Reply To Jess

Jess Said,

Dr. Jason, I am quite confused with my expected due date calculation. My last menses is on 25th july 2009 and thus my EDD should be on the 1st may 2010. but according to my gynea calculation my EDD is on 18th may 2010. He did the calculation by depending on the fetus size through ultrasound scanning. which calculation is more reliable? Please advise.

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Hi, Jess,

Since the first day of your last menses was on 25/7/2009, so it was correct to say that your expected date of delivery was on 1/5/2010, based on Naegeles’ s calculation formula.

However, Naegeles’s calculation formula is only useful and accurate if your menses is regular and the menses interval is 28 days apart.

If your menses is not regular, or the menses interval is not 28 days apart, this calculation formula is not inaccurate.

In your first 3 months ( 1^st trimester ) of the pregnancy, ultrasound scan is very reliable to accurately calculate the actual date of expected date of delivery.

If your expected date of delivery (EDD) based on Naegeles’ formula is within 1 week from the ultrasound scan date, the doctor will usually refer your EDD to the Naegeles’ calculation.

However, if the calculation date is more than 1 week compared with the first trimester ultrasound scan date, the doctor will usually follow the ultrasound scan date.

Since your delivery date is approaching, I wish you a safe labour and happy motherhood.

Cheers!