There’s something amusing about insulting the parentage of someone you shared a womb with. 
A friend of mine is half of a set of fraternal twins, and she said her twin brother was born much bigger and robust than she was, plus she’s always had asthma and a few other chronic medical issues, while he’s healthy as the proverbial horse.
If the mother carries to term, it shouldn’t be an issue. From what I’ve read, most babies can be born up to 3 weeks early with no issues whatsoever, and from 4 to 8 weeks early with only minor problems.
In a sad example of a FOAF, her one girl’s blood supply had to pass through the other girl first. Second girl’s heart had to pump doubly hard and little girl of course didn’t grow normally. They were delivered super-early and little girl died.
Just be glad your twin wasn’t Professor X!
If the parentage were in doubt? Sure, unless the two potential fathers were identical twins.
Awful. Sounds to me like they were identical twins, though. Fraternal twins have their own placentas and blood supply, because those structures are formed from the fertilized egg.
–Cliffy
:smack: Of course you’re right.
I seem to recall hearing she had NOT taken fertility drugs.
Sometimes stuff just happens with no clear cause.
In actual fact, this may be more common than realized - prior to the late 20th Century we had no way to look inside the womb prior to birth or so closely determine conception dates. This might have happened rarely but regularly throughout human history and we’d never know - they wouldn’t appear any different than regular fraternal twins at birth, even with different sizes, because twins are not uncommonly of different size and weights at birth.
I wonder how this story will turn out. Every other time I’ve heard of this happening, it’s been revealed to be a hoax.
How are they so certain of the conception dates? I remember when I was pregnant (admittedly, more than 20 years ago) the conception date was a best guesstimate based on the estimated window of ovulation based on what I remembered being the first day of my last period. Not an exact science if you ask me. Do they do it differently now?
They do an initial estimate based on LMP of course, but also early ultrasounds are common nowaways (I had them at 6 weeks with both kids, as I’d had miscarriages and they wanted to determine viability / heartbeat). If a later ultrasound had showed 2 fetuses, well, they might argue that they simply missed one the first time, or they might say superfetation had occurred. Presumably “missed one” is far more common.
They also can use the ultrasound for size estimates to try to determine gestational age, though as the pregnancy progresses, normal variation in growth patterns would make it less accurate. So an ultrasound at 5 months, showing one fetus at 20 weeks and one at 22 weeks size-wise wouldn’t prove anything.
Look up Twin-to-Twin Transfusion Syndrome. Nancy Grace’s kids didn’t have it because they’re not identical (m/f twins) and her daughter was half the size of the son, so even without TTTS there can be big differences between twins.
If twins are suspected (if hormone levels are higher than expected for one baby, for example) they will indeed do an early ultrasound. They are pretty accurate. In the first few weeks when there is rapid growth a difference of 2 weeks would be evident.
ETA: I am guessing there was a change in hormone levels after the second egg was fertilized. That would create a hormone shift that would be different than regular twins also.