What Should a Blood Test Check for During Pregnancy?

Blood tests are an important part of prenatal care because they help your OBGYN monitor your health and your baby’s development. While ultrasounds and physical exams provide valuable information, blood work can reveal concerns that may not cause obvious symptoms.

During pregnancy, blood volume increases, hormones shift, nutrient needs rise, and your immune system adjusts. Routine prenatal blood tests may check for anemia, blood type, Rh factor, infections, immunity, thyroid concerns, gestational diabetes risk, and nutrient deficiencies.

Dr. Joseph Leveno, OBGYN at Medical City Plano, Texas, helps patients understand why certain labs are recommended at different stages of pregnancy. For patients in Plano and those traveling from Wylie and Garland, blood testing can help catch concerns early and guide safer prenatal care.

Blood Type and Rh Factor Testing

One of the first pregnancy blood tests checks your blood type and Rh factor. Your blood type may be A, B, AB, or O, and your Rh factor may be positive or negative. This matters because Rh incompatibility can happen when a pregnant patient is Rh negative and the baby is Rh positive.

If Rh incompatibility is possible, your provider may recommend Rh immunoglobulin during pregnancy or after delivery. This helps reduce the chance of your body forming antibodies that could affect the baby or future pregnancies.

Complete Blood Count During Pregnancy

A complete blood count, often called a CBC, looks at red blood cells, white blood cells, hemoglobin, hematocrit, and platelets. This test can help check for anemia, infection signs, and platelet concerns.

Anemia is common during pregnancy because the body needs more iron to support increased blood volume and the baby’s growth. Symptoms may include fatigue, weakness, dizziness, shortness of breath, or feeling more worn down than expected.

Dr. Leveno encourages patients to speak up if something feels off. “Pregnancy can make you tired, but you still know your body. If you are feeling unusually weak, dizzy, or worn down, blood work can help us understand what is going on and what we can do to support you.”

If anemia or another concern is found, your provider may recommend dietary changes, iron supplementation, follow-up labs, or additional evaluation.

Why Are Infection and Immunity Tests Important?

Infection and immunity testing is important because certain infections can affect pregnancy, delivery planning, or newborn care. Early screening allows your provider to identify risks and take appropriate steps when needed.

Common prenatal blood tests may screen for:

• HIV
• Hepatitis B
• Syphilis
• Rubella immunity
• Sometimes varicella immunity or other tests based on history

Rubella immunity is checked because rubella infection during pregnancy can be serious. If you are not immune, your provider can document that information, discuss ways to avoid exposure, and plan for postpartum vaccination if appropriate.

Gestational Diabetes Screening

Gestational diabetes screening is often done between 24 and 28 weeks of pregnancy, although some patients may be tested earlier if they have certain risk factors. This screening checks how your body processes sugar during pregnancy.

Gestational diabetes can happen even in patients who did not have diabetes before pregnancy. Pregnancy hormones can affect how insulin works, which may cause blood sugar levels to rise. If blood sugar stays too high, it can increase the risk of complications for both mother and baby.

Screening typically involves drinking a glucose solution and having blood drawn afterward. If the first screening is elevated, additional testing may be recommended. When gestational diabetes is diagnosed, many patients can manage blood sugar with nutrition changes, activity, monitoring, and regular prenatal care, while some may need medication.

Thyroid, Iron, and Vitamin Levels

Thyroid function may be checked during pregnancy, especially if a patient has symptoms, a history of thyroid disease, or certain risk factors. Thyroid hormones help support metabolism, energy, and baby’s brain development.

Iron and vitamin levels may also be checked when symptoms or health history suggest a possible deficiency. Low iron can contribute to anemia, while low vitamin D, B12, or other nutrients may affect overall wellness. Targeted testing can be helpful when there are dietary restrictions, prior deficiencies, or ongoing concerns.

Book a Prenatal Care Appointment

Prenatal blood testing is one part of a bigger care plan. It can help identify concerns early, confirm that your body is getting the support it needs, and guide safer decisions throughout pregnancy.

If you are pregnant, planning to conceive, or due for prenatal testing, schedule a woman's wellness or prenatal appointment with Dr. Leveno at Medical City Plano.

Published by Dr. Joseph Leveno, OBGYN | Medical City Plano | Serving Collin County, TX | (972) 596-5821

Educational purposes only. Not medical advice.