A pregnancy that reaches or exceeds 42 weeks (>=294 days) is called a post-term pregnancy. It accounts for 5–10% of childbirths. The perinatal mortality rate is approximately 3–6 times that of full-term childbirth. The survival of the fetus in a post-term pregnancy primarily depends on placental function. (1) If placental function is normal, the fetus continues to grow, resulting in a higher birth weight or even macrosomia, or difficult delivery due to skull calcification. (2) If the placenta ages due to postmaturity, leading to insufficiency, reduced placental blood flow, and inadequate oxygen supply, the fetus stops growing and develops a "little old man" appearance (postmaturity syndrome). Hypoxia causes the fetus to pass meconium, staining the amniotic fluid, fetal skin, amniotic membrane, and umbilical cord. At birth, these infants have low Apgar scores and a high mortality rate.

bubble_chart Clinical Manifestations

1. Gestational age ≥42 weeks; 2. Decreased fetal movement; 3. Fundal height or abdominal circumference larger or smaller than expected for gestational age; 4. Ultrasound indicating reduced amniotic fluid; 5. Abnormal NST (non-stress test) results on electronic fetal monitoring; 6. Low 24-hour urine estriol levels.

bubble_chart Diagnosis

1. After repeated verification, the pregnancy has reached or exceeded 42 weeks; 2. Decreased fetal movement, with fewer than 10 movements in 12 hours; 3. Urinary estriol <10mg/24 hours, or urinary estriol/creatinine ratio (E/C) <10 or a 50% decrease; 4. Non-reactive NST test on electronic fetal heart monitoring, or advanced stage decelerations or severe variable decelerations observed in the oxytocin challenge test (OCT); 5. Ultrasound measurement shows dark areas of amniotic fluid.