3,297. A Yavam Disqualifies but Does Not Enable
Terumos 8:4
If the pregnant daughter of a Yisroel was married to a kohein who died, her servants may not eat terumah because of the fetus. This is because only a born child enables others to eat terumah, not a fetus. If the fetus is a chalal (and the widow has other children, who are valid kohanim), then the fetus does not disqualify the servants from eating terumah. Rather, they may eat it because of the children who are valid kohanim. Once this chalal is born, the servants may no longer eat terumah.
Terumos 8:5
A yavam (in halacha 8:1) is as follows: If the daughter of a Yisroel must perform yibum with a kohein, she may not eat terumah. This is derived from Leviticus 22:11: “When a kohein acquires a soul,” and this man has not yet acquired her. However, if the daughter of a kohein must perform yibum with a Yisroel, she may not eat terumah because of the yavam, as per verse 13: “She shall return to her father’s house as in her maidenhood,” which excludes a woman awaiting yibum.