gestation period


Also found in: Dictionary, Thesaurus, Medical, Legal, Wikipedia.

Gestation period

In mammals, the interval between fertilization and birth. It covers the total period of development of the offspring, which consists of a preimplantation phase (from fertilization to implantation in the mother's womb), an embryonic phase (from implantation to the formation of recognizable organs), and a fetal phase (from organ formation to birth).

There is widespread confusion over the duration of the gestation period in humans because of the way in which it is defined medically. The time of ovulation, and hence the time of fertilization, is difficult to determine in humans, so for purely practical reasons doctors measure the duration of pregnancy as the interval between the last menstrual period and birth, which is typically about 40 weeks or 280 days. For comparison with other mammals, however, the true gestation period between fertilization and birth in humans is about 267 days.

The length of the gestation period in mammals depends primarily on body size and the state of development of the offspring at birth. Large-bodied mothers have big offspring that take longer to develop, and development is also prolonged for offspring that are born at an advanced stage of development. Compared to all other mammals, human beings are found to have one of the longest gestation periods relative to body size.

One remarkable feature of mammalian gestation periods is that they show very little variability within a species. After excluding exceptional cases, departures from the average usually lie in a range of no more than ±4%. This is one of the smallest degrees of variability found in any biological dimension. See Reproductive system

gestation period

[jə′stā·shən ‚pir·ē·əd]
(embryology)
The period in mammals from fertilization to birth.
References in periodicals archive ?
When we infer the gestation period of Sunda pangolin, calculated from the start and end date of housing a female together with a male, to the date of parturition separately, we can calculate a "likely" minimum and maximum gestation period.
The gestation period could be anything from 85 to 105 days.
Frozen embryo babies typically had a longer gestation period than those born from fresh embryos, the research also found.
The kid was born with a weight of 1.3 kg to the foster mother with normal gestation period on 9th March' 2012 after two years of standardization and efforts of Dr.
(a) that she is entitled to the termination of her pregnancy upon request during the first 12 weeks of the gestation period;
What - to the nearest month - is the gestation period of a horse?
The animals have a slow gestation period of 9 1/2 months and typically have one calf per year.
The rating is constrained by the early stage of project implementation having long gestation period and elevated project implementation risk.
In New York, many coyotes give birth to 4-6 pups in March and April, following a two-month gestation period. Active rearing occurs from spring through early summer.
We also determined periods of reproductive activity such as fertilization, gestation period and size at maturity.