These techniques all increase the likelihood of a multiple birth. Women choosing to start families later in life, increased use of contraception and lower fertility overall also play a role, the review says. But the emphasis is now on singleton pregnancies, which are safer, says Prof Monden. "This is important as twin deliveries are associated with higher death rates among babies and children, and more complications for mothers and children during pregnancy, and during and after delivery," he says. Twins have more complications at birth, are more often born premature and have lower birth weights and higher still birth rates.
