Gestation is the period of development during the carrying of an embryo, fetus, or reptilian embryo inside viviparous animals.[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.

The time interval of a gestation is called the gestation period. In human obstetrics, gestational age refers to the fertilization age plus two weeks. This is approximately the duration since the woman's last menstrual period (LMP) began.


In mammals, as well as reptiles, pregnancy begins when a zygote (fertilized ovum) implants in the female's uterus and ends once the fetus leaves the uterus.

On the main article link above, are average and approximate gestation values ordered by number of days (note: human gestational age is counted from the last menstrual period; for other animals the counting method varies, so these figures could be 14 days off)


Human pregnancy can be divided roughly into three trimesters, each approximately three months long. The first trimester is from the last period through the 13th week, the second trimester is 14th–27th week, and the third trimester is 28th–42nd week.[2] Birth normally occurs at a gestational age of about 40 weeks, though it is common for births to occur from 37 to 42 weeks.[2] From the 9th week of pregnancy (11th week of gestational age), the embryo is called a fetus.

Various factors can come into play in determining the duration of gestation. For humans, male fetuses normally gestate several days longer than females and multiple pregnancies gestate for a shorter period.[3]

Other Languages
العربية: حبل (تكاثر)
asturianu: Xestación
বাংলা: গর্ভকাল
беларуская: Цяжарнасць
беларуская (тарашкевіца)‎: Цяжарнасьць
български: Бременност
español: Gestación
euskara: Ernaldi
فارسی: آبستنی
français: Gestation
galego: Xestación
한국어: 잉태
hrvatski: Gestacija
Bahasa Indonesia: Gestasi
қазақша: Буаздық
Kreyòl ayisyen: Jestasyon
मराठी: सगर्भता
Nederlands: Gestatie
norsk: Drektighet
norsk nynorsk: Fostertid
polski: Ciąża
português: Gestação
română: Gestație
русский: Беременность
Scots: Gestation
sicilianu: Gistazzioni
Simple English: Gestation
srpskohrvatski / српскохрватски: Gestacija
svenska: Dräktighet
Tiếng Việt: Thai kỳ