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.

The researchers analysed data from nearly 55,000 twin births in Pennsylvania from 2003-2013.

Gaining too little weight was also linked with having babies that were small for their gestational age and gaining too much was tied to overly-large babies and caesarean deliveries.