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

Choice A reason: Normal weight women should gain 11.5 to 16 kg during pregnancy, according to the Institute of Medicine (IOM) guidelines. This is based on the body mass index (BMI) of 18.5 to 24.9 before pregnancy.

Choice B reason: Underweight women should gain 12.5 to 18 kg during pregnancy, according to the IOM guidelines. This is based on the BMI of less than 18.5 before pregnancy. Underweight women are at risk of having low birth weight infants, so they need to gain more weight to support fetal growth and development.

Choice C reason: Adolescents are encouraged to strive for weight gains at the upper end of the recommended scale, according to the IOM guidelines. This is because adolescents are still growing themselves and need extra nutrients and calories to meet their own needs and those of the fetus.

Choice D reason: In twin gestations, the weight gain recommended for a single fetus pregnancy should not be simply doubled. The IOM guidelines suggest that women with twin gestations should gain 16.5 to 24.5 kg if they have a normal weight before pregnancy, 14 to 22.5 kg if they are overweight, and 11 to 19 kg if they are obese.

Choice E reason: Obese women should gain at least 7 to 11.5 kg during pregnancy, according to the IOM guidelines. This is based on the BMI of 30 or more before pregnancy. Obese women are at risk of having complications such as gestational diabetes, preeclampsia, and cesarean delivery, so they need to limit their weight gain to avoid further complications.

Choice A reason: Amniocentesis for fetal lung maturity is not an expected diagnostic procedure for a pregnant woman with bright red, painless vaginal bleeding. It is a procedure that involves inserting a needle into the amniotic sac to obtain a sample of amniotic fluid, which can be used to assess the fetal lung development. It is usually done in late pregnancy or preterm labor, not in the second trimester.

Choice B reason: Contraction stress test (CST) is not an expected diagnostic procedure for a pregnant woman with bright red, painless vaginal bleeding. It is a test that involves stimulating uterine contractions, either by nipple stimulation or oxytocin infusion, to evaluate the fetal heart rate response. It is used to assess fetal well-being and placental function, not to diagnose the cause of bleeding.

Choice C reason: Internal fetal monitoring is not an expected diagnostic procedure for a pregnant woman with bright red, painless vaginal bleeding. It is a method of measuring the fetal heart rate and uterine contractions using electrodes or catheters that are inserted through the cervix and attached to the fetal scalp or the amniotic sac. It is usually done during labor, not in the second trimester.

Choice D reason: Ultrasound for placental location is an expected diagnostic procedure for a pregnant woman with bright red, painless vaginal bleeding. It is a test that uses sound waves to create an image of the uterus, the placenta, and the fetus. It can help to determine the position and attachment of the placenta, which can be the cause of bleeding if it is low-lying or covering the cervix (placenta previa).

Choice E reason: None of the above is not a correct answer. There is one expected diagnostic procedure for a pregnant woman with bright red, painless vaginal bleeding, which is ultrasound for placental location.