פּירוש אויף ויקרא 12:5

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

ואם נקבה תלד, and if she gives birth to a female child, etc. Why does the Torah not describe the birth with the word וילדה as it did in the case of a male child? Torat Kohanim write: "how would I have known that the legislation of impurity due to giving birth applies not only in the case of a female child being born but also if a child of undetermined sex or a bisexual child had been born? The Torah writes אם נקבה תלד וטמאה, "if she gives birth to a female she is ritually impure" to teach us that the basic ritual impurity depends on the birth process not on the sex of the baby being born." I most certainly do not want to dispute what Torat Kohanim has written, but I do want to add something to that comment. Perhaps the author of this comment arrives at his conclusion by the failure of the Torah to write simply וכי תלד נקבה, "if she gives birth to a female," with the verb at the beginning of the sentence instead of at its end. This latter sequence of the words would have indicated that what the woman gave birth to would result in her becoming ritually impure only if the baby was definitely female. As it is, the wording allows also for babies of indeterminate sex.

וששים יום וששת ימים תשב על דמי טהרה, “and she will remain in a state of blood of purification for sixty six days.” The Torah made a minor change in the description of the blood during those sixty six days, calling it על דמי טהרה, whereas the thirty three days of the parallel period after the birth of a male bay are called as remaining בדמי טהרה. The reason is that after the birth of a male child the mother has to observe these thirty three days under all circumstances, whereas in the case of a female child having been born, it is theoretically possible that the mother has already aborted a new embryo during the 80 days since she gave birth, in which case these days might not have to be observed in full.