Gestation Period for Humans
Gestation period for humans refers to the time during which embryo or fetus develops inside a mother's womb or the period from conception to birth which is estimated to be 260 days.
Gestation period or the duration of pregnancy cannot be precisely calculated since exact time of ovulation and fertilization cannot be identified. Therefore, gestation period is determined from the first day of the last menstrual period. However, other factors as well determine gestation period in humans.
The interval of gestation period in humans is estimated to be around 40 weeks or 280 days. Gestation period in humans may normally last from 37 to 42 weeks or between 259 and 294 days. That means that in average pregnancy the birth occurs during this period of time. This is considered to be healthy pregnancy. However, when birth occurs before 37 gestation weeks it is considered pre-term and if labor happens after 294 days or 42 gestation weeks it is called post-term. Pre-term birth is risky due to underdevelopment while post-term is dangerous because of septic poisoning.
There are different stages of gestation development that can clarify length of pregnancy period. Gestation period in humans can be divided into three trimesters, each three months long.
The First Trimester
At the beginning of the first trimester, the mature egg is fertilized and implanted into the womb. During the first month the lungs are formed, the heart starts beating and the spinal cord is growing. In the second month head and facial features are shaping, including eyes and mouth. Hands and feet are also forming. At the beginning of the third month heartbeat of the fetus can be heard in an ultrasound. The fetus is around 3 cm long, fingers and toes are formed as well as sexual organs. At the end of third month, fetus is approximately 8 cm long and develops immunity towards infections thus the risk of miscarriage is lower.
The Second Trimester
At the start of the fourth month, the baby has fine hair covering the body and can curl the fingers. In the fifth month, senses are developed and the skin is protected by a layer of a waxy secretion. At the end of the sixth month, the baby has strong and coordinated movements and the digestive and immune system are forming.
The Third Trimester
At the beginning of the last three months, almost every organ, except for the lungs, begins to function. During the seventh month the brain starts to develop. The movements decrease because of the baby’s large size. The baby is positioned for the birth, with its head down. The baby is fully formed in the ninth month and gains around 200 g per week.