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Initial Prenatal Visit

• Aneuploidy
  • American College of Obstetrics and Gynecology (ACOG) recommends:
    • All women should be offered screening before 20 weeks
    • All women should have the option for having a more invasive procedure instead of screening regardless of maternal age
      • Amniocentesis
      • Chorionic villus sampling
  • Two major categories of screening available
    • Specific maternal serum biomarkers
      • Primarily trisomy 21 and 18
    • Maternal circulation cell-free DNA
      • More sensitive
      • Assesses trisomy 21, 18, 13, and sex chromosome aneuploidies

• Carrier Screening
  • ACOG recommends:
    • All women should be offered carrier screening for cystic fibrosis, spinal muscular dystrophy, thalassemias, and hemoglobinopathies
    • Fragile X
      • All women with a family history of intellectual disability, developmental delay, or autism
    • Each provider develop a screening strategies for ethnic-specific and panethnic populations
  • If there is a (+) screening test in the mother, then the reproductive partner should be offered screening

• Standard Panel Laboratory Screening
  • ABO and Rh Screen
    • RhD(-) women should receive prophylactic anti(D)-immune globin at 28-weeks
  • Complete Blood Count and RBC Indices
    • 1^st Screen for anemia
  • Documentation of Rubella and Varicella Immunity
    • Rubella IgG
    • Varicella IgG
  • Urinalysis and Urine Culture
    • Urine Protein – establish baseline to compare if patient develops pre-eclampsia or eclampsia
    • Untreated, asymptomatic has higher rates of developing pyelonephritis, pre-term birth
  • HIV Screen
    • ACOG recommends “opt-out” approach
  • Hepatitis B
    • HBsAg regardless of immunization status
  • Chlamydia
    • Nucelic Acid Amplification Test (NAAT) of endocervical/vaginal swab or urine
  • Syphilis
    • Can screen with either a non-treponemal or treponemal test, but a (+) screening test is confirmed with a treponemal test

• Selective Screening in 1^st Trimester
  • Thyroid Function – TSH only
  • Overt diabetes screening
    • Obtain HgbA1C if BMI > 25 (23 in Asian Americans) AND at least one of the following:
      • Gestational diabetes in previous pregnancy
      • HgbA1C > 5.7%, impaired glucose tolerance, or impaired fasting glucose on previous testing
      • 1^st degree relative with diabetes
      • African-American, Latino, Native American, Asian American, Pacific Islander
      • History of cardiovascular disease
      • Hypertension (> 140/90 or on medication)
      • Age > 40yr
      • HDL cholesterol < 35 mg/dL or triglyceride > 250 mg/dL
      • PCOS
      • Physical inactivity
      • Other insulin resistance conditions
    • If HgbA1C > 6.5%, then treat as overt diabetes
    • If HgbA1C (-), then screen again at 24-28 weeks
  • Infections
    • Gonorrhea
      • NAAT from endocervical/vaginal swab
    • Hepatitis C
      • High risk patient should be screened with anti-HCV antibody or HCV RNA
    • Tuberculosis
      • Screen with tuberculin skin test or interferon-gamma release assay (IGRA) only if:
        • Suspicion for recent TB infection
        • Immunocompromised
    • Others
      • Toxoplasmosis, trichomonas, herpes simplex, cytomegalovirus, Zika, and Chagas are available for at risk patients or in endemic regions
  • Lead
    • Women with symptoms of lead exposure or risk factors

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15-24 Weeks

• These are not universal and are options available to mothers
• Quadruple Test
  • Maternal serum alpha-fetoprotein level
  • Unconjugated estriol
  • Human chorionic gonadotropin
  • Inhibin A

• Fetal ultrasound
  • Can be used to screen for neural tube defects and other fetal anomalies, as well as screen the mother for a short cervical length (< 25mm) that can increased her risk of spontaneous preterm birth

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24-28 Weeks

• Gestational Diabetes Screening
  • Two-Step Approach
    • Step One – Screening
      • 50g, one-hour glucose challenge test REGARDLESS of time of day or last meal
    • Step Two – Diagnostic
      • 100g, three-hour oral glucose tolerance test
        • Traditionally diagnostic after 2 elevated values, but newer data suggests that one may be OK
      • 75g, two-hour oral glucose tolerance test
        • Diagnostic after a single elevated value, but patient must be fasting

• Complete Blood Count with iron and folate studies
  • 2^nd anemia screening

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28-36 Weeks

• Sexually Transmitted Infection Screening
  • HIV, syphilis, chlamydia, gonorrhea, hepatitis B and C
  • Based on either previous (+) result or evidence of risk factors

• Screen for group B beta-hemolytic streptococcus
  • Vaginal and rectal swabs
  • (+) results treated with intrapartum prophylaxis

• Screen for Fetal Growth Restrictions (<10^th percentile weight for gestational age)
  • Indicated in third trimester in pregnancies at high risk
    • Infections, fetal anomalies, preeclampsia, gestational HTN and DM, alcohol use, placental/cord abnormalities

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References

1. ACOG Practice Bulletin No. 77: screening for fetal chromosomal abnormalities. Obstetrics and gynecology. 2007; 109(1):217-27. [pubmed]
2. ACOG Practice Bulletin No. 88, December 2007. Invasive prenatal testing for aneuploidy. Obstetrics and gynecology. 2007; 110(6):1459-67. [pubmed]
3. ACOG Committee Opinion No. 752: Prenatal and Perinatal Human Immunodeficiency Virus Testing. Obstetrics and gynecology. 2018; 132(3):e138-e142. [pubmed]
4. Roberts SW, Sheffield JS, McIntire DD, Alexander JM. Urine screening for Chlamydia trachomatis during pregnancy. Obstetrics and gynecology. 2011; 117(4):883-5. [pubmed]
5. Hughes BL, Page CM, Kuller JA. Hepatitis C in pregnancy: screening, treatment, and management. American journal of obstetrics and gynecology. 2017; 217(5):B2-B12. [pubmed]
6. ACOG Practice Bulletin No. 190: Gestational Diabetes Mellitus. Obstetrics and gynecology. 2018; 131(2):e49-e64. [pubmed]
7. Centers for Disease Control.  Group B Strep (GBS).  https://www.cdc.gov/groupbstrep/guidelines/new-differences.html
8. Bricker L, Medley N, Pratt JJ. Routine ultrasound in late pregnancy (after 24 weeks’ gestation). The Cochrane database of systematic reviews. 2015; [pubmed]