Fertility/ reproductive facts or myth?

Here’s a couple things I have heard more than once, and wondering if anyone knows which ones are facts, which are myths?

An older dad is more likely to have a daughter

A couple is more likely to have a boy if they have sex in the missionary position

A woman is carrying a girl if her baby bump is lower and wider, and her hips spread more as opposed to her stomach protruding out She is carrying a boy if her bump is high up and out like a basketball and she doesn’t get ‘hippy’

A woman is carrying a girl if the baby’s heart rate is slower in utero, and its a boy if the heart rate is higher

A woman is more likely to conceive around the time if a full moon

This can easily be dismissed: the chance of conception correlates with the phase of the woman’s menstrual cycle, not of the moon.

They’re all myths.

Yes, I know it has to first of all be around the time of her ovulation. But is she more likely to get pregnant if she ovulated during a full moon ?

The only one that’s true is that older (over 40) fathers are more likely to have daughters than sons. The same is true of older mothers. Graphs here: http://www.psychologytoday.com/blog/the-scientific-fundamentalist/201104/why-are-older-parents-more-likely-have-daughters

We’re not sure by what mechanism this happens, although the leading theory is that with age, genetic errors in the production of sperm are more likely, and fetuses with medical conditions are more likely to die before birth if they are boys. Boy fetuses at all paternal/maternal ages are “weaker” and die more often than girl fetuses.

The rest are total nonsense.

That my have been the case if women’s cycle synced up with the full moon, but they don’t. So, since the effects of the moon’s gravity and light is negligible on reproductive organs, then there is no way for it to have an effect.

My brother, father of 18 children told me that the odds of producing a male is increased if one enters from the rear. He says that the distance to the egg is shorter, and the male sperm is faster, but they tire more quickly. Not scientific, just his observations.

Really dude !!! Without offending your religious beliefs, I’d lend very little credence to a guy who fathered 18 kids in this day and age. I hope they were different women.

For what it’s worth, my wife’s OB said that for all the myths about gender determination that are complete bullshit, the heart rate one has some truth to it. And this is a guy that didn’t generally give off an air of quackery or nutjobbery.

He also gave a caveat that you can’t really use it for anything close to reliable gender determination, because what you’re talking about are overlapping bell curves with a slight offset in their peaks. I get the impression that it’s a curious phenomenon for large populations, but meaningless for individual cases.

“Not scientific” here means “total bull.”

Ha, that’s funny, the myth I follow states the opposite - a high bump means a girl.

Worked for me :wink: (well, the high bump, then the four ultrasounds that also confirmed “girl”, I didn’t just run out and start buying pink&purple on the basis of the bump!)

am. 77494,

? Why would the fact he had alot of children make him less credible? If anything, it seems like he would have more experience than a man with no kids…Lyon totally lost me on this line of ‘reasoning’

18 kids… How many boys and girls? :smiley:

As for position vs. sex, who keeps track of this stuff, unless the excuse is “but we only did it once…” I thought that excuse ended about age 18. “She loved it this way, and the one child we had was a girl, so therefore…”

I think a lot of these myths - esecially sex selection/prediction - are self-reinforcing because they are bound to be right 50% of the time, and old wives are less likely to remember when the prediction failed. (“Experimental error”).

Even any valid sex selection effects are more likely going to influence odds by a few percent - great when you’re the house and it’s blackjack with thousands of bets, but a one-shot 52%-48% really is not going to matter a whole lot.

Re the heart rate one: my mother’s doctor, who correctly identified the sex of my three older siblings using this test, predicted that I would be a boy. My parents chose a boy’s name, and advised their only daughter, who very much wanted a sister, that she would have another brother.

But I was a girl! The doctor was surprised. My parents were surprised, and had to quickly think of a girl’s name. (My dad chose it because Mom got to pick the first three kids’ names.)
The only person not surprised was my sister. When told that she had the sister she wanted, she calmly said, “I know. I asked God to make her a girl.”