If a woman's last menstrual period (LMP) is September 12, 2019, what will be her EDD?

Appeared in: P.CHO-2019

Explanation

The Estimated Date of Delivery (EDD) is calculated using Naegele's rule, a standard method in obstetrics.
Naegele's rule states: EDD = First day of Last Menstrual Period (LMP) + 7 days - 3 months + 1 year.
Applying this rule to an LMP of September 12, 2019, results in an EDD of June 19, 2020.
Calculation: September 12, 2019 + 7 days = September 19, 2019.
Then, September 19, 2019 - 3 months = June 19, 2019.
Finally, June 19, 2019 + 1 year = June 19, 2020.

Option A: This date is incorrect. It would result from an inaccurate application of Naegele's rule, possibly by subtracting 4 days from the LMP before performing the rest of the calculation.
Option B: This date is incorrect. It may be the result of adding only 3 days to the LMP date instead of the correct 7 days.
Option D: This date is incorrect. It could be the result of a calculation error, such as adding 17 days to the LMP instead of 7.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Calculation of Estimated Date of Delivery (EDD) using Naegele's Rule as background academic context rather than a clinical decision trigger.
Accurate EDD calculation is crucial for scheduling antenatal visits, timing of screening tests (e.g., for gestational diabetes), and assessing fetal growth.
Naegele's rule is an estimate and assumes a regular 28-day menstrual cycle. For women with irregular cycles, an early ultrasound is more accurate for dating the pregnancy.
Only about 5% of women deliver on their exact EDD. The due date is a guide, and labor can be expected anytime between 38 and 42 weeks.

How to Approach the Question

Identify the key information provided in the question, which is the Last Menstrual Period (LMP): September 12, 2019.
Recall the standard formula for calculating the Estimated Date of Delivery (EDD), which is Naegele's rule.
Apply Naegele's rule: Add 7 days to the LMP date, then subtract 3 months, and finally add 1 year.
Step 1: September 12 + 7 days = September 19.
Step 2: September (9th month) - 3 months = June (6th month).
Step 3: 2019 + 1 year = 2020. The resulting date is June 19, 2020.

Concept Tested & Keywords

Concept Tested: Calculation of Estimated Date of Delivery (EDD) using Naegele's Rule
Stem keywords: last menstrual period (LMP), EDD
Lead-in keywords: what will be
Clinical cues: LMP: September 12, 2019

QAkl7Q-OV_YdJbTOfGPzl_

E6 Comprehensive Textbook of Community Health Nursing for BSc Nursing Students Part 2 — Subpart A (pp 1-275 of 550) p. 195-197

E6 Obstetrics Williams p. 19-35

Practise the full P.CHO-2019

Attempt every question from this paper in a timed mock, then review the full solution for each one.