The Apgar scoring is the first measure by which a newborn is evaluated for the first time in life. Introduced by Virginia Apgar in 1952, it is now the world-wide used method for reporting status of the infant and response to resuscitation immediately after birth on several time points.The advantage of this screening tool is a standardized assessment, when properly applied. Due to its predictive value it is supported the usefulness of the Apgar scoring (Iliodromiti, 2014) that is why it is included in many national guidelines and World Health Organization policy (WHO, 2013). Behavioral genetics suggests the genetic and environmental influence on newborn characteristics. The Apgar score is affected by many factors, but less is known on its genetic effect. Some authors calculated correlation coefficients for the Apgar scores of first and second born twins (Dolgun et al, 2016), of monozygotic and dizygotic pairs (Riese, 1990; Franchi-Pinto et al., 1999).Previous international studies have demonstrateda number of risk factors (socioeconomic, demographic, medical) for low Apgar scores orasphyxia, although results and definitions differ (Svenik, 2015).
Thus, the research question remains: what are the contributions of genetic and environmental factors on the early health indicators of newborn twins measured by Apgar scores? The aim of this study is to estimate heritability of Apgar score using classical twin modeling.
The data on Apgar score and prenatal parameters in twins comes from a longitudinal study in which the twin families were volunteer members of the Netherlands Twin Registry (NTR) maintained by the Department of Biological Psychology at VU University in Amsterdam. The NTR recruits families with twins a few months after birth. The study sample comprised 15124 twins that were born from 2005 to 2015. All cases with missed zygosity, with the time difference between birth of first and second twin more than 24 hours or missed were excluded. Finally, the sample of 5205 twin pairs was included in the analysis: 1773 monozygotic (MZ) and 3432 dizygotic (DZ) pairs.
The study has identified that the status of the newborn twins changes significantly in the first minutes after birth: the frequency of high Apgar score increases from 16,6% at 1st minute to 72% at 5th minute. The Apgar scores measured at 1-, 5-, 10-minute after birth are correlated between first and second born in both monozygotic and dizygotic pairs. The zygosity does not have a significant main effect on the Apgar score. The heritability of the Apgar score is 8-9%. The combined influence of environmental factors shared by twins is 51-52%. Birth order, sex and perinatal characteristics (gestational age, fetal presentation at birth, mode of delivery, birth weight and time between birth of first and second born) have a significant effect on the Apgar score.
References
Dolgun ZN, Inan C, Altintas AS, Okten SB, Sayin NC. Preterm birth in twin pregnancies: Clinical outcomes and predictive parameters.Pak J Med Sci. 2016;32(4):922-926.
Idiodromit S., Mackay D., Smith G.C.S., Pell, J.P., Nelson S.M. Apgar score and the risk of cause-specifi c infant mortality: a population-based cohort study. Lancet 2014; 384: 1749–55
Franchi-Pinto, C., Dal Colletto, G.M.D., Krieger, H. and Beiguelman, B. (1999). Genetic effect on Apgar score. Genet. Mol. Biol. 22: 13-16.
Riese M.L. (1990) Genetic influence on neonatal temperament. Acta Genet.Med Gemellol. 39: 2-7-213
Svenik M., Brudin L., Blomberg M. Preterm birth: a prominent risk factor for low Apgar scores. BioMed Research International. Volume. 2015, Article ID 978079, 8 pages, 2015.
WHO. Countdown to 2015 for maternal, newborn and child survival: accountability for maternal, newborn and child survival. Geneva: World Health Organization, 2013.
abstract_Odintsova_Boomsma_bga2018.pdf 