Period
Menstruation is produced by the flaking of the endometrium, the innermost lining of the uterus which has the function of receiving and nourishing the fetus during a possible pregnancy.
In the fertile period of every woman, from menarche to menopause, the endometrium goes against rather regular cyclical changes, supported by changes in hormone levels (LH, FSH, estrogen and progesterone).
In the first phase of the menstrual cycle there is the exfoliation of the external endometrial surface, formed by columnar ciliate cells that overhang blood, lymphatic and mucus-producing glands. Thus menstruation begins, small blood losses (around 40 ml in all) mixed with mucus and cellular residues. At the same time, the growth of some follicles begins in the ovary, but only one of them will be brought to complete maturation.
Once menstruation has ended, the superficial circulation of the endometrium is gradually reconstituted, which increases gradually until ovulation. At this point, the mature follicle releases the egg cell, which migrates into the fallopian tubes to be fertilized by the spermatozoa. If this magical event takes place, conception begins.
Fertilization
From the fusion of the genetic patrimony of the spermatozoon with that of the oocyte, a cell called zygote originates, which goes against a long series of mitotic divisions, to form a cluster of cells, called blastula, shaped like a blackberry. It will be just the blastula, about a week after fertilization, to implant itself in the maternal endometrium, thus concluding the phase of conception.
The implantation phase also lasts about seven days and consists of three distinct events: the approach to the endometrium, its adhesion to the same and the last phase of penetration (invasion). "Magically", therefore, the plant ends around the 14th day after fertilization, or the 28th day of the menstrual cycle, when menstruation would return without pregnancy.
During Pregnancy
According to what has been said, menstruation NEVER occurs during pregnancy, precisely because their appearance would signal an endometrial exfoliation and the loss of the fetus; if anything, during the initial stages of gestation, the woman may experience "false menstruation", small bleeding losses with a completely different biological significance.
At the time of implantation, for example, the woman may experience a slight blood loss, which lasts only two or three days with a limited flow but often sufficient to temporarily "hide" the state of pregnancy.
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Common questions
Is the absence of menstruation always synonymous with pregnancy?
The delay or non-arrival of menstruation after the menarche (the woman's first menstrual flow) is not necessarily an indication of ongoing pregnancy. Strong stress, worries, strict diets, rapid weight loss, excessive physical activity, nutritional deficiencies of various kinds, gynecological infections or systemic diseases, can be accompanied by amenorrhea (disappearance of the menstrual cycle for at least three months) and oligomenorrhea (menstruation spaced by intervals longer than canons 28-30 days).
Can you risk a pregnancy by having sex during menstruation?
The chances of getting pregnant due to sexual intercourse consumed during menstruation are low, but absolutely not null.
Not all menstrual cycles, in fact, have exactly the same duration and the first phase, the one that goes from the last menstruation to ovulation, varies. Furthermore, spermatozoa can survive in the cervix for up to 3-4 days after intercourse.
How long does it take for menstruation to reappear after pregnancy?
During breastfeeding ovulation continues to be suspended, provided that the lactation hormones are secreted on a regular basis, so that the newborn is exclusively breastfed, both day and night, at regular intervals and less than four hours . Normally menstruation will reappear only at the end of breastfeeding and in any case within six months of delivery.
Unfortunately the contraceptive efficacy of breastfeeding, although good, is not absolute, so much so that some women may experience the reappearance of menstruation already during lactation; again, however, especially in the first weeks after pregnancy, it may simply be "false menstruation", in the specific case of so-called lochiazioni, blood loss combined with pregnancy residues that occur during the puerperium.
False menstruation in pregnancy, when to worry?
There may be many reasons for episodes of more or less intense bleeding during pregnancy. Sometimes these are serious problems, for example for an ectopic pregnancy or placental abnormalities, sometimes not. For this reason, it is important to report any false menstruation during pregnancy to your gynecologist or treating doctor.
