Pregnancy Week-by-Week Guide

Forty weeks. Each one covered in real detail — baby's development that week, what your body is going through, the symptoms you're likely to feel, what's worth doing, what to watch out for, and what to eat. Built to be the only weekly guide you'll need.

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How pregnancy weeks are counted

Pregnancy is counted from the first day of your last menstrual period (LMP) — not from conception. That sounds odd, but it's because conception happens around two weeks into your "pregnancy" by this convention, and your LMP is the most reliable date most people can confirm. So week 1 of pregnancy is actually the week of your last period, before you were pregnant. Conception usually happens around week 3.

A full-term pregnancy is 40 weeks from LMP, divided into three trimesters: weeks 1–12 (first), weeks 13–27 (second), and weeks 28–40 (third). Most babies are born between 37 and 42 weeks. "Early term" is 37–38 weeks; "full term" is 39–40 weeks; "late term" is 41 weeks; "post term" is 42+. Only about 5% of babies arrive on the exact due date — most are within a 2-week window before or after.

First trimester (weeks 1–12)

Pregnancy is confirmed. Baby's organs form. Symptoms like nausea, fatigue, and food aversions are typical. The highest risk window for miscarriage — but if you reach week 12, the risk drops to about 1–2%.

Second trimester (weeks 13–27)

Often the easiest trimester. Energy returns, the bump becomes visible, and you feel baby's first kicks. The 20-week anatomy scan happens around the midpoint. Many people share their pregnancy publicly in this window.

Third trimester (weeks 28–40+)

Baby grows fast. Your body prepares for delivery. Time to install the car seat, pack the hospital bag, finalize the birth plan, and pre-register at the hospital. Watch for preeclampsia and preterm labor signs.