Motor nerve conduction velocity for assessment of gestational age in twins

During the period from October 1, 1979 to March 31, 1981, 40 maturity tests were made on 20 pairs of twins at the Department of Obstetrics at Berlin-Neukölln Hospital. We therefore used the motor nerve conduction velocity (NCV) of the ulnar nerve combined with the Farr system. Only those children whose gestational age was absolutely certain were examined. A strong correlation emerged between the NCV level for twins and singles (r = 0.8 at p less than 0.0001), so that it was possible to establish the maturity age of twins to an accuracy of +/- 1 week. The levels of the NCV measurement within a pair of twins showed a high degree of agreement (r = 0.9 at p less than 0.0001) in which the average fluctuation amounted to 0.5 m/s = 2-3 days. Even when there was a large variation in the weight of the twins (greater than 300 g or greater than 15%), there were only minimal differences (r = 0.9 at p less than 0.0001). On the other hand, the Farr system deviated significantly in a false-positive direction up to the 38th week of gestation. Measuring the motor NCV of the ulnar nerve proved to be a simple and precise method to assess the neonatal gestational age in twins.