What pregnancy week 13 means
Last week of the first trimester. “13 weeks pregnant” means 13 weeks have passed since the first day of the last menstrual period — the standard way pregnancy is dated. Conception usually happened about two weeks after that date, so the baby’s own age (fetal age) is roughly 11 weeks. Week 13 runs from 13 weeks 0 days to 13 weeks 6 days; on the following day the pregnancy is 14 weeks.
Your baby at 13 weeks
Vocal cords are forming, and the baby’s body is starting to grow faster than the head. The placenta now produces most of the hormones that support the pregnancy.
A common way to picture it: the baby is now about the size of a lemon — roughly about 7.4 cm and about 23 g. These are averages; babies grow at different rates, and ultrasound measurements vary.
Your body at 13 weeks
This is the final week of the first trimester. Nausea and tiredness ease for many people over the coming weeks, and appetite often returns.
Care and appointments around week 13
The window for combined first-trimester screening closes at 13 weeks 6 days. If you planned to have it and have not yet, check with your provider.
The timing of tests and appointments differs between countries and care providers. If anything worries you — such as bleeding, severe pain, fluid leaking, fever — contact your midwife, doctor or maternity unit straight away rather than waiting for your next appointment.
Week 13 in your pregnancy timeline
Week 13 is in the first trimester (weeks 1–13) and in pregnancy month 3, which covers roughly weeks 9–13. The second trimester begins in 1 week.
| Pregnancy start (first day of last period) | |
|---|---|
| Estimated conception | |
| Second trimester begins (14 weeks) | |
| Third trimester begins (28 weeks) | |
| Full term (39 weeks) | |
| Estimated due date (40 weeks) |
Dates assume you are exactly 13 weeks 0 days today. For dates based on your own last period, use the calculator above or the main Pregnancy Calculator.
13 weeks pregnant in days and months
13 weeks is 91 days of pregnancy — 33% of a 40-week pregnancy. Counted in calendar months, 13 weeks is about 3.0 months, which is usually described as month 3 of pregnancy. Months are only a rough grouping; healthcare professionals almost always talk in weeks and days because they are more precise. See Pregnancy Month Calculator for how weeks map to months.