Ultrasonic assessment of the high rate of human multiple pregnancy in the first trimester

Abstract

The ultrasonic examination of 6,690 pregnant patients showed a greater number of multiple pregnancies than usually observed at delivery: 71 per cent of twin gestations diagnosed before 10 weeks were singletons when delivered.

The Vanishing Twin

“…Furthermore, when these women were followed to term, the number of twins observed at delivery was considerably less than the number of twin conceptions originally identified during the first trimester [8,10,13,15,17,20,22,35,41]. These observations have led to the concept of the "vanishing twin," a term which has gained a modest degree of acceptance in recent years and has provided biologists and clinicians with new information regarding the true incidence of human twinning.…”

“…Numerous reports of serial ultrasonographic examinations of pregnant women have demonstrated the "disappearance" of at least one of two gestational rings [8,10,13,15,17,20,22,35,41]. Furthermore, when these women were followed to term, the number of twins observed at delivery was considerably less than the number of twin conceptions originally identified during the first trimester [8,10,13,15,17,20,22,35,41].…”

“…Furthermore, the number of twins observed at delivery was significantly less than the number of twin conceptions originally identified by ultrasound during the first trimester. These observations led to the concept of the "vanishing twin" [8,10,13,15,17,20,22,35,41].In order to obtain reference and personal data on this subject, we reviewed the literature and corresponded with members of the International Society for Twin Studies and obstetricians affiliated with Northwestern University Medical School, Chicago, Illinois. The nine studies that have documented this phenomenon cite "disappearance" rates ranging from 0% to 78%, depending on patient population and timing of ultrasonography [8,10,13,15,17,20,22,35,41].…”

“…Furthermore, the number of twins observed at delivery was significantly less than the number of twin conceptions originally identified by ultrasound during the first trimester. These observations led to the concept of the "vanishing twin" [8,10,13,15,17,20,22,35,41].…”

“…The nine studies that have documented this phenomenon cite "disappearance" rates ranging from 0% to 78%, depending on patient population and timing of ultrasonography [8,10,13,15,17,20,22,35,41]. Several explanations are offered: physiological mechanisms of "disappearance" (resorption or formation of a blighted ovum or fetus papyraceus), artifactual error, incomplete scanning technique, and poor quality ultrasound equipment.…”