More than half of pregnant women are overweight or obese at the start of pregnancy and the figure is rising, data shows.

A new report on just over 714,000 women using NHS maternity services found that 309,854 already had weight problems at the start of pregnancy, with 18,379 of these women being morbidly obese.

Of the overall group, more than half (50.4%) were overweight or obese at their first NHS appointment in 2016/17, up from 47.3% the year before.

According to the NHS, being overweight increases the risk of complications for pregnant women and their babies, including miscarriage, stillbirth and conditions such as spina bifida.

The overall risk of miscarriage under 12 weeks is one in five (20%) but rises to one in four (25%) for women with a body mass index (BMI) over 30.

A BMI over 30 also triples the risk of gestational diabetes, high blood pressure and pre-eclampsia, while overweight women are more likely to suffer blood clots, or to need assistance in delivery including an emergency Caesarean section.

The new report – the National Maternity and Perinatal Audit – looked at 728,620 births (97% of the total) in NHS maternity services in England, Scotland and Wales between April 2016 and March 2017.

It found a small increase in induction rates (27.9% to 29.2%) over the period, and worked out that 36.9% of women having a single baby gave birth with no intervention such as epidural.

Experts noted that some NHS trusts have higher than expected rates of encephalopathy, a component of baby brain injury, in the first three days of life and said more needed to be done to look at variation across the health service.

Variation between hospitals was also noted for the percentage of women suffering serious tears during labour or experiencing major bleeding after birth.

The rate of instrumental births (using forceps or ventouse) also varied from 6.8% to 18.4% among maternity services.

Professor Russell Viner, president of the Royal College of Paediatrics and Child Health (RCPCH), said: “For the first time, over half of women are being recorded as overweight or obese during pregnancy.

“Every parent wants to give their baby the best start in life, however this raises several red flags for both women’s and children’s health.”

He said: “For mothers, being overweight during pregnancy comes with significant risks including gestational diabetes, pre-eclampsia, miscarriage and postpartum haemorrhage.

“Meanwhile, babies born to overweight parents are much more likely to become overweight children and are more likely to suffer from life-long conditions such as Type 2 diabetes.

“Women must be supported before conception, during pregnancy and after birth to ensure the healthiest possible outcome for both themselves and their child.

“With the right support, it is possible to stop this dangerous cycle from being repeated.”

Professor Lesley Regan, president of the Royal College of Obstetricians and Gynaecologists (RCOG), said: “All women should expect to receive the best possible care during pregnancy and childbirth.

“National initiatives to improve maternal and neonatal care are making impressive headway to ensure services are as safe and personalised as possible for women, the vast majority of whom have a safe birth.

“But we must not be complacent since this report highlights marked variation in standards of care persist, particularly around birth complications, such as severe perineal tearing and obstetric haemorrhage.”