During the period 07/05 - 06/06 (4 weeks) 465 women attended the Rosie Maternity Hospital for obstetric indications. NP and OP swabs were obtained from 457/465 women upon admission (98%). 18 (3.84%) women had more than one swab taken either due to prolonged inpatient admission beyond 7 days, or reattendance within the 4 week period. Self-reported ethnicity was available for 99.5% of women. The majority of our population consisted of White British, Irish or European ancestery (407/465, 87.5%) and this is reflective of the local population in Cambridgeshire. The median gestational age at the time of the admission swab was 39 weeks (Interquartile range (IQR) 37-40 weeks). Six women (1.3%) attended in the postnatal period due to obstetric concerns. The median duration of inpatient stay for all patients was two days (IQR 1-3). The median duration of follow-up in the post-natal period was 5 days (IQR 3-9).
None of the women had a cough on admission. 37/465 women developed a fever either during labour or following delivery (7.9%). All 37 women had a negative result on admission, and the fever was attributed to an obstetric cause. Two women were admitted with breathlessness on a background of cardiac disease. One woman developed symptoms of fever or sore throat four days after delivery. Advice from Public Health England at the time was to contact a national helpline and she was lost to follow up.
Only one woman in our cohort tested positive over this four-week interval. This woman had neither cough nor fever on admission, but had symptoms of altered taste and smell four weeks prior to her admission. To ensure that this was a true positive, swabs were repeated (but not included in our current analyses for TAT) until she tested negative. As this patient remained symptom-free during admission, she would be the only true asymptomatic COVID-19, giving an asymptomatic carriage rate of 0.22% (1/457; 95% confidence interval: 0.04-1.23%). Knowledge of her results enabled HCW to convert from using standard surgical masks, plastic aprons and gloves to full personal protective equipment when caring for this patient.
Result turnaround times (TAT) were verified and available for 432/457 (94.5%) samples. The median TAT was 5.3 hours (IQR 2.6-8.9) (Figure 1). 424/457 (92.7%) were returned within 24 hours. Where sample turnaround times were absent, these were due to an underestimation of turnaround times rather than a delay in sample processing. This information was gleaned from verbatim entries in the patient records regarding the sample obtained, and the results entered. As no specific record of time was entered, these were excluded from further analyses. A small percentage (16/465, 3.4%) of women declined to be swabbed on admission. 5/16 (31.2%) women were in discomfort from labour and declined testing. No reasons were given for the remaining 11 women who declined testing.
Four hundred and seven articles were screened for title and abstract and 46 full-text articles assessed for inclusion. 17 universal screening studies[14–30] (Table 1) were selected to assess if the prevalence of COVID-19 positive pregnant women correlated with local prevalence rates as these papers fulfilled our prespecified criteria above.
We found a correlation between the test positivity with the regional background prevalence rates of COVID-19. There was a direct correlation between the number of confirmed cases at the peak (R2=0.41, p=0.0053) (Figure 2B) and end of the study period with those who tested positive (R2=0.48, p=0.002) (Figure 2C), but not with the number of confirmed cases at the start of the study period (R2=0.004, p=0.82) (Figure 2A). There was no correlation between the proportions of asymptomatic pregnant carriers with background infection rates (Figure 3).
Only three papers reported turnaround time. Breslin et al reported an average of 8 hours for 43 women screened [Conventional PCR, (New York, New York)] and LaCourse et al reported a median turnaround time of 2.5 hours for rapid testing [DiaSorin Simplexa (MDX Liaison) EUA assay, n=82 women] and 7.1 hours for routine PCR (Seattle, Washington). London et al reported an average turnaround time of 5 hours using GeneXpert PCR in a cohort of 75 women (Brooklyn, New York).