Which analysis of maternal serum may predict chromosomal abnormalities in the fetus?

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: Magnesium sulfate does not improve patellar reflexes and increase respiratory efficiency. In fact, it may cause hyporeflexia and respiratory depression as adverse effects. These are signs of magnesium toxicity and require immediate intervention.

Choice B reason: Magnesium sulfate does not prevent a boggy uterus and lessen lochial flow. A boggy uterus is a sign of uterine atony, which can lead to postpartum hemorrhage. Lochia is the normal vaginal discharge after childbirth. Magnesium sulfate has no effect on these conditions.

Choice C reason: Magnesium sulfate does not shorten the duration of labor. It may actually prolong labor by relaxing the uterine muscles and inhibiting contractions. Magnesium sulfate is not used to induce or augment labor.

Choice D reason: Magnesium sulfate is used to prevent and treat convulsions in women with preeclampsia and eclampsia. Convulsions are a life-threatening complication of severe hypertension during pregnancy. Magnesium sulfate acts as a central nervous system depressant and anticonvulsant. It reduces the risk of seizures and lowers blood pressure.