Thinking about this - I believe we're in a period of huge flux wrt parenting practices. I think things are changing more quickly now than they have in the past and will in the future.
What is mean is, I think there are 3 phases to parenting practices. Using for example MrsBadger's metaphor of eating rhubarb in pregnancy:
Phase 1: You do as advised by your mum, sisters, friends. Each person's advice is based on a knowledge of a tiny number of babies (tens or a few hundreds). They all ate rhubarb in pregnancy and "it never did me any harm".
Phase 2: Proper evidence based population research comes out, showing that eating rhubarb in pregnancy carries a risk of a rare but devastating complication. In 1 in every 10 million mums, rhubarb causes the baby to grow an extra head and dress up as a Star Trek character.
The problem is, you can't tell who is at risk. So Public Health bodies advise that all mothers avoid rhubarb. As the result of a "Crumble Out Rhubarb" campaign, incidences of 2 headed Spock impersonators decline rapidly and everyone heaves a sigh of relief.
But the price is high. For every 1-in-10-million babies that is saved, there are 1-in-10-million-minus-1 women who are being denied a lovely pudding.
Eventually, further research leads to :
Phase 3: It is discovered that the problem only occurs in women lacking the enzyme Rhubarb Antiklingonase. Testing for this enzyme becomes standard antenatal practice. A few women are warned off rhubarb and the rest are told it is perfectly safe.
Well, for a lot of the issues we discuss here like weaning and cot death, the research is still at phase 2. We know certain things are risky, we know the risk probably doesn't apply to everyone, but we don't know whether the risk applies to our own child or not.
To me, it seems obvious with phase 2 stuff to avoid rhubarb, ie always to choose the path of lesser risk. My children might discover that avoiding rhubarb was unnecessary. I am fine with that. I can say, "I looked at the risks and took the best decision I could at the time."
You can't do better than that imo.