Second trimester · 22 weeks to go
| Fact | Week 18 |
|---|---|
| Days of pregnancy | 120–126 since LMP |
| Gestational age span | 17w0d to 17w6d |
| Trimester | Second trimester (weeks 14–27) |
| Pregnancy month | Month 2 (weeks 5–8) |
| Average length | 5.6 in (crown to rump) |
| Average weight | 6.7 oz |
| Size comparison | a bell pepper |
| Weeks remaining | 22 (40-week due date) |
Week 18 is yawning and hiccuping week. Myelin starts coating the nerves, and if the baby is a girl, her uterus and fallopian tubes are in place; a boy's genitalia are visible enough to spot on ultrasound.
Ears shift to their final position and hearing sharpens. The brain's areas for smell, taste, sight, hearing, and touch are specializing. Blood vessels are clearly visible through the translucent skin.
Gestationally, week 18 means you are 17 weeks and 0 to 6 days pregnant, day 120 to day 126 counted from the first day of your last period. This is week 5 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 18.
Rise slowly from lying to sitting to standing; your blood pressure runs lower now. Book the anatomy scan for weeks 18 to 22 if you haven't.
Weeks of pregnancy don't map cleanly to calendar months, but the common division puts week 18 falls in month 2 of pregnancy (weeks 5–8). Week 18 is part of the second trimester, which runs from week 14 to week 27. Gestationally, week 18 means you are 17 weeks and 0 to 6 days pregnant.
At week 18 the baby averages 5.6 in long and weighs about 6.7 oz, roughly the size of a bell pepper. 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.