When I was attending my husband’s high school reunion recently he introduced me to a set of twins I had not met before. Though the men were essentially identical in coloring and features, they were very different in size. One was several inches taller than the other, and considerably more “robust” looking. I researched this phenomenon the next day and discovered they had dealt with some serious sibling rivalry even before they were born. These two men had coped with twin-twin transfusion syndrome as fetuses, putting the life of both at risk and marking them for life with their stark differences.

Twin-twin transfusion syndrome occurs when twins who share a single placenta also share a blood supply. Within each baby has his own piece of the placenta, their blood circulation is connected. This results in the babies sharing their blood flow. This is a serious problem when one baby receives more blood than the other. In this situation, the recipient grows more rapidly than the donor. This is not just about one baby being here than the other. Rather, it can place the lives of both fetuses in very serious trouble. Disproportionate growth also leads to disproportionate urinary output, which has serious implications for the amount of amniotic fluid around the babies. While it seems that the baby not receiving enough blood flow may be the one most likely to be at risk, they may be receiving excessive blood flow may experience tremendous strain to his heart, and excessive amniotic fluid. Both of these conditions can lead to fetal death.

In mild to moderate cases of twin-twin transfusion syndrome, one baby will grow bigger and stronger than the other, proposal survive. This results in newborns that are distinctly different in size, but often this difference levels out as the twins grow older. More serious cases of the syndrome can lead to twins who, like the pair at my husband's high school, continue to look very different throughout their lives. The donor twin may end up suffering from a variety of physical conditions resulting from his disproportionately low development prior to birth.

The most severe cases of this syndrome lead to the early death of one or both fetuses. This is why it is critical for the syndrome to be detected as early as possible so that appropriate measures can be taken to protect both baby. There are a variety of treatment options available, and practitioners evaluate their patients based on the extent of the shared blood supply, the growth patterns of the babies, and the health of the mother when determining which measure may be most appropriate. These treatments range from complete bed rest supplemented by extreme doses of protein to invasive treatments involving intrauterine surgery to separate the blood supply, and give each baby a better chance at survival.

Source: Quintero RA, et al. Stage-based treatment of twin-twin transfusion syndrome, American Journal of Obstetrics and Gynecology, May 2003, Volume 188, Issue 5, pp 1333-1340.