Unborn Baby Development at 17-20 Weeks
By the end of this month you can definitely feel your unborn baby development due to the cantaloupe-sized uterus at the level of your navel. Other growth milestones include:
- Your baby weighs around three-quarters of a pound, and measures between 8-10 inches long. This is about half the length baby will be at birth.
- Baby’s legs, now around the size of your little finger, continue growing, become more muscular, and make their presence felt as tiny flutter kicks.
- He waves his growing, but still tiny, arms. On ultrasound, you may see him sucking his thumb and making a fist.
- Baby hair is beginning to appear on his upper lid, eyebrows and head.
- His skin, previously thin and transparent, now begins to accumulate fat deposits.
- Baby’s oil glands start to secrete a waxy substance that mixes with his dead skin cells to form a cheesy coating, called the Vernix caseosa, which acts like a sort of wetsuit protecting the little swimmer’s skin from chapping.
- Fine, temporary hair—called lanugo (meaning “wool”)—covers most of his body and helps to hold the vernix on the skin.
- Baby’s digestive system functions better now, and he regularly swallows amniotic fluid and urinates into it.
- By this month of unborn baby development, baby’s middle ear structures have formed, enabling baby to hear sound.
- Still, baby cannot yet survive outside the womb at this stage because his lungs are still undeveloped.