| 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. |