What do people still do based on outdated science, but should probably stop?

Give birth on their backs, cut the cord as soon as the baby is out, and then rush off to wash it.

So much wrong with all of those. Giving birth on your back might be convenient for the medical staff, but it’s a terrible position to give birth. Get upright, move your hips and let gravity do a lot of the work.

If you want a horribly gross example, imagine that you've had constipation for the last week. You’ve taken a laxative, and finally that big poop is on the move. Would you rather go to the toilet with a book and let it ease out in its own time, or lie on your back with a bedpan under you and a bunch of strangers yelling, “PUSH!?

When the baby is born, the umbilical cord is its lifeline. If it’s not breathing, it’s still getting oxygen through the cord. As long as the cord is still pulsing, don’t cut it. The cord is carrying blood belonging to the baby, up to half a pint. Cutting the cord before the blood goes into the baby can deprive it of a significant amount of blood. For no reason.

Taking the baby off to wash it

Yes, the baby looks messy, but that vernix is a protective layer for the baby’s skin and will sink in if you left it alone. Note that the cord in this photo is still pulsing and is full of blood.