The Torah forbids Kohanim from contracting Tum’at Met – the status of ritual impurity that one obtains through contact with a human corpse. A Kohen may thus not enter a cemetery or be under the same roof as a human corpse.

When the Torah introduces this prohibition, it says, "Emor El Ha’kohanim Beneh Aharon…" ("Tell the Kohanim, the sons of Aharon…"). The Sages inferred from the phrase "Beneh Aharon" ("the sons of Aharon") that this prohibition applies only to male Kohanim, and not to females. As such, it is entirely permissible for a Kohen’s daughters to enter a cemetery and attend a funeral, as the prohibition of Tum’at Kohanim applies only to males.

If a Kohen’s wife is pregnant, and she is informed on the basis of an ultrasound that the fetus is a boy, is she allowed to enter a cemetery, or must she avoid Tum’at Met because she is carrying a male Kohen? If she is pregnant with a girl, then she is certainly allowed to visit a cemetery, since neither she nor the fetus is included in the prohibition of Tum’at Kohanim. But if she is pregnant with a boy, is she required to stay away from cemeteries?

Hacham Ovadia Yosef, in his work Yabia Omer, rules that a Kohen’s wife may attend funerals and visit cemeteries during pregnancy, even if she knows that the fetus is male. An unborn fetus is considered part of the mother, and therefore the prohibition of Tum’at Kohanim does not apply, even if it is ascertained that it is male. Just as the woman herself is allowed to come in contact with Tum’a, her fetus is likewise allowed to come in contact with Tum’a.

However, this applies only during the pregnancy. As soon as a male Kohen is born, the prohibition of Tum’at Kohanim immediately takes effect, even during infancy. Rav Yosef Shalom Elyashiv thus ruled that when a Kohen’s wife is pregnant, she should make a point of determining the child’s gender, so that if the child is a boy, she can prepare to avoid Tum’at Met from the moment of birth. Many hospitals are arranged in such a way that people in the maternity ward become Tameh when a patient in the hospital dies. When a Kohen’s wife is pregnant, the couple should determine whether the child is a boy, and, if it is, they should ensure to have the delivery performed in a hospital that has arrangements to ensure that there is no Tum’at Met in the maternity ward (assuming, of course, there is no life-threatening need to have the delivery in a different hospital). This can be ascertained through consultation with hospital administration personnel.

Rav Elyashiv’s ruling is cited in the work Mamlechet Kohanim (p. 169).

Summary: It is permissible for a Kohen’s wife to enter a cemetery or attend a funeral during pregnancy, even if she knows the fetus is male. During pregnancy, a Kohen’s wife should determine the child’s gender through an ultrasound, and if it is a boy, she should arrange to have the delivery performed in a hospital that is arranged in such a way that the infant will not become Tameh.