What blood work is recommended at 10 weeks of gestation?

Blood Work Recommended at 10 Weeks Gestation

At 10 weeks of pregnancy, comprehensive first-trimester blood work should include: complete blood count, blood type and antibody screen, hepatitis B surface antigen, HIV testing, rubella immunity, syphilis serology, and consideration of fasting glucose and TSH testing, particularly in women with risk factors. 1

Essential Laboratory Tests

The following tests form the core of first-trimester screening and should be performed at or around 10 weeks gestation:

Infectious Disease Screening

• Hepatitis B surface antigen (HBsAg) testing is mandatory to identify carriers and prevent mother-to-child transmission, which is highly effective when identified early 1, 2
• HIV antibody testing should be performed as early as possible in all pregnant women, as highly active antiretroviral therapy can dramatically reduce vertical transmission 1, 2
• Syphilis serology is essential for early detection and treatment, as benzathine penicillin G remains highly effective when administered during pregnancy 3, 2
• Rubella IgG antibody testing identifies susceptible women who will require postpartum vaccination 1, 3

Hematologic and Blood Type Testing

• Complete blood count (CBC) screens for anemia and other hematologic abnormalities that may require intervention during pregnancy 1, 3
• Blood type and antibody screen is critical to identify Rh status and detect atypical antibodies that could cause hemolytic disease of the newborn 1, 3

Metabolic Screening

• Fasting blood glucose should be performed in all women to screen for pre-existing diabetes, with particular emphasis on high-risk women (sensitivity 80%, specificity 90%) 1
• Thyroid-stimulating hormone (TSH) testing is recommended, especially for women with pre-existing diabetes, thyroid disorders, or other risk factors 1, 3

Additional Testing Based on Risk Factors

High-Risk Populations

• Hepatitis C virus (HCV) screening should be offered to women with risk factors including history of injection drug use, intranasal drug use, or other high-risk behaviors (sensitivity 95%, specificity 95%) 1, 4
• Chlamydia and gonorrhea screening should be performed in women younger than 25 years or those at increased risk, with repeat testing in the third trimester for ongoing risk 2

Women with Chronic Medical Conditions

• For women with chronic hypertension: baseline liver enzymes, renal function tests, and uric acid levels should be obtained 1
• For women with pre-existing diabetes: hemoglobin A1C, comprehensive eye examination, and urinary albumin-to-creatinine ratio are recommended 1

First-Trimester Aneuploidy Screening Options

At 10 weeks gestation, you are approaching the window for first-trimester combined screening:

• First-trimester combined screening (performed between 11-14 weeks) includes nuchal translucency (NT) measurement via ultrasound plus serum markers: pregnancy-associated plasma protein A (PAPP-A) and free beta-hCG 1, 3
• This screening has a detection rate of approximately 70% for Down syndrome with a 5% false-positive rate 1
• All women should be offered the option of invasive diagnostic testing (CVS or amniocentesis) regardless of maternal age 1

Note that at exactly 10 weeks, the patient is slightly early for the NT measurement (which requires 11-14 weeks), but serum markers can be drawn and held until the appropriate gestational age for NT measurement 3.

Critical Pitfalls to Avoid

• Do not delay hepatitis B screening - this is crucial for preventing mother-to-child transmission and must be completed in the first trimester 1
• Do not postpone glucose screening in high-risk women - women with risk factors for diabetes should be tested as early as possible, not waiting until the routine 24-28 week screening 1
• Do not fail to provide adequate counseling about aneuploidy screening options, including the benefits, risks, and limitations of different tests 1, 3
• Do not overlook baseline laboratory assessment in women with chronic medical conditions such as hypertension or diabetes 1
• Do not forget to reinterpret results if gestational age is revised by 2 or more weeks after ultrasound dating 3

Cervical Screening

• Cervical cytology (Pap smear) should be obtained at the initial prenatal visit if due per routine screening guidelines 1

Important Timing Considerations

While you are ordering tests at 10 weeks, be aware that:

• MSAFP screening for neural tube defects will be offered later, optimally between 16-18 weeks gestation, even if first-trimester screening is performed 3, 1
• Gestational diabetes screening for average-risk women occurs at 24-28 weeks 1
• Group B streptococcus screening occurs at 35-37 weeks gestation 5