Some feel down when they look at images of celebrities who "bounce back" into shape, and many wish they could turn to their midwives for help with managing their weight.
The survey of more than 6,000 mothers for Netmums and the Royal College of Midwives (RCM), found 61 per cent thought their midwife did not have enough time to discuss weight and nutritional concerns at their first antenatal appointment.
Most (84 per cent) thought the care they received from midwives on the topic was "neutral", "poor" or "very poor", and 73 per cent would like to see midwife-led classes on the NHS focusing on healthy eating and weight.
Of those surveyed, 64 per cent thought it was the role of midwives to provide encouragement and support on nutrition and losing weight.
While pregnant, women said their image of themselves ranged from "disgusting", "elephant-like" and "fat ugly big, embarrassing" to occasional thoughts of "happy and proud".
Almost half admitted to being worried about their weight during pregnancy, with concerns over how much they should gain and shedding the pounds afterwards.
Some 41 per cent said they were overweight when they got pregnant, or weighed more than they would have liked.
Many were confused about what was considered overweight in pregnancy and whether they would have their chances of giving birth naturally cut dramatically.
In July, a report from the National Institute for Health and Clinical Excellence (Nice) said obesity levels among pregnant women have reached epidemic levels. Around one in five pregnant women are obese, and more are overweight.
Obese pregnant women are at greater risk of pregnancy complications and are more likely to experience miscarriage, difficult deliveries, premature birth and to require a Caesarean.
Lindsay Ritchie, 28, from Northern Ireland, said in response to today's survey: "I have been trying, unsuccessfully to lose weight as my daughter is almost two-years-old now but I am still five stone overweight.
"If the likes of Tess Daly and Holly Willoughby can get back to pre-pregnancy size in weeks, why can't I?"
Katie Hide, 22, from Uxbridge, said: "Celebrity mothers do not lead a normal life like a working mum like me, who has to work 11 hours a day.
"They (celebrities) have a totally different world to ours.
"They and the media put too much pressure on women to be perfect."
The report was released on the eve of the RCM's annual conference in Manchester.
Netmums co-founder, Sally Russell, said: "The results from this survey are clear cut and shocking: you are more likely to have a Caesarean (either elective or emergency) if you are already overweight before you become pregnant.
"It's important that mums-to-be don't panic, as most women do have a normal vaginal delivery, but it is a wake-up call to midwives to support women better throughout their pregnancy and inform them of their options.
"Many women worry about their weight even when they are not pregnant.
"During pregnancy, with the big changes in body shape and weight, plus an increased interest in health generally, women overwhelmingly feel they wanted to have the chance to discuss these matters with a healthcare professional.