Background; About 50% of cases of threatened miscarriage terminate in complete miscarriage and loss of pregnancy. If pregnancy continues, the sub optimal events have been reported more; like preterm delivery and Preeclampsia, Aim and objectives; to evaluate the effect of threatened abortion on fetal growth and premature rupture of membrane and to evaluate the effect of threatened abortion on other adverse pregnancy outcomes as abortion, preterm labor, preeclampsia, placenta previa, IUGR and cesarean section, Subjects and methods; This is a prospective case-control study, was conducted on 152 pregnant women, at Obstetrics and Gynecology department at Al-Hussein Hospitals, Al-Azhar University, divided into 2 groups: (Group I): included 76 women presenting with symptoms of threatened abortion at or below 20 week of gestation, (Group II): Included 76 women who don't have any symptoms of threatened abortion, during the period from March 2021 to September 2021, Result; there is a significant difference between the groups regarding preterm labor, neonatal death, low birth weight and NICU admission, Conclusion; Threatened miscarriage is associated with increased incidence of adverse pregnancy outcome. The risk is specially increased in premature rupture of the membranes, preterm delivery and neonatal birth weight. Women with threatened abortion should be instructed about the adverse maternal and neonatal outcome of their condition and given an explicit counseling concerning compliance with healthy life style,