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.