Fetal Development: Second Trimester 

Watching your baby grow is filled with moments of wonder and excitement. From tiny movements to developing facial features, every stage brings new milestones. We’ve outlined your baby’s progress during months 4 through 6, highlighting key developments and what you might expect. (Sizes and weights are approximate.) 

Month 4

By the end of month 4:

• Baby is developing reflexes such as sucking and swallowing, and may begin thumb-sucking
• Baby is around 5 inches long
• Fingers and toes are well defined
• Sex is identifiable
• Skin is bright pink, transparent and covered with soft, downy hair
• Sweat glands are forming on palms and soles
• Tooth buds are developing
• Weight is about 4 ounces

While recognizably human, the baby is not yet able to survive outside the womb. 

Month 5

By the end of month 5:

• Baby is 8 to 10 inches long
• Eyebrows, eyelids and eyelashes appear
• Hair begins to grow on baby’s head
• Internal organs are maturing
• Lanugo, a soft woolly hair, covers baby’s body (some may remain for a short time after birth)
• Mother begins to feel fetal movement
• Weight is about 1 pound 

Month 6

By the end of month 6:

• Baby is able to hiccup
• Baby is 11 to 14 inches long
• Eyelids begin to part and eyes open sometimes for short periods
• Skin is covered with a protective coating called vernix
• Weight is about 1¾  to 2 pounds 

As your baby continues to grow and change, these monthly milestones offer a glimpse into the incredible journey happening inside you.