That's exactly it, Hetty. I think it's great that women are told the current advice, but often it runs contrary to the advice of their own mothers, and in any case the advice shifts constantly.
One of the impacts of this is, as you say, that mothers and pregnant women are infantilised, and another is that many seem to be incapable of making decisions of their own. Whether it is swaddling, 'wake windows', 'tummy time', baby-led weaning or whatever, life seems so regimented these days, with babies constantly 'working on skills' and 'transitioning to' whatever stage comes next. It all feels a bit joyless to me, and my antennae twitch when the advice is monetised. Buy this swaddle, join my babysleep course for only £20 a month etc.
I'm not suggesting that expectant mothers swill gin and smoke 20 a day, and if it is found that soft cheese or raw egg is harmful then of course they should be told, but I really don't think it is up to anyone else to get involved with decisions that they make for themselves. They are adults, who are soon to be responsible for another life as well as their own - treating them like children is unacceptable, I think.