A pregnant lady's LMP is on 5th July. Her EDD should be?

Appeared in: WCL Staff Nurse - 2019

Explanation

Naegele's rule is a standard method to estimate the Expected Date of Delivery (EDD).
The rule involves adding 9 months and 7 days to the first day of the Last Menstrual Period (LMP).
LMP is 5th July.
Calculation: 5th July + 9 months = 5th April (next year).
Then, 5th April + 7 days = 12th April.
Therefore, the EDD is 12th April.

Option A: Calculating from 5th July, 2nd January is only about 6 months later, not the full 9 months and 7 days required for a term pregnancy.
Option B: This date is approximately 15 days short of the correct calculation. Adding 9 months to July 5th gives April 5th, but only adding 7 days makes the final date April 12th, not March 28th.
Option D: This date is only about 3 months after the LMP, which is far too short for a full-term pregnancy. This might result from incorrectly subtracting months instead of adding them.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Calculation of Expected 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, performing timely screenings, and managing the timing of delivery.
Naegele's rule is a quick and useful estimation but has limitations. It assumes a 28-day cycle, which is not universal. For irregular cycles, ultrasound dating is more reliable.
What if the patient's cycle was 35 days long? The EDD would need to be adjusted. The calculation would be: LMP + 9 months + 7 days + (35 - 28 days) = 12th April + 7 days = 19th April. The nurse must always inquire about cycle regularity.

How to Approach the Question

Identify the key information given: the Last Menstrual Period (LMP) is 5th July.
Recall the formula for calculating the Expected Date of Delivery (EDD), which is Naegele's rule: EDD = LMP + 9 months + 7 days.
Apply the formula step-by-step. First, add 9 calendar months to the LMP date.
Starting from July, count forward 9 months: August (1), September (2), October (3), November (4), December (5), January (6), February (7), March (8), April (9). This brings the date to 5th April of the following year.
Next, add 7 days to this new date: 5th April + 7 days = 12th April.
Compare the calculated date (12th April) with the given options to find the correct answer.

Concept Tested & Keywords

Concept Tested: Calculation of Expected Date of Delivery (EDD) using Naegele's Rule
Stem keywords: pregnant lady, LMP, 5th July, EDD
Lead-in keywords: should be
Clinical cues: Age/sex group narrows the expected diagnosis, intervention, or normal reference range.

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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 WCL Staff Nurse - 2019

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