Hepatitis B virus: Hep B rarely cause complications during a pregnancy for your baby. However, testing is important because Hep B does attack the liver eventually. You can only get Hep B through sexual contact, shared needles, or bodily fluids. Because your baby is exposed to many of your bodily fluids during the birth process he may be exposed. If you are positive for Hep B, your baby will almost certainly be given a Hep B immune globulin and a vaccine to protect against exposure immediately after birth.Syphilis, HIV and other sexually transmitted diseases: it's important to test for STDs because if you're a carrier, you'll need treatment asap or your baby's health can be severely compromised (in some cases a baby can die when exposed to an STD), not to mention your own current health and your future fertility. Rubella (German measles): This blood test will show if your body is carrying immune defenses against rubella. Rubella can cause serious complications if you're exposed during pregnancy (especially during the first trimester). Some complications include, miscarriage or stillbirth and birth defects related to hearing, growth, heart problems, and mental disabilities are also possible. If you're not immune, you can't get vaccinated during pregnancy BUT you can avoid anyone with rubella and be sure to get vaccinated before your next pregnancy. Blood glucose levels: This is tested (often more than once) because your glucose levels diagnose or show your risks for gestational diabetes. Anemia: this is important to test for as anemia during pregnancy can affect both your health and your baby's health. Your blood type, and that of the fetus: all people have a blood type of A, B, AB, or O. But your blood can either be positive or negative in type as well. If you have negative blood, you're lacking an Rh antigen protein which can cause complications if the baby you're carrying is Rh positive. Cystic fibrosis carrier testing: Cystic fibrosis is an incurable (currently) genetic illness that causes problems with digestion and breathing. The sooner this is diagnosed the better the outcome. In the past children with CF died very young, but now there are treatments available that make it possible for CF patients to live into and well-past their 40s. White couples are at the highest risk of having a baby with CF. Sickle Cell Anemia: This tests for Sickle Cell Disease, and you're usually only given this if you're in a specific ethnic group (African Americans are at the highest risk, but other groups are affected as well). Of course there are any number of blood tests you may be given during your pregnancy, these above are just the most common. You also have the right to refuse any blood work, but consider that choice carefully. In many cases early detection of an issue is the best way to help ensure a healthy baby.