Twin pregnancies: Are they more common than we think?

Abstract

In order to establish the true incidence of spontaneous multiple conception and to evaluate the phenomenon of the 'vanishing twin', the charts of the 6341 women on whom a diagnostic ultrasound was performed at between 7 and 14 weeks gestational age at the Rotunda Hospital during 1991 were reviewed. Out of 173 twin pregnancies there were 90 cases of normal ongoing twin pregnancy, 81 cases of blighted ovum or missed abortion coincident with an ongoing singleton pregnancy, and two cases of two blighted ova. Thus the incidence of multiple gestation is higher in early pregnancy than would be expected according to Hellin's law.