The time during which the embryo or fetus gets fully developed in the uterus is called the gestation period or pregnancy. But in the case of gestation period for humans, the accurate time of ovulation and therefore the time of fertilization is hard to determine. So most of the time, the start of the gestation period is taken to be from the beginning of the previous menstrual period. Also, there are many more factors that decide the time that the embryo takes to develop into a full-grown baby.
How Long is the Gestation Period for Humans
This interval between the last menstrual period to childbirth is roughly 40 weeks. Thus, the gestation period for humans in days can be calculated as 280 days. However, the actual gestation period, as compared to other mammals, is around 267 days. But then what is the average gestation period for humans? It is taken to be about 259 to 294 days. Therefore, if the birth occurs in between 259 to 294 days, it is considered to be normal, while if it takes place before 259 days, it is termed as pre-term, and if it happens after 294 days, it is called post term.
To understand the human gestation period, it is important to analyze the various stages of pregnancy development. In the following paragraphs, the human gestation period has been divided into periods of three months, for the purpose of better understanding.
Gestation Stages - First Three months
At the beginning of this period, the egg gets fertilized and attaches itself to the wall of the womb. The growth starts with the formation of a heart and spinal cord. In the second month, the growth proceeds to more human form, and head and facial features start taking shape along with feet and muscles. Some time after the end of the second month, the heartbeat can be sensed by using ultrasound. At this point, the fetus has grown ten thousand times bigger than that at the time of conception. The third month sees the formation of the finger, toes and the sexual organs. By the end of the last week, the baby becomes around 8cm long and is less susceptible to infections. So the chances of miscarriages are reduced.
Gestation Stages - Second Three months
Fine hair start to appear all over the body of the baby during the beginning of the fourth month. Now it can curl its fingers. The fifth month witnesses the development of the senses of the baby along with its other body parts. A white substance engulfs the baby at this point, to protect its skin. At the end of the sixth month, the baby gains more control over its movements, and its digestive and immune system start to take form.
Gestation Stages - Last Three months
The functioning of almost all the major organs, except the lungs, begins. Most importantly, the brain development commences during the seventh month. In the eight month, the baby becomes capable of opening and closing its eyes, and its position is almost like it would be during birth. Even during the ninth month, growth is not fully complete but its full formation has taken place. After this point, the baby gains around 200g per week. More than 90% babies do not arrive at the predicted date.
Although the above account of the gestation period for humans is quite detailed, the actual process is quite complex. Even if you can determine the pregnancy due date yourself, considering the last menstrual period as the starting point, consulting a doctor is always helpful.