A woman diagnosed with marginal placenta previa gave birth vaginally 15 minutes ago. At the present time she is at the greatest risk for:

Choice A reason:

Nagele's rule for calculating the estimated date of confinement (EDC) involves subtracting 3 months from the first day of the last menstrual period and adding 7 days. For February 13th, subtracting 3 months gives us November 13th, and adding 7 days gives us November 20th. This is the most accurate calculation for the estimated date of confinement.

Choice B reason:

This choice is not accurate according to Nagele's rule. Adding 7 days to November 13th would give November 20th, not November 27th.

Choice reason:

This choice is not accurate according to Nagele's rule. Adding 7 days to November 13th would give November 20th, not November 21st.

Choice D reason:

This choice is not accurate according to Nagele's rule. Subtracting 3 months from February 13th would give November 13th, not November 14th.

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.