A patient presented at 20 weeks of gestation. The patient’s LMP was 9th January. What will be the estimated date of delivery?
**Core Concept**
Naegele's rule is a method for estimating the date of delivery based on the last menstrual period (LMP) and the gestational age. This rule assumes that ovulation occurs on day 14 of a 28-day menstrual cycle, and that fertilization occurs shortly after ovulation. The estimated date of delivery (EDD) is then calculated by adding 7 days to the first day of the LMP and subtracting 3 months.
**Why the Correct Answer is Right**
To calculate the EDD using Naegele's rule, we first determine the first day of the LMP, which is January 9th. We then add 7 days to get January 16th. Next, we subtract 3 months from the resulting date, which gives us October 16th. Therefore, the estimated date of delivery is October 16th.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not take into account the correct application of Naegele's rule, which involves adding 7 days to the first day of the LMP and subtracting 3 months.
**Option B:** This option is incorrect because it does not accurately calculate the EDD based on the LMP.
**Option C:** This option is incorrect because it does not apply Naegele's rule correctly.
**Clinical Pearl / High-Yield Fact**
It is essential to remember that Naegele's rule assumes a regular 28-day menstrual cycle and ovulation on day 14. This rule is not accurate for women with irregular cycles or those who have undergone fertility treatments.
**Correct Answer: C. October 16th**