Maternity Nursing: Antepartum Q 32
A client arrives at a prenatal clinic for the first prenatal assessment. The client tells a nurse that the first day of her last menstrual period was September 19th, 2013. Using Naegele’s rule, the nurse determines the estimated date of confinement as:
A. July 26, 2013
B. June 12, 2014
C. June 26, 2014
D. July 12, 2014
Correct Answer: C. June 26, 2014.
Accurate use of Naegele’s rule requires that the woman has a regular 28-day menstrual cycle. Add 7 days to the first day of the last menstrual period, subtract three months, and then add one year to that date.
Option A: An average pregnancy lasts 280 days from the first day of the last menstrual period (LMP) or 266 days after conception. Historically, an accurate LMP is the best estimator to determine the due date.
Option B: Naegele’s rule, derived from a German obstetrician, subtracts 3 months and adds 7 days to calculate the estimated due date (EDD). It is prudent for the obstetrician to get a detailed menstrual history, including duration, flow, previous menstrual periods, and hormonal contraceptives. These factors are used to determine the length of her cycles and ovulation period.
Option D: There are several fallacies with Naegele’s rule. First, a woman may not accurately recall the first day of her menstrual cycle. Second, this method assumes a woman’s cycle is exactly 28 days, with ovulation occurring at day 14, however, it does not consider menstrual cycles with shorter or longer durations. Third, there are small variations in the duration between fertilization and blastocyst implantation. Last, this method cannot differentiate between menstrual bleeding and early pregnancy bleeding.