Comparison of Maternal and Infant Outcomes in SARS-CoV-2 Infected Pregnancies and Contemporaneous General Population Pregnancies from British Columbia

A national surveillance program on SARS-CoV-2 in pregnancy was initiated at the beginning of the pandemic in Canada (CANCOVID-Preg). An analysis of data from CANCOVID-Preg observed higher rates of preterm birth in SARS-CoV-2 infected pregnancies compared to non-infected, contemporaneous pregnancies in the pre-Omicron era.1McClymont E. Albert A.Y. Alton G.D. Boucoiran I. Castillo E. Fell D.B. et al.Association of SARS-CoV-2 Infection During Pregnancy With Maternal and Perinatal Outcomes.JAMA. 2022 May 24; 327: 1983Crossref PubMed Scopus (93) Google Scholar Given the importance of region-specific differences in SARS-CoV-2 infection and the lack of provincial data comparing SARS-CoV-2 infected pregnancies to a contemporaneous cohort, we compared BC pregnancy outcomes between data collected under CANCOVID-Preg and contemporaneous pregnancy outcomes in the BC population. The population level cohort was obtained from the BC Perinatal Data Registry (BCPDR) of Perinatal Services BC (PSBC).2Perinatal Services BC, British Columbia Perinatal Data RegistryYears Provided: 2014 to 2021. Resource Type: Extract data.Data Provided on. 2022; Google Scholar This registry contains line-level maternal and infant data abstracted from obstetrical and neonatal medical records on nearly 100% of births in BC. This study was approved by the Research Ethics Board at the University of British Columbia (H20-01196). The study period included deliveries between March 1, 2020 – March 31, 2021. Maternal outcomes, including gestational diabetes, pregnancy-induced hypertension, and mode of delivery were compared. Infant outcomes, including birth outcome, resuscitation required at birth, APGAR score at 5 minutes <7, birth weight, NICU admission, and preterm birth were compared. To assess the relationship between group and the binary outcomes above, we used logistic regression models, both unadjusted and adjusted (for maternal age, maternal weight, and pre-existing diabetes/hypertension, to control for baseline characteristics that may elevate risk of adverse pregnancy outcomes) to estimate odds ratios and 95% confidence intervals. Adjusted models excluded cases where data on confounders were missing. To account for correlation in multiple infants from the same mother, we included a random intercept in these models. For outcomes with more than two responses such as degree of preterm birth or admission weight (high, normal, low) we used multinomial logistic regression to test for any differences between groups. There were 259 mothers and 261 infants from SARS-CoV-2 infected pregnancies (BC CANCOVID-Preg) and 44,751 mothers and 45,414 infants from general population pregnancies (BCPDR) included in the analysis. Table 1 summarizes the effect estimates of maternal and infant outcomes between the SARS-CoV-2 infected and contemporaneous population level cohort. SARS-CoV-2 infected pregnancies were more likely than all pandemic time period pregnancies to deliver by caesarean section (aOR 1.56, 95% CI 1.17-2.09). SARS-CoV-2 and were also more likely to be affected by gestational diabetes (aOR 2.21, 95% CI 1.58-3.08). This was also seen separately for insulin-controlled gestational diabetes (aOR 2.08, 95% CI 1.26-3.43) and diet-controlled gestational diabetes (aOR 1.78, 95% CI 1.17-2.73). There was little difference in pregnancy induced hypertension between cohorts in adjusted analyses, although the confidence interval was wide (aOR 0.90, 95% CI 0.50-1.62). Infants from SARS-CoV-2 infected pregnancies were more likely to have APGAR scores <7 at five minutes (aOR 1.90; 95% CI 1.02-3.53) and require NICU admission (aOR 1.63; CI 1.01-2.64). Infants from SARS-CoV-2 infected pregnancies were also more likely to be stillborn (aOR 4.89; 95% CI 1.51-15.79), although this estimate was based on only four stillbirths among infected pregnancies. The preterm birth rate was higher in SARS-CoV-2 infected pregnancies (10.9% vs 7.8%), but confidence intervals after adjustment for the association were wide (aOR 1.24, 95% CI 0.71-2.16). Odds of low and high birthweights were similar in adjusted analyses (aOR 1.08, 95% CI 0.60-1.95; aOR 0.86, 95% CI 0.51-1.43, respectively).Table 1Odds ratios of maternal and infant outcomes for SARS-CoV-2 infected pregnancies relative to all pandemic pregnancies in British Columbia from March 1, 2020 – March 31, 2021.OutcomeAdjusteda (Ref: All Pregnancy)All pregnanciesNo. (%)Pregnancies with maternal SARS-CoV-2 infectionNo. (%)NOdds Ratio (95% CI)pMaternal Outcomes(N = 44,751)(N = 259)Caesarean delivery (Ref: vaginal delivery)16,841 (37.6)122 (47.1)339261.56 (1.17-2.09)0.003Gestational diabetes (any type)6,294 (14.1)66 (25.5)339282.21 (1.58-3.08)<0.001Insulin-controlled gestational diabetes (Ref: no gestational diabetes)2,357 (5.3)23 (8.8)339242.08 (1.26-3.43)0.004(Diet-controlled gestational diabetes (Ref: no gestational diabetes)3,937 (8.8)33 (12.7)1.78 (1.17-2.73)0.0077Pregnancy induced hypertension3,071 (6.9)19 (7.3)339300.90 (0.50-1.62)0.715Infant Outcomes(N = 45,414)(N = 261)Preterm birth (Ref: term birth) <37 weeks3,537 (7.8)28 (10.9)339871.24 (0.71-2.16)0.442Late preterm 34-36 weeks2,754 (6.1)22 (8.6)1.21 (0.69-2.14)0.503Moderate preterm 32-33 weeks385 (0.9)4 (1.6)1.90 (0.60-6.00)0.277Very preterm 28-31 weeks and extremely preterm <28 weeksb398 (0.9)2 (0.8)0.64 (0.09-4.59)0.656Any resuscitation requiredc4,768 (10.5)25 (9.6)343641.13 (0.71-1.78)0.608Apgar <7 at 5 minutes1,462 (3.2)12 (4.6)343031.90 (1.02-3.53)0.042Low birth weight <2500g (Ref: normal birth weight; 2500g-4000g)2,806 (6.2)22 (8.4)343481.08 (0.60-1.95)0.793High birth weight >4000g (Ref: normal birth weight; 2500g-4000g)4,536 (10.0)19 (7.3)0.86 (0.51-1.43)0.554Stillbirth180 (0.4)4 (1.5)343704.89 (1.51-15.79)0.008NICU admissiond3,266 (7.2)27 (10.3)343701.63 (1.01-2.64)0.046aModels were adjusted for maternal age, maternal weight, and pre-existing diabetes/hypertension. Adjusted models excluded cases where data on confounders were missing.bThere were 0 cases of "extremely preterm" in the SARS-CoV-2 infected cohort, so this was combined with "very preterm"cResuscitation required in the SARS-CoV-2 infected cohort included free flow, IPPV mask, intubation, CPAP, CPR, and other; resuscitation required in the all pandemic-time pregnancies included oxygen, IPPV mask, IPPV ETT, chest compressions, and drugs administereddNICU admission in the SARS-CoV-2 infected cohort included levels 1, 2, and 3; NICU admission in the all pandemic-time pregnancies included levels 2 and 3 only Open table in a new tab aModels were adjusted for maternal age, maternal weight, and pre-existing diabetes/hypertension. Adjusted models excluded cases where data on confounders were missing. bThere were 0 cases of "extremely preterm" in the SARS-CoV-2 infected cohort, so this was combined with "very preterm" cResuscitation required in the SARS-CoV-2 infected cohort included free flow, IPPV mask, intubation, CPAP, CPR, and other; resuscitation required in the all pandemic-time pregnancies included oxygen, IPPV mask, IPPV ETT, chest compressions, and drugs administered dNICU admission in the SARS-CoV-2 infected cohort included levels 1, 2, and 3; NICU admission in the all pandemic-time pregnancies included levels 2 and 3 only This study demonstrated that SARS-CoV-2 infected pregnancies prior to widespread vaccination, with the early variants, had higher odds of adverse pregnancy outcomes, contributing to the existing literature that SARS-CoV-2 infection in pregnancy was associated with a higher risk of certain adverse pregnancy outcomes.