Background: Preterm birth: defined as any live birth occurring through the end of the last day of the 37^th week (259^th day) following the onset of the last menstrual period. Low-dose aspirin (LDA) has been noted to reduce the preterm birth (PTB) rate in multiple meta-analyses of the preeclampsia (PreE) prevention trials. It is unclear if this effect of LDA is entirely due to a reduction in indicated PTB versus reductions in preterm premature rupture of membranes (PPROM) or spontaneous PTB. In the Maternal-Fetal Medicine Unit (MFMU) high-risk aspirin (HRA) study, a near significant decrease in PTB was found despite no effect on preeclampsia. The objective of this study was to assess the impact of LDA on indicated PTB, spontaneous PTB, and PPROM PTB in the MFMU HRA study population. Aim of the work: This study aim to assess the efficacy of 17 alpha hydroxyl progesterone and low dose aspirin in reducing the rate of preterm birth in pregnant women at this risk. Patients and Methods: Study type: A double blinded randomized placebo controlled clinical trial. Study settings: This study conducted at outpatient clinic of Ain Shams University Maternity Hospital. Time of the study: The study was held from August 2016 to November 2017. Results: Data was analyzed according to the intention-to-treat principle. In a total 400 women whom recruited in the study, 160 were excluded. So we ended in to 240 women whom randomized and allocated in to 2 groups to intervention. Primary outcome measure was preterm birth. The most important secondary outcome is a composite of poor neonatal outcome (including bronchopulmonary dysplasia (BPD), periventricular leucomalacia, intraventricular hemorrhage, necrotizing enterocolitis, retinopathy of prematurity (ROP), sepsis and perinatal death).There was no statistically significant difference between both groups as regarding to age, gravidity, parity, body mass index, mean cervical length, and number of previous preterm labor. There was no significant difference between two groups as regard preterm premature rupture of membranes (P.PROM).There was no significant difference between two groups as regard time of delivery there was no significant difference between both groups in Need for NICU admission, neonatal birth weight, APGAR score, fetal complications (RDS, jaundice, BPD, HIE, NEC, bleeding, sepsis or even neonatal death).Long term neurodevelopmental complications was not conducted at this study as it needs more time.In maternal complications there was no significant difference between both groups. Conclusion: Further randomized controlled trials with larger sample size should be done to demonstrate the efficacy of low dose Aspirin in prevention of preterm labor and its complications.