Workplace exposure to plasticizers and pesticides may lower a woman's fertility and increase her chances of having a lower birthweight baby, suggests research published online in Occupational and Environmental Medicine.

The researchers base their findings on 6,000 women during various stages of their pregnancy, with due dates between 2002 and 2006. The women were part of a long term study tracking the health of their children from fetal development to young adulthood (Generation R study).

Each of the women was comprehensively assessed. This included physical examination, questionnaires and interviews, during which they were asked how long it took them to conceive and what paid work they had done.

They were also asked about the types of jobs and activities they had performed and a job exposure matrix was used to assess their working conditions, including physical workload and exposure to chemicals during pregnancy.

The average age of the women was 30, and more than two thirds (68%) said they had planned their pregnancy. Around half the women were of black or minority ethnic origin.

Among the 3,719 who provided information on time to conception, a period of 6 to 12 months or in excess of a year was reported by 15% and 10%, respectively. Six months to conception is considered to be long.

Around one in 20 (5.5%) had a preterm birth (under 37 weeks of pregnancy) and just over 1% gave birth before 34 weeks.

Some 15% of babies weighed less than 3,000 g at birth and 5% were deemed to be of low birthweight (under 2,500 g).

Older age, lower educational attainment, ethnicity, and smoking and drinking all affected time to conception and birthweight. These are all known risk factors.

Physically demanding work did not affect fertility or birthweight. If anything, regular handling of loads weighing 5 kg or more was associated with improved fertility and heavier babies at birth. But this finding could be the result of healthier women taking on these jobs, say the authors.

But women exposed to phthalates - substances used to make plastics more flexible - and pesticides were more than twice as likely to take six months or longer to conceive and to have lower birthweight babies, although the overall numbers were small, say the authors.

Source: British Medical Journal