- Rabba bar Sheila quotes Rav Mattana in the name of Shmuel as teaching that they once identified an afterbirth as connected to a birth that had taken place ten days before.
- Rabba bar bar Ḥana quotes Rabbi Yoḥanan as teaching that they once identified an afterbirth as connected to a birth that had taken place 23 days before (Rav Yosef argued that it was 24 days).
- Rav Aḥa son of Rav Avira quotes Rabbi Yitzḥak as teaching that once the birth of a second child followed the first birth that had taken place 33 days before (Rav Yosef argues that it was 34 days).
Finally, Rabbi Avin bar Rav Adda quotes Rav Menaḥem ish Kfar She’arim (or, perhaps, Beit She’arim) as saying there was an incident with a woman who was pregnant with twins where the birth of the second child took place 33 days after the first – Yehuda and Ḥizkiyya the sons of Rabbi Ḥiyya.
These statements, and, in particular, the testimony regarding Yehuda and Ḥizkiyya the sons of Rabbi Ḥiyya, appear to present a problem to Rav who ruled that two children in a single pregnancy are always born immediately after one another (see yesterday’s daf). This is particularly difficult, since Rav was Rabbi Ḥiyya’s nephew and must have known the circumstances of his cousins’ birth.
Tosafot explain that Rav recognized the possibility that there may be a longer time difference between births, but since it was such an unusual occurrence it was not taken into consideration by the halakha.
The Ran suggests that Rav’s statement only applied to situations where both fetuses were fully developed. If one had not yet developed, it may remain in utero even for an extended period of time.
In the Gemara, Abaye explains the circumstances of Yehuda and Ḥizkiyya’s birth based on the Rabbinic idea that normal gestation cycles were either seven or nine months long. Although this approach is rejected by modern science, the possibility of superfetation – of double pregnancy where a fetus is formed during an existing pregnancy – does exist in rare cases.