Reduction in Spontaneous and Iatrogenic Preterm Births in Twin Pregnancies During COVID-19 Lockdown in Melbourne, Australia: A Multicenter Cohort Study
Authors: Manno Juliana M , Marzan Melvin B , Rolnik Daniel L , Potenza Stephanie , Pritchard Natasha , Said Joanne M , Palmer Kirsten R , Whitehead Clare L , Sheehan Penelope M , Ford Jolyon , Mol Ben W , Walker Susan P , Hui Lisa 
Published: May 2023

Background

Melbourne, Australia, recorded one of the longest and most stringent pandemic lockdowns in 2020, which was associated with an increase in preterm stillbirths among singleton pregnancies. Twin pregnancies may be particularly susceptible to the impacts of pandemic disruptions to maternity care due to their higher background risk of adverse perinatal outcomes.

Objective

To compare the rates of adverse perinatal outcomes in twin pregnancies exposed and unexposed to lockdown restrictions in Melbourne.

Study Design

Multicenter retrospective cohort study of all twin pregnancies birthing in public maternity hospitals in Melbourne. We compared perinatal outcomes between a pre- pandemic group (‘unexposed’) and two lockdown-exposed groups: exposure 1 from 22 March 2020 to 21 March 2021 and exposure 2 from 22 March 2021 to 27 March 2022. We analyzed routinely-collected maternity data on all twin births≥20 weeks where outcomes were available for both infants. The primary outcomes were rates of preterm birth<37 weeks and all-cause stillbirth. Multivariable log-binomial regression models were used to compare perinatal outcomes between the pre-pandemic group and women in whom weeks 20+0to 40+0of their pregnancy occurred entirely during each lockdown-exposure period. Perinatal outcomes were calculated per infant; maternal outcomes were calculated per pregnancy.

Results

We included 2267 women birthing twins. Total preterm births<37 weeks were significantly lower in the exposure 1 group compared with the pre-pandemic group (63.1% vs 68.3% respectively; adjusted risk ratio, aRR 0.92 95% CI 0.87-0.98, p=0.01). This was mainly driven by fewer spontaneous preterm births (18.9% vs 20.3%; aRR 0.95 95%CI 0.90- 0.99, p=0.04) and a trend to fewer iatrogenic preterm births (44.1% vs 48.1%; aRR 0.97 95%CI 0.92-1.03, p=0.39). There were also significantly lower rates of preterm birth<34 weeks in the exposure 1 group compared with the pre-pandemic group (19.9% vs 23.0%, aRR 0.93 95%CI 0.89-0.98 p=0.01). Total iatrogenic births for fetal compromise were significantly lower (13.4% vs 20.4%; aRR 0.94 95%CI 0.89–0.98, p=0.01). There were fewer special care nursery admissions (38.5% vs 43.4%; aRR 0.91 95%CI 0.87-0.95, p<0.001). There was no associated difference in all-cause stillbirths (1.5% vs 1.6%; aRR 1.00 95%CI 0.99-1.01, p=0.82), birthweight<3rdcentile (5.7% vs 6.0%; aRR 1.00, 95%CI 0.98-1.02 p=0.74) or neonatal intensive care unit admissions in the exposure 1 group compared to the pre-pandemic group. In contrast, when comparing the pre-pandemic group with exposure 2 group, there was no significant difference in the rates of preterm birth<37 or <34 weeks. However, during exposure 2 the rate of preterm birth<28 weeks was significantly higher (7.2% vs 4.8%; aRR 1.03 95%CI 1.01-1.05, p=0.04) and infants were more likely to be admitted to a neonatal intensive care unit (25.0% vs 19.6%; aRR 1.06 95%CI 1.03-1.10, p<0.0001) compared with the pre-pandemic period.

Conclusions

Melbourne’s first lockdown-exposure period was associated with fewer twin preterm births<34 and <37 weeks without significant differences in stillbirths or adverse newborn outcomes. These lower rates were not sustained in the second exposure period. Pandemic conditions may provide important lessons for future antenatal care of twin pregnancies, including prevention of preterm birth and optimal timing of birth.