Conception, Gestation, and Determination of Fetal Sex

If someone’s wife conceived, and he said [a prayer], “Let it be [God’s] will that my wife shall give birth to a male [child]”—this is a prayer in vain. [ . . . ]

[Hebrew] It has been taught [in a baraita]: For the first three days, one should ask for [divine] mercy that [the seed] will not decompose.

From three to forty [days], one should ask for [divine] mercy that [the fetus] will be male.

From forty days to three months, one should ask for [divine] mercy that [the fetus] will not be a sandal [compressed fetus].

From three to six [months], one should ask for [divine] mercy that [the fetus] will not be stillborn.

From six to nine [months], one should ask for [divine] mercy that [the fetus] will come out safely.

However, does this plea for mercy have any effect? Did not R. Isaac ben R. Ami say: If a man emits seed first, [the woman] gives birth to a female [child]? But if a woman emits seed first, she gives birth to a male [child]. As it is said: If a woman emits seed, she will give birth to a male [child] (Leviticus 12:2).

[If that is the case,] what are we dealing with [regarding the prayer for a male child]?

[This is only effective] when both [man and woman] emit seed at the same time.