Dietary advice, contrary to the impression that its givers and its takers strive to make, is not rocket science. Nor is it particularly modern or new. Vronsky, Tolstoy explained in Anna Karenina at the turn of the 20th century, maintained the weight demanded of him by his regiment by steering clear of sugary and starchy foods.
It worked for him, and there is no reason why it should not for everybody.
Pregnancy is neither modern nor new either, but you'd imagine from the plethora of warnings now showered on people having babies that no foetus could possibly come to term without some magical application of exactly the right amount of all that is "good", and nothing whatsoever of anything that is "bad". I suppose that it is possible that a person might become confused by the reams of advice, sometimes conflicting, that are now showered on pregnant women. But all this shows is that too much of anything is by definition too much. Even dietary advice.
So, even if you are pregnant, too much in the way of sugary and starchy foods can still be discerned when the tops of your arms start to look like the tops of your legs. People moan on forever about "losing the baby weight" when what they really mean is that they sat around using their pregnancy as an excuse for stuffing their faces, and later started regretting it. They took in more calories than their bodies needed, and ignored the evidence that they were doing so. That's it. The mystery of fatness revealed. Even pregnant fatness.
Certainly, while one should not take literally that old canard about eating for two, it is important that pregnant women take in nutrients for themselves and their baby as well. Again, this is easy to do, not hard. For pregnant women, just as for all of us, it is better to know what you are eating in order that you actually know when "too much" has been had. Processed or pre-prepared foods are therefore not ideal, as you don't know, unless you have the time to study every packet in the supermarket, quite what the ingredients are. Despite all the fuss that is made, it is quite easy to eat healthily. This means plenty of vegetables and fruit, good quality protein and unrefined carbohydrates. Treats are fine, but if you are having them all the time, then they are not treats.
Some foods, it is true, carry a higher risk of food poisoning than others. It is never a great idea to go out of your way to get ill while pregnant, so it's sensible to steer clear of the pâtés, shellfish, uncooked eggs and so on. Likewise, it is not a good idea to have loads of booze. If you might, in the future, agonise forever that perhaps Barnaby's dyslexia was because of that half-glass of spritzer at your sister's wedding, then it is best not to drink at all. Or, in fact, to have children.