Pregnant women may be ‘eating for two’ — or more — but when it comes to twin pregnancies, gaining too much weight may be as bad as gaining too little, a US study suggests.

There isn’t a lot of evidence for an ideal amount of weight gain in a twin pregnancy, the study team writes in Obstetrics & Gynecology. But, in a large analysis of twin pregnancies, they found that both very high and very low weight gain was associated with more preterm births and infant death.