What is twin birthweight discordance?

The purpose of this study was to define the level of twin birthweight discordance across gestational age at which perinatal morbidity, neonatal death, or congenital anomalies were more likely to occur. One hundred ninety-four sets of twins (1982-1985) were retrospectively studied. Discordance was defined as (birthweight of larger-birthweight of smaller/birthweight of larger) x 100. The mean discordance was 10.3 +/- 8.5% (26 to 32 weeks = 7.6 +/- 5.9%; 33 to 36 weeks = 9.5 +/- 9.5%; 37 to 42 weeks = 11.4 +/- 8.5%) (p = 0.07). The occurrence of morbidity, neonatal death, and anomalies was increased with prematurity or the occurrence of small for gestational age in both twins. However, neither morbidity, neonatal death, nor anomalies were significantly related to level of discordance. These data demonstrate that prematurity and birthweight below the tenth percentile may present a greater threat to twins than does birthweight discordance. These findings should be given due consideration in planning antepartum management.