I have the feeling that there is something wrong with the articles and the sentence in general...
Because motives, like concealing the birth of a child or killing one’s own infant in order to avoid stigmatization, did not apply for married women, it was not acceptable within society when they actually did kill their newborn.
I should have added some more context I guess.
This is about infanticide in the 18th-century. It's supposed to mean that unmarried women who got pregnant because they were sexually forced into a relationship couldn´t avoid a trial if they killed their newborn because the patriarchal/religious society punished them heavily in any case. There were more reasons one could think of than to avoid stigmatization which were all mentioned before this sentence in the essay. Those were, for example, not being able to provide for the child and being cast away from the household these women worked in resulting in poverty.