrome, version 1.1, 2025
• WHO guideline on infertility, recommendations, Hum Reprod 2026
• ICMART, International Glossary on Infertility and Fertility Care 2025, Hum Reprod 2026
• NICE NG257, Fertility problems, NICE, March 31, 2026
• NICE NG257, Defining infertility and initial assessment, NICE, 2026
• NICE NG73, Endometriosis, Recommendations, NICE, 2024
• WHO, Report of a technical consultation on birth spacing, 2007
• Fertility evaluation of infertile women, ASRM, 2021
• Definition of infertility, ASRM, 2023
• Optimizing natural fertility, ASRM, 2022
• Subclinical hypothyroidism in the infertile female population, ASRM, 2024
• Tobacco or marijuana use and infertility, ASRM, 2024
• Uterine septum, a guideline, ASRM, 2024
• Diagnosis and treatment of luteal phase deficiency, ASRM and SREI, 2026
• Recurrent pregnancy loss, ASRM, 2026
• ATA 2026 Guidelines, Thyroid Disease in Preconception and Pregnancy, Thyroid 2026
• ESHRE guideline Unexplained infertility, Hum Reprod 2023
• ESHRE guideline Endometriosis, Hum Reprod Open 2022
• ESHRE guideline Ovarian Stimulation 2025, Hum Reprod 2026
• ESHRE guideline Recurrent pregnancy loss 2022, Hum Reprod Open 2023
• International PCOS guideline 2023, Teede HJ et al., Hum Reprod 2023
• New name PMOS for PCOS, Teede HJ et al., Lancet 2026
• EAU Guidelines Male Infertility, European Association of Urology, 2026
• Fact sheet Polycystic ovary syndrome, WHO, 2026
• Fact sheet Endometriosis, WHO, 2025
• Iodine before and during pregnancy, Healthy Start network (Gesund ins Leben), 2026
• Folic acid before and during pregnancy, Healthy Start network (Gesund ins Leben), 2026

Studies and registries

• German IVF Registry, Yearbook 2024
• Cox CM et al., Infertility prevalence 1990 to 2021, Hum Reprod Open 2022
• Passet-Wittig J et al., Prevalence of infertility in Germany, J Reproduktionsmed Endokrinol 2016
• Hudecova M et al., Long-term reproductive outcome in PCOS, Hum Reprod 2009
• Legro RS et al., Letrozole versus clomiphene in PCOS, NEJM 2014
• Dhillon-Smith RK et al., TABLET trial, NEJM 2019
• van Dijk MM et al., T4LIFE trial, Lancet Diabetes Endocrinol 2022
• Wang H et al., Levothyroxine for TPO antibodies and IVF, JAMA 2017
• Dreyer K et al., H2Oil trial, NEJM 2017
• Tur-Kaspa I et al., Sonohysterography in infertility, Fertil Steril 2006
• Pritts EA et al., Fibroids and infertility, Fertil Steril 2009
• Pérez-Medina T et al., Polyps and insemination, Hum Reprod 2005
• Rikken JFW et al., TRUST trial, Hum Reprod 2021
• Marcoux S et al., Laparoscopy in mild endometriosis, NEJM 1997
• Chen I et al., Hormonal suppression in endometriosis surgery, Cochrane 2020
• Hamdan M et al., Endometriosis and ART, Obstet Gynecol 2015
• Cozzolino M et al., Adenomyosis and IVF, meta-analysis 2022
• Vercellini P et al., Adenomyosis and IVF, Hum Reprod 2014
• van der Steeg JW et al., Overweight and spontaneous pregnancy, Hum Reprod 2008
• Boivin J et al., Emotional distress and ART outcome, BMJ 2011
• Crawford NM et al., Luteal phase and natural fertility, Fertil Steril 2017
• Wilcox AJ et al., Incidence of early loss of pregnancy, NEJM 1988
• Magnus MC et al., Maternal age and risk of miscarriage, BMJ 2019
• Kangatharan C et al., Interval to the next pregnancy after miscarriage, Hum Reprod Update 2017
• Lund M et al., Prognosis in recurrent miscarriage, Obstet Gynecol 2012

Law, health care, and medicines

• Who covers the costs?, familienplanung.de, 2026
• Tests in women, familienplanung.de, 2026
• Section 27 of Social Code Book V
• Section 27a of Social Code Book V
• Directive on Assisted Reproduction, Federal Joint Committee (G-BA)
• IVF Fund Act (IVF-Fonds-Gesetz), Legal Information System of Austria (RIS)
• KLV Annex 1, Federal Office of Public Health (BAG), Switzerland, 2026
• Prescribing information for letrozole 2.5 mg, as of August 2023
• Prescribing information for clomiphene 50 mg, as of August 2016
• Prescribing information for cabergoline 0.5 mg, as of April 2023
• Prescribing information for levothyroxine 50/100 µg, as of November 2023
• Prescription Drug Ordinance (AMVV), Annex 1, accessed October 4, 2026