My search-engine hits mostly fall into one of two categories: song lyrics inquiries and searches for information about twins. I'm not so helpful for that first group (unless you're interested in some Cyndi Lauper lines -- if so, I've got you covered).
The twins-related hits are of more interest to me. There's a lot of misinformation out there about twins. I'm happy to do my part to debunk some of the strange things people seem to believe about twins, but I don't claim to be an expert. That said, here's what I know:
Fraternal twins can be hereditary, but only through female blood lines. Fraternal twins happen when a woman releases two (or more) eggs in an ovulation cycle, and both (all) of those eggs are then fertilized. Because it all has to do with how many eggs a woman releases during her cycle, the man has nothing to do with it. Men cannot influence whether or not a woman will have twins, even if the man is a twin or has twins in his family.
A woman who is related to a woman who has given birth to fraternal twins can think of herself as having twins in her family, so to speak, although that's by no means a guarantee that she will have twins (Nanette beat the odds there). And I know lots of moms of twins who don't have a hereditary predisposition for multiples (Rug's Bug and Mary Beth, to name a few), so heredity doesn't seem to play a very big role in whether you'll have twins or not. Lots of other factors come into play. Obviously, fertility treatments can result in fraternal twins (triplets, quadruplets, etc.). Age, weight, medications that mess with your hormones, and even diet can have an effect on whether you'll have fraternal twins.
So, really, it's a pretty random affair, nearly impossible to predict. If you want to have twins and are trying to make it happen, don't get your hopes up too high. Even fertility treatments aren't a sure-fire method.
Identical (monozygotic) twins are not hereditary. They just happen, and they can happen to anyone. No one really knows why an egg splits, although I've heard it said that fertility treatments might encourage monozygotic twins. Why that would be, I couldn't tell you, but if you're looking at fertility treatments, you're more likely to end up with fraternal twins (or more), not the identical variety.
I believe I've mentioned before that we don't know whether our twin girls are identical or fraternal. Everyone tends to assume that they're identical, and I can understand why. They are quite similar. But I'm not convinced. And I'm also not curious enough to subject them to blood tests to find out for sure. It remains a mystery. (Of course, Jim and Amy say the same thing about their twin boys, and I can't imagine how they could be so blind as to not know that their twins are identical. Is that what everyone says about us, too?)
For lots more fun facts about how to have (or avoid having) twins, check out this link.
8 comments:
I don't care if the girls are fraternal or identical, I just know they're beautiful, and that's all I care about.
I just love it when Paternal Grandma tells people that twins run on her side of the family. I just smile and let her brag. You couldn't convince her otherwise even if you tried.
We knew our twins were fraternal from the first. There were two amniotic sacs. Plus they don't look anything alike. Now if the A twin and the 3rd kid had been born at the same time, we might be wondering.
Since I don't have a kid, I think all of them look the same anyway until they are about 10 or so.
I am getting tired of the word verification, although I understand your reasoning. Blech.
Yeesh! Just put up with the word verification a bit longer, okay? I'll take it off in a few days and see if the spammers come back.
RB, you know that two amniotic sacs doesn't necessarily guarantee fraternal twins, right? My twins had two amniotic sacs. From what I understand, identical twins develop completely separate systems, like fraternal twins, if the egg splits very early. The later the egg splits, the more likely the twins are to share an amniotic sac, and if it waits too long to split, that's when you end up with conjoined twins.
I should've clarified that. They had separate sacs AND placenta. Thus making it about 70% certain that they were fraternal.
Well said. Perhaps I should keep a copy of this with me for all those curious cashiers and folks in doctors' office waiting rooms. Not that I mind chatting, but you sum it up so well.
Well mine are obviously identical. ;) Haha, I crack myself up!
I know the best way to have twins for me, get pregnant--with my luck, they would be a fraternal set and they would each split and give me quads.
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