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Difficulty: MediumNormal Pregnancy and Prenatal Care

Match each gestational age milestone during an uncomplicated pregnancy with the most appropriate routine prenatal screening or intervention recommended by standard obstetric guidelines.

  • Initial prenatal visit (typically 8-10 weeks gestation)ABO/Rh typing, rubella immunity status, HIV screen, RPR, and hepatitis B surface antigen
  • 15 to 22 weeks gestationMaternal serum quad screen (if early screening declined) and comprehensive fetal anatomic ultrasound
  • 24 to 28 weeks gestation50-g 1-hour glucose challenge test and prophylactic administration of anti-D immune globulin (if indicated)
  • 36 to 37 6/7 weeks gestationRectovaginal culture to assess for maternal Group B Streptococcus colonization

Answer

The initial prenatal visit corresponds to baseline infectious and immunologic screening (ABO/Rh, HIV, RPR, Hepatitis B, Rubella). The 15-22 weeks interval corresponds to the maternal serum quad screen and fetal anatomic survey. The 24-28 weeks interval corresponds to the glucose challenge test and potential anti-D immune globulin administration. The 36-37 6/7 weeks interval corresponds to Group B Streptococcus rectovaginal screening.
Each gestational milestone in an uncomplicated pregnancy aligns with specific physiological changes and developmental stages. The first visit focuses on baseline labs (blood type, HIV, RPR, Hep B, Rubella). The mid-second trimester (15-22 weeks) is designated for structural and neural tube defect screening via quad screen and ultrasound, as organogenesis is complete. The late second trimester (24-28 weeks) targets peak insulin resistance with the glucose challenge test and addresses Rh alloimmunization risk. Finally, the late third trimester (36-37 6/7 weeks) requires GBS screening to guide intrapartum prophylaxis because maternal colonization is transient and must be assessed close to delivery.

Step-by-Step Solution

1
Identify the primary objectives of the first trimester prenatal visit.
Baseline laboratory testing is required to identify infectious diseases (HIV, syphilis, hepatitis B), immunologic status (rubella, varicella), and maternal blood type (ABO/Rh) to prevent vertical transmission and alloimmunization.
Early detection allows for timely intervention (e.g., antiretroviral therapy, penicillin) to optimize maternal and fetal outcomes.
2
Determine the screening focus of the mid-second trimester (15-22 weeks).
This period is targeted for neural tube defect screening (via maternal serum alpha-fetoprotein or quad screen) and the comprehensive fetal anatomic ultrasound (typically 18-22 weeks).
Fetal structures are sufficiently developed by this stage to evaluate organogenesis and placental location.
3
Recall the late second trimester (24-28 weeks) milestones.
Universal screening for gestational diabetes with a 50-g glucose challenge test is performed. Repeat antibody screening and prophylactic anti-D immune globulin are given to Rh(D)-negative patients.
Placental hormone-induced insulin resistance peaks late in the second trimester, making it the optimal time to detect gestational diabetes. Prophylactic anti-D prevents alloimmunization during the third trimester.
4
Identify the standard late third trimester (36-37 6/7 weeks) intervention.
Universal rectovaginal screening for Group B Streptococcus (GBS) is conducted.
Screening within 5 weeks of expected delivery provides the highest negative predictive value for GBS colonization, guiding intrapartum antibiotic prophylaxis to prevent neonatal sepsis.

Key Concept

Routine prenatal care requires specific screening modalities tied strictly to gestational age to identify and mitigate maternal, fetal, and neonatal risks at their optimal physiological windows.
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Normal Pregnancy and Prenatal Care

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