In this trimester, you may have tests to check for birth defects, the baby's growth, and gestational diabetes.

It can show whether your fetus has signs of some birth defects. This test is done between weeks 15 and 20 of pregnancy.

First, the fetus is located with ultrasound. A thin needle is then inserted into your belly. The doctor keeps the needle from touching the fetus by watching the screen.

The procedure is painless and takes less than one-half hour. You may be able to see your baby -- or may even be given a copy of the sonogram to take home with you.

When a mother is Rh negative and the fetus is Rh positive, there can be health risks for the fetus.

Nonstress and contraction stress testing checks whether your baby is getting enough oxygen and nutrients from your blood.