The Mitzva of having children is to have a boy and a girl. If someone gives birth to a Tumtum (who's organ is covered by a membrane and we can't tell if it's a boy or a girl) he's not Yoitzeh the Mitzvah (with another child,) even according to the Rambam that holds that from the Torah, even if one is in doubt whether he had fulfilled a Mitzvah or not, he's Yoitze (but the Rabanan requires him to make sure the Mitzvah is definitely done.) Since the child as is cannot reproduce, so it doesn't count towards the Mitzvah of P'ru Ur'vu.
If the membrane of the Tumtum rips and he's found to be a male, according to the Rambam that Paskins that he's able to have children, then he can be counted as a male child towards the Mitzvah of P'ru Ur'vu. The Rosh Paskins that it's a Sufeik whether it can have children, so he's only Sufeik Yoitze.
If it rips and she's found to be a female, then Tzurech Iyun if she can have children. |
Minchas Chinuch 
