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IVF - increased chance of twins..

(19 Posts)
Tinkerisdead Tue 14-Oct-08 17:15:23

My DH asked me a question yesterday that i couldnt answer and told him i would ask the multiple mums on here.

our friends are going through IVF and quite rightly, Dh commented that this would increase their chance of twins as two embyros have just been implanted. But then he asked whether they have just as an increased risk of identical twins and i dont know?

If (in laymans terms) an egg divides to create identical twins, would this still occur for IVF? I know that naturally the fertilised egg would travel through the fallopian tube and could divide and then implant to get identical twins. Would their be sufficient time for this to happen in IVF? Could they still divide before implantation if they have been put back in as a single blastocyst?

i hope that makes sense as i was fascinated by the question and hope MN can answer it.

kitstwins Tue 14-Oct-08 22:49:05

You are more likely to get non identical twins than identical twins with an IVF pregnancy. Largely because non-identical twins occur naturally when you double-ovulate (i.e. ovulate two eggs during a monthly cycle), which is a fairly rare occurance. However IVF clinics heavily influence the odds by routinely replacing two embryos (although guidelines are changing on this). We were told by our clinic that our chance of a twin pregnancy was 1 in 4 following our blastocyst transfer of two embryos.

An identical twin pregnancy cannot be influenced by IVF as you can't manipulate an embryo to split, so the odds of it happening are around the same as a 'naturally' conceived identical twin pregnancy. I had heard that blastocysts were more likely to 'split' but as blastocysts occur in every reproductive stage (assisted or 'natural') I'm not sure how they've calculated this.

Basically, if they have two embryos replaced then they have a higher than average chance of non identical twins. Around 1 in 80 non-assisted pregnancies results in twins and within that, you have both non-identical and identical twins so it's difficult to sift out which are more common in natural conception. I'd say identical twins following IVF aren't impossible but they have around the same chance as if they'd conceived without IVF.

As for when they'd divide into twins, this would occur after embryo transfer and before implantation. Implantation tends to happen a few days after transfer so a split/twin embryo would never be seen at the point of transfer.

Sorry this is rather garbled and 'layman' but I hope it helps a bit. I'm one of the 1 in 4 statistics. Well, my twins are. We had two blastocysts put back, were given dire warnings on the 'risks' of twins and triplets but went ahead anyway. My multi-celled wonders are currently sleeping off the day's excitement in their bed upstairs!

Good luck to your friends.

Tinkerisdead Wed 15-Oct-08 10:11:50

Thanks Kitstwins, thats what i tried to articulate to DH. I just thought as you say that the egg would divide before implant and by definition, they are in the body longer with natural conception, as opposed to IVF, as they would have already been travelling down the fallopian tube. Great answer for me to pass on to my DH though.

yes fingers crossed for our friends, they should find out if they are pregnant about two weeks before i deliver and i think i'd be crushed for them if it failed. This is their second attempt. Im so glad you got your gorgeous twins, I can see how emotionally draining IVF can be, great that it worked for you smile congrats x

kitstwins Wed 15-Oct-08 10:27:43

I'm not sure if the embryos are in the body longer with non-assisted conception, although I'm a bit sketchy on this so could be way off the mark. I had thought that clinics tried to replicate a 'natural' reproduction as much as possible. However, I do know that with identical twins the 'split' can occur at varying stages in initial embryo development (i.e. before implantation) resulting in varying levels of 'identicalness' (apologies for the made up word). For example, with mirror-image twins I think the split happens quite late.

I really hope your friends get a positive result. If they've had blastocysts put back they're in with a really, really good chance.


Tinkerisdead Wed 15-Oct-08 10:29:22

ohhhh god this gets more fascinating now. i think im gonna start googling twins. thank you...

Neenztwinz Thu 16-Oct-08 14:12:05

There does seem to be a strangely high number of people who have id twins as part of triplets after IVF. Anecdotally I am sure I have heard of four or five. Id twins are only 3 in 1000 chance so it seems strange if there are more in triplets, somehow it seems more likely the egg will split after being artificially created and implanted.

Just my thoughts, not based on any scientific understanding!

kitstwins Thu 16-Oct-08 15:08:59

No, I think you're right. My clinic told me that there was a higher chance of one of my blastocyst embryos splitting, which would in turn lead to either triplets (if both embryos took - id twins and a single embryo) or idential twins (if only one embryo took). Presumably from the slight 'twiddling' (such a medical term) during the IVF process. I think they recognise that identical twins tend to happen more frequently through IVF than they do in non-assisted cycles. I didn't know the stats were 3 in 1000 and I don't know what the rates of identical twins through IVF are but I would guess that they are higher. Like you, the two sets of triplets I know of (don't know them personally) are both IVF and both from two embryos.

I think it's such early days for IVF and even though I'm astounded by the knowledge of fertility doctors, I still sense that in, say, twenty years time they will understand so much more about IVF and fertility. Perhaps in twenty years time people will be astounded that IVF cycles used to be so hit and miss/more likely to fail than succeed. I hope so - it would be just reward for all the pioneering work and an ease to much heartache.

janinlondon Thu 16-Oct-08 15:27:14

Yes - though we don't know why. Here's the latest review:

Monozygotic twinning associated with assisted reproductive technologies: a review.
(Aston KI, Peterson CM, Carrell DT)
Andrology and IVF Laboratories, Department of Surgery, University of Utah School of Medicine, Salt Lake City, Utah 84108, USA.

Twin birth rates have increased markedly in developed countries since the 1970s for two primary reasons: increasing maternal age and the advent and increasing use of fertility treatments. In addition, monozygotic (MZ) twin pregnancies have been reported to occur at a significantly higher rate following assisted reproductive technologies (ART) procedures compared with the natural incidence. Twin pregnancies are of concern due to a dramatically increased risk of associated complications. Monozygotic twin pregnancies carry a 10-20% risk of twin-twin transfusion syndrome, and monoamniotic monochorionic twins are additionally at risk for cord entanglement. While the mechanisms and contributory factors for dizygotic twinning are well established, very little is known about the mechanisms involved in MZ twinning or the factors that contribute to its occurrence. In this review, we will discuss a number of potential mechanisms involved in MZ twinning and explore factors that may be contributing to the increased incidence of ART-associated MZ twins. An improved understanding of the factors that contribute to increased MZ twinning associated with ART will help to elucidate the poorly understood mechanisms involved in the process and will further aid in reducing the overall incidence of multiple pregnancies with their associated risks following ART procedures.

Aimsmum Thu 16-Oct-08 15:32:51

Message withdrawn

Tinkerisdead Thu 16-Oct-08 16:12:47

Thanks so much for these answers. My Dh is gonna be so impressed. So i was wrong, theres a greater risk of twins full stop both identical and non identical than usual.

Two week wait for our friends now so heres hoping. Thank you all for such great answers. i love mumsnet you can ask anything obscure and get a response.

Tinkerisdead Thu 16-Oct-08 16:16:52

actually on this subject then, if anyone still looking at the thread, would there be an increased risk of disability if the embryo has been "handled" in its creation. Could it make it more unstable as it were, could genetic material be damaged in the handling?

Patti70 Fri 17-Oct-08 10:01:18

God this is really interesting, just found out a friend of my is having triplets after having 2 blastos put back in. Didn't realise how common it was!

janinlondon Fri 17-Oct-08 10:10:33

I think unlikely Docs wife - as they use IVF for genetic selection in cases of life threatening inherited disorders - so just choose the chromosomally unaffected embryos to put back? Would seem a bit pointless if actual process was affecting the genetic make up.

kitstwins Fri 17-Oct-08 12:21:39

Doctorswife interesting point you raise in the potential for increase in disabilites through the meddling. I read Prof. Winston's book and he touches on this subject in one of the chapters.

The current thoughts are that IVF, although 30 years old, is still very 'new' in medical terms and they won't understand the full impact until at least a generation has passed. I remember the excitement when Louise Brown, the first 'test tube baby' became pregnant and had a baby as, although there was no reason to suggest that she couldn't have a child, fertility doctors had been concerned that the process of assisted conception could somehow impact on her reproductive health. It also raised the question, unanswered until then, as to whether infertility was hereditary. Obviously until then, infertile couples had not had the children to prove or disprove this. IVF answered this question.

They won't really understand the full impact (if any) of IVF until a few generations have passed but I know there are concerns. I think there always are when we 'interfere' in nature as it can often be so subtle. There can be a very fine tipping point. So the concerns about increased cancer risks (in women who have had IVF) and the impact on long-term health of IVF babies won't be understood for several decades more. Only then will a fuller picture emerge. Winston does mention the concern that some of the solutions used in IVF (i.e. the liquids used to store eggs, sperm and embryos before transfer) could potentially be harmful, but again only time will tell. The oldest IVF baby is only 30 (or 31) and so we have to wait until a generation of IVF babies have lived before we get a clear picture and pattern. There is also the argument that in fifty years time, when we start to understand what, if any, impacts there have been, medicine will have advanced so that we might well be able to address these health issues.

It sometimes worries me when I think about it - that all those drugs I took and all that embryonic twiddling that took place could somehow have an impact on the future health of me and my babies. And I'm wary that when we've meddled with medicine before the outcomes haven't always been fantastic (Dolly the Sheep - not quite the same thing, but often held up as an example of what happens when doctors/scientists 'play God'But then I think that it's not a certainty, it's a fractional possibility that only time will tell. And all I can do in the meantime is enjoy motherhood and the babies that the gift of IVF gave me.

For all of the above and all of the potential risks I thank God for IVF. Every day in fact.

Fascinating topic this - really interesting to read all the stats and thoughts.

Tinkerisdead Fri 17-Oct-08 13:11:50

Kitstwins - thats really interesting. Im absoultely fascinated around the debate. I know one couple who successfully had an ivf baby after 7 attempts and now my friends. Its one of those emotive subjects that i cant really ask said friends these questions when they literally darent breathe as they wait to see whether implantation takes place.

I must admit, as im 36 weeks pregnant that im fascinated by the physiology of pregnancy now and even more so in IVF as i truly find it miraculous that science can do something so sophisticated. To time the hormone injenctions, to monitor follicles, to sift out just one sperm from millions, even to have invented hollow needles that are small enough to inject a single sperm. For anyone who ever questions whether it is acting god, i find it a miracle that we have developed the technology to do this...and i havent received the treatment. amazing.

coochybottom Fri 17-Oct-08 17:25:01

I have ID boys aged nearly 6. They were conceived "naturally" after 4 years of trying and having being diagnosed with secondary unexplained infertility. I often wonder whether there was some problem somewhere that resulted in me having ID twins when I did eventually become pregnant. Maybe my eggs werent that "strong" or something?? I have also been told that ID twins are more likely straight after a miscarriage. I know of one such case. Any more info girls, this is really interestin!smile

MilaMae Fri 17-Oct-08 20:41:26

KitstwinsI've recently seen a consultant as was concerned about the IVF drugs I took,he said it's not the IVF drugs that are risky but Chlomid(which I also took)if it's taken for longer than 6 months.

Has anybody written anything about future health risks for ivf dc,you've got me worried now?

kitstwins Sun 19-Oct-08 11:16:02

Milamae I don't think there are any risks - I think it's more a question that we won't really understand the full implications of IVF until a few generations have passed. I think the concerns tend to be more with the patients rather than the doctors. I know that I questioned the wisdom of injecting myself with months-worth of hormones in just three weeks, and questioned whether the process of ICSI (my twins were ICSI babies) would in some way damage the delicate structures of my embryos.

I think the problem is that doctors don't know for sure because the time hasn't elapsed. It is unlikely, but no definitive answer/reassurances can be given as they literally have to wait another fifty years or more before a full picture emerges. And I suppose a doctors inability to answer those questions could cause a certain amount of alarm ("you're not saying no, but you're not saying YES either.....,etc., etc.).

Interestingly, I read an article in which it was suggested that although there were concerns as to the potential for increased health risks through IVF (both for the mother and embryo) there was also the conflicting argument that IVF parents tended to be incredibly healthy and that may well act in their (and their embryo's favour). Certainly I've never been so healthy in the months preceding my IVF cycle and my pregnancy - no alcohol, vitamin supplements, tonnes of fruit and veg, organic food, etc., etc. I'm willing to bet on that alone that I gave my babies the best start in life possible and also that I gave myself the best detox possible (I think those IVF drugs are well and truly flushed from my system).


MilaMae Sun 19-Oct-08 20:16:15

My boys are ICSI too and you're right we were soooooo healthy in the run up to treatment. A lot of other embryos are probably exposed to far more.

I think Winston was concerned about the freezing solution(mine were FET)but he wrote that chapter before freezing had become so widely used.

Don't worry about the effects the drugs had on you unless you had years of chlomid, my consultant insisted the IVF drugs aren't the ones they are concerned about just the chlomid.

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