וּֽבְשִׁלְיָתָ֞הּ הַיּוֹצֵ֣ת ׀ מִבֵּ֣ין רַגְלֶ֗יהָ וּבְבָנֶ֙יהָ֙ אֲשֶׁ֣ר תֵּלֵ֔ד כִּֽי־תֹאכְלֵ֥ם בְּחֹֽסֶר־כֹּ֖ל בַּסָּ֑תֶר בְּמָצוֹר֙ וּבְמָצ֔וֹק אֲשֶׁ֨ר יָצִ֥יק לְךָ֛ אֹיִבְךָ֖ בִּשְׁעָרֶֽיךָ׃
Y para con su chiquita que sale de entre sus pies, y para con sus hijos que pariere; pues los comerá escondidamente, á falta de todo, en el cerco y en el apuro con que tu enemigo te oprimirá en tus ciudades.
Rashi
ובשליתה AND TOWARDS HER שליה — i.e. towards her little children; towards all these will her eye be evil when she eats one of them so that she will not give of the flesh to those that are still with her (to those that are still living).
Ibn Ezra
The placenta is the place where the fetus lives while in its mother’s womb.
Rashbam
שליתה, according to the Talmud Niddah 24, literally her afterbirth. The Talmud, in this case quotes the peshat, plain meaning.