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Fertilization, step by step
Fertilization, a happy combination of circumstances?
Prerequisite for fertilization: a sperm must meet an egg. A priori, nothing very difficult. But for this to work and for there to be fertilization, we must have had intercourse within 24 to 48 hours of ovulation.
Knowing that the survival rate of a sperm is 72 hours on average and the egg only remains fertile for 12 to 24 hours, the probability of conceiving a child in a 28-day menstrual cycle is therefore quite low. Especially since other parameters must be taken into account, such as the good quality of the ovum and sperm, possible health problems… Also, it is quite normal that we have to try several times before achieving fertilization and giving birth, 9 months later, to a small end!
Hence the interest in knowing your menstrual cycle well (especially if it is irregular). In order not to get confused in the information, we use simple tools to locate his ovulation date.
In video: The clear egg is rare, but it does exist
On the way to fertilization
During sex, the vagina will collect millions of sperm. Made up of a head and a flagellum, they will try to survive and make their way to the egg to fertilize it. However, the road is long and winding to reach the uterine tubes where this fertilization will take place.
Through the cervical mucus, 50% of sperm are thus eliminated, in particular those which have morphological anomalies (absence of head, flagellum, not fast enough…). They are indeed unable to fertilize the egg. The others continue on their way. Barely 1% of the sperm from the ejaculate make it through the cervix and uterus.
The race against time continues! While the egg has been expelled from ovary and slides into one of the fallopian tubes, the spermatozoa – now in the uterus – will go up to the tube where the egg “hides”. The few hundred remaining sperm try to get closer to their target. Despite the few centimeters that remain to be covered, it represents a huge effort for them as they are on average only 0,005 centimeters.
The meeting between sperm and egg
About 2/3 of the fallopian tube, the sperm join the egg. Only one will be the lucky one: the one who will succeed in crossing the envelope protecting the ovum and entering it. This is fertilization! By penetrating the ovum, the “victorious” sperm loses its flagellum and then sets up a sort of impassable barrier around it in order to prevent other spermatozoa from joining it. The great and wonderful adventure of life can then begin … Next step: implantation!