Obese expectant mothers are having a "major impact" on the NHS due to increased risk of complications and the need for extra equipment and staff, according to research out today.
A study found that obese pregnant women need more one-to-one care, which can have an impact on waiting times for other patients.
Obese women are also more likely to need extra scans and tests, have more caesarean deliveries, need more specialist equipment and have less choice when it comes to giving birth than other women.
They suffer higher rates of infection and can need extra support with breastfeeding, and there are added risks for the baby, the study said.
A total of 16 maternity units in the North East were studied, with 33 heads of midwifery, midwives, obstetricians and other professionals taking part in interviews for the research.
The authors, from the Centre for Food, Physical Activity and Obesity Research at the University of Teesside, published their results in BJOG: An International Journal of Obstetrics and Gynaecology.
They said interviewees described maternal obesity as "having a major impact on service, specifically in relation to the level of care required, the cost and resource implications, complications and risk to the mother and infant".
The authors concluded: "Healthcare professionals caring for women in pregnancy feel that maternal obesity has major implications for service delivery.
"The impact relates to resources and cost implications, additional care requirements because of the complications that arise and the impact on the health of the mother and her infant, the restrictions in care options for the women, difficulties in carrying out certain procedures, and the impact on the psychological health of the mother.
"Some healthcare professionals feel that maternal obesity is a public health issue, and there is concern relating to the lack of national guidance on which to base local policy for the care of obese women in pregnancy."
Previous studies have concentrated on the effects of obesity on pregnant women but this research examines the impact on service delivery in the NHS.
The study noted that obese expectant mothers are at increased risk of high blood pressure and diabetes in pregnancy, while risks to the child include being born overweight and birth defects.
There are also more complications in labour and the need for more induced births and Caesareans, it said.
Health professionals told the researchers that issues over equipment most frequently involved scales with a too-low maximum weight limit, and theatre tables which could not take extra weight.
Some trolleys also "take the weight but not the girth", one head of midwifery said.
Another told how a lack of an operating table big enough for elective Caesareans meant those women were transferred to the gynaecology theatre list, which happened about twice a month.
"The gynae theatre table is also required when an emergency Caesarean is required, which disrupts the theatre list and impacts on the waiting times as well," they added.
Another said specialist equipment was needed "such as longer length needles for spinal anaesthesia (and) the need to open additional equipment to hold fat back during Caesarean section."
All the maternity units had a policy of routine referrals for consultant-led care when the mother was obese.
But six units said they had been forced to change their policy on referring women for consultant-led care because the caseload was too great.
That meant they had raised their BMI (body mass index) cut-off points so only the most obese women were referred to consultants.
When it came to extra tests, two units said obese mothers needed glucose tolerance tests at the start and towards the end of pregnancy, and six units said extra scans were needed "as it was more difficult to see the foetus and determine the foetal size and presentation".
One clinical midwifery manager said: "The excess layers of fat also make it more difficult to palpate to determine foetal lie when the mother is obese, and there are difficulties when doing ultrasound scans and listening to the foetal heart.
"During labour it is more difficult to pick up the contractions and foetal heart rate, and this can lead to misinterpretation of what is being picked up, which determines the outcome.
"For example, the labour might be misinterpreted as being abnormal which could lead to an unnecessary change in the plan of action, Caesarean etc."
Nine units said obese mothers-to-be had less choice when it came to giving birth.
Some units had restrictions on pool births because of "lifting and handling issues for staff" and also the risk of needing an emergency intervention, such as a Caesarean.
Two units also said they discouraged obese mothers from having home births because of the higher risk.
Most (11) units said any complications after birth mainly related to a higher rate of infection and slower wound healing in obese women.
The health professionals identified several areas for the future management of obese expectant mothers, including improved links with dieticians and weight management experts.
They also suggested pre-pregnancy counselling "and every effort to intervene should be made in those women who are overweight or obese prior to the pregnancy being established".
Another measure could be to introduce a routine system of monitoring the height and body weight of pregnant mothers.
Professor Carolyn Summerbell, who heads up the University of Teesside's Centre for Food, Physical Activity and Obesity Research, said: "We're not trying to blame or stigmatise obese pregnant mothers and we would certainly not recommend that overweight mums-to-be go on crash diets.
"But our initial findings show reasons for concern with obese pregnant mothers, and there is a lack of weight management guidance and support readily available for them."