Women with greater working demands tend to have a higher risk of small babies and preterm birth, according to recent findings.
A team from University College Dublin, Ireland, examined figures on 676 women who were working at the time of their first prenatal visit, and delivered a single baby. The women gave information on their health, income, lifestyle and employment, and this was linked to their medical records during pregnancy and the infant’s records.
Potential risk factors at work were defined as high physical work demands, being on a temporary contract, working shifts, and working long hours (40 hours or more per week).
Results showed “significant and strong associations” between these high physical work demands and low birthweight (less than 2,500g/5.5 lbs). There was a significant link between temporary work contracts and preterm birth (before 37 weeks’ gestation). The researchers point out that the link to preterm birth may be due to poorer working conditions, i.e. stress and anxiety because of job insecurity, that are common under temporary work contracts.
Overall, babies born to women who were exposed to at least two of the four occupational risk factors had a nearly five-fold risk of having a birthweight of 2,500g or less and a more than five-fold risk of preterm delivery.
Researcher Dr. Isabelle Niedhammer explained, “Our prospective research analyzed a large number of occupational exposures and linked them with adverse pregnancy outcomes (low birthweight, preterm delivery, and small-for-gestational age). This is one of the few prospective studies on pregnancy outcomes that include working conditions.
“This study underlines that more attention should be given to women’s working conditions during pregnancy,” she said, “and effort should be intensified towards reducing exposure to physical work demands, shift work, and long working hours for pregnant women. Special attention should also be given to pregnant women working on temporary contracts.”
The research is published in BJOG: An International Journal of Obstetrics and Gynaecology. Journal editor Professor Philip Steer commented, “It is well known that physical and psychological stress in pregnant women can lead to adverse birth outcomes. This interesting piece of research has given doctors and midwives more information about non-medical reasons for an increased incidence of low birthweight and preterm delivery.”
Professor Steer believes this research makes it all the more important for women to attend their antenatal appointments so that risk factors can be identified in the early stages of pregnancy. He said that in these cases, “appropriate arrangements can then be made for the care of the woman and her baby.”
In a December 2007 review, experts looked at various environmental factors that have been linked to “adverse pregnancy outcomes.” Drs. Nazli Hossain and Elizabeth Westerlund Triche from Yale University School of Medicine say that stress is an established risk factor.
They write, “Maternal stress has been found to be associated with birth defects, low birthweight, preterm delivery and early onset preeclampsia.” The experts cite a study suggesting that job stress and “chronic exposure to work” have been linked with preterm deliveries.
A further study found that increased job strain in the first 20 weeks of pregnancy was linked to preeclampsia, i.e. high blood pressure during pregnancy that can have serious effects on the mother and infant. In this study, the researchers believed the trigger to be an increased release of catecholamines, the so-called “fight or flight” hormones released by the adrenal glands. Levels among the women under job strain were double those of other women, on average.
A 2006 study on women carrying out irregular or shift work found that the risk of having a small-for-gestational-age infant was significantly increased. The rate was even higher when these working patterns were combined with night hours, standing, lifting loads, noise, and high psychological demand combined with low social support. On a positive note, this study also indicated that “elimination of the conditions before 24 weeks of pregnancy brought the risks close to those of unexposed women.”
The Yale University experts conclude, “Environmental factors do play an important role in maternal health. They make an important contribution towards placental problems like low birthweight, intrauterine growth restriction, as well as have long term effects on neuronal and behavioral development in adult life.”
Niedhammer, I. et al. Occupational predictors of pregnancy outcomes in Irish working women in the Lifeways cohort. BJOG, Published online April 7, 2009.
Triche, E. W. and Hossain, N. Environmental factors implicated in the causation of adverse pregnancy outcome. Seminars in Perinatology, Vol. 31, August 2007, pp. 240-42.