Multiple birth statistics WHAT IS THE LIKELIHOOD OF HAVING TWINS OR MORE? In the UK about one in every 65 pregnancies results in a multiple birth. There has been an upward trend in the numbers over the last 20 years. The rise is attributed to fertility treatments, the survival rates of premature babies and women starting their families later. However, the multiple birth rate is now slowing in line with the singleton birth rate. Incidence of multiple births in the UK, 2019*

England & Wales Scotland Northern Ireland UK

Twins 9,656 717 384 10,757

Triplets and above 143 9 4 156

* source Office of National Statistics/General Registry Office, Scotland & Northern Ireland Statistics & Research Agency What are the chances of twins again are much higher. They may or may not share a placenta. having identical Women who have a family history (monozygotic) twins? of non-identical twins have a Characteristics such as size and The likelihood of having identical higher chance of producing non- personality depend on non- twins is about 1 in 250 (about identical twins themselves as genetic factors, so may be 0.5%). there is a genetically linked different. tendency to hyper-ovulate. Identical twins do not run in Triplets and more are formed in families. They occur when a There is no known genetic link for this way too, but may be in single embryo splits in two soon identical twinning. different combinations. after fertilisation. This is why Identical or non-identical? Non-identical twins are created identical twins have identical when a woman produces two Whether the babies are identical DNA. eggs at the same time and both or non-identical depends on how are fertilised by a different sperm. What is the likelihood of the babies are formed. having more than one set of The fertilised egg is called a Identical twins occur in about one zygote and these non-identical twins? third of multiple pregnancies. twins are known as dizygotic or If existing twins are identical the Known as monozygotic twins, a fraternal twins because they grew chance of having another set is single egg is fertilised then splits from different zygotes. the same as most women, about into two (or very rarely three or The babies are more alike than 1 in 250. If the twins are non- more) creating identical babies any brother or sister and may be identical the chances of having with the same genes, physical both male, female or one of each. features and sex. NICE guidelines for multiple to just one IVF cycle on the NHS. What is Twin-to-twin pregnancies What guidelines and policies Transfusion Syndrome? NICE (National Institute for are in place for fertility TTTS occurs in about 10-15% of Clinical Excellence) publishes treatment? identical twins that share a guidelines which set national placenta. TTTS twins share some NICE guidelines recommend three standards aimed at achieving the of the same circulation, resulting fully funded IVF cycles for all best care and best outcomes for in the transfusion of blood from patients who meet set criteria and multiple pregnancies. one twin (the donor) to the other are aged under 40. In many cases (the recipient) in the womb. NICE QS46 recommends health it recommends a single embryo professionals looking after transfer. In most cases the donor twin may multiple birth patients adhere to become smaller and anaemic due Woman aged 40-42 may have a eight standards which clearly to not having enough blood double embryo transfer. describe what high-quality care supply. The recipient twin has a looks like and can be measured. Some women may go abroad for higher blood volume, which can treatment where more embryos strain the foetus’s heart and lead Our Maternity Engagement may be implanted. to heart failure. Project set out to prove that following the NICE guidance There is also a chance that The donor twin is also likely to works and we were encouraged embryos split in the womb have a decreased urinary output, by the results. creating multiple births. leading to lower than normal levels of amniotic fluid, whereas In fact, if you take the best case Are there risks associated the reverse is true of the recipient scenario from St George’s with multiple births? twin. Excess fluid in the recipient Hospital, London, after five years Multiple pregnancies3 are, twin can be uncomfortable for the the lives of up to 100 stillborn compared to singletons, sadly pregnant mother and puts babies could be saved each year twice as likely to be stillborn and pressure on the cervix that can if all maternity units across the UK are 4.3 times more likely to result lead to ruptured membranes and followed NICE QS46. This would in neonatal death compared with early delivery. result in a twin stillbirth rate of singleton pregnancies. Sadly 1.85 per thousand which is below The implications of TTTS can be there is also a higher risk of the 2016 singleton stillbirth rate of serious and in severe cases disability. 3.861. doctors may recommend laser Through our Maternity ablation surgery which involves What effect has IVF had on Engagement (T-MEP) Project, we closing the twins’ connecting multiple pregnancies? aim to reduce these figures by blood vessels, or amnioreduction, On average 211% of In Vitro working with teams to encourage where excess fluid is drained. Fertilisation pregnancies result in full take up of NICE QS46. either twins or triplets compared with 1-2% of natural conceived For more information visit www.twinstrust.org For confidential, pregnancies. emotional support contact Twinline for free on 0800 138 0509.

1 https://www.npeu.ox.ac.uk/downloads/files/mbrrace-uk/reports/MBRRACE-UK%20Perinatal% Multiple embryos are sometimes 20Surveillance%20Full%20Report%20for%202016%20-%20June%202018.pdf transferred during a cycle to save 2 costs and boost success chances, https://www.bionews.org.uk/page_138328 3 especially if the couple are limited Reports | NPEU (ox.ac.uk)