Study design and intervention
During this double-blinded, parallel-group clinical study, participants were randomly assigned to the control group and the intervention group at a 1:1 ratio. Women participants who meet the eligibility criteria were recruited and stratified according to their body mass index (BMI). All participants were divided into four groups underweight (BMI<18.5 kg/mSubsequently, participants took GOS supplements in the intervention group or placebo containing fructooligosaccharides (FOS) in the control group from the first trimester (T1). In intervention group, GOS (6 g/100 g) and sialic acid (3 g/100 g) were the primary ingredients. The control group mainly contained FOS (3 g/100 g). The purities of GOS and FOS were 90% and 93% (w/w) on dry matter respectively. The dietary supplements were provided by the Beijing Sanyuan Foods Co. Ltd, Beijing, China. The dosage of the supplements was 60g per day. In order to improve pregnancy health care and strengthen adherence, both the two groups were provided with supplements containing nutrients, minerals and vitamins at each visit timepoint. The trial process followed the double-blind principle of researchers and participants.