Title: How Your Fetus Grows During Pregnancy | ACOG
Headings: How Your Fetus Grows During Pregnancy
FAQs
How Your Fetus Grows During Pregnancy
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If you have further questions, contact your ob-gyn.
A Guide to Pregnancy from Ob-Gyns

Content: Skin is thin and see-through but will start to thicken soon. Toenails form. Neck is defined and lower limbs are developed. Hearing starts to develop. Lungs begin to form tissue that will allow them to exchange oxygen and carbon dioxide when breathing starts after birth. What happens during weeks 17 to 20 of pregnancy? The part of the brain that controls motor movements is fully formed. Digestive system is working. Ears, nose, and lips are recognizable on an ultrasound exam. In girls, the uterus and vagina are starting to form.