Background
Consanguinity defined as the sexual union between two related individuals has been previously an infrequent practice in Australia, but recently there has been migration from countries with widespread practice of consanguinity. There is limited and conflicting evidence in the literature that suggests consanguinity to be associated with adverse obstetric outcomes.

Aim
To assess the effect of consanguinity on perinatal outcomes.

Materials and Methods
A retrospective analysis of singleton births over a ten‐year period at an Australian tertiary hospital. The data were extracted from the hospital obstetric database and analysed for an association between consanguinity and perinatal outcomes, including stillbirth. Main outcome measures were stillbirth, threatened premature labour, fetal congenital abnormality, perinatal mortality and neonatal outcomes.

Results
There were 46 399 singleton births recorded over the ten‐year study period, and 44 004 had consanguinity data available. The overall consanguinity rate was 5.5% (n = 2565), which remained consistent over the study period at our institution. Consanguinity was associated with higher rate of threatened premature labour (5.6% vs 4.7%, P = 0.003), fetal congenital abnormality (4.2% vs 3.1%, P = 0.004), perinatal mortality (2.4% vs 1.0%, P < 0.001) and reduced risk of hypertension in pregnancy (5.3% vs 3.4%, P < 0.001). Consanguinity was an independent risk factor for stillbirth with a relative risk of 2.88 (P < 0.001, 95% CI 1.98, 4.18). Conclusion Women from consanguineous relationships are at higher risk of adverse perinatal outcomes, including stillbirth. Given the 5% prevalence of consanguinity in our obstetric population, these findings have significant implications for preconception counselling, obstetric care and health resource allocation.