Twins (IMAGE) University of Birmingham Caption Approximately one in 60 pregnancies are twins; an incidence increasing in the UK because of the use of artificial reproductive techniques and a rising maternal age. Credit University of Birmingham Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.