Length of human gestation and determination of the date of birth - term pregnancies

Abstract

Until recently it considered the length of human gestation of 280 days from the time when conception occurred, until the birth of the child. These 280 were divided arbitrarily in 10 lunar months of 28 days and this is arbitrary because in reality the bone lunar month interval between two moons is 29 days and 12 1/2 hrs. At least 10 months should be replaced by 9 solar lunar months of 30 days and 10 1/2 hrs. Until recently there were only three ways to determine the date of delivery. The usual method of adding 280 days starting from the 1st. day of the last menstrual period; This method is subject to many errors. The patient can not remember exactly or may intentionally falsifying the date of your last menstrual period or may confuse the blood of implementation by a period. Finally this calculation method is based on the assumption that ovulation 14 days after the 1st happens. day of the last menstrual period.