In vitro fertilization-embryo transfer (IVF-ET) is a common approach for women with blocked fallopian tubes or unexplained infertility and for men with very low sperm counts. A husband and wife have arrived for their preprocedural interview. The husband asks the nurse to explain what the procedure entails. The nurse's most appropriate response is:

Choice A reason: This is not the correct answer, as the pregnant woman does not use glucose at a more rapid rate than the nonpregnant woman. In fact, the pregnant woman has lower fasting glucose levels and higher postprandial glucose levels than the nonpregnant woman. This is because the pregnant woman adapts to the increased fetal demand for glucose by increasing her insulin secretion and decreasing her hepatic glucose production.

Choice B reason: This is the correct answer, as placental hormones are antagonistic to insulin, thus resulting in insulin resistance. Insulin resistance is a condition where the cells do not respond well to insulin and require more insulin to maintain normal glucose levels. Placental hormones, such as human placental lactogen, progesterone, and cortisol, increase the insulin resistance of the maternal tissues, especially in the second and third trimesters of pregnancy. This is to ensure that the fetus has enough glucose supply, as the placenta is not insulin resistant and can transport glucose to the fetus².

Choice C reason: This is not the correct answer, as pancreatic function in the islets of Langerhans is not affected by pregnancy. The islets of Langerhans are clusters of cells in the pancreas that produce hormones, such as insulin and glucagon, that regulate glucose metabolism. Pregnancy does not impair the function of the islets of Langerhans, but rather stimulates them to increase their size and number. This is to compensate for the increased insulin resistance and glucose demand of the pregnancy.

Choice D reason: This is not the correct answer, as the pregnant woman does not increase her dietary intake significantly. The pregnant woman needs to consume adequate calories and nutrients to support the fetal growth and development, but not excessively. The recommended weight gain during pregnancy depends on the pre-pregnancy BMI of the woman, but generally ranges from 11 to 16 kg. The recommended calorie intake during pregnancy is about 300 kcal more than the pre-pregnancy intake, which is equivalent to one extra snack per day.

Choice A reason: Vibroacoustic stimulation is a technique that uses sound to stimulate the fetus and elicit a response. It is sometimes used in conjunction with the nonstress test (NST), not the CST. The NST measures the fetal heart rate (FHR) in response to fetal movement, while the CST measures the FHR in response to uterine contractions.

Choice B reason: A negative CST result means that the FHR does not show any late decelerations during at least three contractions in a 10-minute period. 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 indicate uteroplacental insufficiency, which means that the placenta is not delivering enough oxygen and nutrients to the fetus. A negative CST result is reassuring and suggests that the fetus is well-oxygenated and can tolerate labor².

Choice C reason: The CST is not an invasive test, as it does not involve inserting any instruments or devices into the uterus or the fetus. However, it does require stimulating contractions, either by giving the pregnant woman oxytocin (a hormone that causes uterine contractions) or by having her rub her nipples (which also releases oxytocin). The contractions can be uncomfortable and may trigger preterm labor in some cases.

Choice D reason: The CST is not more effective than the NST if the membranes have already been ruptured. In fact, the CST is contraindicated (not recommended) in women who have ruptured membranes, as it can increase the risk of infection and bleeding. The NST is a safer and simpler alternative to the CST, as it does not require stimulating contractions. However, the NST may not be as reliable as the CST in detecting fetal compromise.