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The pregnancy period is broadly divided into three trimesters. The first trimester begins from the first week and continues till the 12th week. The second trimester has its duration from 12 to 24 weeks and the second trimester goes from 24 to 40 weeks. But the development of the baby occurs in every week. However there is a need to look at the period for each respective month. During the first week of the first month the cells split into two after thirty hours conception. Till the third day the cell (zygote) divides into 16 cells. On the fourth and fifth day the zygote migrates to the uterus from the fallopian tube and on the last day of the week the zygote which is now known as blastocyst plants itself into the plump uterine lining (endometrium). On the second week of the firs month the baby has grown as much as the size of the grain or rice. The process of diving cells goes on rapidly which is the basis of forming the various body systems. The slowly developing neural tube finally become the central nervous system (brain and spinal cord). The baby, now an embryo is around 3mm in length. By this stage, a special hormone is secreted to avoid mother from having menstrual period. |
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