Abstract： Objective To explored the effect of sildenafil in treatment of pregnant women with pulmonary arterial hypertension.Methods From January 2012 to November 2013,64 pregnant women with pulmonary arterial hypertension (PAH) were randomly divided into group and control group.Control group:16 cases with mild and 16 cases with moderate PAH.To treatment with low-flow oxygen,low-salt diet therapy,cardiac,etc.sildenafil group:15 cases were mild pulmonary hypertension,and 17 cases moderate PAH.Treatment sildenafil 25 mg,rid in this study.Then the variation of the blood oxygen saturation,pulmonary artery systolic pressure,hemodynamic parameters and pregnancy outcome,including delivery modes,neonatal weight,morbidity of mother and fetus were compared.Results (1) Cardiac function and pulmonary hypertension:control group:the proportion of cardiac functional class Ⅰ-Ⅱ reduced from 81％ (26/32) to 56％ (18/32) significantly after treatment (P ＜ 0.05).Sildenafil group:the proportion of cardiac functional class Ⅰ-Ⅱ increased from 75％ (24/32) to 84％ (27/32) significantly after treatment (P ＜ 0.05).Between two groups,the proportion of mild and moderate turning to server PAH patients were significant differentce (P ＜ 0.05).(2) The pregnancy outcome of two group:the premature birth rate,low birth weight rate and cesarean section rate of 9％ (3/32),9％ (3/32)and 69％ (22/32)in sildenafil group were significantly lower than 16％ (5/32),19％ (6/32) and 81％ (26/32) in control group (P ＜0.05).The rate of vaginal delivery,term pregnancy and neonatal weight of 31％ (10/32),91％ (29/32) and (3 214 ±306) g in sildenafil group were different with 19％ (6/32),84％ (27/32) and (3 004 ±458) g in control group (P ＜ 0.05).(3) Hemodynamic parameters:in control group,arterial partial pressure of oxygen,oxygen saturation and left ventricular ejection fraction,pulmonary systolic pression were (80 ± 5) ％ to (72 ±8)％,(87 ±8) to(83±9) mmHg(1 mmHg=0.133 kPa),0.77 ±0.24 to 0.70 ±0.38 and (63 ±9) to (69 ± 12) mmHg before and after treatment,which showed remarkable decreased trends(P ＜ 0.05).The other parameter were not significantly different (P ＞ 0.05).In sildenafil group,arterial partial pressure of oxygen,oxygen saturation and left ventricular ejection fraction,pulmonary systolic pression showed increased trend before and after treatment,which were (80 ± 9) ％ to (88 ± 9) ％,(84 ± 3) to (89 ± 7) mmHg,0.70 ± 0.32 to 0.79 ± 0.27 (P ＜ 0.05),in the mean time,pulmonary systolic pression showed decreased trend from (65 ± 18) to (60 ± 13) mmHg (P ＜0.05).The other parameter did not show significant different (P ＞ 0.05).Conclusions Sildenafil treatment can significantly improve the clinical symptoms,cardiac function and hemodynamic parameters.It also could significantly improve pregnancy outcomes,reduce premature delivery,the incidence of low birth weight children,and cesarean section rate.