A substantial number of pregnancies are unplanned
Women ignore healthy eating and lifestyle advice before a pregnancy, even when it is planned, a study shows.
Researchers questioning 12,500 UK women found very few who later got pregnant were taking enough folic acid or met recommendations on alcohol intake.
And they were only slightly less likely to smoke than those who did not get pregnant within a few months, the British Medical Journal reported.
Pre-pregnancy health messages need better promotion, the researchers said.
The University of Southampton team questioned women aged 20-34 about their diet, alcohol consumption, smoking, supplement use and physical activity.
The women were then asked whether they intended to become pregnant in the next year.
In all, 238 women became pregnant within three months, and 71 of those were pregnant within one month.
Those who became pregnant were only slightly more likely to comply with the recommendations.
For example, 74% were non-smokers compared with 69% of those who did not get pregnant.
And 51% drank less than four units of alcohol a week compared with 46% who did not get pregnant - the level that was recommended at the time of the study.
Only 44% of women had taken any folic acid supplements and 5.5% had taken enough to meet the recommended daily amount.
Once they know they are pregnant, considerably more women follow the guidelines.
Study leader Professor Hazel Inskip said the researchers had been shocked at the findings.
She said no amount of advice would help those not intending to have a baby - 23% of those who got pregnant in the study - but recommendations were not widely promoted for those who were planning a family.
"The folic acid is the easiest recommendation to follow. It's not difficult to get some folic acid supplements and to keep taking them, but it was pretty small numbers taking it.
"The alcohol one is much more difficult - it's much harder to give that up when you don't want to tell people you're trying to get pregnant."
PLANNING A PREGNANCY?
Take 400µg folic acid a day
Eat at least five portions of fruit and vegetables a day
She added the alcohol message - which was recently changed to avoiding alcohol altogether - was the most challenging to get across because drinking was so embedded in the national culture.
"The big problem is women don't know when they're going to get pregnant It could take a month, it could take two years, and that's a long time to be carrying on doing these things."
Men should also take responsibility by making the lifestyle changes to support their partner, she said.
Bridget Benelam, nutrition scientist at the British Nutrition Foundation said: "Having a healthy lifestyle is important for everyone, but is particularly so for women who may become pregnant because this can affect the health of their baby, not only at birth but throughout life.
"It is worrying that so few women in this study appeared to follow nutritional and lifestyle recommendations before pregnancy and it is very important that we communicate these messages to women who might become pregnant to improve both their health and the health of future generations."