Your developing baby – week 18

by Kaiser Permanente |
Fetus at week 18, illustration

By week 18, your baby is about 6 inches long from head to rump, weighs around 7 ounces, and is about the size of a bell pepper.

This week your baby's:

  • Umbilical cord is thickening. It continues to carry blood and nutrients.
  • First bowel movement (meconium) is beginning to collect in the intestines.
  • Inner ears are developing, and your baby may begin to hear sounds.

Fine, downy hair called lanugo and a white creamy substance called vernix cover your baby’s body, creating a waterproof barrier that protects their skin from drying out in the amniotic fluid. 

Other exciting developments? An ultrasound can probably recognize your baby’s sex. And you might start to feel your baby moving between now and week 22 as your baby is becoming bigger and more active.

At first, your baby’s movements may feel like fluttering or “butterflies.” As the baby grows and becomes stronger, you’ll probably feel these movements more.

This article has been created by a national group of Kaiser Permanente ob-gyns, certified nurse-midwives, pediatricians, lactation consultants and other specialists who came together to provide you with the best pregnancy, birth, postpartum, and newborn information.

Some of the content is used and adapted with permission of The Permanente Medical Group.