Intervention participants gained less weight from randomization to 34 weeks gestation ( 5.0 vs. 8.4 kg , mean difference = -3.4 kg , 95 % CI [ -5.1 -1.8 ] ) , and from randomization to 2 weeks postpartum ( -2.6 vs. +1.2 kg , mean difference = -3.8 kg , 95 % CI [ -5.9 -1.7 ] ) .