title: [Calculation of gestational age. Methods and problems].
abstract: Gestational age assignment is one of the most important issues in perinatal medicine. Nowadays, the first day of the last menstrual period, when available, is still used as the basis for calculation of gestational age and expected day of confinement. However, most frequently this date is uncertain or even unknown, and thereby gestational age can be confidently estimated by ultrasonographic biometry until 22 weeks of gestation. There is no uniform dating policy when both a valid last menstrual period and ultrasonographic dates are available in determining the date of confinement. When both methods are compared, there are obvious advantages of routine scanning in the first half of pregnancy.
authors.affiliation: Departamento de Ginecologia e Obstetrícia, Hospital de S. João Faculdade de Medicina do Porto, Porto.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Matias
authors.forename: Pedro
authors.initials: P
authors.lastname: Tiago
authors.forename: Nuno
authors.initials: N
authors.lastname: Montenegro
mesh_terms: D005260:Female; D005865:Gestational Age; D006801:Humans; D011247:Pregnancy; D011263:Pregnancy Trimester, Third