I sometimes jokingly refer to having children as spawning – for example, “She went on early mat leave, but has she spawned yet?” A friend of mine recently used the word whelp for the same purpose, as in “She was huge then, but that was before she whelped.”
I enjoyed the sound of that, partly because I could picture someone saying, “Welp, she had the kid,” and partly also just because of the novelty of the usage. Of course we may think it a bit impolite or derogatory to use the term, since it compares birthing humans to birthing dogs. But somehow we don’t have a problem with calling a child a kid, which originally refers to a young goat.
Probably more of the issue is that whelp is itself a derogatory term for a youth – it tends to imply unruly or impertinent behaviour. We may, as a culture, love dogs now – if a person is walking down the street with a young dog, strangers will feel free to come up to it and say, “Oh, puppyyyy, hi, puppyyyyyyy,” et cetera – but our language bears the marks of a different attitude: however much we may like our female lapdogs, bitch is not a nice word.
I’m inclined to think the sound may also have something to do with it. Yes, it sounds like well (especially since we have generally neutralized the wh/w sound distinction) and it has help in it, but it also has echoes of whale and wail and whip and yelp. In fact, it rather sounds like the noise made by a young dog, especially one that is upset or in pain. (It’s related to very similar words in other Germanic languages, but no one is sure what the original source was. So it could have been imitative. But we don’t know.)
In the entry for this word – the noun, a whelp, as opposed to the derived verb, to whelp – dictionaries tend to tell us helpfully that it has largely been superseded by puppy. I certainly suspect sound has played some role in that. Can you see a person going up to a little dog on the street and saying, “Oh, whelp, hi, whelp”?