Important Obstetrics Facts For The USMLE Step 1 and 2 exams

by / Sunday, 27 June 2010 / Published in OB/GYN


Premature Delivery – Is delivery between 20-37 weeks, 500-2500g


Term Delivery – Is a delivery after 37 weeks


At 12 weeks – At pubic Symphysis

At 16 weeks – Midway from pubis symphysis to umbilicus

At 20 weeks – At umbilicus

Between 20-36 weeks – Height correlates with weeks of gestation

Triple Marker Screen (15-18 weeks) 1. hCG  2. Alpha FetoProtein  3. Estriol


Group B Strep testing – Done at 35-37 weeks

RhoGAM – Given at 28-30 weeks and 72hr post-delivery

Gestational Diabetes Mellitus – is caused by human placental lactogen (hPL) which antagonizes insulin

  • Maternal complications include: Hyperglycemia, ketoacidosis, increased UTI risk, 2x increase in PIH, retinopathy
  • Fetal complications: Macrosomia (>4500g), neonatal hypoglycemia, abruption due to size, 3-4x increase in congenital anomalies
  • Diagnose with 1hr OGGT done at 24-48 weeks/ or at onset of prenatal care, if +ve confirm with 3hr OGGT.
  • 3hr 100g OGGT: 1st hr <180, 2nd hr <155, 3rd hr <140
  • Insulin is OK during pregnancy but will not cross placenta
  • Oral hypoglycemics are contraindicated in pregnancy because they cross the placenta

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