General Obstetrics, Antenatal Care, and Intrapartum Management
Core concepts
General obstetrics rewards a structured approach. Dating: crown–rump length in the first trimester is the most accurate; later, biometric ultrasound has error that grows with gestation. Antenatal care includes folic acid, blood group and antibody screen, infection screening, aneuploidy screening, gestational diabetes testing, and preeclampsia risk assessment. Intrapartum care: confirm the onset of labor, assess fetal lie, position, and station, and use a partogram. The cardiotocograph is described by baseline rate, variability, accelerations, and decelerations; category I is normal, category III is abnormal. Active phase arrest is diagnosed at ≥6 cm dilation with ruptured membranes and either ≥4 hours of adequate contractions or ≥6 hours of inadequate contractions. Postpartum hemorrhage is blood loss ≥1000 mL or any loss with hemodynamic compromise; uterine atony is the commonest cause.
Traps
Do not use fundal height to date a pregnancy when an early scan exists. Distinguish early decelerations (head compression) from variable decelerations (cord compression) and late decelerations (uteroplacental insufficiency). A “normal” CTG does not exclude all acidosis, but it makes it unlikely. Avoid diagnosing failure to progress before the active phase.
Worked example
A nullipara at 6 cm, ruptured membranes, adequate contractions for 4 hours with no change in dilation has active-phase arrest. Options include oxytocin augmentation if contractions are inadequate and cesarean delivery if adequate. The examination trap is calling this “latent phase” because she is only 6 cm.
Rule of thumb: before intervening in labor, ask: is the power adequate, is the passage adequate, and is the passenger well oxygenated?