23 (95% CI 0.78, 1.96) vs external referents. BYL719 mw When preterm births, which is an intermediary outcome and not a confounder, were introduced in the above-mentioned model in a last step, the estimated birth weight was slightly reduced for children with maternal and paternal exposure, now −91 g (95% CI −170, −12). The estimates for other groups did not change. Thus, preterm births did not explain the observed reduced birth weight, and we are likely to observe intrauterine growth retardation. Also, the risk for growth retardation which fulfilled criteria for “small for gestational age” (Källén 1995) was increased when the mother was exposed during the pregnancy, with OR 2.15 (95% CI 1.45, 3.18;
singletons only, adjusting for the sex of the child, maternal age and parity, smoking and ethnicity, and with mother incorporated as random effect). The corresponding ORs in the groups with paternal exposure only, and with no exposure, did not differ significantly from the external referents. The lower birth weight among both girls and boys was mainly observed during the latter part of the observation period. In a crude analysis, only adjusting for sex, the weight difference between children Luminespib with both maternal and
paternal exposure and the internal reference group for the period 1988–2001 was −164 g (95% CI −260, −68). The corresponding figures for the period 1973–1987 was −21 g (95% CI −113, 71). Similarly, the effect on sex ratio TCL was most marked during the latter period, with OR 1.70 (95% CI 1.23, 2.36) for having a girl, vs OR 0.95 (95% CI 0.69, 1.32) during the early period. Also preterm births were more common in the latter period, OR 2.27 (95% CI 1.27, 4.06) vs 0.50 (95% CI 0.22, 1.13) in the early period. Discussion The present analysis gives a crude picture of reproductive outcome among rubber employees, using blue-collar employment in the
rubber industry during an assumed full-term pregnancy and/or sperm production and maturation period as the only available proxy for exposure. Such a crude measure of exposure would rather tend to underestimate effects, compared to analyses with a more refined measure of exposure. The strengths of our study are the availability of prospectively collected information on potential SNS-032 price confounders for all births, and the use of an external reference cohort of food workers which are likely to have no exposure to chemical agents that have reproductive toxicity, but otherwise being similar with respect to manual work and socioeconomic background. This is of importance, as it has been shown that maternal adulthood class had an impact on birth weight in Sweden during the period that we have studied (Gisselmann 2006), accentuating over time (Gisselmann 2005). The use of an internal referent cohort, and even more the additional exposure–crossover analysis comparing siblings among rubber workers families, further reduced the influence of unmeasured confounders.