WEDNESDAY, June 27 (HealthDay News) -- Standing for long periods of time or working more than 40 hours a week while pregnant may affect the baby's development, Dutch researchers report.
In the new study, women who had jobs in sales, child care and teaching, which required spending many hours on their feet, had infants with heads about 3 percent smaller than women who worked in other jobs during their pregnancies, the researchers found.
Whether this makes a difference in the long-term development of the child isn't known, said lead researcher Alex Burdorf, from the department of public health at Erasmus University Medical Center in Rotterdam.
"We are not sure about that," he said. "But there are clear indications that a smaller head may negatively affect cognitive [brain] development."
Exactly how it might play a part in any one child's development isn't predictable, "but at a group level a smaller head is seen as a negative start," Burdorf said.
The only women who need to be concerned are those who stand all day and "whose doctor has indications that weight gain or fetal growth is less than expected," he added.
The study established an association, and not a cause-and-effect link, between working conditions and baby size.
The report was published in the June 27 online edition of Occupational and Environmental Medicine.
For the study, Burdorf's team collected data on more than 4,600 pregnant women. The women were asked about their work situations including whether their jobs required lifting, standing, walking, long hours or night work.
The researchers measured the development of the babies throughout the pregnancy and after birth. They found that physically demanding work had no effect on the infant's size, weight or whether the child was premature.
There was also no effect on infants of mothers who worked right up to the mon
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