Drawing of a sagittal cross-section of a fetus in the pregnant parent's amniotic cavity.
Drawing of a fetus in utero.

Gestation is the period of development during the carrying of an embryo, and later fetus, inside viviparous animals (the embryo develops within the parent).[1] It is typical for mammals, but also occurs for some non-mammals. Mammals during pregnancy can have one or more gestations at the same time, for example in a multiple birth.[2]

The time interval of a gestation is called the gestation period. In obstetrics, gestational age refers to the time since the onset of the last menses, which on average is fertilization age plus two weeks.[3]

  1. ^ Mckay RJ, Lucey JF (June 1964). "NEONATOLOGY". The New England Journal of Medicine. 270 (23): 1231–6 CONTD. doi:10.1056/NEJM196406042702306. PMID 14132827.
  2. ^ Keith L, Oleszczuk JJ (January 1999). "Iatrogenic multiple birth, multiple pregnancy and assisted reproductive technologies". International Journal of Gynaecology and Obstetrics. 64 (1): 11–25. doi:10.1016/S0020-7292(98)00230-6. PMID 10190665. S2CID 31814692.
  3. ^ Liao JB, Buhimschi CS, Norwitz ER (June 2005). "Normal labor: mechanism and duration". Obstetrics and Gynecology Clinics of North America. 32 (2): 145–64, vii. doi:10.1016/j.ogc.2005.01.001. PMID 15899352.

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