The term gestation refers to the process through which a fetus or embryo develops in a female mammal. Generally, gestation applies to mammals as well as some specific non-mammals. During pregnancy, mammals can have only one gestation or even more than one gestation at a go. Gestation period refers to the time or duration over which gestation happens. In human beings, gestational age applies to the age of the fetus or embryo including two weeks. In other mammals, the gestation period does not necessarily include extra time. In humans, the fetal age is calculated from the start date a woman’s previous menstrual period. Pregnancy in mammals starts after implantation of a zygote in the uterus wall and ends when the fetus gets out of the uterus. In human beings, the gestation period is divided into three stages commonly known as trimesters. Each trimester lasts for about three months. Usually, the initial trimester lasts up to week 13, the second runs from week 14 through to week 27 and the third from week 28 to week 42. Generally, birth in human beings occurs at around week 40 though anytime between week 37 and 42 is considered normal.
Pre and Post-term Births
The average gestation period in human beings is about 38 weeks. A birth is termed as pre-term when the fetus is removed from the uterus before the 37th week. Children who are born before week 37 are vulnerable to certain health risks. Pre-term birth is a leading cause of infant deaths. It is estimated than one in every six deaths in infants is as a result of pre-term birth. Post-term births happen when a pregnancy stays for more than 42 weeks. In most cases, when this happens, labor is induced to force the birth of the baby before this period is exceeded. The other common approach used in such cases is surgical operation.