What is the cause of early decelerations in the fetal heart rate (FHR) of a laboring woman?

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: Diabetes mellitus is not a direct consequence of inadequate weight gain during pregnancy for the infant. However, maternal diabetes can increase the risk of fetal macrosomia (large birth weight), congenital anomalies, and neonatal hypoglycemia (low blood sugar) in the infant.

Choice B reason: Down syndrome is not a direct consequence of inadequate weight gain during pregnancy for the infant. Down syndrome is a genetic disorder caused by an extra copy of chromosome 21 in the cells of the fetus. The risk of having a baby with Down syndrome increases with maternal age, but it is not related to maternal weight or nutrition².

Choice C reason: Spina bifida is not a direct consequence of inadequate weight gain during pregnancy for the infant. Spina bifida is a neural tube defect that occurs when the spine and spinal cord do not form properly in the fetus. The main risk factor for spina bifida is a lack of folic acid (a B vitamin) in the mother's diet before and during pregnancy.

Choice D reason: Intrauterine growth restriction (IUGR) is a condition in which the fetus does not grow as expected and has a low birth weight. IUGR can have many causes, such as placental problems, infections, chromosomal abnormalities, and maternal factors. One of the maternal factors that can contribute to IUGR is inadequate weight gain during pregnancy, especially in underweight women. IUGR can increase the risk of complications for the infant, such as preterm birth, low Apgar score, hypothermia, hypoglycemia, and breathing problems⁵.