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1st Trimester Lab Work

The first trimester labs are fairly standard across the USA and serves as the initial screen anemia, infection, immune status, and blood type and antibody status. It is a panel test made up of a blood test and urine sample. These are typically ordered on the first visit. The results are usually back for me to review within four (4) days and will populate to your secure patient portal as soon as I have a chance to review them. I will include comments with the blood work letting you know it is ok or letting you know if something needs to be done. You will also be able to see the actual lab result form direct from the laboratory. This includes your values and the reference ranges defining “normal” for each value. It’s important to know that “normal” is often benchmarked to non-pregnant patients, and there are several indices in the blood count specifically that will flag as abnormal but are actually totally normal for pregnancy. If my comments say normal, it means that it is ok.

Tested areas and comments follow.
HBV/HIV/RPR: These represent the blood borne infections that are required testing by Texas Department of State Health Services. It’s part of the panel and follows a “no questions asked” strategy of testing. This is the first of three times a woman is tested during the pregnancy (also third trimester and on hospital admission).

Rubella Status: Rubella is the R in the MMR (Measles Mumps and Rubella Vaccine). It is standard to screen for Rubella as a surrogate for MMR vaccine antibody status during pregnancy. Up to one third of women have lost immunity to the MMR vaccine received as a child by the time they reach adulthood. Knowing the status allows a woman who is non-immune to avoid known outbreaks of MMR (also a good idea for those who are immune by the way), but importantly it lets us know to offer the booster vaccine prior to discharge from the hospital after delivery. MMR is a live vaccine and is not given during pregnancy.

Antibody status: We use the indirect coombs test to screen for blood antibodies. While rare, having antibodies to known blood antigens could pose a risk of the body rejecting the pregnancy. Having a positive on this screen warrants follow up testing of your spouse as next step to see if any risk exists.

Blood Type and Rh factor: This is part of the panel and is important enough to be checked with each pregnancy even if you know your blood type. We are particularly interested in the Rh factor to determine if a person is Rh negative. Negative Rh is common (O negative in particular is the Universal Blood Donor type). Rh negative mothers are susceptible to Rh isoimmunization if the baby or other blood exposure is Rh positive. Since there is not an easy way to test the baby, the standard prevention is a preventative injection of Rhogam or Rhophylac at 28 weeks or with any significant bleeding, including after delivery.

CBC: Complete Blood Count (or CBC) is a standard blood screen for anemia and platelet abnormalities. There are greater than 10 other data points on your results that I look at, but it can be confusing. I’m particularly interested in the hemoglobin and hematocrit, as markers of anemia, and your platelets. WBC or white blood cells can be elevated above normal in a typical pregnancy and this is ok. There are other measures such as MCV and MCHC which help describe the quality of the blood cells. These can also vary with pregnancy from non pregnancy. In general, a hemoglobin score greater than 11.0 is normal for pregnancy, even though that could read out low compared to non pregnancy. I may recommend an iron supplement even at greater than 11.0 depending on how the rest of the analysis looks.

Urine Culture: This is to screen for bacteria in the urine. Many women have what is called asymptomatic bacteria or excess bacteria colonizing the urine. This is a significant risk factor for developing a kidney infection or even sepsis and preterm labor of pregnancy. A positive screen is simply treated with an antibiotic specific to the bacteria and then we typically will rescreen the urine each trimester to be sure it doesn’t come back.
This sums up the standard labs. Of course, there may be some more specific labs recommended based on a patient’s individual history including early screen for diabetes, thyroid, recurrent pregnancy loss panel, vitamin deficiency and more.

Kyle P. McMorries, MD, FACOG


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