The significance of birth weight difference in discordant twins: a level to standardize?

Objective. To evaluate the significance of different degrees of birth weight discordance in twin pregnancies. Design. Population based study. Method Three hundred and eighty-four twin gestations over 20 weeks of gestation during a two-year period ending in 31.12.1995 were retrospectively analyzed. Twins were stratified into six categories according to the percent difference in infant birth weight. The difference in percents was calculated from the larger twin; (Birth weight of larger twin - Birth weight of smaller twin)/Birth weight of larger twin and multiplied with 100. The relationship between different categories and the subsequent perinatal and neonatal outcomes was assessed. Results. Among 384 pairs thirteen patients were identified to have single fetal demise and fourteen patients were documented to have dead fetuses of both twin pairs. Of 357 twin gestations studied 137 (38.4%) had discordance of <10% and 36 experienced discordance of >30% (10.1%). The frequency of low APGAR score (<7) in women with >30% discordance was higher than that of <10% group (16.7% vs. 9.5%). Intensive care for infants was required in 30 infants with >30% birth weight discordance (41.7%) and in 24 cases with <10% birth weight discordance (8.8%). Thirty-three percent of cases with discordance of >30% experienced neonatal mortality whereas the corresponding figure for patients with <10% discordance was 1.5%. Conclusion. We postulate that definition of discordant growth in twin gestations should be categorized with respect to gestational week since the level of discordance prejudicing fetal or neonatal jeopardy may vary in different stages of pregnancy.