Multiple births occur approximately once in every 87 pregnancies, and in almost all instances that result in live births the infants are approximately of the same degree of maturity and have relatively similar weights. Occasionally however, there is a marked difference in the size, weight, and apparent maturity of the infants. The purpose of this paper is to report a set of live-born dizygotic twins weighing 2 lb. 8 oz. (1130 gm.) and 6 lb. (2710 gm.), respectively, with a marked dissimilarity in size and maturity and to discuss the possible mechanisms involved in producing the variations noted.
Male twins were born at full term of a 33-year-old woman after a pregnancy which had been complicated by a nephrectomy during the second month of pregnancy because of hematuria, "staghorn calculus," and pyelonephritis. The first twin weighed 6 lb. (2710 gm.); the second, 2 lb. 8 oz. (1130 gm.).