What pregnancy week 21 means
Stronger movements. “21 weeks pregnant” means 21 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 19 weeks. Week 21 runs from 21 weeks 0 days to 21 weeks 6 days; on the following day the pregnancy is 22 weeks.
Your baby at 21 weeks
Movements are more coordinated, and the baby has periods of activity and rest. Taste buds are developing, and the bone marrow is beginning to make blood cells.
A common way to picture it: the baby is now about the size of a carrot — roughly about 27 cm and about 360 g. These are averages; babies grow at different rates, and ultrasound measurements vary.
Your body at 21 weeks
Kicks may now be strong enough for a partner to feel from the outside. Leg cramps and mild ankle swelling, especially later in the day, are common.
Care and appointments around week 21
Sudden swelling of the face or hands, severe headache or visual changes should be reported straight away, as they can be signs of a condition that needs checking.
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 21 in your pregnancy timeline
Week 21 is in the second trimester (weeks 14–27) and in pregnancy month 5, which covers roughly weeks 18–22. The third trimester begins in 7 weeks.
| Pregnancy start (first day of last period) | |
|---|---|
| Estimated conception | |
| Third trimester begins (28 weeks) | |
| Full term (39 weeks) | |
| Estimated due date (40 weeks) |
Dates assume you are exactly 21 weeks 0 days today. For dates based on your own last period, use the calculator above or the main Pregnancy Calculator.
21 weeks pregnant in days and months
21 weeks is 147 days of pregnancy — 53% of a 40-week pregnancy. Counted in calendar months, 21 weeks is about 4.8 months, which is usually described as month 5 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.