Reference for Niddah 53:22

והא אמר מר

and twenty-three days in that of the embryo.<span class="x" onmousemove="('comment',' The second of the incidents supra. This is quite possible where both embryos were born in the seventh month, since all agree that a child may be viable even if the full number of seven months was not completed. ');">¹⁹</span>

Jastrow

Jastrow