In the first week after conception, pregnancy practically does not manifest itself in any way, but changes are already beginning to occur in the body. Over the next 9 months (40 weeks), they will become more and more noticeable: the body will begin to rebuild to ensure the full and safe development of the embryo. During pregnancy, the so-called functional systems "mother-fetus" and "mother-placenta-fetus" are formed, the ultimate goal of which is the birth of a healthy child. This mechanism is unique and has no analogues: it is not the embryo that adapts to the characteristics of the mother's body, but the body creates within itself an optimal environment for the development of the fetus. Even before conception, the processes that occur in a woman's body during the menstrual cycle are aimed at preparing suitable conditions for the fertilization of the egg. In a certain phase of the cycle, called ovulation, it is easiest to get pregnant: the cell has matured, all conditions are met.
Menstruation. The menstrual cycle of a woman is divided into several periods:
• menstruation, during which the endometrium lining the walls of the uterus separates and comes out along with the unfertilized egg. This happens if pregnancy did not occur during the previous cycle. With menstruation, the follicular phase of the ovaries begins. The dominant follicle is determined and develops, which will later give life to a mature egg;
• The ovulatory phase occurs approximately on the seventh day of the cycle and lasts about three days. During this time, the follicle reaches maturity and at the end of the phase it breaks, releasing an egg ready for fertilization;
• Ovulation is the process during which the egg leaves the follicle and descends from the ovary into the fallopian tube. This takes about an hour, the cell retains the ability to be fertilized for about another day;
• The luteal phase, which is the second half of the cycle, proceeds differently depending on whether fertilization has occurred or not. Either the implantation of a fertilized egg occurs, or the gradual death of the endometrium.
Conception. Ovulation lasts a short time, and the ability to fertilize the egg lasts only about a day or two. It is impossible to track this process on your own: some women talk about characteristic symptoms and even pain, but this is a very individual and unreliable indicator. Sometimes a characteristic discharge (cervical mucus), an increase in basal temperature can serve as a marker, but all these signs have an error and are not able to give accurate results. Nevertheless, pregnancy can also occur if sexual intercourse took place a few days before ovulation: healthy spermatozoa, entering the uterine cavity, remain viable for 3-4 days.
Implantation of the ovum. Over the next few days, under the influence of muscle contractions and mucosal cilia, the fertilized egg moves towards the exit from the fallopian tube, that is, to the uterus. Approximately in the same period, the process of crushing begins: the cells of the zygote begin to divide, but its total size does not increase, each subsequent cell becomes smaller than the previous one. Having descended into the uterus, the zygote reaches the blastocyst stage in a few days, after which it gets rid of the membrane and implants inside the endometrium - the lining of the uterine walls. Under the influence of the hormone progesterone, aimed at maintaining pregnancy, the endometrium becomes thicker and surrounds the fetal egg from all sides. Implantation allows you to protect the embryo and additionally nourish it with a secret that is produced by the endometrial glands. It usually takes several days from conception to implantation, and the countdown of the first embryonic week does not start from it, but from the moment the zygote is formed.