Determinants of monozygotic twinning in ART: a systematic review and a meta-analysis

AbstractBACKGROUNDThe incidence of monozygotic twins (MZT) after ART appears to be higher than the incidence after spontaneous conceptions contradicting the aim of ART to avoid multiple pregnancies because of the associated risks.OBJECTIVE AND RATIONALEThe aim was to study the frequency of MZT after IVF and ICSI and how it is influenced by the day of embryo transfer, maternal age, zona pellucida manipulation, controlled ovarian stimulation, stimulation protocol, culture media and embryo quality.SEARCH METHODSOriginal studies and reviews were identified by searching the PubMed, Embase and Cochrane databases up to March 2017. The inclusion criterion was publications focusing on the five study questions related to MZT in our study. The exclusion criteria were articles that did not include blastocyst transfer, were on non-humans, were not published in peer-reviewed journals, and were based only on case studies. All of the articles were categorized according to the Oxford Centre for Evidence-based Medicine ’s ‘Levels of Evidence’, and quality and risk of bias assessment was performed with ‘The Cochrane Collaboration’s Risk of Bias Tools’. A meta-analysis was performed to study the impact of the day of embryo transfer on the MZT rate.OUTCOMESThe literature search resulted in a total of 42 articles, including 38 original studies, for analysis. The included original studies reported a MZT rate with blastocyst transfer from zero to 13.2%. Our meta-analysis found a higher f...
Source: Human Reproduction Update - Category: OBGYN Source Type: research