Second trimester: What's happening to your baby

Even before you feel it, your baby is moving inside your uterus. Your baby moves his arms and legs, sucks his finger, floats up and down, and hears the sounds of your voice and your environment. Loud noises may even startle your baby. You may notice your baby responding to music and familiar voices. As your baby's movements become strong enough for you to feel, you'll begin to learn your baby's patterns.

Baby's development: Weeks 14 to 26

Week 14	Hair and eyebrows are growing. Heartbeat is strong enough to hear with ultrasound. Starts to drink amniotic fluid (the fluid surrounding the baby).
Week 15	Middle ear bones harden, so baby can hear.
Week 16	Fine, downy hair called "lanugo" appears all over body and face. External genital organs are developed enough to be seen with ultrasound. Developing skin is transparent.
Week 17	Baby can hear sounds outside the mother's body and will jump when startled. Fingernails and toenails begin to appear. Baby may begin thumb-sucking.
Week 18	Baby is moving much of the time now. Skeleton would be clearly outlined if X-ray was performed. Baby measures 8 inches long.
Week 19	Buds for permanent teeth begin to form. Baby drinks amniotic fluid, which is filtered through the kidneys and excreted back into the amniotic sac. Baby may get hiccups.
Week 20	Baby's movements can now be felt by mother. Baby is 8 1/2 inches long and weighs 8 to 16 oz.
Week 21	Skin is becoming opaque. Tongue is fully developed.
Week 22	Vernix, a greasy, white, cheesy-looking substance, is beginning to form on the baby's skin to protect it (most of the vernix will disappear before birth).
Week 23	Heartbeat can be heard with a stethoscope.
Week 24	Vital organs are developed enough for the baby to survive outside the womb. Lungs are immature, however, and the baby would need breathing assistance if born now. Baby measures about 14 inches long and weighs 1 to 1 1/2 pounds.
Week 25	Bone centers begin to harden.
Week 26	Fat stores are beginning to form.

Related Links

What's happening to your body

Second trimester

First published: 10/04/2002
Last updated: 06/19/2003

Reviewed by: Allina Patient Education experts