Twins May Be Cute But They Can Also Be Dangerous

Tempting as it may be and logical as it may seem to some patients, the transfer of multiple embryos and any resulting twin pregnancy risks the lives of all involved.

By comparing the DNA of NASA astronaut Scott Kelly to his identical twin brother, a study that quickly went viral on social media suggested space travel might be responsible for at least a temporary change in gene expression, renewing again the public fascination with twins.

The lure of the existence and appearance of twins extends beyond the Kelly brothers with frequent media attention given to twins born to celebrities like George and Amal Clooney, Beyoncé and Jay-Z, Neil Patrick Harris and David Burtka, and many more. The Bachelor’s Arie Luyendyk Jr. reportedly is hoping that he and his new fiancé will “get lucky” and have twins. Fraternal twins also graced a recent National Geographic cover with their differences in appearance prompting a conversation about race and gene expression.

Society’s fascination with twins has also resulted in increased requests from fertility patients for the transfer of multiple embryos in order to achieve a twin pregnancy.

As a clinical psychologist in the Division of Reproductive Endocrinology and Infertility at Northwestern University, I counsel multiple patients a week who share their feelings of frustration when they learn they are restricted to use of a single embryo at a time. Many fertility clinics worldwide and medical societies have instituted single embryo transfer (SET) policies for young women (<37) with high quality embryos or for patients with genetically screened embryos in an effort to reduce the likelihood of a twin or other multifetal pregnancy.

Identical twins account for less than 1 percent of all births with or without fertility treatment when one embryo divides into two fetuses. Fraternal twins, twins that generally do not look the same and may not be the same sex, occur when two or more eggs are ovulated, or more frequently when patients have two or more embryos transferred in IVF.

As an identical twin myself, I have witnessed firsthand the fascination that others have with twins. My twin and I received a great deal of attention from strangers, teachers, and neighbors throughout my life because my sister and I looked so similar. Now, once others know I am a twin they often remark on how much “fun” or how much “easier” they think it would be to have twins. The logic presumably being that with twins, you can cutely dress them the same, finish family building quicker, spend less money on fertility treatment, have a unique parenting experience, and potentially feel better knowing that twins have a built-in friend with whom to share their lives.

But the truth is, having twins can also be extremely risky to the women who carry them, to the fetuses themselves, and to the families into which they are born if they are born at all.

Numerous pregnancy complications increase in multifetal pregnancies. The most common is preterm delivery with nearly 60 percent of twin pregnancies resulting in premature birth. Premature delivery increases the risk of in utero or post-birth demise of one or both twins as well as potential chronic medical conditions, such as spina bifida or cerebral palsy.

Maternal risks, such as gestational diabetes, hypertension, and death also increase in multifetal pregnancies. The medical costs incurred when such pregnancies go awry can cost hundreds of thousands to millions of dollars. Reductions in quality of life and increased risk of divorce are also found in families with twins and the grief following the premature delivery and death of a twin is often profound.

The goal of a having a singleton pregnancy and SET in IVF for young women or women with genetically screened embryos not only reduces pregnancy risks but research shows that the transfer of more than one embryo may actually reduce pregnancy chances. Any excess frozen embryos may be useful for future treatment if needed as they may have similar pregnancy rates as non-frozen (fresh) embryos. Ultimately, lack of insurance coverage for IVF or other non-medical contraindications do not justify compromising the safety of patients and their future children by engaging in the risky decision to transfer multiple embryos.

Single embryo transfer in IVF and the birth of singleton babies is the safest way to build families. Tempting as it may be and logical as it may seem to some patients, the transfer of multiple embryos and any resulting twin pregnancy risks the lives of all involved. With single embryo transfer, the benefits outweigh the costs and just might save lives and families.

Dr. Angela Lawson is a clinical psychologist and Associate Clinical Professor in the Departments of Obstetrics and Gynecology & Psychiatry at Northwestern University Feinberg School of Medicine and is a Public Voices Fellow.

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