STUDY QUESTION
Are all twin births following single embryo transfer (SET) monozygotic?
SUMMARY ANSWER
Between 1 in 10 and in 1 in 5 twins born after SET are the result of a concurrent natural conception.
WHAT IS KNOWN ALREADY
The twinning rate after SET is higher than following natural conception. Most studies of twins following SET have incorrectly assumed monozygosity or have not been abl...
