Multiple Pregnancies Following Assisted Conception (Scientific Impact Paper No. 22, 2026 Third Edition)

Plain Language Summary Multiple pregnancy is a preventable complication of in vitro fertilisation (IVF). Multiple pregnancies are often the result of a treatment approach that means more than one embryo is placed into the womb during each IVF treatment cycle in the belief that this may increase the chance of a successful pregnancy resulting in a live birth. In reality, this approach has led to a higher rate of IVF multiple pregnancies, ranging between one in three and one in seven pregnancies across many parts of the world, including the UK. Multiple pregnancy carries higher risks for both the mother and babies, most notably the risk of premature birth leading to an increased chance of early death or long‐term physical or learning disability. At present, there is no available treatment that can prevent premature birth in multiple pregnancies. The number of multiple pregnancies resulting from IVF treatment can be reduced by placing one embryo per IVF treatment cycle (single embryo transfer, SET) into the womb and freezing other embryos so that they can be used at a later date. Explaining this approach to women and their partners and families is essential in agreeing to this approach. Over the past 15 years, many of those involved in providing fertility treatment, including the independent regulator, medical professional societies, all fertility treatment clinics and patient advocates, have worked together to encourage the practice of placing a single embryo per IVF treatment cycle into the womb to reduce the chance of multiple pregnancy. Those efforts have been hugely successful in reducing multiple pregnancy rates following IVF—from one in four pregnancies in 2009 to one in 16 pregnancies in 2019—without reducing the overall chance of achieving a pregnancy per IVF treatment cycle. The multiple pregnancy rate can be lowered even further to below one in 20 pregnancies with additional improvements to the IVF treatment process. This is likely to lead to more clinics and more women, their partners and families choosing single embryo transfer, particularly if the NHS is prepared to fund three full IVF treatment cycles across the whole of the UK.