Changes in Preterm and Low Birthweight Birth Rate During the COVID-19 Lockdown at Two San Francisco Hospitals

The COVID-19 lockdown impacted interactions with the health care system and societal stress levels. Previous US-based studies suggest that pandemic lockdowns may have lowered preterm birth rates although there are mixed findings from different settings. We evaluated the impact of COVID-19 on preterm birth and low birthweight rates at two San Francisco hospitals.

We compared rates of preterm birth (< 37 weeks) and low birthweight (< 2500 g) in San Francisco at a safety net hospital and an academic medical center during two time periods early in the COVID-19 pandemic compared with the same months from the prior year: from March to May 2019 and 2020 and August to December 2019 and 2020. We calculated crude rates for preterm birth and low birth weight as well as compared maternal and infant birth demographics and health characteristics during these same time periods using descriptive statistics. Secondly using a cross-sectional study design, we used logistic and linear regression models to evaluate risk for preterm birth, gestational age at birth, and low birthweight adjusting for confounders comparing the lockdown period with the pre-COVID year. All analyses were conducted using Stata 15.0.

From August to December 2019 to 2020, the preterm birth rate decreased from 13.20 to 7.96% in the combined hospital data (p < 0.01), and the low birthweight rate decreased from 11.33 to 9.70% during the same time period (p = 0.13). We did not find a comparable reduction from March to May 2019 to 2020. Maternal age at delivery was significantly younger during the lockdown period, August to December, than in the prior year (36.29 ± 5.69 versus 37.15 ± 5.68 years p < 0.01) and parity was greater (0.83 ± 1.15 versus 0.74 ± 1.04, p = 0.03) but there were no other significant differences in race or ethnicity, infant sex or type of delivery (vaginal versus Cesarean section) from 2019 to 2020. In a logistic and linear regression model adjusting for maternal age and infant sex and other confounders, the lockdown period from August to December was protective against preterm birth (OR 0.65, 95%CI 0.51-0.82) and associated with overall longer gestational duration (Coeff 0.23, 95%CI 0.07-0.39). The August to December lockdown period was also associated with greater birthweight (Coeff 43.76, 95%CI 2.19-85.34).

In San Francisco, COVID-19 lockdowns lowered the preterm birth and increased gestational duration in infants comparing 2019 with 2020 for August to December. The reduced in preterm birth rates may be related to the overall strict lockdown measures that San Francisco implemented compared with other US cities. WHAT THIS STUDY ADDS TO THE CLINICAL WORK?: This study suggests that COVID-19 lockdowns lowered the preterm birth rate in August -December 2020 compared with the same months in 2019 in two hospitals in San Francisco. San Francisco had strict lockdowns compared with other areas of the country and fewer deaths. The stay-at-home measures could possibly have reduced stress for pregnant women or had other positive benefits that reduced the preterm birth rate.