London - It is the perfect excuse for mothers-to-be to unplug the vacuum and abandon the washing up - housework could be bad for baby.
Research suggests the "boring and repetitive" nature of household chores raises the odds of giving birth prematurely. Exercise, however, is good for mother and unborn child.
Researchers asked almost 12 000 new mothers how much they had exercised during pregnancy - including housework.
The women were also asked about their jobs, the weight of their babies and whether they were born early.
And the information showed that mentally unstimulating work, including doing jobs around the house day-in day-out, increased the chances of giving birth at least three weeks early by up to 25 percent.
Although it isn't clear why, researchers think it may be that boring tasks increase levels of stress hormones involved in triggering labour. The study, published in the journal Perinatal Epidemiology, also threw up some other interesting results.
For instance, women who work night shifts seem to have slightly heavier babies. Again it isn't clear why, but may simply be that those who work through pregnancy are healthier in general.
The research also showed sedentary lifestyles raised the odds of having an underweight baby, while strenuous exercise did no harm to either mother or baby.
Researcher Hajo Wildschut, of Erasmus University in Rotterdam, said: "Pregnancy is not a disease.
"In fact, most women who are pregnant are healthy and most of them are being delivered of perfectly healthy babies.
"Women who are healthy and do not have pregnancy complications should not restrict their activities in order to achieve a better pregnancy outcome. They may safely continue their normal daily physical activities, including strenuous activities like jogging, squash and weight training even until late in pregnancy."
The Royal College of Obstetricians and Gynaecologists said that in most cases, exercise in pregnancy is safe.
Spokesman Patrick O'Brien said: "Exercise is good in pregnancy, it keeps you aerobically fit, it keeps your weight under control, it probably reduces the chances of difficulties and it makes it easier to deal with the birth and afterwards."
Asked whether mothers-to-be should leave the housework to someone else, he said: "I wonder if the corollary is true: if you're overdue and want to bring on labour, maybe you should get the ironing out!" - Daily Mail