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

Choice A reason: Variability refers to the fluctuations in the FHR that are irregular in amplitude and frequency. It reflects the balance between the sympathetic and parasympathetic nervous systems of the fetus. A normal variability is between 6 and 10 beats/min, which indicates a healthy and well-oxygenated fetus.

Choice B reason: 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 caused by uteroplacental insufficiency, which means that the placenta is not delivering enough oxygen and nutrients to the fetus. Mild late decelerations are not reassuring and may indicate fetal hypoxia or acidosis².

Choice C reason: FHR should change as a result of fetal activity, such as movement, sleep, or stimulation. A change in the FHR indicates a responsive and well-oxygenated fetus. A lack of change in the FHR may indicate fetal distress or compromise.

Choice D reason: The average baseline rate is the mean FHR rounded to increments of 5 beats/min during a 10-minute window, excluding periods of marked variability, accelerations, or decelerations. A normal baseline rate is between 110 and 160 beats/min. A baseline rate between 100 and 140 beats/min is not necessarily abnormal, but it may indicate fetal bradycardia (slow heart rate) or tachycardia (fast heart rate), depending on the gestational age and other factors.

Choice A reason: A previous birth of a large infant (macrosomia) is a risk factor for gestational diabetes mellitus (GDM). A large infant may indicate that the mother had high blood glucose levels during pregnancy, which can cause the fetus to grow larger than normal. Women who have had a large infant are more likely to develop GDM in subsequent pregnancies.

Choice B reason: Underweight before pregnancy is not a risk factor for GDM. In fact, being overweight or obese before pregnancy is a risk factor for GDM, as it increases insulin resistance and makes it harder for the body to use glucose effectively.

Choice C reason: A previous diagnosis of type 2 diabetes mellitus is not a risk factor for GDM. It is a contraindication for GDM, as it means that the woman already has diabetes before pregnancy. GDM is a condition that develops during pregnancy and usually resolves after delivery.

Choice D reason: Maternal age younger than 25 years is not a risk factor for GDM. In fact, being older than 25 years is a risk factor for GDM, as it increases the risk of insulin resistance and other metabolic changes that can affect glucose tolerance.