Samiyeh Kazemi - PhD Student of Reproductive Health, Student Research Committee, Department of Midwifery and Reproductive Health, School of Nursing and Midwifery, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
Farin Soleimani - Associate Professor/MD, Pediatric Neurorehabilitation Research Center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran.
Sara Kazemi - MSc Student of Health Education, Department of Health Education & Health Promotion, Faculty of Medical Science, Tarbiat Modares University (TMU),Tehran, Iran
Anoshirvan Kazemnezhad - Professor of Biostatistics, Department of Biostatistics, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran.

Background: Incidence of polyhydramnios in various studies has been reported from 0.2 to 3.9%. Approximately, 50-60% of cases are idiopathic with no known etiology. We aimed to investigate perinatal outcomes of idiopathic polyhydramnios with a normal ultrasound. Materials and Methods: In this study, Persian and English databases including Barakatkns, SID, Magiran, Medline, Science Direct, Scopus, Cochran, Embase, and ProQuest were searched for articles published from 1950 to August 2018. The search procedure was conducted with keywords related to idiopathic polyhydramnios , perinatal outcomes , normal ultrasound , and their equivalents in Mesh and PICO. In meta-analysis, first we quantified heterogeneity by using I2 statistics and tested using the Cochran’s Q test. Even when a low heterogeneity was detected, a fixed-effects model was applied, and for more than 75% of heterogeneity, random-effects model was used. The Forest Plot chart was drawn up and the relative risk (RR) estimate for each study (ES), the pooled estimate of RR by combining all the studies and its 95% CI, and the P-value associated with it, were indicated. Results: In this study, 13 articles involving 325,426 pregnant women were included for the Meta-analysis. The RR and 95% CI of Caesarian Section (C.S), 1.61(1.25-2.07), macrosomia, 1.84(1.40-2.42), preterm delivery, 2.45(1.29-4.64), NICU admission, 2.90(1.77-4.74), Apgar score min 5 <7, 2.79(1.18-6.57), fetal distress, 1.69(1.02-2.80), and large for gestational age (LGA), 2.27(1.38-3.72), were determined. We found a higher RR of perinatal outcomes including NICU admission, Apgar score min 5<7, preterm delivery, and LGA. RR other perinatal outcomes such as macrosomia, fetal distress, and C.S. were lower. Conclusion: Idiopathic Polyhydramnios was significantly associated with adverse perinatal outcomes. Intensive intrapartum monitoring and further attention in the postpartum are warranted.

idiopathic-polyhydramnios, Meta-analysis, normal ultrasound, Perinatal outcome