Chizkuni's alternate suggestion for having male children

Note: Slightly adult-themed, just like the other recent Tazria post. You might wish to skip this.

This ties into two previous parshablog posts. One is the previous post, of the famous midrash in Niddah that if the woman gives forth seed first, she will bear a male child. The second concerns another famous midrash of how the Israelite women in Egypt gave birth to sextuplets. Ibn Ezra connects it to contemporary medicine, which (falsely) believed that a woman had seven chambers in the womb. To expand to a perush based on the most expansive theory: The ones on one side were for males; on the other side for females, and the one in the middle for an androgynus, so there would not be a seventh, for that would not be a blessing. This is the medical theory propounded by Bartholomeus Anglicus.

Here is the beginning of the commentary of Chizkuni on the parsha, skipping down 8 lines, to וילדה זכר. He is surely thinking of the famous midrash in masechet Niddah, about how to attain male offspring:

"And gives birth to a male child": It is found in a sefer, in Toldot {generations? a book on reproduction}: There is in a woman seven holes {=chambers of the womb}, three on the right and three on the left, and one in the middle. When the {man's} seed enters into that of the right, she gives birth to a male; and if it enters into that of the left, she gives birth to a female; and if it enters the middle one, she gives birth to a tumtum {one of indeterminate gender, where the genitals are internal} or a hermaphrodite.

When she sleeps, soon after intercourse, on her right side, the sperm enters into those holes {chambers} of the right, and she gives birth to a male; and the ritual impurity speeds to go out, and therefore, she is only ritually impure for seven days, and is ritually pure for thirty-three days.

And when she sleeps, soon after intercourse, one her left side, the sperm enters in the holes of the left, and she gives birth to a female, and the ritual impurity does not speed to leave; therefore, she is ritually impure for two weeks.

And this is {the intent of the verse in Shir Hashirim 8:3}:

ג שְׂמֹאלוֹ תַּחַת רֹאשִׁי, וִימִינוֹ תְּחַבְּקֵנִי.

3 His left hand should be under my head, and his right hand should embrace me.

in order to beget male-children.

If I may be so bold to explain Chizkuni's explanation of this pasuk from Shir Hashirim. The pasuk refers to the lovers after they have engaged in intercourse. And they are now sleeping together, or resting together. On which side is the man sleeping, on his left or his right side? His left hand is under her head, rather than on top of it. And his right hand is embracing her, presumably resting on top of her. This only works if he is resting on his left side, rather than his right side.

What is the woman's orientation? She could be facing him, or else facing away from him, such that they are "spooning." Chizkuni's assumption appears to be that the woman is facing him. Thus, if he is on his left side, she is on her right side, and so the seed will enter one of the right chambers, and she will bear a son rather than a daughter.

I would also note that the pasuk seems to be in the imperative, or at the least, that is how it is translated in the JPS translation. Perhaps this is something Chizkuni also picked up upon. He should do X and Y. Why? To have male children.