There is no word equivalent to “cuckold” for women.
In medieval times, a man whose wife deceived him with another man was called a cuckold, a pejorative term which fortunately isn’t used much anymore. The origin of the term “cuckold” is revealing. If you are interested in ornithology, the study of birds, you may have come across accounts of the habits of the cuckoo bird. Cuckoos solve the problem of the perpetuation of their species by the simple expedient of laying eggs in other bird’s nests and departing, leaving other birds of another species to raise the young cuckoos.
Once upon a time, observers might signal the approach of a man who was committing adultery with someone’s wife, or who had designs in that direction, by warning the husband with a whispered “cuckoo, cuckoo.” Eventually, the term got changed around to refer to the betrayed not the betrayer and became “cuckold.”
Shakespeare and other authors perpetuated the literary myth that such a man was burdened with a set of horns on his head, which others could see, but of which he was blissfully unaware. It was another version of the truism that the husband, or the wife, is often the last to know. In Italy, one of the most unforgivable insults still is to make the sign of the “cornu” at someone: taking your index and pinkie and putting them on top of your head to resemble horns.
On the issue of bastard children, there are some real legal and moral differences in the situation of single women compared with married ones. If you are single, you might decide to have a child but choose not to get married. You have a right to become a mother without becoming a wife. It’s the contention of many that, as long as you expect nothing of the father, you don’t need to have his consent or, indeed, don’t even need to inform him. It would seem that, if such is your intent, having a child through artificial insemination would be a better alternative, but there is nothing to stop you using the old-fashioned way if this is your decision.
However, if you’re married, any child you have is legally the child of your husband and is assumed to be so socially and emotionally. A husband has the right to certainty of the parenthood of “his” own children. As the lyrics from The King and I caution, “But blossom never ever float from bee to bee to bee.” A basic assumption is that the married woman having an affair has no right to get pregnant by another man. Her body is her own, as is her sexuality; but her children are to be shared for as long as she stays married, and usually after that.
The married woman must be especially scrupulous and fastidious not to let herself get pregnant by her lover rather than by her husband.