Strengths and Limitations
Our sample represents the population of pregnant women from a large geographical area in metropolitan Melbourne covered by catchments of our three maternity hospitals during a defined period in the constantly changing pandemic. The main limitation of this study is the fact that testing was performed on a limited number of mostly asymptomatic pregnant women as an opt in test, and at a single point in time. The results cannot be generalised to populations with higher rates of disease prevalence or to other age groups. Our sample did, however, include a group of women with potential symptoms of COVID-19, whose test results were negative. A single nasopharyngeal swab may potentially fail to identify a proportion of infected individuals15, and it has been suggested that serial testing may be necessary to minimise false negative results16. These issues are, however, less problematic in low prevalence populations, in which the predictive value of a negative result is very high, reliably ruling infection out in asymptomatic individuals.