Twin Pregnancies After IVF


As promised, each Thursday, we will now offer you a piece of educational, science, or research related information. The purpose of our #ThursdayThoughts post is to share with you fact-based content that can enlighten and assist you on your fertility journey. Enjoy our post! Helping to Create New Beginnings….

Twin Pregnancies After IVF

Monozygotic twins are also known as identical twins. This type of twin comes from one egg as opposed to dizygotic or fraternal twins which come from 2 separate eggs.  It is well known that twins are more common in patients undergoing ART (assisted reproductive technology), mainly due to double embryo transfer.  This is why single embryo transfer is recommended for most good-prognosis patients, as it decreases the chance of having fraternal twins.

One question that continues to be studied is whether IVF increases the risk of monozygotic twinning  A recent systematic review and meta-analysis was done looking at this issue (Andrea Busnelli, MD et al. Fertility and Sterility. February 2019: Volume 111, Issue 2, pages 302-317).  The review evaluated several different factors/techniques that are used in IVF such as extended embryo culture, assisted hatching, type of insemination, embryo biopsy, frozen embryos, female age, and oocyte donation.   The results showed that there was an increase in monozygotic twinning when using extended embryo culture (blastocyst) vs cleavage stage transfer.  There was also an increased risk in women <35 years old and when using conventional IVF vs ICSI.  However, more data are needed before drawing any firm conclusions.

Although blastocyst culture may be associated with increased risk for monozygotic twinning, growing embryos to blastocyst stage allows for more successful single embryo transfers, significantly reducing the risk of dizygotic twins (the most common types of twins resulting from ART).  The overall reported incidence of monozygotic twins after IVF is still very low (<2%) which means these findings should not affect the use of extended culture at this point.  Based on these studies, there is potentially a higher risk of monozygotic twinning with blastocyst transfer. However, overall risk for multiples is decreased when single blastocyst transfer is utilized.  In addition, it is unclear whether the rate of monozygotic twinning is higher among IVF patients compared to natural pregnancies; observational bias is an issue in many studies involving IVF.

For more information regarding fertility treatments and its risks and benefits, please call the Fertility Institute of Hawaii at 808-545-2800 to schedule an appointment with a physician, or visit our website at for more information.


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