Impact of COVID-19 variants in the pregnant South Auckland population: a
case control study with COVID-free controls
Objective Little has been published about maternity
outcomes from New Zealand’s unique handling of the COVID-19 pandemic.
Objectives were to determine obstetric outcomes between the variants,
identify risk factors, and whether the changes to healthcare delivery
affected pregnancy outcomes. Design This was a case
control study comparing singleton pregnancies affected by the Delta and
Omicron strains of COVID-19. The COVID 19-free controls were from 2019.
Setting & Population The largest tertiary maternity
unit in New Zealand providing taxpayer funded healthcare to a
multi-ethnic, high deprivation index population with complex health
needs. Methods Data were extracted from electronic
record systems and further verified by reviewing patient’s notes. The
risk of an event was modelled with logistic regression. The multivariate
analyses adjusted for known clinical risk factors and other significant
differences between the groups. Main Outcome Measures
Outcomes of interest included admission for COVID-19, adverse pregnancy
outcomes, including placentally-mediated ones. Results
In the study population of > 8,000 pregnancies, Delta
variant was associated with significantly worse maternal and obstetric
outcomes. Fetal anomalies and most placentally-mediated adverse outcomes
of pregnancy in the COVID-19 affected cohort did not persist once
adjusted for underlying maternal risk factors, except for a 4-fold
increased risk of stillbirth. Vaccination was protective against
admissions and severe disease (OR 0.19;95%CI 0.11-0.32).
Conclusions While the Delta variant has been associated
with poorer outcomes, modifications to the delivery of maternity care
during the pandemic could have unintended consequences on how patients
utilised healthcare; this may have contributed to poorer outcomes.