What pregnancy week 17 means
Building fat and bone. “17 weeks pregnant” means 17 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 15 weeks. Week 17 runs from 17 weeks 0 days to 17 weeks 6 days; on the following day the pregnancy is 18 weeks.
Your baby at 17 weeks
Cartilage in the skeleton is turning into bone, and the baby is starting to build fat stores that will help regulate body temperature after birth. Sweat glands are forming.
A common way to picture it: the baby is now about the size of a pomegranate — roughly about 13 cm and about 140 g. These are averages; babies grow at different rates, and ultrasound measurements vary.
Your body at 17 weeks
As the bump grows, your centre of gravity shifts. Back ache and changes in balance are common, and many people start sleeping on their side.
Care and appointments around week 17
If you are planning travel, it is common to discuss it with your provider; the second trimester is often considered the most comfortable time to travel.
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 17 in your pregnancy timeline
Week 17 is in the second trimester (weeks 14–27) and in pregnancy month 4, which covers roughly weeks 14–17. The third trimester begins in 11 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 17 weeks 0 days today. For dates based on your own last period, use the calculator above or the main Pregnancy Calculator.
17 weeks pregnant in days and months
17 weeks is 119 days of pregnancy — 43% of a 40-week pregnancy. Counted in calendar months, 17 weeks is about 3.9 months, which is usually described as month 4 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.