High levels of environmental pollution may increase the rates of twin births, suggests research in Occupational and Environmental Medicine.
Researchers investigated the rates of twin births of mothers living in the vicinity of a toxic waste incinerator in the Hesse region of Germany. The rates were compared with those of two other areas without obvious environmental pollution in Hesse, and assessed against regional birth records from 1994 to 1997.
Twinning rates in areas near the toxic waste incinerator were more than twice as high as those in the two comparison areas.
The researchers also assessed the proportion of mothers undergoing fertility treatment, as this can increase the likelihood of twin births. This proportion was highest (8.3%) among women from one of the areas without a toxic waste incinerator. And the prevalence of twinning was no higher among women undergoing fertility treatment.
Analysis of birth records showed that in areas where people lived close to the toxic waste incinerator, or other heavy industries in the region, the twin birth rate was up to twice that of other areas.
The authors conclude that there may therefore be a link between industrial pollution and the rate of twin births.
The rate of multiple births, which have not resulted from fertility treatment may also be an indicator of the extent of exposure to other environmental factors that could detrimental effects on health, they suggest.