Association of maternity formula supplementation during pregnancy with small for gestational age birth in Chinese newborns

•A large-scale study with 28 136 subjects is a guarantee of sample representativeness.•Total small for gestational age (SGA) status has no association with maternity formula supplementation.•Women with maternity formula are associated with a reduced risk of twin SGA.•Maternity formula supplements during the first trimester are more beneficial for twin SGA.