683 - Does Chorionicity Hold The Key? Birth Weight, Gestational Age, And Developmental Outcomes In Twins

Publication Number: 2666.683

Chiara Ionio, Catholic University of Milan, Milano, Lombardia, Italy; Gianluca Lista, Asst fbf Sacco, Milan, Lombardia, Italy; Giulia Ciuffo, Catholic University of the Sacred Heart, Milan, Lombardia, Italy; Caterina Colombo, Ospedale dei Bambini V Buzzi, Milano, Lombardia, Italy; Irene Daniele, NICU, V.Buzzi Children's Hospital, Milan, Milan, Lombardia, Italy; Francesca Castoldi, NICU V.Buzzi Children's Hospital, Milan, Lombardia, Italy; Francesca Viaroli, NICU Buzzi children’s hospital, Milan, Lombardia, Italy; Paola Fontana, NICU V.Buzzi Children's Hospital, Milan, Lombardia, Italy; Ilaria Stucchi, Vittore Buzzi Children's Hospital, Milano, Lombardia, Italy; Marinella Micanti, NICU Vittorio Buzzi Children Hospital, Milan, milan, Lombardia, Italy; Francesco Cavigioli, NICU V.Buzzi Children's Hospital Milan Italy, Milan, Lombardia, Italy

Background: Monochorionic (MC) and dichorionic (DC) twin pregnancies carry specific perinatal risks linked to placentation and prematurity. While birth weight (BW) and gestational age (GA) predict development in singletons, their role across chorionicity types and the impact of intra-pair BW discordance on developmental disparities require clearer characterisation. The influence of GA/BW and of the intra pair analysis in preterm twins on neurodevelopmental outcomes is debated.

Objective: To assess associations of BW and GA with outcomes within each group of preterm infants (Monochorionic, Dichorionic and non twins).
To test whether intra-pair BW differences predict outcome differences within twin pairs.

Design/Methods: Cross-sectional study of all non twins (NT) (N=157), MC (N=174), and DC (N=27) preterm infants born in a III level NICU (2008-2015) and undergoing follow up; intra-pair analyses included 65 twin pairs. Outcomes: behavioural (CBCL), cognitive (WPPSI), developmental (SR), and perceptual (TPV) at 5 years of age. Apgar, BW and GA came from records; intra-pair differences were calculated. Analyses: ANOVA and Pearson correlations (p < 0.10).

Results: As expected, the groups largely differs in demographic characteristics (Figure 1).
Associations between BW/GA and outcomes were group-specific (Figure 2). In NT, higher BW related to better cognition and fewer internalising issues. In MC, BW/GA showed inverse associations with cognitive and language outcomes. Lower BW/GA led to stronger language and math skills, and higher BW predicted fewer behavioural problems. In DC, higher BW/GA related to better developmental and perceptual outcomes.
Intra-pair analyses: greater BW discordance significantly predicted larger cognitive differences (WPPSI Total IQ: r=0.384, p=0.040) and was also linked to wider motor disparities (SR Psychomotor: r=0.382, p=0.096) (Figure 3).

Conclusion(s): The developmental effects of BW/GA differ by chorionicity. In MC, BW/GA showed inverse associations with cognitive/language advantages, but higher BW predicted fewer behavioural issues. In DC, higher BW/GA was related to significant developmental and perceptual benefits. Greater intra-pair BW discordance was strongly linked to larger cognitive and motor gaps, underscoring its clinical impact. These exploratory findings support chorionicity-specific monitoring and confirm that BW discordance must guide interventions to reduce disparities.This supports its role as a key marker for prenatal management and delivery timing. Future prospective studies with paired populations will allow useful comparisons between groups.

Figure 1 Demographic characteristics of the infants in the three groups
GA: gestational age; BW: birth weight; MC monochorionic; DC dichorionic;
* ANOVA correlations NT vs MC vs DC (p < 0.10)

Figure 2 Birth Weight/Gestational Age vs Outcome by Group: Pearson Correlation Table
* Bold values indicate correlations significant at p<0.10 or better.

Figure 3 Correlation between Birth Weight (BW) Discordance and Intra-Pair Developmental Disparities
BW birth weight; WPPSI cognitive scale, SR 5 developmental scale