Routine ultrasound scanning for the detection and management of twin pregnancies.

One thousand five hundred fifty-one private patients underwent routine ultrasound scanning in part to detect twins. Five thousand nine hundred fifty private patients acted as controls and underwent ultrasound scanning only when indicated by conventional obstetric standards. When diagnosed, twin pregnancy was treated with increased bed rest, nutritional counseling and careful monitoring, with delivery in a tertiary-level center. No significant differences between the two groups could be demonstrated in maternal age, parity or incidence of twin pregnancy. A significant difference could be shown, however, in the early detection of twin pregnancy. By the end of the 24th week, 94% of the twins in the routinely scanned group had been diagnosed as compared to only 68% in the controls (p = 0.03). A significant improvement in perinatal outcome was also demonstrated in the routinely scanned patients as compared to the controls. The incidence of any unfavorable outcome in any infant was reduced from 60% in the controls to 25% in the routinely scanned patients (p = 0.0007). This reduction was due to a reduced incidence of low birth weight, smallness for gestational age, prematurity, depressed Apgar scores and stillbirths. When all twins diagnosed prior to the 25th week of pregnancy were compared with those diagnosed after that week, similar findings were demonstrated.