Zygosity testing results and questioning science (long)

festivus

I am in infrequent poster here but wanted to share my test results, as they call into question the science that has been posted here as a link suggesting that 4d and 5d transfers during an IVF cycle cannot lead to di/di ID twins. While I think that info is probably accurate most of the time, my results are reminder that everyone is an individual.

For those that saw my post a copuple months ago, I was questionning whether my di/di twins might be identical for a few reasons. Some family members who saw them frequently had difficulty distinguishing them, and they had grown to look more, not less, similar since birth. On top of that, I did IVF...while my progesterone was >40 at ER or ET (I forget which day they tested), it was only 6.3 or 6.7 (something like that, definitely 6 point something...) the day I got my first positive beta (and while on supplements). My mother's intuition told me that maybe the reason for the low progesterone was losing one of the 2 embies we transferred. My nagging feeling continued after many inspections of feet, hands, ears, hairlines, eyebrows, etc. They have the same very unusual eye color, the same ridiculously fat feet (not wide, but fat top to bottom!), the same little line on the underside of their noses, a couple of the same quirky mannerisms, etc.

However, while I was suspicious my twins were ID, I held off on testing because of a link posted here (I think by peakay???) about how the day of the split determines di/di, mono/di, or mo/mo. Based on that, it looked like it was scientifically impossible for my di/di twins, the result of a 4dt, to be ID. Despte that info and the skepticism of some family and friends (even DH), I just had them tested, and they are indeed ID.

Just wanted to post, as I know I struggled with whether to spend the money for the test, especially knowing that the science suggested my gut instinct was wrong. I just wanted to know for sure either way and was sick of feeling silly when people asked if they were ID and gave me the side eye when I said I didn't know. Regardless of the results, I was just at a point where I needed to know.

All that said, DH jokes that the "lab" is some guy flipping a coin and mailing back a letter (ok, heads, these ones are ID; tails, they're frat!).

Edited for clarity: Just trying to make clear I was referring to 4/5dt and the possibility of di/di ID twins, not mom/mo or mo/di.

pea-kay

Wow, that's very interesting! I definitely can't pretend to know everything about IVF, so I guess my instinct was wrong. Certainly, they look identical, I just didn't think it was possible! Very interesting!

pea-kay

Also, did you ever post your u/s pics here? The early ones? I'd be interested to see what they look like again. Like, how far apart were their sacs? Just curious.

erinruns

I would love to have seen that link, because I've never heard that science about ID twins.  The embryo generally splits between 4-9 days.  I did IVF with a 5 day transfer and there has never been a question that my girls are identical.   I've also heard that 5dt have a higher incidence of splitting and identical twins.  

There are so many misconceptions out there about ID twins.  I once read a blog post where the blogger thought her twins split at 6 weeks.  Now that is definitely not possible!

So glad you got your answers! 

festivus

I didn't ever post u/s pics here. I'll try and scan them so I can post. There were always clearly 2 sacs, with one much smaller from the start. Since we had done IVF and knew it wasn't possible that 2 eggs had been released at different times (which could account for the difference), the doctors speculated that 1 implanted several days later than the other. Now that I know they're ID, that seems even more strange but certainly possible, I guess.

macchiatto

I don't know much about IVF, but that's really interesting! Thanks for posting and letting us know. They really look ID to me in your siggy pic!

festivus

erinruns:

I would love to have seen that link, because I've never heard that science about ID twins.  

I thought I had the link bookmarked, but I don't. Pea-kay, would you repost the link?

jcath

I didn't see the original link either...interesting.  I had a 5dt transfer of one blast and ended up with two babies. I have heard that sometimes there is a rogue embryo but I had always insisted on SET and so they only prepared one embryo to transfer. My early u/s's only have one sac, we didn't see a membrane until 13 weeks and even then it was clearly a membrane, not two distinct sacs.

lovemygs

All of this is so interesting to me! We did a 5dt, and it has been very clear from the beginning (to my RE and now my MFM) that they are ID. 

I know ICSI and AH can have a hand in splitting an embryo, both of which we did.  

festivus

cakpeterson:

All of this is so interesting to me! We did a 5dt, and it has been very clear from the beginning (to my RE and now my MFM) that they are ID. 

I know ICSI and AH can have a hand in splitting an embryo, both of which we did.  

Sorry for the confusion- I was referring solely to di/di ID twins. I'm assuming if it's "obvious" you're having ID twins, then they must be mo/mo or mo/di, correct? Good luck with the remainder of your pregnancy!

lovemygs

festivus:

cakpeterson:

All of this is so interesting to me! We did a 5dt, and it has been very clear from the beginning (to my RE and now my MFM) that they are ID. 

I know ICSI and AH can have a hand in splitting an embryo, both of which we did.  

Sorry for the confusion- I was referring solely to di/di ID twins. I'm assuming if it's "obvious" you're having ID twins, then they must be mo/mo or mo/di, correct? Good luck with the remainder of your pregnancy!

Gotcha! I misunderstood. Yes, mine are mono/di.  

caden

Interesting! It was Wiki that told us that Day 4 and after IDs have to be mo/di (or mo/mo). It sourced, but still. Glad to have this info corrected! Here's the (apparently incorrect) chart from wiki:

pea-kay

caden:

Interesting! It was Wiki that told us that Day 4 and after IDs have to be mo/di (or mo/mo). It sourced, but still. Glad to have this info corrected! Here's the (apparently incorrect) chart from wiki:

If I posted any link, it would have been to something like this. This is generally accepted to be when everything happens, but I guess there are some exceptions!