To describe birth prevalence of rare craniofacial anomalies and associations with antenatal and perinatal factors.
All live and stillbirths in Western Australia between 1980 and 2010 were identified from the Western Australian Birth Registrations and the Midwives Notification System (also provides information on antenatal and perinatal factors). Rare CFA [Craniosynostosis, craniofacial microsomia and others (Pierre Robin, Van der Woude and Treacher Collins syndrome)] were ascertained from the Western Australian Register of Developmental Anomalies and linked to other data sources. Trends in prevalence, adjusted for sex and Indigenous status were investigated by Poisson regression presented as annual percent change (APC). Strengths of association of related factors were assessed using multivariable log-binomial regression adjusted for sex, Indigenous status, birth year, socioeconomic disadvantage and remoteness and reported as risk ratios with 95% confidence intervals.
There was a temporal increase in prevalence of metopic synostosis [APC:5.59(2.32,8.96)] and CFM (Goldenhar syndrome) [APC:4.43(1.94,6.98)]. Rare CFA were more likely among infants born preterm, as twins or higher order multiples, with growth restriction, to older parents, to mothers undertaking fertility treatments and with pre-existing medical conditions specifically epilepsy, diabetes or hypothyroidism. Prenatal identification of rare CFA was uncommon (0.6%).
Our findings indicate a steady increase over time in prevalence of metopic synostosis and CFM (Goldenhar syndrome). Possible associations of fertility treatments and pre-existing maternal medical conditions with rare CFA require further investigation.

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