What is the cause of early decelerations in the fetal heart rate (FHR) of a laboring woman?

The correct answer is d. Amenorrhea.

Choice A: Chadwick’s sign is a non-specific, early sign of pregnancy that is typically characterized by a bluish discoloration of the cervix, vagina, and vulva. The Chadwick sign can typically be observed as early as six to eight weeks after conception, and commonly disappears shortly after birth. However, it’s not a definitive indication of pregnancy, and the absence of it on physical exam does not exclude a potential pregnancy.

Choice B: Hegar’s sign is a non-specific indication of pregnancy that is characterized by the compressibility and softening of the cervical isthmus (i.e., the portion of the cervix between the uterus and the vaginal portion of the cervix). It typically presents between the fourth and sixth week of pregnancy and may be present until the 12th week of pregnancy. However, the Hegar sign is not a definitive indication of pregnancy, and the absence of it does not exclude a potential pregnancy.

Choice C: A positive pregnancy test By 10 weeks, a home pregnancy test would almost certainly show a positive result if the woman is pregnant. This is because the hormone human chorionic gonadotropin (hCG), which is produced by the placenta after implantation of the embryo into the uterine wall, would be present in high enough levels to be detected by the test. However, a positive pregnancy test is not a presumptive sign of pregnancy, but rather a probable one.

Choice D: Amenorrhea, or the absence of menstrual periods, is often considered the most presumptive sign of pregnancy. This is because it’s one of the first noticeable signs of pregnancy for many women. By 10 weeks of gestation, the woman would likely have missed two menstrual periods if she usually has regular cycles. However, while amenorrhea is a common early sign of pregnancy, it can also be caused by various other conditions or factors such as stress, significant weight loss or gain, or certain medical conditions. Therefore, a missed period should be followed up with a pregnancy test to confirm pregnancy.

Choice A reason: Nonreactive is not the correct result, as it indicates that the FHR does not show adequate accelerations with fetal movement. A nonreactive NST means that the FHR does not increase by at least 15 beats/min for at least 15 seconds in a 20-minute period. A nonreactive NST may suggest fetal hypoxia (low oxygen) or fetal sleep.

Choice B reason: Reactive is the correct result, as it indicates that the FHR shows adequate accelerations with fetal movement. A reactive NST means that the FHR increases by at least 15 beats/min for at least 15 seconds twice or more in a 20-minute period. A reactive NST is reassuring and suggests that the fetus is well-oxygenated and healthy.

Choice C reason: Positive is not the correct result, as it is not used to describe the NST. Positive is a term used for the contraction stress test (CST), which is a different test that measures the FHR in response to uterine contractions. A positive CST means that the FHR shows late decelerations (decreases in the FHR that begin after the peak of a contraction and return to the baseline after the contraction ends) with at least 50% of the contractions. A positive CST indicates uteroplacental insufficiency (a condition where the placenta does not deliver enough oxygen and nutrients to the fetus) and fetal distress.

Choice D reason: Negative is not the correct result, as it is also not used to describe the NST. Negative is another term used for the CST, which is a different test that measures the FHR in response to uterine contractions. A negative CST means that the FHR does not show any late decelerations during at least three contractions in a 10-minute period. A negative CST is reassuring and suggests that the fetus is well-oxygenated and can tolerate labor.