Last menstrual period

View the Birth Control Options Slideshow
Our Menstruation Main Article provides a comprehensive look at the who, what, when and how of Menstruation

Medical Definition of Last menstrual period

Last menstrual period: By convention, pregnancies are dated in weeks starting from the first day of a woman's last menstrual period (LMP). If her menstrual periods are regular and ovulation occurs on day 14 of her cycle, conception takes place about 2 weeks after her LMP. A woman is therefore considered to be 6 weeks pregnant 2 weeks after her first missed period.

A woman's obstetric date is different from the embryologic date (the age of the embryo). The obstetric date is about 2 weeks longer than the embryologic date.


Quick GuideWomen's Health: Nutrition and Health Care Reform

Women's Health: Nutrition and Health Care Reform

Subscribe to MedicineNet's Women's Health Newsletter

By clicking Submit, I agree to the MedicineNet's Terms & Conditions & Privacy Policy and understand that I may opt out of MedicineNet's subscriptions at any time.

Reviewed on 5/13/2016

Health Solutions From Our Sponsors