Working in late stages of pregnancy is as harmful to babies as smoking, study finds

7 August 2012


Women who work past their eighth month of pregnancy are more likely to have babies with a lower birth weight, a new study has found.

Researchers from the University of Essex analysed data from women in three longitudinal studies, including 17,483 mothers participating in the Millennium Cohort Study. The researchers found that women who continued working in the late stages of pregnancy had babies on average half a pound lighter than those who stopped working between six to eight months – an effect equal to that of smoking while pregnant.

Babies whose mothers worked or smoked throughout pregnancy grew more slowly in the womb. Past research has shown that babies with low birth weights are at higher risk of poor health and slow development. They may also suffer from multiple problems later in life, such as lower chances of completing school successfully, lower wages and higher mortality.

The new study showed that women with lower levels of education benefited significantly from stopping work early, which may suggest that the effect is more marked for those doing physically-demanding work. The effect was also more pronounced among older mothers. There was no effect on babies of mothers under 24-years-old who continued to work.

The study also revealed that women who became mothers in 2000-01 worked longer into their pregnancy than those who gave birth 10 years earlier. Thirty per cent of mothers from the Millennium Cohort Study worked up to their eighth month, compared to 16 per cent of those in the British Household Panel Study, which includes babies born as early as 1991.

Speaking to the Guardian, Professor Marco Francesconi, one of the study’s authors, said: “We need to think seriously about parental leave, because – as this study suggests – the possible benefits of taking leave flexibly before the birth could be quite high.” He added that the government should consider incentives for employers to offer more flexible maternity leave to women who might need a break before, rather than after, their babies were born.

Full citation:

Del Bono, E., Ermisch, J. and Francesconi, M. (2012) Intrafamily resources allocations: A dynamic structural model of birth weight. Journal of Labour Economics, 30(4), pp. 657-706.

Media coverage of this research:

Press Association: Longer work ‘lowers birth weight’

Guardian: Work after eight months of pregnancy is as harmful as smoking, study finds

Medical Daily: Working after eight months of pregnancy may be just as harmful as smoking