Wednesday, February 29, 2012

Finally we have proof! Doctors often misinform parents about zygosity

Throughout my pregnancy, my OB and the ultrasound technician told us our boys were absolutely, positively, no-doubt-about-it fraternal. Yes, my doctor said, identicals can have separate placentas and sacs, but mine implanted too far apart to be identical.
Their placentas were on polar opposite sides of the uterus.
Identical twins implant more closely, he said.
He was wrong.
And he has company.
In a new study from University College London, researchers found that doctors wrongly told parents their identical twins were fraternal in 27.5 percent of the cases. Like my guys, those twins had their own sacs and placentas.
The study also found that 2 percent of parents were wrongly told their fraternal twins were identical because doctors did not realize their separate placentas had fused into one. Overall, 15 percent of twin parents were misinformed about zygosity.
I have long suspected the statistics involving identical twins are skewed.
This proves it.
So many parents find out long after birth that their twins are identical through DNA testing. That information is never reported to any statistic-gathering source. If this study hold true in the US, then statistics showing the odds of having identical twins is about 3 in 1,000 are way off.
It has become a game on online twin forums: Guess whether the twins are identical while the parents await results of DNA testing. In most every case where parents of di/di had trouble telling their twins apart, the results showed they were, indeed, monozygotic, or identical.
I have come across just as many parents of look-alike twins in real life and virtually who decline testing despite their gut feelings. Either they can't afford the $100 to $200 fee or they see slight differences between their twins and accept those as evidence their twins are fraternal.
We could have done that do that with our guys.
Matthew has a slighter build and a thinner face. Jonathan is much more muscular and has a rounded face -- a little more body fat in his cheeks. But that scenario is true of most identicals. One usually has a slightly different facial shape than the other.
In some of those cases, parents brushed off their identical suspicions because their hospitals "tested" the placentas and the results showed they were dizygotic, or fraternal.
Our own doctor fell for that until I pressed him for more information and he checked with the hospital.
It turns out hospitals check only whether placentas are fused. The hospital techs either definitively declare the zygosity according to the results or the pass the results on to doctors or midwives who were told in medical school that two placentas equals fraternal.
The doctors or midwives then pass that misinformation on to parents.
Remember this: hospitals DO NOT do DNA testing.
In the defense of OBs, midwives and ultrasound technician, zygosity is irrelevant in caring for pregnant women. What matters is only whether there is one placenta or two, and one sac or two. So they really don't need to know for medical purposes.
That doesn't, however, excuse the giving of misinformation.
In our case, a fellow soccer mom who was a neonatologist educated me.
She told me that identical twins implant separately when the split occurs immediately after conception -- within the first few days. Matthew and Jonathan probably became two far up in the fallopian tube, she said, allowing them to fall and implant independently, just like fraternal twins.
At the very least, our OB should have told us he didn't know.
He should have known that he didn't know.
All doctors, midwives and ultrasound technicians should know that they can't be certain with same-gender twins until after the babies are born. Though the information is medically irrelevant during pregnancy, there is no excuse for being misinformed about something so relevant to the field in general or for passing that information on to parents.


Shelly Cunningham said...

I was also told that my twins were fraternal- no question. And then (in my ignorance) when they were born with such different birth weights (nearly seven pounds & just over four pounds) I thought that confirmed their "different-ness" and believed they were fraternal. But as they grew, and we studied them more my mom, who has a nose for a good mystery, said she would really be interested in a DNA test. So she bought them one for their first birthday. Sure enough, they are identical.
I shared this story with a 45 year old woman at work who befriended me & helped care for the twins while my husband was in night school and it prompted her & her twin sister to get a DNA test. They grew up believing they were fraternal, arguing with schoolmates and extended family members that they did NOT look the same. Turns out that for four and a half decades, they were wrong. They are identical.
I really wish the public and medical professionals in particular were more informed on such issues. Thank you for sharing!

pyjammy pam said...

Very well said! My idiotic OB couldn't even read an u/s or else he would have known immediately mine were monochorionic, so we went the whole pregnancy not knowing if they were ID, frat, or a mix of the two. DNA testing was what gave us the answer. In retrospect, it's SO obvious they were identical from the beginning (you can see my first u/s on youtube if you click on the link at the top of my blog - but at the time, I knew nothing about twinning (or, uh, tripleting.)

now my mission is to get people who have di/di twins that look similar to get them tested.

Nanner said...

Ahhh, THANK YOU for finding this. I always had that sneakin' suspicion too! I have oft pondered the multitude of twins I pass by in my local Mother of Multiples club, in stores and at parks who look to my untrained eye EXACTLY alike, yet the mothers claim there is just NO possible way the they are identical because [insert personality, talent or subtle physical appearance difference here]. Yet, I am the mother of 2 sets of identical twins. And they have different personalities, and slight variances in appearance. You soon realize that the entire age-old statistic that identical twins occur in about 1 in 250 pregnancies is probably not based on any relevant data whatsoever. Afterall, did they actually DNA test a sample of twins large enough to derive that number? Or ask the mothers? Or perhaps they were still relying on the old 'placenta' method we know is inaccurate. Or maybe it is based on how many shared an amniotic sac (also inaccurate). Either way, just sniffing the air around me in the twins community, it seems there are probably more identical twins than anyone realizes. Thank you for sniffing this out!

Twinsmom said...

Shelly, how strange that must have been for those 45-year-old twins! I'm 45 now and I can't imaging finding something like that out now. It might seem minor, but I'm sure their twinness is a huge part of their identity and finding out that their parents had been misinformed for so long had to rock their boat a bit.
Pyjammy Pam, clearly identical and most adorable!
Nanner, it seems I see identical twins all over the place, especially in malls and in play areas. I find it hard to believe that I can encounter so many if those statistics are accurate. I'm sure the statistics are way off. I'm hopeful that the credibility of this study will help change things.

Twinsmom said...

pjammy pam, I have a friend with identical triplets back in Cincinnati. Whenever I've felt overwhelmed, I've thought of her and the patience with which she handles her girls and the constant stream of curious onlookers (She also has two older kids, one with Downs). You triplet moms (Especially those with identicals) have all of my respect and loads of my admiration!!

swissarmymama said...

Thank you! I think we're going to be getting our boys' DNA tested pretty soon. I've had a sneaking suspicion that they were identical since before they were born, and now at 16 months even other family members have trouble telling them apart. I get them mixed up occasionally! We were told for the same reasons (separate sacs, separate placentas) that they HAD to be fraternal and I'm so glad to have more of a reason to go ahead and get the DNA testing done. They were an ounce apart at birth and have some minor differences (like slightly difference face shape, much like your boys), but don't look NEARLY as different as other fraternal twins I know.

Melissa said...

Our twin club runs evenings for expectant twin mums, and those with two placentas nearly always say they are having fraternal twins,...maybe I say. (unless ofcourse they are boy/girl). I know a few parents of clearly identical twins who say they are fraternal and seem to get upset if you suggest it may be otherwise.

In-Cybertown said...

That is exactly the same as my twin boys who are 6 now, separate sack, but they are identical, I was told by one paediatrician if you can take the right hand of one twin and the left had of the other and they make a pair, or with their feet, their identical. Not to mention the fact, obviously no one can tell who is who even I get it wrong!

Darlene said...

Thank you so much for this information. I recently had di/di twin boys and at birth, they looked nothing alike. Now at 5 months, they look almost identical, to the point both me and my husband have a hard time telling them apart! Their pediatrician keeps telling me it's almost impossible for them to be identical and refuses to test them. After reading this, we are definitely going to pursue a DNA test.

Anonymous said...

I had di/di identical boys. Found out as a study was being done at the hospital in winnipeg, canada. We have a group of M.O.M's (mom's of multiples) here and through this study, I know of about 10 other di/di identical twins born here. They have come to the conclusion it is more common than they thought.