Should singleton birth weight standards be applied to identify small-for-gestational age twins?: analysis of a retrospective cohort study

Abstract

Background Twin birth weight percentiles are less popular in clinical management among twin pregnancies compared with singleton ones in China. This study aimed to compare the incidence and neonatal outcomes of small for gestational age (SGA) twins between the use of singleton and twin birth weight percentiles. Methods This was a retrospective cohort study of 3,027 pregnancies with liveborn twin pairs at gestational age of > 28 weeks. The newborns were categorized as SGA when a birthweight was less than the 10th percentile based on the singleton and twin references derived from Chinese population. Logistic regression models with generalized estimated equation (GEE) were utilized to evaluate the association between SGA twins and neonatal outcomes including neonatal unit admission, neonatal jaundice, neonatal respiratory distress (NRDS), neonatal asphyxia, ventilator support, hypoxic ischemic encephalopathy (HIE), bronchopulmonary dysplasia (BPD), necrotizing enterocolitis (NEC), intracranial hemorrhage (ICH), culture-proven sepsis, neonatal death within 28 days after birth as well as the composite outcome. Results The incidence of SGA was 33.1 % based on the singleton reference and 7.3 % based on the twin reference. Both of SGA newborns defined by the singleton and twin references were associated with increases in neonatal unit admission, neonatal jaundice and ventilator support. In addition, SGA newborns defined by the twin reference were associated with increased rates of BPD (aOR, 2.61; 95 % CI: 1.18–5.78) as well as the severe composite outcome (aOR, 1.93; 95 % CI: 1.07–3.47). Conclusions The use of singleton birth weight percentiles may result in misdiagnosed SGA newborns in twin gestations and the twin birth weight percentiles would be more useful to identify those who are at risk of adverse outcomes.

Adverse neonatal outcome in twin pregnancy complicated by small‐for‐gestational age: twin vs singleton reference charts

“…In this study, we have shown that twin charts are better than singleton charts at identifying twins at increased risk of neonatal morbidity and mortality. We assessed SGA classified based on both birth weight and EFW, which is in contrast to previous studies that mostly used birth weight only 23,24 . From the obstetrician's perspective, classification as SGA based on EFW and its association with adverse outcome are clinically more relevant than birth weight-based classification.…”

Gestational hypertensive disease and small for gestational age infants in twin pregnancy: A systematic review and meta‐analysis

“…Currently, some research suggested that the singleton reference was not sufficient to identify twin pregnancies. 51,52 Twin growth charts optimized the identification of SGA in twins, reducing unnecessary medical interventions in twin pregnancies. 53 In our review, not all literature included used the twin birth weight reference to diagnose SGA, in this case we chose to extract the data of the single birth reference.…”

“…When referenced to twin weight, GHD is significantly associated with SGA. Currently, some research suggested that the singleton reference was not sufficient to identify twin pregnancies 51,52 . Twin growth charts optimized the identification of SGA in twins, reducing unnecessary medical interventions in twin pregnancies 53 .…”

Twin charts should be the standard reference to assess growth in twin pregnancy

“…Several investigators have reported on the diagnostic accuracy of twin-specific charts versus singleton charts for various adverse outcomes such as stillbirth, hypertensive disorders of pregnancy, and neonatal morbidity and mortality for foetuses classified as SGA according to these charts [28,63–69,70 ▪▪ ,71,72]. There is consistent evidence from large independent cohorts that the strength of association with adverse perinatal and maternal outcomes is stronger when FGR was diagnosed using twin-specific standards compared with when singleton references were used.…”