TEALE FENNING

mridulaben · Posted: Wed Jan 24, 2007 10:28 am Post subject: Monozygotic twins

Situs invertus occurs more commonly than in general population

wolverine · Century Club Joined: 16 Jan 2007 Posts: 393

My understanding is that situs inversus or loss of organ orientation and symmetry is a rare autosomal recessive condition and can be part of primary cilliary dyskinesia or Kartagener syndrome. Has no racial predilection, male to female is 1:1 and therefore it's not more common in monozygotic twins. Although I was itching to say true as MC twins could be associated with all the abnormalities of this world! Although there are reports of one of the monozygotic twins with situs inversus which mean that it is not only genetically determined.

rpwalavalkar · Teale Fenning Administrator Joined: 20 Jul 2006 Posts: 946

TRUE

Some monozygotic twins are known as "mirror twins" or mirror image twins. These are identical twins with opposite features, that is, one may be right-handed and the other left, mirrored hair curls, etc. This condition is comparatively rare in humans: about 25% of all identical twins are mirrored. It results from a late split of the fertilized egg at around 9-12 days. One mirror may have situs inversus, where some or all of the organs are on the opposite side of the body, such as the left ventricle of the heart on the right (dextrocardia). Such conditions are usually associated with a higher incidence of other birth defects.

ref-- Wenk RE, Houtz T, Brooks M, Chiafari FA (1992). "How frequent is heteropaternal superfecundation?". Acta geneticae medicae et gemellologiae 41 (1): 43-7. PMID 1488855
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Nick Raine-Fenning · Posted: Wed Jan 24, 2007 5:39 pm Post subject:

I also thought this was true - not sure why but have seen the two words / phrases in association lots of times - enough, in fact, to make a MCQ true Wink

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EMAK · Century Club Joined: 26 Nov 2006 Posts: 570

I couldn't find it but I think True.

jilly · Joined: 16 Jan 2008 Posts: 15

another MCQ;
In relation to monozygotic twins, the incidence is approx 25% of all twin pregnancies?

I have figures of 1 in 100 for twins in the UK and 3 in 1000 for monozygotic twins - making MZ twins about 1/3rd of all twins - which is about 25%??? Do anyone else have any figures?

Thanks

SallyC · Joined: 12 Jul 2007 Posts: 50 Location: Oxford

The figures I have are;
Twins 15:1000
MZ twins 3.5:1000
This would indeed make them 25% of all twin pregnancies.

Xerxes I · Posted: Thu Jan 24, 2008 5:31 pm Post subject:

Agree with Sally. 15 in 1000 is a more recent figure (1997?), used to be 1% in mid 80s.

rpwalavalkar · Teale Fenning Administrator Joined: 20 Jul 2006 Posts: 946

hi guys,

this is from the RCOG HFEA consultation document of june 07

In UK the incidence of twins has risen from 9.0 per 1000 births in 1985 to 14.2 per 1000 births in 2000 and the incidence of triplets has quadrupled in the same time period (Office of national statistics series DH3, No 32, London 2000).

In 2001, 145 in every 10,000 maternities resulted in the birth of twins, while 4 in every 10,000 maternities led to triplets or more. The rates are higher for older women -among women aged over 40, twins accounted for 194 in every 10,000 maternities, and triplets for 11 in every 10,000 maternities.

for women aged under 20, twins accounted for 61 in every 10,000 maternities and triplets for less than 1 in every 10,000 maternities

ref -- Department of Health, statistics and surveys 2001. Available from: http://www.doh.gov.uk/public/statlink.htm

so 15 per 1000 is a right figure to quote.

r
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Dr Miss. Raj Walavalkar MBBS MRCOG
TealeFenning Administrator
SR O&G Wessex Region

nibbs07 · Joined: 03 Dec 2007 Posts: 9 Location: Hampshire

few more MCQs regarding multiple pregnancy-

timing of separation is usually >14 days
structural defects are usually concordant
upto 20% of twins diagnosed in 1st trimester proceed only as singletons

Smile

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Nibbs

Nick Raine-Fenning · Posted: Thu May 15, 2008 6:50 pm Post subject:

Can I add some as well? These are very important to us in an IVF unit especially with the big drive for single embryo transfer (SET). So:

With regard to twin pregnancy:

1. the miscarriage rate is twice that of singletons

2. the risk of early miscarriage is 40%

3. the risk of late miscarriage (12-24 weeks) is 12%

4. the incidence of preterm delivery is 22%

5. the incidence of early preterm delivery (before 32 weeks) is four times that for singleton pregnancies

6. they have twice the chance of being SGA

7. are associated with a caesarean section rate of 40% or more

8. risks are higher for IVF twins than for spontaneously conceived twins

9. have a higher indicence of stillbirth even if normally grown

10. have a stillbirth rate comparable to that seen in high risk mothers

11. have a much higher rate of RDS for comparable gestational ages

12. have a 6% chance of congenital abnormality for each twin

That will keep you busy! Smile

nibbs07 · Joined: 03 Dec 2007 Posts: 9 Location: Hampshire

Ummm very informative

Thanks Nick

Nibbs
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Nibbs

salihabduallah · Joined: 04 Sep 2007 Posts: 100

Most of them seems true as multiple pregnancy particularly after IVF carries high incidence of almost all obstetrical complications.
BUT : Percentage >> dificult to conclude.

rpwalavalkar · Teale Fenning Administrator Joined: 20 Jul 2006 Posts: 946

Nick,

please end the suspense, where will i get this twin preg data?

r
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Dr Miss. Raj Walavalkar MBBS MRCOG
TealeFenning Administrator
SR O&G Wessex Region

cpeedahsa · Century Club Joined: 21 Apr 2007 Posts: 792

cpeedahsa · Century Club Joined: 21 Apr 2007 Posts: 792

cpeedahsa · Century Club Joined: 21 Apr 2007 Posts: 792

cpeedahsa · Century Club Joined: 21 Apr 2007 Posts: 792

Nick Raine-Fenning · Posted: Sat May 24, 2008 12:22 pm Post subject:

100% so far Asha!

The figures are quite scary aren't they!

Let's try and go through the whole lot as you will then have a nice set of facts to help formulate an essay on single embryo transfer and the risks of multiple pregancy which is as hot a topic as you could get! Very Happy

cpeedahsa · Century Club Joined: 21 Apr 2007 Posts: 792

Thanks Nick for these teasers,
The actual figures are indeed very scary.
Starting a fellowship in genetics in July ... and in the process of relocating...to Boston
I will get back with the rest soon.

a