Fetal Immersion?
‘The Fetus Is A Limb Of Its Mother’
(Yevamos 78a)
The Gemara (Temurah 25b) cites a Tannaic dispute as to whether a fetus is considered a limb of its mother (“ubbar yerech immo”) or an independent entity (“ubbar lav yerech immo”).
Rava on our daf states that if a pregnant woman converts to Judaism, her tevilah when converting covers her fetus as well. Therefore, when her child is born it need not immerse in a mikveh to become Jewish.
Initially, the Gemara assumes that this halacha is based on the principle that a fetus is viewed as part of her mother’s body.
No Interposition
Later, though, the Gemara suggests that this halacha conforms even with the view that “ubbar lav yerech immo.” Even though the fetus is not a limb of its mother, it still immersed in a mikveh (together with its mother) and therefore need not immerse in a mikveh again.
Immersion Without Circumcision?
The Ritva (Yevamos 47b) maintains that the fetus is fully Jewish at birth even it is a boy. Generally, the conversion process for male converts entails both tevilah and milah, but since at the time of the fetus’s immersion it was unfit to be circumcised, it assumed the status of a female ger whose conversion is effected with tevilah alone.
The Ramban and Rashba disagree; they maintain that the baby boy is not fully Jewish until he is circumcised.
Pidyon HaBen
The Mishnah (Bechoros 46a) states that if a woman converts while she is pregnant with her bechor, he is subject to the mitzvah of pidyon haben since he was born to a Jewish mother.
The Keren Orah (Yevamos 78a) notes that this mishnah seems to support Ritva’s position that the fetus becomes a full-fledged convert at the time of its mother’s conversion. According to the Ramban, it is difficult to understand why he is subject to the mitzvah of pidyon haben considering that he wasn’t born fully Jewish.
The Point Of Conversion
In answer, the Keren Orah explains that the tanna of the mishnah in Bechoros maintains that “ubbar yerech immo.” According to this position, the fetus is completely Jewish when born. When his mother converted, her fetus automatically became Jewish by virtue of the fact that it was part of her body (not because it personally underwent a conversion process).
The Ramban maintains that the baby boy is not fully Jewish until he is circumcised only according to the position that “ubbar lav yerech immo.”