Introduction
Soon after the onset of the COVID-19 pandemic, several reports showed an
increased risk of severe illness in pregnant women with SARS-CoV-2
compared with those non-pregnant, and adverse pregnancy outcomes
including preterm birth.1 On the other hand, a more
recent Italian study showed that most infected pregnant women and
newborns had good outcomes.2 Recently, the
Euro-Peristat Research Network3 raised concern about
the fact that one major gap in assessing the real effects of the
pandemic on maternal and child health was the limited availability of
comprehensive population-based routine data.
Research has also accumulated on the effects of the pandemic on the
general population of pregnant women and their infants, possibly due to
mitigation strategies and changes in women everyday life. During the
early months of the pandemic, a reduced preterm birth (PTB) rate, in
comparison with that in the previous years, was recorded in
Denmark,4 in one hospital in
Ireland,5 and in one Italian
Region,6 where also an increase in stillbirths was
observed. Another study, performed in a single hospital in London,
reported only an increase in stillbirths but not in PTB
rates.7 These reports were based on relatively small
samples, and limited, especially for stillbirths, also by a possible
change in referral patterns of pregnant women.
A first systematic review and meta-analysis of 31 studies published
until January 8th 2021 addressing the indirect effects
of the pandemic on perinatal outcomes confirmed a slight reduction in
PTB (< 37 weeks gestational age, GA) in high-income but not in
low-income countries and, vice versa, an increase in stillbirths in
low-income countries only.8
A more recent systematic review
and meta-analysis of 44 studies9 found that the odds
of PTB during the pandemic period were significantly reduced in
single-centre/single-health-authority studies, while there was no
difference in larger studies based on regional/national data. No
difference was documented in the rate of stillbirths in the pandemic
period compared to the non-pandemic one, though these conclusions might
be hampered, according to the authors, by more limited data. The review
once again concludes that there is still a need of studies in bigger
countries largely affected by COVID-19 pandemic like India, Brazil, UK
and Italy and based on national registries, to investigate the impact of
the pandemic on perinatal health at a population level.
The aim of the present study was
to provide national
population-based estimates of the PTB and stillbirth rates during the
pandemic period compared to a historical period. In order to account for
the natural variation in PTB over time, and the abrupt implementation of
public health measures and disruption of routines of care, we also
analysed the temporal trend in monthly incidence of PTB before and after
the implementation of mitigation measures.