אשה כי תזריע וילדה זכר, the sages in Niddah 31 explain the term תזריע in our verse as “when a woman experiences her orgasm before her male partner the child born from such a union will be a male. The perception underlying this is that the woman’s “seed” is the moisture which she excretes from time to time at the time she engages in physical union with her partner does not enter into the formation of a male embryo. Her “semen” is active in suppressing the effect of the man’s semen. But her blood enters the semen of the male it moistens and provides addition impetus to the man’s semen,

כימי נדבת דותה, for during the first seven days after her giving birth she is like a menstruating woman regarding her ritual status.

וביום השמיני ימול, for by that time the blood of his mother has congealed [dry blood does not confer impurity. Ed.] As a result the baby has become ritually cleansed, no moist blood being attached to it.

בדמי טהרה, although this blood could not have originated from a new ovulation but dates back to the last ovulation before she had become pregnant, whatever had happened at that time is no longer relevant the whole appearance of that blood having changed completely.

TWO WEEKS. Because the excesses increase in the birth of a female.

וכפר עליה, for during all the days that she had been excreting blood her thoughts had been preoccupied with the phenomenon of semen, etc, and she had therefore not been in a fit state of mind to enter the precincts of the Temple and offer sacred matters.