- published: 24 Oct 2014
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Gestation is the carrying of an embryo or fetus inside a female viviparous animal. Mammals during pregnancy can have one or more gestations at the same time (multiple gestations).
The time interval of a gestation is called the gestation period. In human obstetrics, gestational age refers to the embryonic or fetal age plus two weeks. This is approximately the duration since the woman's last menstrual period (LMP) began.
Human pregnancy can be divided into three trimesters, each three months long. The first trimester is from the last period to the 13th week, the second trimester is from the 14th to 27th week, and the third trimester is from the 28th week to 42 weeks.
In humans, birth normally occurs at a gestational age of about 40 weeks, though a normal range is from 37 to 42 weeks. (about 9 months)
In mammals, pregnancy begins when a fertilized zygote implants in the female's uterus and ends once the fetus leaves the uterus.
Below are average and approximate values ordered by gestation period (note for humans gestational age is counted from the LMP, for other animals the counting method varies, so these figures could be 14 days off):
Plant a seed, watch it grow
We're going to reap what we sow
Yeah, the Earth she does know
She lets us grow what we grow
Yeah, the days they are long
Make you grow up to be strong
Yeah, my woman she will bloom
All the buds we'll take soon
90 days, 90 nights, we'll wait for the light
It will change to the twelve, then to ten it will go
When it hits the ten, we are near heaven
And the time it is ripe, to take all her life
Cut, cut down
Hung, hung upside down
Cure, cure her
Then, then the wait
Cure, cure us