Obstetrics
Obstetrics covers antenatal care, intrapartum management, and the major causes of maternal morbidity in Oman and internationally. The OEOG favors questions on hypertension, hemorrhage, diabetes, and fetal surveillance.
Core rules
- Dating by first-trimester ultrasound (crown-rump length up to 13+6 weeks) is more accurate than LMP; it changes the estimated delivery date when the discrepancy exceeds 5-7 days depending on gestation.
- Screen for gestational diabetes at 24-28 weeks using a 75-g OGTT; IADPSG thresholds are fasting ≥5.1, 1 h ≥10.0, and 2 h ≥8.5 mmol/L.
- Give anti-D 500-1500 IU at 28 weeks to RhD-negative unsensitized women, plus within 72 hours of delivery if the baby is RhD positive; check with a Kleihauer test after sensitizing events.
- Postpartum hemorrhage: blood loss ≥500 mL after vaginal birth or ≥1000 mL after cesarean, or any loss with hemodynamic compromise. Start uterine massage, oxytocin, tranexamic acid 1 g IV within 3 hours, and escalate to balloon tamponade or surgery.
- Preeclampsia: new hypertension after 20 weeks plus proteinuria or maternal organ dysfunction. Delivery is the only cure; magnesium sulfate prevents and treats eclampsia.
Worked example
A 30-year-old G2P1 at 39 weeks has a 700-mL blood loss after vaginal delivery, a boggy uterus, and pulse 118. Reasoning: this meets the definition of PPH and the uterus is atonic. Call for help, empty the bladder, massage the uterus, give an oxytocin infusion and tranexamic acid 1 g IV, and check hemoglobin and coagulation. If bleeding continues, move to balloon tamponade and then surgical options. Do not wait for a falling hemoglobin to act.
Traps
- Treating a 600-mL loss as normal because the woman is stable; PPH is defined by volume and trend.
- Using LMP-based dating when an early scan is available.
- Omitting anti-D after a sensitizing event such as miscarriage or amniocentesis.