The nurse is calculating the estimated date of confinement (EDC) using Nagele's rule for a client whose last menstrual period started on February 13th. Which date is most accurate?

Choice A: February 6-7 is incorrect. This is too late for the woman's fertile period, which occurs around the time of ovulation. Ovulation usually happens about 14 days before the next period starts, which would be around January 22 for a 28-day cycle¹.

Choice B:In a 28-day menstrual cycle, ovulation typically occurs around day 14 (counting from the first day of the last menstrual period). Since the first day of the last period is January 8, day 14 falls on January 22. The fertile window consists of the five days leading up to ovulation and the day of ovulation (January 17–22), as sperm can survive in the reproductive tract for up to 5 days, and the egg remains viable for about 24 hours after ovulation.January 22-23 is the most fertile period, with ovulation occurring around January 22 and the egg remaining viable for fertilization on January 23.

Choice C: January 30-31 is incorrect. This is after the woman's fertile period, which ends about a day after ovulation. Ovulation usually happens about 14 days before the next period starts, which would be around January 22 for a 28-day cycle.

Choice D: January 14-15 corresponds to cycle days 7-8, which is too early for ovulation in a typical 28-day cycle. Ovulation generally occurs around day 14 (January 22). The follicular phase (the first half of the cycle) is when the follicles in the ovary mature, and estrogen levels rise to trigger ovulation. At this point (January 14-15), the egg is not yet released, and the uterus is still preparing for ovulation, making conception unlikely.

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.