No abstract

The proportion of male births declines with increasing gestation, even when time of conception is known. This male excess appears to be strongest for spontaneous preterm births. Studying the sex ratio of preterm births by medical risk factors may clarify why the male excess is absent in some populations. The possibility that obstetric decision-making affects the sex ratio of indicated births must be considered.

Study objective: To analyse the relation between preterm birth and working conditions in Europe using common measures of exposure and to test whether employment related risks varied by country of residence. Design: A case-control study in which cases included all consecutive singleton preterm births and controls included one of every ten singleton term births in each participating maternity unit. Data about working conditions were obtained by interview from women after delivery. Setting: Sixteen European countries. Participants: The analysis included 5145 preterm and 7911 term births of which 2369 preterm and 4098 term births were to women employed during pregnancy. Analyses of working conditions were carried out for women working through at least the third month of pregnancy. Main results: Employed women did not have an excess risk of preterm birth. Among working women, a moderate excess risk was observed for women working more than 42 hours a week (OR = 1.33, CI = 1.1 to 1.6), standing more than six hours a day (OR = 1.26, CI = 1.1 to 1.5), and for women with low job satisfaction (OR = 1.27, CI = 1.1 to 1.5). There were stronger links in countries with a lower overall level of perinatal health and a common practice of long prenatal leaves. Conclusion: These findings show that specific working conditions affect the risk of preterm birth. They also suggest employment related risks could be mediated by the social and legislative context. S tudies on the relation between employment and preterm delivery have yielded contradictory results.1 The decision to work during pregnancy reflects a large variety of factors such as education, social support, and health status that are independently linked to the risks of preterm birth. [2][3][4] In many studies, women who are employed have a lower risk of preterm birth than women who are not employed.