Menstrual History

Important Dates During Pregnancy

by Anai Rhoads

The average pocket EDC calculator is based on the first day of the last menstrual cycle in a 28-day cycle, so attention must be paid to the interval between the patient's periods (i.e. if the interval is 35 days instead of 28 days, then the EDC will be one week later than that determined by the pocket calculator; the opposite would hold true for a 21-day interval). Reliable dating by last menstrual period requires that the patient has had three consecutive regular, normal periods and not to have been on hormonal birth control during that time.

Pregnancy Test