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: A fetal heartbeat auscultated with a Doppler or a fetoscope is a positive sign of pregnancy, as it confirms the presence of a living fetus in the uterus. A Doppler is an electronic device that uses sound waves to detect the fetal heart rate, while a fetoscope is a stethoscope-like instrument that amplifies the fetal heart sounds. The fetal heartbeat can be heard as early as 10 to 12 weeks of gestation with a Doppler and 18 to 20 weeks of gestation with a fetoscope.

Choice B reason: Quickening is the first perception of fetal movement by the pregnant woman, usually felt between 16 and 20 weeks of gestation for first-time mothers and 13 to 16 weeks of gestation for experienced mothers. However, quickening is not a positive sign of pregnancy, as it can be subjective and mistaken for other sensations, such as gas, hunger, or muscle spasms².

Choice C reason: Morning sickness is a common symptom of pregnancy that involves nausea and vomiting, usually in the first trimester. However, morning sickness is not a positive sign of pregnancy, as it can be caused by other factors, such as food poisoning, stress, or medication.

Choice D reason: A positive pregnancy test is a probable sign of pregnancy, not a positive sign. A pregnancy test detects the presence of human chorionic gonadotropin (hCG), a hormone produced by the placenta, in the urine or blood of the woman. However, a positive pregnancy test does not guarantee a viable pregnancy, as it can be influenced by the timing, the quality, or the interpretation of the test. A positive pregnancy test can also occur in cases of ectopic pregnancy, molar pregnancy, or miscarriage.

Choice A reason: Fetal sleep cycles are a normal physiological cause of decreased variability in the FHR, which is the fluctuation of the baseline FHR above and below 2 cycles per minute. Fetal sleep cycles usually last 20 to 40 minutes and do not affect the fetal well-being.

Choice B reason: Umbilical cord compression is an abnormal cause of decreased variability in the FHR, as it reduces the blood flow and oxygen delivery to the fetus. It can also cause variable decelerations, which are abrupt decreases in the FHR below the baseline.

Choice C reason: Altered cerebral blood flow is an abnormal cause of decreased variability in the FHR, as it indicates a compromise in the fetal central nervous system. It can also cause late decelerations, which are gradual decreases in the FHR after the peak of a contraction.

Choice D reason: Fetal hypoxemia is an abnormal cause of decreased variability in the FHR, as it reflects a severe lack of oxygen in the fetal blood. It can also cause sinusoidal pattern, which is a smooth, undulating waveform in the FHR.