Second trimester · 23 weeks to go
| Fact | Week 17 |
|---|---|
| Days of pregnancy | 113–119 since LMP |
| Gestational age span | 16w0d to 16w6d |
| Trimester | Second trimester (weeks 14–27) |
| Pregnancy month | Month 2 (weeks 5–8) |
| Average length | 5.1 in (crown to rump) |
| Average weight | 4.9 oz |
| Size comparison | a turnip |
| Weeks remaining | 23 (40-week due date) |
Week 17 is padding season: brown fat starts forming under the skin, readying the baby for temperature control after birth. The skeleton keeps converting from rubbery cartilage to bone, and the heartbeat may be audible with a Doppler.
The brain is rewiring for finer control, and the umbilical cord thickens and strengthens. Sweat glands are forming. The baby now weighs close to a third of a pound and practices constant small movements.
Gestationally, week 17 means you are 16 weeks and 0 to 6 days pregnant, day 113 to day 119 counted from the first day of your last period. This is week 4 of the second trimester (weeks 14–27). Prenatal appointments run about every four weeks in this stretch. Week 20 brings the anatomy scan window (weeks 18–22). Across this trimester the baby more than triples in weight, so expect your bump, your appetite, and eventually your waddle to keep pace with the calendar. 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 17.
Moisturize the growing belly to ease itching. Move slowly when standing up; round ligament pain is startling but harmless.
Weeks of pregnancy don't map cleanly to calendar months, but the common division puts week 17 falls in month 2 of pregnancy (weeks 5–8). Week 17 is part of the second trimester, which runs from week 14 to week 27. Gestationally, week 17 means you are 16 weeks and 0 to 6 days pregnant.
At week 17 the baby averages 5.1 in long and weighs about 4.9 oz, roughly the size of a turnip. 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.