Methods
We performed a cross-sectional study at Victoria’s largest maternity service, Monash Health, that provides birthing services across three hospitals in southeast metropolitan Melbourne, Victoria, Australia. There are about 10,000 births in the service each year (nearly one in seven of all Victorian births).
During the two-week period from 6th to 19th May 2020, inclusive, women attending routine antenatal visits were offered SARS-CoV-2 testing. We also included pregnant women who had testing in other sectors of the hospital (maternity ward, birth suite, pregnancy assessment unit, or COVID-19 screening clinic) with possible symptoms of the disease. In the weeks that preceded routine screening, we had adopted the following strategies in our three maternity hospitals to reduce exposure of patients, relatives and staff: a significant number of antenatal consultations (approximately 60%) were shifted to a telehealth model, with face-to-face appointments reserved for visits at 28, 36 and 40 weeks of pregnancy, or when deemed necessary by the attending health professional; all women were routinely asked about recent travel, known contacts and the presence of recognised COVID-19 symptoms; if symptoms were present, women were advised to attend the COVID-19 screening clinic and not to attend their antenatal appointment; all women attending the clinic or the hospital had body scanning temperature check on arrival; no support persons were allowed during clinic consultations or ultrasound examinations, and only one support person was allowed during labour and birth; and all health care professionals attending births wore protective equipment (PPE) after appropriate training.
Combined oropharyngeal and nasopharyngeal swabs were collected as recommended7 and according to national guidelines8 using FLOQSwabs® and transported in UTM medium (Copan, Brescia, Italy) by a trained health professional (nurse or midwife) wearing appropriate PPE consisting of a gown, nonsterile gloves, eye protection and a protective mask. SARS-CoV-2 testing was then performed utilising multiplex-tandem polymerase chain reaction (PCR, AusDiagnostics, Mascot, Australia), an assay with demonstrated high sensitivity and specificity (>99.9%)9.
In the screening period, additional data were collected regarding maternal age, weight, height, parity, gestational age, recent overseas travel since the beginning of the pandemic and presence or absence of COVID-19 symptoms during the week that preceded the test. Gestational age was calculated according to the first day of the last menstrual period, or by the sonographic measurement of fetal biometric parameters when the gestational age given by ultrasound differed from that provided by the last menstrual period by more than one week.
To evaluate the context in which the tests were performed in the antenatal clinic, statistics concerning the daily number of cases in Australia and the state of Victoria were obtained from the Australian Government Department of Health website10.
The primary outcome of the study was the proportion of pregnant women with a positive SARS-CoV-2 test. Continuous variables were assessed for normality by inspection of histograms and quantile-quantile (Q-Q) plots. Since the distributions of continuous baseline variables were not Gaussian, metric and ordinal variables were summarised as the median and interquartile range (IQR). Categorical variables were expressed as absolute number and percentage. The proportion of positive results was reported with its 95% confidence interval. Statistical analysis was performed in Stata version 16.1 (StataCorp. 2019. Stata Statistical Software: Release 16 for Macintosh. College Station, TX: StataCorp LLC).
Review of the screening results was approved by the local Human Research Ethics Committee (approval number QA/66029/MonH-2020-219471).