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In order to have a standard reference point, the normal pregnancy duration is assumed by medical professionals to be 280 days (or 40 weeks) of gestational age. Furthermore, actual childbirth has only a certain probability of occurring within the limits of the estimated due date.
The estimated date of delivery (EDD), also known as expected date of confinement, [1] and estimated due date or simply due date, is a term describing the estimated delivery date for a pregnant woman. [2] Normal pregnancies last between 38 and 42 weeks. [3] Children are delivered on their expected due date about 4% of the time. [4]
An ultrasound showing an embryo measured to have a crown-rump length of 1.67 cm and estimated to have a gestational age of 8 weeks and 1 day. Crown-rump length (CRL) is the measurement of the length of human embryos and fetuses from the top of the head (crown) to the bottom of the buttocks (rump).
A pregnancy is considered term at 37 weeks of gestation. It is preterm if less than 37 weeks and postterm at or beyond 42 weeks of gestation. American College of Obstetricians and Gynecologists have recommended further division with early term 37 weeks up to 39 weeks, full term 39 weeks up to 41 weeks, and late term 41 weeks up to 42 weeks. [24]
The fetus is considered full-term at the end of the 39th week of gestational age. It may be 48 to 53 cm (19 to 21 in) in length. The lanugo is gone except on the upper arms and shoulders. Fingernails extend beyond fingertips. Small breast buds are present on both sexes. Head hair is now coarse and thickest.
Different terms are used to describe prenatal development, meaning development before birth. A term with the same meaning is the "antepartum" (from Latin ante "before" and parere "to give birth") Sometimes "antepartum" is however used to denote the period between the 24th/26th week of gestational age until birth, for example in antepartum ...
If conception is defined as at implantation, ectopic pregnancies could not be called pregnancies. However, some medical professionals who oppose birth control, [15] such as Walter Larimore of the Focus on the Family group, have argued that the medical definition of conception should include fertilization. [16]
However, the mother's body does provide gas exchange. [23] The young of ovoviviparous amphibians are sometimes born as larvae, and undergo metamorphosis outside the body of the mother. [24] The fish family Syngnathidae has the unique characteristic whereby females lay their eggs in a brood pouch on the male's chest, and the male incubates the ...