A placenta previa in which the placental edge just reaches the internal os is more commonly known as:

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: Vascular volume increases during pregnancy to meet the increased oxygen and nutrient demands of the fetus, not to compensate for decreased renal plasma flow. In fact, renal plasma flow increases by 50% to 80% during pregnancy to facilitate the excretion of metabolic wastes.

Choice B reason: Vascular volume increases during pregnancy to ensure adequate blood supply to the uterus and other organs, not to prevent maternal and fetal dehydration. Dehydration can occur due to vomiting, diarrhea, or inadequate fluid intake, and it can be prevented by drinking enough fluids and replacing electrolytes.

Choice C reason: Vascular volume increases during pregnancy to provide adequate perfusion of the placenta, which is the main organ of gas exchange and nutrient delivery for the fetus. The placenta receives about 10% of the maternal cardiac output at term.

Choice D reason: Vascular volume increases during pregnancy to support the growth and development of the fetus and the maternal tissues, not to eliminate metabolic wastes of the mother. Metabolic wastes are eliminated by the kidneys, lungs, skin, and gastrointestinal tract.