Gestational age-specific distribution of twin birth weight discordance

Optimal threshold for birth weight discordance: Does knowledge of chorionicity matter?

OBJECTIVE

To establish the optimal threshold of birth weight discordance (BWD) for prediction of stillbirth, perinatal mortality and morbidity in twins born in British Columbia with or without chorionicity information.

STUDY DESIGN

This is a retrospective population-based cohort study of twins born in British Columbia from 2000 to 2010. Data from one hospital was used to adjust for chorionicity. Multivariate generalized estimating equation and receiver operating characteristic curve analyses were performed to evaluate the predictability of BWD in comparison with other fetal anthropometric measurements. Positive likelihood ratio is used to estimate test accuracy. Survival analysis was conducted to take gestational age and other confounders into account.

RESULTS

We analyzed two cohorts, with (pairs=1493) and without (pairs=6328) chorionicity information, of which 1.5% experienced stillbirth, 2.9% suffered perinatal mortality and 22.6% identified with perinatal morbidities. BWD was a significant predictor of stillbirth. Standard receiver operating characteristic curve analysis and survival analysis suggested that BWD of ⩾30% is the optimal thresholds for stillbirth and perinatal mortality irrespective of chorionicity. However, the P-value for predictive accuracy of BWD was nonsignificant for perinatal morbidity, after adjusting for confounding variables engaging multivariate analysis. Sex discordance can be used as a proxy for chorionicity.

CONCLUSION

BWD is a good predictor for stillbirth. A BWD cutoff limit of 30% and higher has optimal accuracy for detecting perinatal mortality.

Growth curves for twins in Slovenia

Abnormalities of fetal growth are more common in twins. We introduce the growth curves for monitoring fetal growth in twin pregnancies in Slovenia. Slovenian National Perinatal Information System for the period between 2002 and 2010 was used to calculate birth weight percentiles for all live born twins for each week from 22nd to 40th week. The calculated percentiles of birth weight for all live-born twins in Slovenia served as the basis for drawing 'growth' curves. The calculated growth curves for twins will help accurately diagnose small or large twin fetuses for their gestational age in the native central European population.

[Fetal growth in multiple pregnancy]

A close surveillance of fetal growth in multiple pregnancies is mandatory for the prevention and/or reduction of neonatal morbidity and mortality. Multiples have the same genetically determined growth potential as singletons. However, this growth potential is restricted by the functional capacity of the placenta and uterus. Multiples show a specific growth pattern compared to singletons. Nevertheless, for clinical surveillance, the 10th percentile of singleton growth charts may be used, because significant differences, which may define normally grown multiples as small for gestational age or growth restricted, can only be detected at higher gestational ages, when most of the multiples may have already been delivered. At higher gestational ages, obstetricians should take into account the specific growth pattern for multiples. In multiples with growth discordance, it is necessary to consider or exclude the various causes, and if necessary the clinical follow-up has to be intensified.