Maternal smoking during pregnancy and risk of cryptorchidism: a systematic review and meta-analysis
The risk factors for undescended testes in male infants and the underlying pathogenesis still remain unclear. The aim of this study is to identify the relationship between maternal smoking during pregnancy and risk of cryptorchidism. A systematic review was conducted using appropriate search terms to identify articles pertaining to maternal smoking during pregnancy and risk of cryptorchidism. Entries up to December 23, 2017 were taken into consideration, without any language or regional restriction. The crude ORs and their 95% CIs were computed by using the fixed-effect model. Twenty studies involving 111,712 infants were included in our meta-analysis. The risk of having a male infant with cryptorchidism was significantly different between mothers who smoked during pregnancy and those who did not (pooled crude OR 1.18, 95% confidence interval [CI] 1.12–1.24, p < 0.00001).
What is Known:
• Preterm and low birth weight have been definitively shown to be risk factors for cryptorchidism.
• The relationship between with maternal smoking during pregnancy and risk of cryptorchidism remains controversial all the time.
What is New:
• Mothers who smoked during pregnancy had a 1.18 times higher risk of having a child with cryptorchidism as compared to those who did not smoke.
• Evidence has been found that maternal smoking during pregnancy is a definitive risk factor for cryptorchidism.
KeywordsCryptorchidism Maternal smoking Meta-analysis
I would acknowledge the support of Dept. of Urology of Children’s Hospital of Chongqing Medical University, the financial support of National Natural Science Foundation of China, and I would especially express my thanks to Professor John Hutson for language editing.
CJY and SDW conceived and designed the meta-analysis. CJY and YW independently searched the Pubmed, Cochrane Librery, Web of Science database, China National Knowledge Infrastructure (CNKI), WanFang Data, VIP database and China Biology Medical disc (CBM), and independently extracted the data. CJY led analysis and interpretation of data, drafted the manuscript and revised content based on feedback. YW acted as second reviewer. XLT and BL assisted with the retrieval of the database and acquisition of data. LJS and CLL assisted with the interpretation of data and provided critical revision of drafts. TL, DWH, and GHW assisted with the conception and design, interpretation of data, and critical revision of drafts. SDW acted as the corresponding author, provided funding support, assisted with interpretation of data, provided critical revision of drafts and acted as the third (mediating) reviewer.
This study is supported by the National Natural Science Foundation of China (No. 81571425), Scientific and Technological Research Program of Chongqing Municipal Education Commission (KJ1600229), and Postgraduate scientific research innovation project of Chongqing Medical university (CYB16105).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
This article does not contain any studies with human participants or animals performed by any of the authors.
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