Gestational diabetes in twin pregnancy: prevalence and long-term implications.

During the period 1971-1991 at the Mercy Hospital for Women, gestational diabetes (GDM) was diagnosed in 3,447 of 61,914 tested singleton pregnancies (5.6%) and 59 of 798 tested twin pregnancies (7.4%, p = 0.025). A difference was apparent in the period 1971-1980, when the prevalences of GDM in singleton and twin pregnancies were 3.0% and 5.6% respectively (p = 0.012), but not in the period 1981-1991 when the corresponding prevalences were 7.4% and 8.4% (p = 0.36). Of the 59 patients in whom a diagnosis of GDM in a twin pregnancy was made, 27 attended the follow-up programme. These patients were matched to a control group of 27 patients who had GDM in a singleton pregnancy with similar characteristics for known risk factors for the development of permanent diabetes mellitus. On WHO criteria diabetes mellitus occurred in 5 (18.5%) of the subjects and 2 (7.4%) of the controls (p = 0.21). The difference in prevalence of GDM in twin and singleton pregnancies is less now that the overall prevalence of the disease has more than doubled (1971-1980 versus 1981-1991). Although the increased rate of permanent diabetes mellitus after twin pregnancy is not statistically significant, it would seem wise to make a special effort to enroll these women in the follow-up programme.