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You may not mind much whether your baby is a boy or a girl, but you do care whether he or she is healthy. As part of your regular visits with an obstetrician, you will undergo a variety of tests that will help to monitor your baby's progress and ensure a healthy delivery.

What screening tests do you need, and when should you expect them?

Routine Exams
At your first obstetrician's visit—and pretty much every one after—your doctor will measure your weight and the "height" of your uterus to track your baby's growth. Your blood pressure will also be taken to screen for preeclampsia, which may cause high blood pressure and vision loss for the mother and can harm the baby.

Urine samples are also taken routinely to measure levels of sugar, protein and bacteria. While some sugar in the urine is common for many pregnant women, too much may signal gestational diabetes, diabetes caused by pregnancy. Too much protein may be a sign of a urinary tract infection, kidney disease or high blood pressure.

First Trimester
During the first trimester, your obstetrician will take a complete medical history to assess your pregnancy risks. Some conditions may increase the risk of complications, so be sure to tell your doctor about any concerns or medications you may be taking. Several tests will also be performed to check on the health of both you and your baby:

Blood Test—A routine blood test during pregnancy is used to look for various things including syphilis, immunity to chicken pox and rubella, blood type and Rh factor. If you have a negative Rh factor, a component of the blood, and the baby is positive, your body may attack it. This is a fairly common occurrence and is usually treated without a major problem. In rare instances, anemia is possible.
Fetal Ultrasound—As early as the fifth week of pregnancy, a fetal ultrasound may be performed. During this test, a handheld instrument is placed either on top of the uterus or inside the vagina. This device measures the way sound waves are reflected to create an image of your growing baby. A vaginal fetal ultrasound can help to detect an ectopic pregnancy (when the fetus is growing somewhere other than the uterus).
Chorionic villus sampling (CVS)—In a CVS, a few cells are taken from the placenta between the eighth and twelfth week of pregnancy and checked for various genetic disorders, including Down syndrome. This is not considered a routine exam and is generally performed only if there is a family history of genetic illness.
HIV Test—An HIV test is routinely performed to determine your HIV status and help to prevent a possible HIV infection from spreading to the baby.

Second Trimester
During weeks 13 through 27, you can expect your doctor to perform the following tests:

Electronic fetal heart monitoring—Starting at 20 weeks, a doctor can listen to your baby's heartbeat with a special stethoscope to determine the heart rate and check its overall health. Fetal ultrasound may also be performed to check the baby's progress.
Glucose Tolerance Test (GTT)—Your doctor gives you sugar water to drink and then draws blood at regular intervals. This measures how fast the body is metabolizing sugar. Any irregularities may indicate gestational diabetes.
Maternal serum screen—While it is not always performed, this blood test looks for indications of birth defects and includes tests for the following substances:
- Alpha-fetoprotein (AFP)—Naturally produced by the baby's liver, a high AFP may indicate a defect of the spine, while a low AFP may indicate Down syndrome.
- Human chorionic gonadotropin (hCG)—Produced by the placenta, the level of hCG increases through the first 14 weeks of pregnancy. If hCG levels are high, it may indicate Down syndrome.
- Estriol—Produced by the placenta, levels can first be detected during the ninth week of pregnancy. Low levels of estriol may be a sign of Down syndrome.
- Inhibin-A—A relatively new screening, Inhibin A is a protein produced by the baby and its placenta. If it is measured at abnormally high levels, it may indicate Down syndrome.
Amniocentesis—If the serum screen turns out abnormal, or there are other risk factors, an amniocentesis is usually performed. This test analyzes a small amount of amniotic fluid, the liquid that surrounds the baby, to look for over 100 different types of birth defects. It can also determine the sex of your baby.

Third Trimester
By the third trimester, most tests to determine birth defect risks have already been done. However, the following tests will likely be performed to ensure the overall health of your baby and to monitor labor and delivery:

Group B Streptococcus—A blood test can determine if you are infected with group B strep, which can cause severe illness in newborns. If the bacteria is found, antibiotics will be given during labor to protect the baby.
Hepatitis B—If you test positive for hepatitis B, the baby will receive a vaccine against the disease shortly after birth.
Cervical effacement—Closer to delivery, your doctor will check to see how far the baby has dropped into the pelvis and how much the cervix has begun to stretch. These measurements help to monitor the progression of labor. A fetal monitor may also be used.

If your baby needs to be delivered early for whatever reason, an amniocentesis may be performed to see if the fetus's lungs are developed enough.

Hopefully, after nine months of pregnancy, numerous visits to your obstetrician and a lot of medical tests, you will have a happy, healthy baby—be it a boy or a girl.