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 care provider may have different recommendations for weight gain.
Your health care provider may offer you a "first trimester screening test" which combines ultrasound with a blood test to determine whether your baby is at risk for (not whether your baby has) specific chromosomal abnormalities, such as Down syndrome. An abnormal result does not necessarily mean that your baby has a condition — but it may mean more testing is required. Talk to your health care provider about the risks and advantages of this test.