Weeks 9-12

During this month, baby more than doubles his length and weight, going from 1 1/2 inches at the end of the second month to 4 to 5 inches long by the end of the third; he will weigh from one-half to one ounce. Let's look at 10 growth milestones:

1. All of baby's organs are formed, and they will continue to grow and develop during the rest of the time in the womb.
2. Baby's liver, spleen, and bone marrow start making blood cells this month.
3. Baby's teeth begin to form; by the end of this month baby will have twenty little tooth buds beneath his gums.
4. Fingernails, toenails, and rudimentary hair appear.
5. Baby's intestines, previously part of the umbilical cord, now move into the abdominal cavity and become covered with skin.
6. The tongue and vocal cords form this month.
7. The circulatory system is operating, and heart valves are now developing, meaning a heartbeat can be detected by Doppler ultrasound.
8. The external genitalia differentiate clearly into male and female so that by the end of the month ultrasound pictures can often reveal whether baby is a boy or a girl.
9. By twelve weeks the head is around a third of the size of the body.
10. Baby's tiny feet can now kick, but you are unlikely to be able to feel it yet.