Conception, fertilization and implantation
How natural conception takes place
Most women know that at ejaculation, a man deposits millions of spermatozoa into the vagina. The vast majority of these will not make it past the womb. Only a few thousand get to where the egg (ovum) is, which is usually at the outer end of one of the fallopian tubes. Only one of these will actually fertilize the egg. The sperm and egg fuse to form one cell, called a zygote.
This cell will undergo division and vast changes in the following days, resulting in a mature baby made up of billions of cells; most of them specialized for a particular function about 40 weeks later.
What happens 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 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 –
Site of implantation
After the tubal journey, lasting 4 to 5 days, the ball of cells, now numbering 50 to 60, reaches the uterine cavity. Implantation commences around seven days after fertilization and is complete by day 14.
Evidence of implantation
In most cases there is no sign or symptom that herald implantation. In a few cases, there may be light vaginal bleeding. Since this occurs about three weeks or so after the last period –
The serious business of turning this mass of cells into a human being starts after implantation. Even though it is still tiny in size, organs start forming at three weeks and their formation is complete by eight weeks.
Beyond this point, only maturation and increase in size is taking place. There is no new organ formation.
Even though the fetus is only about 2.3 cm in length (less than one inch) at eight weeks, the nose, ears, finger-