A study whose conclusions were published in the medical journal Pediatrics postulates a possible link of the increased incidence of twinning in society to the increased incidence of cerebral palsy.

Based on examining the birth outcomes of over 155,000 children, the researchers from the National Institute of Neurological Disorders and Stroke (NINDS) and the California Birth Defects Monitoring Program (CBDMP) saw that twin pregnancies led to the development of cerebral palsy ten times more often than what is seen among singleton births.

“With the number of twin births on the rise in this country and others, it is vital for us to increase our base of scientific knowledge about this very special population,” said Patricia A. Grady, Ph.D., acting director of the NINDS. “Twins accounted for 10 percent of all cases of CP in this study, and we need to explore the reasons behind that number.”

The study was led by Judith K. Grether, Ph.D, and epidemiologist at the CBDMP, which is part of the California Department of Health Services. Joining her was Karin B. Nelson, MD, acting chief of the NINDS Neuroepidemiolgy Branch. The scientists looked at 2,985 individuals from 1,537 twin pairs born between the years 1983 and 1985 in four counties in Northern California who lived to at least age three. Their findings showed that out of the close to 3,000 children from twinned pregnancies, 20 children from 18 pairs had cerebral palsy. The study found that about seven children out of every one thousand twin children had either moderate or severe CP. In addition, more than 10 twin pairs out of every thousand twin pregnancies had CP in either one or both members.