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Pregnancy & Obstetrics Published 23 October 2026

Why Your Due Date Keeps Changing: LMP Dating vs. Scan Dating, Explained

Written by: Dr. Madhupriya (71791 (TNMC))
SHREE Hospital blog banner explaining why pregnancy due dates change, comparing LMP dating with ultrasound scan dating.
Quick Answer:

Your pregnancy due date may change after an ultrasound because last menstrual period (LMP) dating relies on your menstrual cycle, while an early scan estimates gestational age using the baby’s measurements. First-trimester ultrasound is generally more accurate for dating. A revised due date is often a routine correction and does not, by itself, indicate a pregnancy problem.

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