The Beginning of Pregnancy


The Beginning of Pregnancy

A woman's pregnancy begins with the implantation of a blastocyst (i.e. the fertilized egg in a certain stage of development) in her uterus and, under normal conditions, ends about nine months later with the birth of a baby. However, for certain purposes of medical calculation the beginning of pregnancy is not dated from the time of implantation, but from the first day of the last menstruation. (The reason for this is that a woman is not aware of an implantation, but usually can recall the date of her last menstruation.) According to this timetable, the woman will give birth 280 days (40 weeks) later. Using the same basis for calculation, the date of delivery can also be predicted by this rule of thumb: "Month minus 3, day plus 7.”

How to calculate the day of delivery: “Month - 3, day + 7”


First day of last menstruation:
December 10, or, in numerals, month no. 12, day no. 10.

Month of delivery:






Day of delivery:






Date of delivery:
Month no. 9, day no. 17, i.e. September 17.


[Course 2] [Description] [How to use it] [Introduction] [Conception] [Pregnancy] [Beginning] [Development] [During Pregnancy] [Birth] [Infertility] [Contraception] [Abortion] [Additional Reading] [Examination]