Pregnancy involves a substantial number of blood tests, starting at your very first prenatal visit and continuing through the final weeks before delivery. Most are routine, meaning every pregnant person gets them regardless of risk factors. Others are offered based on your age, medical history, or symptoms that develop along the way. Here’s what to expect and why each test matters.
The First Prenatal Visit Panel
Your first appointment typically includes the most blood draws you’ll have at one time during the entire pregnancy. This initial panel covers a wide range of basics that your provider needs to plan your care.
A complete blood count (CBC) measures your red blood cells, white blood cells, and platelets. It’s the primary way to check for anemia, which is common in pregnancy because your blood volume increases dramatically. Anemia is defined as hemoglobin below 11 g/dL in the first trimester. That threshold dips slightly to 10.5 g/dL in the second trimester (when blood volume peaks and naturally dilutes your red cells) and returns to 11 g/dL in the third. If your levels are low, you’ll likely be started on iron supplements and retested later.
Blood type and Rh factor testing identifies whether you’re type A, B, AB, or O, and whether you carry a protein called Rh factor on your red blood cells. If you’re Rh-negative and your baby turns out to be Rh-positive, your immune system could produce antibodies that attack the baby’s blood cells. Knowing this early allows your provider to prevent complications with a protective injection given between 24 and 28 weeks, and again after delivery if the baby is Rh-positive.
You’ll also be screened for several infections:
- Rubella immunity: This checks whether you’re protected against German measles, which can cause serious birth defects. Most people were vaccinated as children, but immunity can fade.
- Hepatitis B: A routine screen because hepatitis B can pass to the baby during birth. Hepatitis C testing may be added if you have specific risk factors.
- Syphilis: Universal screening at the first visit, since untreated syphilis can cause severe problems for the baby.
- Chlamydia: Tested early because it’s often symptom-free but treatable with antibiotics before delivery.
- HIV: Offered at the first visit, and required by law in some states. Early detection allows treatment that dramatically reduces the chance of passing the virus to the baby.
First Trimester Genetic Screening
Starting at 10 weeks, you may be offered a blood test called noninvasive prenatal testing (NIPT). This test analyzes tiny fragments of the baby’s DNA circulating in your blood. It screens for Down syndrome (trisomy 21), trisomy 18, trisomy 13, and conditions involving the sex chromosomes. NIPT is a screening test, not a diagnostic one, so an abnormal result would lead to further testing like amniocentesis to confirm a diagnosis.
NIPT can be performed anytime from 10 weeks through the end of pregnancy, though most people have it done in the first trimester. It’s available to all pregnant people, though guidelines vary on whether it’s recommended for everyone or primarily for those at higher risk due to age or family history.
Second Trimester Blood Tests
Between weeks 15 and 22, you may be offered a quad screen. This measures four substances in your blood: alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), estriol (a form of estrogen), and inhibin-A. Together, abnormal levels of these markers can flag increased risk for neural tube defects like spina bifida, Down syndrome, and certain abdominal wall conditions. High AFP, for example, can point toward a neural tube defect, but it can also simply mean your pregnancy is further along than estimated or that you’re carrying multiples. Low AFP may suggest a higher risk for Down syndrome.
The quad screen produces a risk estimate, not a definitive answer. If results come back abnormal, your provider will typically recommend an ultrasound and possibly amniocentesis to get a clearer picture.
Rh Antibody Recheck
If you tested Rh-negative at your first visit, you’ll have a repeat antibody screen between 24 and 28 weeks. This confirms your body hasn’t started producing antibodies against the baby’s blood cells. Assuming the screen is negative, you’ll receive a protective injection at that appointment. If the baby is born Rh-positive, you’ll get another dose within 72 hours of delivery.
Gestational Diabetes Screening
Between 24 and 28 weeks, nearly everyone is screened for gestational diabetes. The most common approach is a one-hour glucose challenge test: you drink a sugary solution, and your blood sugar is measured one hour later. A result below 140 mg/dL is considered normal, though some clinics use a lower cutoff of 130 mg/dL.
If your one-hour result falls between 140 and 190 mg/dL, you’ll be asked to return for a longer, three-hour glucose tolerance test. This involves fasting overnight, having your blood drawn, drinking a higher-concentration glucose solution, and then having blood drawn at one, two, and three hours. A result of 190 mg/dL or higher on the initial one-hour test may lead to a gestational diabetes diagnosis without needing the follow-up.
Gestational diabetes affects roughly 2 to 10 percent of pregnancies and is manageable with dietary changes, blood sugar monitoring, and sometimes medication. Left undetected, it can lead to complications like a larger-than-average baby or blood sugar problems in the newborn.
Third Trimester Blood Work
In the final stretch of pregnancy, your provider will likely repeat a few key tests. A CBC is commonly redrawn to recheck for anemia, since your body’s iron demands peak in the third trimester. If you were borderline earlier, your hemoglobin may have dropped below 11 g/dL by now.
Syphilis and HIV may be retested in the third trimester, particularly if you live in an area with higher rates of these infections or if your risk profile has changed. Some providers routinely rescreen everyone. Hepatitis B may also be repeated late in pregnancy if initial results were negative but risk factors exist.
Thyroid Testing
Thyroid function tests aren’t part of the standard panel for every pregnant person, but they’re commonly ordered if you have a history of thyroid problems, symptoms like unusual fatigue or rapid heart rate, or difficulty conceiving. The test measures TSH (thyroid-stimulating hormone). During pregnancy, the normal range is narrower than usual: 0.2 to 2.5 mU/L in the first trimester, and 0.3 to 3.0 mU/L in the second and third trimesters. Both overactive and underactive thyroid function can increase the risk of miscarriage and other complications, so levels outside these ranges are typically treated.
Tests Ordered When Problems Arise
Beyond the routine schedule, certain blood tests are ordered only when your provider suspects a specific issue. If you develop high blood pressure, protein in your urine, or swelling after 20 weeks, blood work to evaluate your liver function, platelet count, and kidney function helps determine whether preeclampsia is developing. A newer blood test measuring the ratio of two proteins related to placental blood vessel health is gaining attention for predicting preeclampsia risk in asymptomatic patients between 24 and 37 weeks, though major U.S. obstetric organizations do not yet recommend it for routine diagnosis.
If you have a family history of blood clotting disorders, sickle cell trait, or other inherited conditions, additional specialized blood work may be drawn early in pregnancy. The specific tests depend entirely on your personal and family medical history, which is one reason that first prenatal appointment tends to involve a very thorough conversation about your background.
What the Timeline Looks Like
Pulling it all together, here’s the general rhythm of blood draws throughout pregnancy:
- First visit (often 8 to 10 weeks): CBC, blood type, Rh factor, rubella immunity, hepatitis B, syphilis, chlamydia, HIV
- 10 to 13 weeks: NIPT if elected
- 15 to 22 weeks: Quad screen if elected
- 24 to 28 weeks: Glucose challenge test, Rh antibody recheck (if Rh-negative), repeat CBC
- 35 to 37 weeks: Possible repeat screens for syphilis, HIV, hepatitis B, and a final CBC
The exact schedule varies by provider and by your individual risk factors. Some people sail through with just the standard tests; others need additional monitoring. Each blood draw is relatively quick, and results typically come back within a few days to a week.