Your Baby's Development From this week until week 20, your baby
will be growing rapidly — increasing in size from about 2 inches
(5 cm) to about 8 inches (20 cm) from crown to rump. To
accommodate all this growth, the blood vessels in the placenta
are increasing in both size and number to provide the baby with
more nutrients. Facial development continues as the ears move
toward their final position on the sides of the head. If you saw
a picture of your baby now, you'd think you had a genius on your
hands — the baby's head accounts for about half of the body
length! Although your baby's reproductive organs are developing
rapidly, the external genitals of boys and girls appear somewhat
similar until the end of week 11. They will be clearly
differentiated by week 14. Nourishing your baby usually requires
that you gain weight — and in most cases, the recommended weight
gain is 25 to 35 pounds (11.33 to 15.87 kg) over the course of
the pregnancy. If you were overweight or underweight before
pregnancy, your health