The incidence of multiple births has risen in the last 30 years. In 2009, 16 women per 1000 giving birth in England and Wales had multiple births compared with 10 per 1000 in 1980. This rising multiple birth rate is due mainly to increasing use of assisted reproduction techniques, including in vitro fertilisation (IVF). Up to 24% of successful IVF procedures result in multiple pregnancies. Multiple births currently account for 3% of live births.
Multiple pregnancy is associated with higher risks for the mother and babies. Women with multiple pregnancies have an increased risk of miscarriage, anaemia, hypertensive disorders, haemorrhage, operative delivery and postnatal illness. In general, maternal mortality associated with multiple births is 2.5 times that for singleton births.
The overall stillbirth rate in multiple pregnancies is higher than in singleton pregnancies: in 2009 the stillbirth rate was 12.3 per 1,000 twin births and 31.1 per 1,000 triplet and higher-order multiple births, compared with 5 per 1,000 singleton births. The risk of preterm birth is also considerably higher in multiple pregnancies than in singleton pregnancies, occurring in 50% of twin pregnancies (10% of twin births take place before 32 weeks of gestation). The significantly higher preterm delivery rates in twin and triplet pregnancies mean there is increased demand for specialist neonatal resources.
Risks to the babies depend partly on the chorionicity and amnionicity of the pregnancy (see appendix E). Feto-fetal transfusion syndrome, most commonly occurring in twin pregnancies (where it is termed twin-to-twin transfusion syndrome), is a condition associated with a shared placenta and accounts for about 20% of stillbirths in multiple pregnancies.
Additional risks to the babies include intrauterine growth restriction and congenital abnormalities. In multiple pregnancies, 66% of unexplained stillbirths are associated with a birthweight of less than the tenth centile, compared with 39% for singleton births. Major congenital abnormalities are 4.9% more common in multiple pregnancies than in singleton pregnancies.
Because of the increased risk of complications, women with multiple pregnancies need more monitoring and increased contact with healthcare professionals during their pregnancy than women with singleton pregnancies, and this will impact on NHS resources. An awareness of the increased risks may also have a significant psychosocial and economic impact on women and their families because this might increase anxiety in the women, resulting in an increased need for psychological support.
The guideline will assume that prescribers will use a drug's summary of product characteristics to inform decisions made with individual patients.