Pregnant women overestimate the risks of taking over the counter and prescribed medication - according to new research from the University of East Anglia (UEA).
The findings reveal that women choose not to medicate common pregnancy symptoms such as nausea, heartburn and aches and pains.
Most worryingly, mums-to-be are choosing not to take medication for UTIs - which can cause significant complications and harm the foetus if left untreated.
Lead researcher Dr Michael Twigg, from UEA's School of Pharmacy, said: "We wanted to find out what women believe about the risks and benefits of taking medication while pregnant.
"We wanted to know how these beliefs and fears relate to actual medication taking - whether they stop women taking medication which is actually safe."
The international research team sought pregnant women or new mothers via popular websites such as Bounty and the Pregnancy Forum.
A total of 1120 volunteers carried out an online survey in which they were asked about which common conditions they had experienced during pregnancy - such as nausea, heartburn, constipation, colds, urinary tract infections, neck and pelvic pains, headaches and sleeping problems.
The women were asked about the extent to which they thought medicines to treat these conditions were harmful or beneficial. They were also asked about whether they deliberately avoided any medicines during pregnancy, and if so which ones.
Finally, the women were asked to rate a range medicines, foods and other substances in terms of how harmful they thought they were for the foetus on a scale of 0-10.
Dr Twigg said: "We found that just over three quarters of the women used some form of medication to treat at least one common condition experienced during pregnancy.
"Relatively few took medication for nausea, constipation or sleeping problems. However these symptoms can be alleviated by changes to diet and lifestyle.
"We also found that a large number of women thought that taking paracetamol during pregnancy was risky and would avoid it. It is however perfectly safe.
"One of the most worrying things we discovered was that many women who experienced a UTI did not take medication for it. If left untreated, UTIs can cause significant complications and harm the foetus.
"A total of 72 per cent of the women said they deliberately avoided using certain medicines during pregnancy - particularly paracetamol, ibuprofen, cough and cold remedies, antihistamines and nasal decongestants - for fear of harming their unborn child.
"Overall, women who did not take medication perceived the risk to be greater than those who chose to take medication.
"What this all shows us is that women need more information about the safety of medications during pregnancy to encourage them to treat conditions effectively. Understanding women's concerns is also essential to promote adherence to prescribed medications during pregnancy.
"Interestingly about 50 per cent of women said they used the internet to source medical information. Many also said they seek advice from pharmacists so it would be beneficial for pharmacists to have better professional training in this area," he added.
'Women's beliefs about medication use during their pregnancy: a UK perspective' is published in the International Journal of Clinical Pharmacy on June 3.