A pregnant woman's diet may not meet her need for folates. A good source of this nutrient is:

Choice A reason: Braxton Hicks contractions are irregular, painless uterine contractions that occur throughout pregnancy. They are a probable sign of pregnancy, not a positive sign.

Choice B reason: Fetal movement palpated by the nurse-midwife is a positive sign of pregnancy, as it confirms the presence of a living fetus in the uterus. It can be detected as early as 16 to 20 weeks of gestation.

Choice C reason: A positive pregnancy test is a probable sign of pregnancy, as it indicates the presence of human chorionic gonadotropin (hCG) in the urine or blood. However, it is not a definitive sign, as other conditions can cause elevated hCG levels.

Choice D reason: Quickening is the first perception of fetal movement by the mother, which usually occurs between 16 and 20 weeks of gestation. It is a presumptive sign of pregnancy, not a positive sign.

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.