Consider prenatal testing

During the second trimester, you might be offered various prenatal screenings or tests:

• Genetic tests. Blood tests might be offered to screen for genetic or chromosomal conditions, such as spina bifida or Down syndrome. If your results are abnormal or worrisome, your doctor will recommend a diagnostic test, typically an amniocentesis. During amniocentesis, a sample of the fluid that surrounds and protects a baby during pregnancy is removed from the uterus for testing.
• Fetal ultrasound. Fetal ultrasound is an imaging technique that uses high-frequency sound waves to produce images of a baby in the uterus. A detailed ultrasound can help your health care provider evaluate fetal anatomy. Fetal ultrasound also might give you an opportunity to find out the baby's sex.
• Blood tests. Blood tests might be offered between week 24 to 28 of pregnancy to check your blood count and iron levels and screen for diabetes that can develop during pregnancy (gestational diabetes). If you have rhesus (Rh) negative blood — an inherited trait that refers to a specific protein found on the surface of red blood cells — you might need a blood test to check for Rh antibodies. These antibodies can develop if your baby has Rh positive blood and your Rh negative blood mixes with your baby's blood. Without treatment, the antibodies could cross the placenta and attack the baby's red blood cells — particularly in a subsequent pregnancy with a baby who has Rh positive blood.