Reproductive · Obstetrics
The facts most likely to be tested
The initial prenatal visit requires screening for blood type and Rh status, rubella immunity, syphilis (RPR/VDRL), HIV, Hepatitis B surface antigen, and asymptomatic bacteriuria via urine culture.
Folic acid supplementation of 0.4–0.8 mg daily is recommended for all pregnant patients to prevent neural tube defects.
Cell-free DNA (cfDNA) testing is the most sensitive and specific screening test for aneuploidy and can be performed as early as 10 weeks gestation.
Gestational diabetes mellitus screening is performed between 24 and 28 weeks gestation using a 1-hour 50g glucose challenge test followed by a diagnostic 3-hour oral glucose tolerance test if positive.
Group B Streptococcus (GBS) screening via rectovaginal culture is performed universally between 36 and 38 weeks gestation.
Rh(D) immune globulin is administered at 28 weeks gestation to all Rh-negative patients who are not already sensitized to prevent alloimmunization.
Tdap vaccination is recommended during every pregnancy, ideally between 27 and 36 weeks gestation, to provide passive immunity to the neonate against pertussis.
Vignette unlocked
A 28-year-old G1P0 woman at 28 weeks gestation presents for a routine prenatal visit. She has no significant past medical history and takes a prenatal vitamin daily. Her blood type is O-negative and her antibody screen is negative. She reports no complaints and fetal heart tones are 145 bpm. Her last visit was at 20 weeks gestation.
What is the most appropriate next step in management regarding her obstetric care?
Administer Rh(D) immune globulin
This vignette tests the requirement for prophylactic Rh(D) immune globulin at 28 weeks gestation in Rh-negative patients to prevent the development of anti-D antibodies.
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High yield triage
Etiology / Epidemiology
Routine care aims to identify high-risk pregnancies and prevent complications. Folic acid supplementation is essential for neural tube defect prevention.
Clinical Manifestations
Monitor for preeclampsia symptoms: new-onset hypertension and proteinuria. Assess for fetal heart tones starting at 10-12 weeks via Doppler.
Diagnosis
Confirm pregnancy via serum beta-hCG. Perform transvaginal ultrasound for accurate dating in the first trimester.
Treatment
Administer prenatal vitamins with iron and folic acid. Avoid live vaccines and NSAIDs in third trimester.
Prognosis
Goal is term delivery (37-42 weeks). Monitor for gestational diabetes and preeclampsia to reduce maternal/fetal morbidity.
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Epidemiology & Etiology
Prenatal care is indicated for all pregnant patients to optimize outcomes. Advanced maternal age (>35) and pre-existing comorbidities (DM, HTN) define high-risk status. Early initiation of care is associated with reduced rates of low birth weight and preterm birth.
Pertinent Anatomy
The uterus becomes an abdominal organ by 12 weeks. The placenta serves as the primary endocrine organ, producing hCG and progesterone to maintain the pregnancy.
Pathophysiology
Physiologic changes include increased plasma volume (leading to physiologic anemia) and increased cardiac output. The RAAS system is upregulated, while systemic vascular resistance decreases. Progesterone induces smooth muscle relaxation, predisposing to GERD and stasis.
Clinical Manifestations
Screen for preeclampsia via blood pressure and urine dipstick at every visit. Red flags include vaginal bleeding, severe headache, visual disturbances, and decreased fetal movement. Quickening typically occurs at 16-20 weeks.
Diagnosis
The transvaginal ultrasound is the gold standard for dating, most accurate at 8-13 weeks. Screen for gestational diabetes at 24-28 weeks using a 50g glucose challenge test (threshold >130-140 mg/dL). Perform Group B Strep screening at 36-37 weeks.
Treatment
Initiate prenatal vitamins with 0.4-0.8 mg folic acid daily. Contraindicated medications include ACE inhibitors, tetracyclines, and isotretinoin due to teratogenicity. Manage nausea with pyridoxine/doxylamine.
Prognosis
Routine monitoring aims to prevent intrauterine growth restriction (IUGR) and preterm labor. Patients with gestational diabetes require strict glycemic control to prevent macrosomia and neonatal hypoglycemia.
Differential Diagnosis
Ectopic pregnancy: positive hCG with empty uterus
Molar pregnancy: snowstorm pattern on ultrasound
Gestational hypertension: HTN without proteinuria
Preeclampsia: HTN with proteinuria or end-organ damage
Hyperemesis gravidarum: severe vomiting with ketonuria