Reference for Yevamot 134:1
אין חוששין למיעוטא ואיבעית אימא לעולם קסבר חוששין למיעוטא דעבדינן ליה תקנתא כרב נחמן אמר שמואל
that no provision need be made against the less usual cases.<span class="x" onmousemove="('comment',' Lit., 'a minority'. I.e., against the possibility that the embryo might be born a viable male. Against the possibility of male births there is the equal possibility of female births, and by adding the minority of miscarrying women to the half of female births, the male births are found to form only a minority. ');"><sup>1</sup></span> Or if you prefer I might say that he<span class="x" onmousemove="('comment',' R. Simeon. ');"><sup>2</sup></span> is of the opinion that provision in fact must be made against the less usual cases also, [but here] a special arrangement might be made<span class="x" onmousemove="('comment',' The embryo is allotted as his share a portion of the estate exclusive of the slaves, who consequently form a portion of the shares of the living brothers, who, as their owners, bestow upon the slaves the right of eating terumah. Where, however, there are only daughters, such an arrangement cannot be made, since in such a case the embryo, in case he is born a viable male, is the sole heir and owner. ');"><sup>3</sup></span>