Pregnant women who are obese are having a "massive impact" on the NHS due to the increased risk of complications, the need for more senior staff, and the cost of extra equipment.

Maternal obesity is having a knock-on effect, with scheduled operations being cancelled when doctors need to use extra large operating tables in theatres normally used for gynaecological surgery.

Obese women require more specialised care - with extra scans and tests, more caesarean deliveries, and a consultant obstetrician being present at the birth. There are more complications, including a higher risk of emergency interventions and of trauma to the baby, and obese pregnant women cannot have water births or, in many cases, home births .

While the financial cost has not been calculated, the impact of maternal obesity on the NHS is laid bare by the study of 16 maternity units in the north-east, published today in the British Journal of Obstetrics and Gynaecology.

Separate Danish research, published in Human Reproduction, reveals that obese or overweight couples are three times more likely to be infertile than those of normal weight. Obesity is known to be a risk for infertility for men and women but the study, of 47,835 couples, is the first to calculate the risk if both partners are overweight. The research also found a direct link between losing weight and a reduction in time spent trying to conceive.