Of those women polled, 60% said they did not know which foods were safe to consume. Foods which caused particular confusion were cheese, shellfish, eggs, tuna and nuts.
Despite recent Government recommendations to cut out alcohol entirely, one in 10 pregnant women said they continued to drink alcohol throughout the nine months.
The average weight gain in pregnancy is 22lb to 33lb and women should increase their diet by around 300 calories a day according to the NHS direct.
However, the nationwide survey of 850 pregnant women and new mums found one in five were getting mixed nutritional messages from their midwives on exactly what they should eat. One in 10 blamed friends for their confusion, according to the poll by Organix.
Lizzie Vann, founder of Organix, said: “While three-quarters of women think more about nutrition when they have children, they are clearly confused about what to eat when they are pregnant.”