The onset of a woman's menstrual cycle is the indication that your body is preparing the uterus for childbirth. As mentioned in previous articles, ovulation starts from the first day menstrual bleeding commenced. Typically, ovulation usually occurs within 14 days of the commencement of this menstruation cycle. This is called the fertility period. This period will last up to 12- 14 days (will vary from one woman to another) and is the ideal time to have intercourse if you are planning to have a child.
During this time an ovum enters the Fallopian tube. The Fallopian tubes are very thin. Consists of fine fibers. The fibers move in such a way that they push the ovum toward the uterus. The ovum will remain in the fallopian tube for up to 48 hours. However, it remains fertile for only half of that time. Meanwhile, after intercourse sperm can remain active inside the female reproductive system for up to 72 hours.
When sperm is released into the vagina it moves into the uterus using its tails across the Cervia. Of the more than 400 million sperm that is initially deposited in the vagina, only around tens of thousands enter the womb. Out of which a few hundred make it up to the fallopian tube. This journey takes 2 - 7 hours. If there is an ovum when the sperm enters the fallopian tube, one of these sperm will penetrate the outer membrane of the ovum. This is called fertilization. Fertilization happens in the middle part of the fallopian tube.
When the ovum is fertilized, one of its two nuclei is the nucleus of the sperm and the other is the nucleus of the egg. Each of these nuclei will consist of 23 chromosomes. When combined it will create 23 pairs of chromosomes. All of this takes less than 12 hours. The fertilized ovum will now commence its process of developing into an embryo. This is also the time the embryo commences its movement into the womb to embed itself onto the wall of the womb. Here it shall remain for a period of 38 weeks!
The date of pregnancy is calculated from the date of the last menstruation. This is not the day you became pregnant. But we can estimate that the date of pregnancy was two weeks after the last menstruation day.
Article by Dr. Krishan de Silva, Obstetrician and Gynecologist at Balapitiya Base Hospital.