Week 23: Fingerprints and footprints form

Twenty-three weeks into your pregnancy, or 21 weeks after conception, your baby starts to have rapid eye movements. Ridges also form in the palms of the hands and soles of the feet that will create the foundation for fingerprints and footprints.

The lungs are starting to make a substance called surfactant. It allows the air sacs in the lungs to inflate and keeps the lungs from collapsing and sticking together when they deflate.

If born preterm, some babies this far along in pregnancy may be able to survive outside the uterus.