A Baby Boy or a Baby Girl?
Without modern technologies that might allow manipulation of gender preference, it is clear that only the Holy One decides who will come into this world. However, there appears to be a hint (remez) in the Torah, specifically in Parshat Tazria-Metzora, about the “mechanism” determining a baby’s gender. I’d like to share some fascinating insights on this topic.
These insights were inspired by the commentary on the second verse of Parshat Tazria in the ArtScroll book Sforno: Commentary on the Torah by Rabbi Ovadiah Sforno, beautifully explained by Rav Philip Pelcovitz. Sforno, a renowned Torah scholar and physician in Italy (later in Bologna), taught Torah and practised medicine until he died in 1550. His dual expertise lends unique depth to his commentary.
While there have been popular works addressing gender determination and the timing of tashmish (intercourse), I suspect there is additional Jewish literature on this topic that I am unaware of. I previously sent you an email about basic genetic principles, and I’ve attached a “genetic article” to this message to avoid repeating chromosome explanations here.
The second verse of Parshat Tazria states:
“Speak to the children of Israel, saying: If a woman conceives [‘tazria’ in Hebrew] and bears a male child, then she shall be unclean for seven days, as in the days of her impurity she shall be unclean.” (Leviticus 12:2)
Our Rabbis interpret this verse to suggest that if a woman “emits seed” first (zera, contained in the word tazria), a baby boy is likely to be born. Here, “emits seed” refers to ovulation (biutz).
Sforno’s commentary on this verse, though complex, is clearly explained by Rav Pelcovitz (with assistance from Dr. Fred Rosner and Rav David Cohen). In my own words, with slight modifications:
If a woman ovulates before the man emits his seed (sperm), her egg may lose some “vitality” by the time the sperm arrives. The sperm, being “fresher,” becomes dominant relative to the “older” egg (which may be hours or days old). Conversely, if the woman ovulates after the man emits his seed, the sperm may lose potency, and the egg becomes dominant.
It is well-known that vaginal fluid is typically acidic (low pH). During ovulation, it becomes more alkaline. This is key to understanding the gender determination process:
The egg contains two X chromosomes, while sperm carries either an X or a Y chromosome. The woman contributes an X, and the man contributes either an X or a Y.
An X from the woman combined with an X from the man results in XX (a girl).
An X from the woman combined with a Y from the man results in XY (a boy).
The Y chromosome, which determines a male child, is less stable in an acidic environment. If the vaginal fluid is acidic (before ovulation), the Y chromosome in sperm is less likely to survive, increasing the chance that the man’s X chromosome will combine with the woman’s X chromosome, resulting in a girl (XX). During ovulation, the vaginal fluid becomes alkaline, creating a more favorable environment for the Y chromosome. This increases the likelihood of the Y chromosome surviving to combine with the woman’s X chromosome, resulting in a boy (XY).
Thus, the Torah’s statement, “If a woman conceives [tazria] and bears a male child,” can be understood as follows: If a woman tazria (ovulates first), the resulting alkaline vaginal environment (caused by ovulation) favors the survival of the Y chromosome, making it more likely to produce a male child (XY).
This topic beautifully blends Torah wisdom with medical insights. I’d welcome any comments or additional perspectives that could further clarify this subject. If you know of relevant articles on the “boy-girl” topic, please share them. Time permitting, and with appropriate sources, I hope to explore this further in the future.
Shabbat Shalom