What happens soon after fertilization?
Things are happening quietly. There is absolutely no way for a woman to tell immediately whether a sexual act has resulted in conception. All those popular novels in which a woman says that "I knew immediately after, that I had conceived" are sheer fantasy.
Within thirty hours of fertilization, the fertilized egg undergoes the first division to form two cells. This is only the beginning of billions of divisions and changes that will take place within the first few weeks of pregnancy.
The dividing ball of cells - which is still quite tiny in size - is, meanwhile, being swept steadily along the tube towards the cavity of the womb, where it will implant.
Does any sign or symptom herald implantation?
In most cases, no. In a few cases,, there may be light vaginal bleeding. Since this occurs about three weeks or so after the last period - and the woman is still unaware of her pregnancy - this light bleeding may be mistaken for a menstrual period. It has been known to cause confusion in dating the pregnancy. However, this problem is easily sorted out using ultrasound scan, provided the woman books for antenatal care within the first half of the pregnancy (which is the norm).
What happens after the embryo has implanted?
The serious business of turning this mass of cells into a human being starts then. Even though it is still tiny in size, organs start forming at three weeks and their formation is complete by eight weeks.
From that point, only maturation and increase in size is taking place.
Even though the fetus is only about 2.3 cm in length (less than one inch) at eight weeks, the nose, ears, finger- and toebuds are already formed.
The absolute sensitivity of this period cannot be overemphasized. Any chemical insults - for example, in the form of drugs taken - during this particular period are likely to have the most profound effect on the fetus.
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