Assuming the menstrual cycle length as 32 days and LMP as June 10th. Which of the following is most likely du… - JIPMER Nursing Officer-2017

JIPMER Nursing Officer-2017

Obstetrics & Gynaecology

Hard

Appeared in: JIPMER Nursing Officer-2017

Explanation

The correct Expected Date of Delivery (EDD) is March 21.
This is calculated by first applying Naegele's rule to the Last Menstrual Period (LMP) and then adjusting for the actual menstrual cycle length.
Naegele's rule (LMP + 9 months + 7 days) assumes a 28-day cycle. For an LMP of June 10th, this gives a standard EDD of March 17th.
Since the actual cycle is 32 days, which is 4 days longer than the standard 28 days, an adjustment of +4 days is required.
The final adjusted EDD is calculated as March 17th + 4 days, which equals March 21st.

Option A: This date would be the result of subtracting 5 days from the standard EDD (March 17 - 5 days), which would be appropriate for a shorter cycle of approximately 23 days (28 - 5 = 23), not the 32-day cycle given.
Option B: This is the EDD calculated using the standard Naegele's rule without any adjustment. This calculation is only accurate for a standard 28-day menstrual cycle.
Option D: This date results from adding 10 days to the standard EDD (March 17 + 10 days). This would imply a menstrual cycle of 38 days (28 + 10 = 38), which is incorrect.

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) with adjustment for non-standard menstrual cycle length as background academic context rather than a clinical decision trigger.
Accurate EDD calculation is fundamental in obstetrics for timing prenatal screenings, monitoring fetal growth, and making decisions about labor induction for post-term pregnancies.
An incorrect EDD can lead to iatrogenic prematurity if induction is performed too early, or increased risks associated with post-term pregnancy if it's performed too late.
What if? If the menstrual cycle was shorter, for example, 25 days, the adjustment would be -3 days (25 - 28). The EDD would then be March 17 - 3 days = March 14.

How to Approach the Question

First, identify the key information provided in the question: the Last Menstrual Period (LMP) is June 10th, and the menstrual cycle length is 32 days.
Recall Naegele's rule for calculating the Expected Date of Delivery (EDD), which is: LMP - 3 months + 7 days. Remember that this rule assumes a standard 28-day cycle.
Apply Naegele's rule to find the unadjusted EDD: June 10th - 3 months = March 10th. Then, March 10th + 7 days = March 17th.
Next, determine the necessary adjustment for the non-standard cycle length. The actual cycle (32 days) is 4 days longer than the standard cycle (28 days).
Apply this adjustment to the unadjusted EDD. Since the cycle is longer, add the difference: March 17th + 4 days = March 21st.
Finally, compare your calculated date with the given options and select the matching one.

Concept Tested & Keywords

Concept Tested: Calculation of Expected Date of Delivery (EDD) with adjustment for non-standard menstrual cycle length.
Stem keywords: menstrual cycle length, 32 days, LMP, June 10th, due date
Lead-in keywords: most likely
Clinical cues: Menstrual cycle length of 32 days: This is longer than the standard 28-day cycle, necessitating an addition to the EDD calculated by the standard Naegele's rule.

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E6 Obstetrics Williams p. 19-35