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Difficulty: Very hardNormal Pregnancy and Prenatal Care

Match each obstetric patient presentation with the most appropriate indicated management or screening plan.

  • 10 weeks gestation; prior pregnancy with trisomy 13; desires the most accurate non-invasive screening.Offer cell-free fetal DNA (cffDNA) testing, as it provides the highest sensitivity and specificity for common autosomal trisomies.
  • 18 weeks gestation; BMI 40 kg/m²; missed first-trimester screening; desires comprehensive aneuploidy and neural tube defect screening.Obtain a maternal serum quadruple screen and detailed fetal anatomy ultrasound; cell-free DNA does not screen for open neural tube defects and has a high failure rate in this patient.
  • 28 weeks gestation; Rh(D)-negative; presents with acute mild vaginal bleeding; initial antibody screen is negative.Administer 300 mcg of anti-D immune globulin and perform a Kleihauer-Betke test or flow cytometry to evaluate for significant fetomaternal hemorrhage.
  • 36 weeks gestation; asymptomatic today; treated for a Group B Streptococcus (GBS) urinary tract infection at 12 weeks gestation.Omit the routine 36-38 week rectovaginal screening culture; the patient is automatically indicated for intrapartum intravenous penicillin prophylaxis.
  • 38 weeks gestation; HIV-positive on combined antiretroviral therapy; maternal viral load is currently 20 copies/mL.Plan for a trial of labor; scheduled cesarean delivery and intrapartum intravenous zidovudine are not indicated at this level of viral suppression.

Answer

The correct matches align each unique clinical presentation with its specific guideline-based management, focusing on exceptions to routine prenatal care such as alternative screening for obese patients, quantitative testing for Rh-negative patients with bleeding, and omitting unnecessary screening in patients already indicated for prophylaxis.
Each presentation represents a specific nuance or exception within standard normal prenatal care guidelines. Accurately managing these edge cases requires understanding the limitations of screening modalities (e.g., cffDNA in high BMI), indications for quantitative fetomaternal hemorrhage testing, and specific thresholds for intrapartum prophylaxis.

Step-by-Step Solution

1
Evaluate the 10-week gestation patient with prior trisomy 13.
Match with cffDNA testing.
cffDNA is the most accurate non-invasive screening for aneuploidy and can be performed from 10 weeks onward.
2
Evaluate the 18-week gestation obese patient who missed early screening.
Match with quadruple screen and anatomy ultrasound.
She requires both aneuploidy and NTD screening. cffDNA does not test for NTDs and has a high failure rate in severe obesity.
3
Evaluate the 28-week Rh-negative patient with vaginal bleeding.
Match with standard anti-D immune globulin and Kleihauer-Betke test.
While routine 28-week prophylaxis is needed, bleeding introduces risk of excessive fetomaternal hemorrhage requiring quantification.
4
Evaluate the 36-week patient with prior GBS bacteriuria.
Match with omitting the screening culture and planning intrapartum prophylaxis.
GBS bacteriuria indicates heavy colonization, automatically qualifying her for antibiotics and making the swab redundant.
5
Evaluate the 38-week HIV-positive patient with undetectable viral load.
Match with trial of labor without intrapartum IV zidovudine.
Viral load < 1,000 permits vaginal delivery, and < 50 eliminates the need for intrapartum IV zidovudine.

Key Concept

Nuanced applications of routine prenatal screening and prophylactic guidelines.
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Topics

Normal Pregnancy and Prenatal Care

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