Abstract： Objective To study whether the current Institute of Medicine (IOM) pregnancy weight gain recommendations vary by pre-pregnancy body mass index (BMI) was suitable to Chinese people.Methods A study was conducted on 4736 term singleton live birth gravidas,who were diagnosed normal glucose metabolism and delivered in Peking University First Hospital in 2005 and 2009,by reviewing the medical records.Based on the pre-pregnant BMI,the selected cases were divided into 3 groups:low body mass group ( BMI ＜ 18.5 kg/m2,n =465 ),normal body mass group ( BMI 18.5 - 24.9 kg/m2,n =3549),over body mass group ( BMI ≥ 25 kg/m2,n =722).All the cases were divided into 3 subgroups based on pregnancy weight gain as below,within,and above the IOM recommendations in each pre-pregnant BMI group.Totally 4736 newborns were divided by birth weight into 3 groups:normal birth weight group ( weight 2500 - 4000 g,n =4339 ),macrosomia group ( weight ≥ 4000 g,n =359 ) and low birth weight group (weight ＜ 2500 g,n =38).The difference of age,gestational age,pre-pregnant weight,pre-pregnant BMI and history of delivery of cases between 2005 and 2009 were analyzed.The difference of pregnancy outcome of women whose gestational weight gain was below,within,and above the IOM recommendations was analyzed.Results (1) Compared to mothers with pregnancy weight gain within IOM recommendations in low body mass group,risk of low birth weight in offspring was elevated tendency with pregnancy weight gain below IOM recommendations ( OR =3.71,95％ CI:0.97 - 14.12,P =0.055 ).(2) In normal body mass group, compared to women with pregnancy weight gain within IOM recommendations, risk of macrosomia in offspring was elevated with pregnancy weight gain above IOM recommendations ( OR =2.14,95％ CI:1.62 - 2.83,P ＜ 0.01 ).( 3 ) In over body mass group,compared to women with pregnancy weight gain within IOM recommendations,risk of macrosomia in offspring was elevated ( OR =3.25,95％ CI:1.65 -6.39,P =0.001 ) and risk of hypertensive disorders complicating pregnancy was high ( OR =1.79,95％ CI:1.04 -3.09,P =0.037 ) in women with pregnancy weight gain above IOM recommendations.Conclusion The current IOM pregnancy weight gain recommendations vary by pre-pregnancy BMI may be suitable to Chinese people.