12th week: The first third is behind you
- Weeks and days
- 11+0 to 11+6
- Month
- 3
- Trimester
- 1
In the last week of the 1st trimester, the fetus grows from about 44 to 54 millimeters. From 11+0 and a length of 45 mm, nuchal translucency can be measured. For many, nausea now eases.
Week 12 of 40
Calculate your weekHow big is the fetus?
44 to 54 mm
By the end of the week, the fetus is about the size of a lime and weighs between about 7 and 14 grams. It now swallows amniotic fluid, and by the end of the week the intestine is usually back in the abdomen.
Crown-rump length on ultrasound according to Robinson and Fleming, weight according to the UNSW Embryology table. A lime usually measures 48 to 62 mm.
This week
Your baby
- The skull bones ossify and become visible on ultrasound.
- The bladder fills and can be seen as a small dark circle in the lower abdomen.
- The heart beats more slowly than in the 10th week of pregnancy; by the 14th week, the rate drops on average to about 156 times per minute.
Your body
- On average, nausea ends at around 12+0, but for half of pregnant women only after the 14th week.
- The hCG levels chart gives no value for the 12th week of pregnancy. After the peak in the 10th week of pregnancy, the level falls. More in the hCG levels chart.
- Your belly becomes a little rounder, but it usually does not get in the way of everyday life yet.
What matters now
- First-trimester screening with nuchal translucency between 11+0 and 13+6. In Germany, it costs €120 to €250, depending on the practice.
- You need folic acid until the end of this week, and you continue to need iodine throughout the pregnancy.
- From the 13th week of pregnancy, the German Standing Committee on Vaccination (STIKO) recommends the flu vaccination for all pregnant women.
Get checked right away: heavy bleeding, severe or persistent abdominal pain, fever, pain when urinating, or vomiting where you cannot keep anything down.
On ultrasound
- 11+0
Nuchal translucency can be measured as soon as the crown-rump length reaches 45 mm, on average at around 11+1.
- 11+0
Skull bones can be seen ossified from this point.
- 12+0
Bladder should be visible by this point, smaller than 7 mm.
In one study, the sex was correctly identified at 11 completed weeks in only 70 out of 100 cases. In Germany, it may only be disclosed after the end of the 12th week of pregnancy anyway.
Frequently asked questions about the 12th week of pregnancy
What is the risk of miscarriage after the 12th week of pregnancy?
In a large London study with an examination between 11+0 and 13+6, about 1 in 100 pregnancies still ended in miscarriage after that. The risk is higher with older age and after previous miscarriages.
Can you see the sex in the 12th week of pregnancy?
Sometimes, but it is uncertain. At 11 completed weeks, boys were wrongly classified as girls in more than half of cases. One week later, accuracy was almost 99 in 100.
When is the nuchal translucency scan?
Between 11+0 and 13+6, at a crown-rump length of 45 to 84 mm. The measurement is part of first-trimester screening; beforehand, you receive counseling under the German Genetic Diagnostics Act (Gendiagnostikgesetz).
Which month is the 12th week of pregnancy?
The last week of the 3rd month of pregnancy and of the 1st trimester. Figures such as 11+3 weeks also belong to the 12th week of pregnancy.
Sources
- Robinson HP, Fleming JE: A critical evaluation of sonar crown-rump length measurements, BJOG 1975;82:702
- Papageorghiou AT et al.: International standards for early fetal size and pregnancy dating based on ultrasound measurement of crown-rump length in the first trimester, Ultrasound Obstet Gynecol 2014;44:641
- Fetal Development, UNSW Embryology
- Bilardo CM et al.: ISUOG Practice Guidelines (updated), performance of 11-14-week ultrasound scan, Ultrasound Obstet Gynecol 2023;61:127
- Hyett JA et al.: Fetal heart rate in trisomy 21 and other chromosomal abnormalities at 10-14 weeks of gestation, Ultrasound Obstet Gynecol 1996;7:239
- Efrat Z et al.: First-trimester determination of fetal gender by ultrasound, Ultrasound Obstet Gynecol 1999;13:305
- Akolekar R et al.: Prediction of miscarriage and stillbirth at 11-13 weeks and the contribution of chorionic villus sampling, Prenat Diagn 2011;31:38
- Gadsby R et al.: A prospective study of nausea and vomiting during pregnancy, Br J Gen Pract 1993;43:245
- Lacroix R et al.: Nausea and vomiting during pregnancy, a prospective study, Am J Obstet Gynecol 2000;182:931
- S2e guideline on first-trimester diagnostics and therapy at 11 to 13+6 weeks of pregnancy, AWMF 085-002, valid until 31 December 2028
- First-trimester screening, familienplanung.de, Federal Institute for Public Health (BIÖG), as of 13 October 2023
- Genetic Diagnostics Act (Gendiagnostikgesetz), § 15, Federal Ministry of Justice
- Folic acid when trying to conceive and during pregnancy, Healthy Start Network (Netzwerk Gesund ins Leben), as of 7 August 2026
- Vaccination during pregnancy (Impfen in der Schwangerschaft), FAQ, Robert Koch Institute (RKI), as of 27 March 2025