Do women have to give up bad habits to get healthy children?

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Jan 21, 2020 20:22
Today morning I visited a lecture about gametogenesis. It is a process of developing and maturing of sperms and eggs during the ontogenesis of an individual. I'd already been familiar with the topic, but the lecture reminded me a really common mistake that people make discussing reproduction health and responsible reproduction. Most people consider women have to refrain from drinking alcohol, taking drugs, smoking, etc in order to get healthy offspring in the future. Women have been constantly criticized because of it, while society does not make such demands of men. Aside from the fact this is simply unfair, this is biologically incorrect. It recalls me of Nicolaas Hartsoeker's hypothesis about the role of men and women in humans' reproduction. Thus, he suggested that a sperm's head contains a really small but completely formed baby, and a woman just incubates. That's ridiculous!

To pursue my thought, I would like to describe the gametes' maturation process in human in general. Cells-precursors of both types of gametes derive from the same embryonic structure and migrate to the developing gonad during embryogenesis. Then depending on which gonad gametes are in and molecule signaling the gonad produces, the gametes differentiate to sperm stem cells (spermatogonia) or eggs stem cell (oogonium). During the embryonic period, these stem cells only reproduce by simple cell division (called mitosis). The number of oogonia reaches around 7 million up to the seventh month of gestation! Most of them die soon and the rest started a special type of cell division that halves the number of chromosomes in the daughter cells (called meiosis). The point is that meiosis consists of two rounds of divisions and of 7 main phases in general. The timing of this specific cell division during the differentiation of gametes is one of the most important differences between maturation of sperms and eggs. In female embryos, oogonia start meiosis shortly before birth and arrest it at the first phase (at this point they turn to primary oocyte). The primary oocytes remain at rest for up to 50 years (until menopause) in the ovaries: starting at puberty usually one oocyte per month completes the first round of meiosis the day before ovulation turning to the secondary oocyte. Then, in case of fertilization by sperm, it completes the second round of meiosis and launches an embryo development. I would like to emphasize that most of the time oocytes do not divide and remain rest, moreover, in females, eggs stem cells do not divide after birth at all. On the contrary, in males, starting at puberty, sperm stem cells divide constantly to maintain their population in testicles and they produce thousands of matured sperms per second. Thousands per second!

So, I think it is still unclear what it all implies. Let me explain. The point is that alcohol, drugs and other toxic chemicals can't harm a cell that does not divide and remain "frozen" for an ages without any changes. However, cell division can be compromised by some chemicals that imply that daughter cells can inherit incorrect number or structure of chromosomes or other potentially harmful mutations. In the case of gametes, it obviously can cause genetic-determined malformations of the fetus. In the case of the presence of potentially harmful mutations in sperm stem cells, nothing canbe done to get healthy sperms.

To conclude, it would be enough for a woman to refrain from drinking and smoking several woman's periods before she wants to get pregnant (and during pregnancy and breastfeeding indeed) while a man should give up bad habits altogether in order to decrease the risk of genetic damage in sperm stem cells that divide constantly and in sperms themselves.