Quadruplet Varieties

Human interest in higher order multiple births can overwhelm the scientific side of things. In mid-April, a Towson, MD couple delivered an unusual set of quads—identical triplet boys and a fraternal male co-quad. The parents, eager for a child, sought artificial reproductive technology (ART), known to be associated with multiple births. In ART, several embryos are usually implanted in the uterus in the hope that at least one will develop into a fetus. (Current trends are toward limiting the number of embryos to avoid the risks of multiples.) The Towson mother had had only two fertilized eggs implanted, but one split twice, giving rise to identical triplets, and the other fertilized egg developed as well. I envy this family their living laboratory. Their unique foursome yields an informative series of genetically informative kinships: three sets of identical twins and three sets of fraternal twins if all the boys are pairs in every possible combination. Given that the quads share the same rearing environment, it will be fascinating to witness the developing similarities and differences in their behavioral and physical traits. Based on the existing twin literature, we can expect the identical twins/triplet to be more like each other than either is to their non-identical brother. The unfolding social relationships will also be fascinating to observe. Research shows that identical twins enjoy closer social relationships, on average, than fraternal twins. It may be that the fraternal quad will feel left out of the identical triumvirate. On the other hand, he may be an assertive leader, directing inter-quad activities. I was fortunate to be able to observe another young quadruplet set close up. Benny, Nicky, Matt and Mike were born to a Canadian couple, Mandy and Rob, who wished to add one common child to their family. (Each partner had had a daughter in a previous relationship.). The “quad boys,” as they are called, were naturally conceived and include a different intriguing array of brothers. They are composed of two sets of identical twins—Benny and Nicky and Matt and Mike. These four present a somewhat different living laboratory, convincing their parents that nature counts for a great deal in human development. At first Mandy tried to decouple the identical twinships by arranging for the fraternal twins to be roommates. This experiment failed miserably because the behaviors and preferences were matched within identical sets, but at odds within fraternal sets. The social affiliations among these young boys are also revealing. Matt and Mike are joined at the hip. It is likely that Nicky and Benny would be too if not for Nicky’s cerebral palsy. Nicky has a fairly severe case of the condition—still, it is his identical twin brother Benny who is his most constant companion. This is interesting, since the boys know nothing about genetic relatedness and no one pressured Benny more than the other two to look out for his brother. We can learn a lot about what drives human social relationship just by watching these four act naturally. Twin studies have been ongoing for years, yet there are few formal studies of triplets and more. It is likely that this will change, given the new reproductive technologies and improved methods for monitoring multiple birth pregnancies.