Gestational age

Gestational age is age of a fetus(or newborn infant) from presumed conception. A full-term human pregnancyis considered to be 40 weeks (280 days), though individuals will vary between 37 and 42 weeks. A fetus born prior to the 37th week of gestation is considered premature and faces increased risk of morbidityand mortality.

The events of embryologicand fetal development usually occur at known gestational ages. This gestational timing of a toxin exposure or infection can be used to predict the potential consequences to the fetus.

The gestational age of an individual infant can be estimated from

1. The mother's knowledge of the date of sexual intercourse.
2. Calculating from her last missed menstrual period(crudely assuming that ovulation and conception would have occurred about two weeks after the last menses).
3. The mother's knowledge of fertility signsrelated to ovulation, particularly cervical mucousquality. This is more accurate than menstrual periodobservations, especially if periods are irregular or oddly-sized. The needed observations are normally made by mothers who use natural family planningmethods to get pregnant.
4. Examination of the newborn infant. In the twentieth century, doctors (especially pediatricians) were trained to recognize the physical changes occurring to the fetus in the latter half of pregnancy so that a maturational age could be estimated.
5. An obstetric ultrasoundduring the pregnancy, whereby sizes of certain fetal body parts are measured.

The gestational age of children conceived by in vitro fertilizationis known to the hour.

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It uses material from the Wikipedia article Gestational age.