Second trimester
Week 16 of Pregnancy
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About the size of a avocado
4.6 in · 11.6 cm · 3.5 oz · 100 g (crown to rump)
Your baby this week
- Some parents feel first flutters — 'quickening' — around now, especially in later pregnancies.
- The eyes make small movements beneath closed lids.
- The tiny heart is pumping about 25 quarts of blood a day.
What you may be feeling
- Thicker hair and 'pregnancy glow'
- Backache begins for some
- Constipation
Gentle tips for this week
- Fiber, water and daily movement are the gentlest fix for pregnancy constipation.
- The quad screen blood test window is weeks 15-20 if it is part of your care.
Common question for week 16
What is the quad screen?
A second-trimester blood test (weeks 15-20) measuring four markers that estimate the chance of neural tube defects and chromosomal conditions. It is optional — discuss whether it fits your plan.
Every pregnancy is different. Sizes are averages, symptoms vary widely, and none of this replaces the guidance of your own provider.