Serial measurement should be used to ascertain a diagnosis of microcephaly

Abstract

Abstract Background: Birth process may affect head size of newborns. A single measurement of maximum occipitofrontal circumference at birth or within 24 hours may lead to under or over diagnosis of congenital microcephaly. The study objectives are 1) to compare head circumferences (HC) at birth, and at day 3 of life, and 2) to evaluate maternal and infant factors associated with increased head circumference by day 3 of life. Method: We conducted a prospective study of 1,131 live births with gestational age over 27 weeks between February and May 2019. All newborns had their HC measured at birth and at day 3 before discharge by trained personnel. The measurement device was similar throughout the study. The WHO and Fenton Growth Charts were used as reference ranges for interpretation. Results: The mean (+/- SD) HC within 24 hours of life and at day 3 of life were 33.58 (+/- 1.53) cm and 33.75 (+/- 1.37) cm. The mean differences were statistically significant, i.e. 0.17 cm (p<0.001). Of the 32 newborns with HC in the range of microcephaly at birth, 25 (78%) had normalized HC at day 3 of life. After adjusting for mode and presentation of delivery, newborns whose mother experienced labor pain (β=0.31, P <0.001) and newborns being either symmetrical SGA or asymmetrical SGA (β= 0.59, P = 0.002; β= 0.37, P = 0.03) had statistically significant increased HC at day 3 of life. Newborns whose mothers experienced labor pain had 0.31 cm increase in HC at day 3 of life when compared to the HC at birth, while symmetrical SGA newborn also had an average of 0.59 cm increased. Parity and gestational age were not associated factors with changes of HC. Conclusion: Serial HC measurement is necessary to ascertain a diagnosis of microcephaly. Clinical Trial Registry: Ethical approval for this study was obtained from the Research Ethics Board at Siriraj Hospital, with the Reference Number Si650/2018. Written parental informed consent was obtained before HC measurement.