Compared with contraction stress test (CST), nonstress test (NST) for antepartum fetal assessment:

Choice A reason: Cerebral compression is the cause of early decelerations, as it reflects the fetal head compression during uterine contractions. Early decelerations are decreases in the FHR that begin and end with the onset and end of a contraction, respectively. They are symmetrical and mirror the shape of the contraction. Early decelerations are normal and benign, as they indicate that the fetus is responding to the increased intracranial pressure and maintaining adequate oxygenation.

Choice B reason: Cord compression is not the cause of early decelerations but of variable decelerations. Variable decelerations are abrupt and irregular decreases in the FHR that vary in onset, duration, and depth. They are usually caused by the umbilical cord being compressed or occluded by the fetal body, the maternal pelvis, or the uterine contractions. Variable decelerations can indicate fetal distress or hypoxia, especially if they are severe, frequent, or prolonged.

Choice C reason: Uteroplacental insufficiency is not the cause of early decelerations, but of late decelerations. Late decelerations are decreases in the FHR that begin after the peak of a contraction and return to the baseline after the contraction ends. They are symmetrical and have a gradual onset and recovery. They are usually caused by the reduced blood flow and oxygen delivery to the placenta and the fetus due to maternal or fetal factors. Late decelerations can indicate fetal distress or hypoxia, and require immediate intervention.

Choice D reason: Spontaneous rupture of membranes is not the cause of early decelerations, but it can be a risk factor for cord compression and variable decelerations. Spontaneous rupture of membranes is the breaking of the amniotic sac and the release of the amniotic fluid, which usually occurs during labor or shortly before it. Spontaneous rupture of membranes can cause the umbilical cord to prolapse or slip into the vagina, where it can be compressed or kinked by the fetal head or the contractions.

Choice A reason: Partial abruptio placentae is not the correct answer, as it does not always require delivery by cesarean section. Partial abruptio placentae is a condition where the placenta partially separates from the uterine wall before the baby is born. This can cause bleeding, pain, and fetal distress. Depending on the severity of the condition, the gestational age, and the fetal status, the delivery may be vaginal or cesarean.

Choice B reason: Ectopic pregnancy is not the correct answer, as it does not require delivery by cesarean section. Ectopic pregnancy is a condition where the fertilized egg implants outside the uterus, usually in the fallopian tube. This can cause bleeding, pain, and rupture of the tube. Ectopic pregnancy is not viable and needs to be removed surgically or treated with medication. It cannot result in a live birth².

Choice C reason: Eclampsia is not the correct answer, as it does not always require delivery by cesarean section. Eclampsia is a severe complication of preeclampsia, a condition where the pregnant woman develops high blood pressure and protein in the urine. Eclampsia can cause seizures, coma, and death for the mother and the baby. The only cure for eclampsia is delivery of the baby, which may be vaginal or cesarean depending on the maternal and fetal condition.

Choice D reason: Total placenta previa is the correct answer, as it always requires delivery by cesarean section. Total placenta previa is a condition where the placenta completely covers the cervix, the opening of the uterus. This can cause painless bleeding, preterm labor, and fetal distress. Vaginal delivery is impossible and dangerous, as it can cause severe bleeding and damage to the placenta and the baby. Cesarean section is the only safe way to deliver the baby.