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Routine Lab Tests

  • Screening for Sexually Transmitted Infections

    There are State mandates requiring syphilis, gonorrhea and HIV testing of all pregnant women to reduce newborn transmission.  In addition to these tests, your clinician will screen for other STI’s. The following information details why these screenings are done in pregnancy.


    Syphilis is caused by the bacterium Treponema pallidum. It can be passed through the placenta at any time during pregnancy, and can have long-term consequences for both mother and baby if left untreated. There are two screening blood tests used to diagnose syphilis; the Venereal Disease Research Laboratories (VDRL) test and the Rapid Plasma Reagin (RPR) test. A VDRL or RPR will be performed in the first and third trimesters.


    Gonorrhea is caused by the bacterium Neisseria gonorrhea. Gonorrhea that generally is transmitted to the baby during its passage through the birth canal can cause eye infections, blood infections and joint problems.

    In some cases, gonorrhea is transmitted earlier in the pregnancy and can be responsible for pre-term delivery and fetal death. If detected, gonorrhea can be treated with antibiotics. All babies receive antibiotic eye ointment at birth in case the disease was present but not detected. Gonorrhea cultures will be done during the first and third trimesters.


    Chlamydia is caused by an organism called Chlamydia trachomatis. It causes infection in the cervix, similar to gonorrhea, and has been associated with premature rupture of membranes and premature labor. A simple swab of the cervix can easily diagnose it and treatment with erythromycin is effective and safe during pregnancy. Chlamydia cultures are routinely done in the first trimester and only done in the third trimester with high-risk women.

    Hepatitis B

    Hepatitis B is a virus transmitted sexually in blood and saliva, as well as through breast milk and the placenta. Hepatitis B vaccine became available in 1982, so you may already be vaccinated.

    Hepatitis B is associated with low birth weight, premature labor, and even fetal loss. Some women may be carriers without displaying signs of infection, and can pass on the infection to their baby. If exposure occurs, the newborn is treated at the time of delivery with immunoglobulin. All newborns are now given their first hepatitis vaccine in the first few months of life. Hepatitis screening will be done with the first trimester blood work.


    Human Immunodeficiency Virus (HIV) is the virus known to cause AIDS. It has been mandated by the State that HIV testing be ordered as part of the first trimester blood work. Treatment for HIV can be started during pregnancy and may prevent transmission of the disease to the fetus. Transmission of HIV from mother to fetus occurs in about 25-35% of pregnancies.

  • Blood Count

    Blood is drawn to obtain a complete blood count (CBC) to screen for anemia and infection. The hematocrit/hemoglobin measures the number of your red blood cells; lower than normal readings indicate anemia. Mild anemia is a common finding in pregnancy, though it can cause fatigue and weakness which can be problematic for both mother and baby. Most cases of anemia are caused by iron deficiency and can be treated by taking iron supplements as prescribed.

    The number of white blood cells you have can indicate the presence of infection in the mother may require treatment, again by your clinician.  Other than the initial screening CBC, testing the white blood count is done on an as needed basis.

  • Urine Testing

    Urine screening tests are performed at each prenatal visit to check for glucose or protein.  Identifying glucose can indicate that your body is having difficulty regulating your blood sugar, while protein can be an indicator of your kidney function.  A urine dip test and/or culture also may be done to screen for urinary tract infections.

  • Blood Type Rh and Antibody Screen

    Blood type and screen are done to determine the mother’s blood type and to screen for antibodies to blood types other than the mom’s. You may recognize this as the ABO system of blood typing where groups consist of type A, B, AB and O. Positive and negative refer to the presence of an antibody to Rhesus or Rh factor discussed below.

  • Rubella Testing

    Rubella or German measles is a viral illness and screening is done with other initial pregnancy blood work. Most women are vaccinated against Rubella in childhood, but if you have not been exposed to Rubella, either by vaccination or having the disease, you may be susceptible. Becoming infected with rubella during pregnancy can be very serious depending on when the exposure occurs.

    If you contract rubella, there is no treatment other than rest and supportive measures. Mothers who become ill with rubella during the first trimester are at most risk because this may cause congenital rubella syndrome in the newborn. This syndrome can cause heart, eye, liver, and brain problems including deafness. If you have not been exposed you should receive a vaccination immediately after delivery. Rubella vaccines cannot be administered during pregnancy because they contain a live virus.

  • Group B Streptococcus Cultures

    Group B Streptococcus (GBS) is normally found in the lower part of digestive tract and the vagina of many healthy women. About 5-35% women are found to have GBS in pregnancy. Most women with GBS may carry it intermittently, with one third of women as chronic carriers. GBS can be passed on to the baby during passage through the birth canal. The risk of transmission is increased with pre-term labor, premature rupture of membranes, prolonged labor, and maternal fever.

    Newborn exposure to GBS can cause a blood infection or meningitis (infection of the membranes surrounding the brain). Symptoms of GBS in the newborn can occur within 48 hours of birth, or up to three months after birth. These symptoms include respiratory distress, pneumonia, and meningitis, and treatment with antibiotics is effective only about 50% of the time.

    It is routine to test mothers for GBS between the 34th and 38th weeks of pregnancy. Using a cotton tipped applicator, specimens for culture of the rectum and vagina are taken. If the culture is positive for GBS antibiotics such as ampicillin will be given either prior to or during delivery to eliminate the bacteria.

  • Screening for Pregnancy Induced Diabetes

    The glucose tolerance test (GTT) is used to screen for gestational diabetes, a condition of pregnancy where the mother’s blood sugars are elevated. During pregnancy, some women develop gestational diabetes and are unable to produce enough insulin to keep their blood sugar level under control. High blood sugar during pregnancy can lead to fetal problems such as macrosomia (large baby), delayed organ development, heart defects, post-term labor, and fetal death.

    You are at risk for developing gestational diabetes if you:
    • are 25 years or older
    • are overweight
    • had gestational diabetes in an earlier pregnancy
    • have a family history of gestational diabetes
    • had a previous baby weighing close to or over 9 lbs.
    • had a stillborn baby
    • had a pregnancy or a child with a congenital anomaly
    • have had more than two miscarriages

    If one or more of these risk factors applies to you, you may be screened earlier than 24 weeks. The assessment consists of 2 phases: a screening test and if necessary, a tolerance test. The screening test involves drinking 50 grams of a sugar solution called glucola. After one hour your blood sugar level is checked. If the result is greater than 130-140 mg/dl this is considered abnormal. In this case you will undergo a glucose tolerance test.

    You will need to fast (no food or drink) overnight for 8-12 hours. In the morning, a fasting blood sugar level will be checked; it should be below 105mg/dl. You receive 100 grams of sugar solution to drink after which your blood sugar level will be testing hourly x 3. If any two of the readings are elevated, the test is considered abnormal.

    If you have an abnormal glucose tolerance test, you will be placed on a special diet and will need to test your blood sugar levels at regular intervals. In most cases careful diet management is sufficient to keep gestational diabetes under control, however, some women may need medications to help maintain their blood sugar levels.

  • Rh Factor

    Along with blood type (A, B, AB or O), everyone’s blood is tested for its Rh factor. If your blood cells contain the Rh antigen, a protein marker on your blood, you are "Rh-positive." If you do not have the Rh antigen you are "Rh-negative." When an Rh-negative mother gives birth to an Rh-positive child, Rh exposure and sensitization occurs from a mixing of maternal and fetal bloods. This can occur with abortions, miscarriages, ectopic pregnancies, amniocentesis, chorionic villus sampling, and trauma, as well as on rare occasions without any apparent cause.

    When this happens, the mother develops antibodies against the Rh antigen, as if it were a foreign substance like a virus. This exposure can cause harm to the current and future pregnancies. Early identification and a simple immunization can prevent this. Rho (D) immunoglobulin or Rhogam immunizations are given at 28 weeks gestation and after delivery. In situations of amniocentesis, chorionic villus sampling, early loss or trauma, a mini dose of Rhogam is given.

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