Objective To investigate the effects of low molecular weight heparin on neonatal outcomes of selective intrauterine growth restriction (sIUGR) in monochorionic diamniotic.Methods A total of 40 pregnant women with sIUGR treated in Jiangxi Provincial Maternal and Child Health Hospital from April 2021 to April 2023 were selected as research objects,and they were divided into control group(20 cases)and treatment group(20 cases)by random number table method.The control group was treated with fetal lung maturation drugs.Based on this,low molecular weight heparin was used in treatment group.The fetal growth and development parameters([long diameter of femur[FL],double parietal diameter[BPD],abdominal circumference [AC] and head circumference [HC]),maternal hemorheology indexes (hematocele volume [HCT],whole blood low tangential viscosity [WBLSV]and whole blood high tangential viscosity [WBHSV]),fetal umbilical artery flow indexes (resistance index [RI],pulsatile index [PI],systolic high blood flow velocity [S]/late diastolic high blood flow velocity[D])and neonatal outcomes(gestational age,length,weight,adverse outcomes at birth) were compared between the two groups.Results FL,BPD,AC and HC in treatment group were higher than those in control group,the differences were statistically significant (P<0.05),RI,PI and S/D were lower than those in control group,the differences were statistically significant (P<0.05).The HCT,WBLSV and WBHSV of pregnant women in the treatment group were lower than those in the control group,and the differences were statistically significant (P<0.05).Gestational age,body length and body weight of newborns in the treatment group were higher than those in the control group,and the differences were statistically significant(P<0.05).The total incidence of adverse outcome in the treatment group(5.00%)was lower than that in the control group(30.00%),and the difference was statistically significant(P<0.05).Conclusion The use of low molecular weight heparin in the treatment of sIUGR can effectively regulate the hemorheology of pregnant women and the umbilical artery blood flow of the fetus,accelerate the growth and development of the fetus,and improve the outcome of the newborn.