Lab

Prenatal Lab

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Prenatal Lab, Antepartum Laboratory Testing

  • Labs
  • Initial - General
  1. Complete Blood Count
    1. Hemoglobin
    2. Platelets
  2. Urine sample
    1. Urine Culture
    2. Urinalysis
      1. Asymptomatic Bacteriuria complicates 15% of pregnancies (Pyelonephritis develops in 30% of cases)
  3. Blood Type
    1. ABO and Rh
    2. Antibody screen (Coombs test)
  4. Rubella Antibody
    1. MMR contraindicated during pregnancy
    2. Administer postpartum MMR if negative
    3. Screen prior to pregnancy and immunize if negative
  5. Syphilis Serology
    1. Universal screening recommended with automated Treponemal test
  6. Hepatitis B Surface Antigen (HBsAg)
    1. Universal screening recommended in U.S.
    2. If at risk, Hepatitis B Vaccine (safe in pregnancy)
  7. Hepatitis C Antibody
    1. ACOG recommends screening as part of Prenatal Labs
  8. Pelvic Exam Initial Labs
    1. Pap Smear
    2. Gonorrhea PCR and Chlamydia PCR
      1. Universal screening recommended
  9. HIV Test
    1. Universal screening recommended
  10. Thyroid Stimulating Hormone (TSH, with reflex Free T4)
    1. See Pregnancy Risk Assessment regarding Thyroid disease risk in pregnancy
    2. See Thyroid Dysfunction in Pregnancy
    3. HIstorically has been a part of routine pregnancy labs in U.S.
      1. However no evidence that universal screening improves pregnancy outcomes
      2. Obtain if history of Thyroid disease or as clinical findings dictate
    4. References
      1. (2020) Obstet Gynecol 135(6):e261-74 +PMID: 32443080 [PubMed]
  • Labs
  • Initial - Specific risk factor directed tests
  1. Vaginitis testing if symptomatic
    1. Bacterial Vaginosis
    2. Trichomonas
    3. Genital Herpes
  2. Group B Streptococcus Culture
    1. Culture both vagina and anus
  3. Sickle Cell Anemia or Sickle Cell Trait screen
    1. Predisposes to Pyelonephritis
  4. Glucose Challenge Test (50 g Glucola drink)
  5. If no maternal history of Varicella infection
    1. Obtain varicella zoster IgG and if negative
      1. Avoid Varicella exposure
      2. If exposed, consider varicella Immunoglobulin
      3. Offer postpartum Varicella Vaccine
        1. Wait 3 months after last RhoGAM shot
    2. Varicella Vaccine is contraindicated in pregnancy
    3. Screen prior to pregnancy and immunize if negative
  • Labs
  • Second Trimester (16-18 weeks)
  1. See Triple Analyte Screen
  2. Consider first trimester screening of trisomy 16, 18
  3. Urine Culture
  • Labs
  • Early Third Trimester (26-28 weeks)
  1. Glucose Challenge Test (50 g Glucola drink)
  2. Hemoglobin
  3. If Rh Negative mother
    1. Repeat Antibody screen (Coombs test)
    2. Administer RhoGAM 300 mcg after blood draw
  4. If mother at risk for Sexually Transmitted Disease (e.g. incarceration, multiple sex partners, Illicit Drug use)
    1. Repeat RPR for Syphilis Testing
    2. Repeat Gonorrhea Culture or Gonorrhea Antigen
    3. Repeat Chlamydia Antigen
    4. Repeat Hepatitis B Surface Antigen (HBsAg)
    5. Repeat HIV Test
  5. If high risk for Preterm Labor
    1. Consider Bacterial Vaginosis screening
    2. Consider Fetal Fibronectin
  • Labs
  • Late Third Trimester (35-37 weeks)
  1. Group B Streptococcus screening