First trimester · 28 weeks to go
| Fact | Week 12 |
|---|---|
| Days of pregnancy | 78–84 since LMP |
| Gestational age span | 11w0d to 11w6d |
| Trimester | First trimester (weeks 1–13) |
| Pregnancy month | Month 1 (weeks 1–4) |
| Average length | 2.1 in (crown to rump) |
| Average weight | 0.49 oz |
| Size comparison | a lime |
| Weeks remaining | 28 (40-week due date) |
Week 12 closes the riskiest chapter: with the first trimester nearly done, miscarriage odds drop sharply. Reflexes have arrived, fingers can curl, toes can flex, and the kidneys are making urine that becomes amniotic fluid.
The intestines, which grew so fast they temporarily herniated into the cord, move fully into the abdomen. The pituitary gland starts making hormones, and bone marrow is gearing up to build white cells. Fingerprints begin etching.
Gestationally, week 12 means you are 11 weeks and 0 to 6 days pregnant, day 78 to day 84 counted from the first day of your last period. This is week 12 of the first trimester (weeks 1–13). Prenatal appointments run about every four weeks in this stretch. Week 14 brings the second trimester. If your cycle runs longer or shorter than the 28 days the due-date math assumes, your ovulation date and due date shift with it, which is why a first-trimester ultrasound remains the gold standard for dating. Every number on this page is an average across pregnancies; your own scan dates and your baby's measurements are what actually describe your week 12.
The nuchal translucency window closes soon, so schedule the NT scan this week if you're doing first-trimester screening. Low-impact exercise is encouraged from here.
Weeks of pregnancy don't map cleanly to calendar months, but the common division puts week 12 falls in month 1 of pregnancy (weeks 1–4). Week 12 is part of the first trimester, which runs from week 1 to week 13. Gestationally, week 12 means you are 11 weeks and 0 to 6 days pregnant.
At week 12 the baby averages 2.1 in long and weighs about 0.49 oz, roughly the size of a lime. Sizes come from fetal growth charts (crown-rump length before week 20), and normal variation week to week is wide; your ultrasound measurements always outrank a chart.