Early in the coronavirus disease 2019 (COVID-19) pandemic, major shifts occurred in health care delivery, including reallocation of staff to other areas of the hospital, decrease in trainees in the hospital, increased use of telehealth, and changes in capacity to conduct elective surgeries and procedures. Similarly, there were societal changes to decrease viral transmission, such as school closures and lockdowns. Studying the effects of these changes is critical as we prepare to navigate the ongoing COVID-19 pandemic and future pandemics.
Studies in nonpregnant individuals have observed increased all-cause mortality during the pandemic in the United States.1 Similarly, in obstetrics, data from the National Center for Health Statistics demonstrate an increase in maternal mortality, from 754 deaths in 2019 to 861 deaths in 2020.2 The proportion of these deaths that are directly attributable to COVID-19 remains unknown. Although some deaths will undoubtedly be linked directly to the virus, other deaths may be due to indirect effects of the pandemic such as medical access disruption or maternal stressors.3 Although those with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in pregnancy are at increased risk of adverse pregnancy outcomes,4–6 especially in the setting of greater COVID-19 severity,4,5 the effect of the pandemic on the outcomes of obstetric patients overall remains uncertain.
Serious maternal morbidity is closely linked to maternal mortality and is often along the pathway to maternal death. Therefore, we sought to evaluate whether birthing individuals during the early COVID-19 pandemic in the United States were at increased risk of death or serious morbidity from common obstetric complications compared with a historical control group at the same hospitals in the year before the pandemic. In addition, we describe the specific hospital-, health care system–, and community-level changes that occurred over the early pandemic at these hospital sites.
This was a retrospective cohort study of pregnant individuals with singleton or twin gestations who gave birth from March through December in the years 2019 and 2020 at one of 17 U.S. hospitals participating in the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) Maternal-Fetal Medicine Units (MFMU) Network’s GRAVID (Gestational Research Assessments for COVID-19) study. Prior publications include patients with SARS-CoV-2 infection and the patients in the randomly selected delivery control group from 2020 who are included in this analysis.4,5 The GRAVID study was performed under waiver of consent with IRB approval at all participating institutions. The study protocol was registered on clinicaltrials.gov (NCT04519502) before the initiation of data abstraction.
The exposure was giving birth during the early COVID-19 pandemic. Patients who gave birth on randomly selected dates in 2020 were included as deliveries during the pandemic. Six weekdays and two weekend days per month were sampled from March through May 2020, when we anticipated the largest surge of COVID-19, and three weekdays and one weekend day per month were randomly selected from June through December 2020. The historical control group was composed of patients who gave birth at the same hospitals before the pandemic (deliveries during 2019); three weekdays and one weekend day per month were randomly selected from March through December 2019. All of the MFMU sites used the same randomly selected delivery dates. Random selection was based on a uniform distribution in which each weekday and weekend day would have equal probability of random selection. Both weekdays and weekend days were sampled intentionally because staffing and delivery volumes were anticipated to differ. Data were abstracted from the medical record by centrally trained and certified research staff, and outcomes were assessed through 42 days postpartum.
The primary outcome was a composite of death from any cause or serious maternal morbidity related to common obstetric complications (hypertensive disorders of pregnancy, postpartum hemorrhage, or infection other than SARS-CoV-2). Serious morbidity was defined by the NICHD MFMU Steering Committee a priori as clinically significant endpoints for morbidity. Serious morbidity related to hypertensive disorders of pregnancy included eclampsia; hemolysis, elevated liver enzymes, and low platelet count (HELLP) syndrome; pulmonary edema on chest X-ray; severe hypertension (blood pressure higher than 160/110 mm Hg) with acute administration of antihypertensive therapy; hepatic rupture; impaired liver function (more than two times the upper limit of normal); renal insufficiency (creatinine level 1.2 mg/dL or greater); thrombocytopenia (platelet count less than 100,000/microliter); and placental abruption. Serious morbidity related to postpartum hemorrhage included transfusion of 4 or more units of packed red blood cells, surgical or radiologic interventions to control bleeding, and related complications. Serious morbidity related to infection included sepsis (infection with end organ dysfunction), bacteremia, endometritis requiring intravenous antibiotic therapy for longer than 24 hours, deep incisional surgical site infection, and pelvic abscess.
The major secondary outcome was cesarean birth. Other maternal secondary outcomes included severe maternal morbidity, defined as recommended by the American College of Obstetricians and Gynecologists and the Society for Maternal-Fetal Medicine as intensive care unit (ICU) admission or transfusion of 4 or more units of blood.7 Rates of ICU admission, length of ICU stay, and length of hospital stay were also evaluated. Neonatal secondary outcomes included perinatal death, neonatal intensive care unit admission, and length of neonatal intensive care unit stay. Among those who delivered at or beyond 20 weeks of gestation, perinatal preterm and term adverse composite outcomes were also evaluated. The preterm composite included fetal or neonatal death, severe bronchopulmonary dysplasia, grade III or IV intraventricular hemorrhage, Bell stage 2A or greater necrotizing enterocolitis, periventricular leukomalacia, stage III or IV retinopathy of prematurity, and neonatal sepsis with positive blood cultures. The term composite included fetal or neonatal death, respiratory support within first 72 hours (beyond support for transition in the delivery room), 5-minute Apgar score 3 or lower, hypoxic ischemic encephalopathy, seizure, infection (sepsis or pneumonia), birth trauma, meconium aspiration syndrome, intracranial or subgaleal hemorrhage, and hypotension requiring vasopressor support. Neonatal outcomes were collected during the delivery hospitalization.
Date of implementation and discontinuation of modifications to hospitals, health care systems, and community risk-mitigation strategies for SARS-CoV-2 during 2020 were recorded at the individual site level. Specific modifications that were recorded are included in Appendix 2, available online at https://links.lww.com/AOG/C932.
Data from the MFMU Network's APEX (Assessment of Perinatal Excellence) cohort study were used to provide estimates on outcome rates for the sample size calculation.8 The rate of serious maternal morbidity in the APEX study was 5.1%. With an estimated sample size of 10,600 deliveries for 2019 and 13,800 deliveries for 2020, the study had more than 90% power to show a 30% increase in the rate of the primary composite maternal morbidity endpoint, assuming that the rate was at least 3% in calendar year 2019 with a two-sided alpha of 0.05. A 30% relative increase in the rate of the composite maternal morbidity endpoint was thought to be a clinically meaningful difference and was selected by the MFMU Steering Committee before study initiation.
For the primary objective, patients who gave birth during the pandemic were compared with patients who gave birth before the pandemic. Descriptive summary statistics were calculated for baseline characteristics and for modifications to hospitals, health care systems, and community risk-mitigation strategies for SARS-CoV-2 during 2020.
For the main analysis, patients who delivered during the pandemic were compared with those who delivered before the pandemic using the Wilcoxon rank sum test for continuous variables and χ2 or Fisher exact test for categorical variables, as appropriate. Multivariable modeling was not performed for outcomes with low frequencies. Covariates for modeling included MFMU site and factors based on clinical relevance, including maternal age, body mass index (BMI, calculated as weight in kilograms divided by height in meters squared) at the first prenatal visit or (if that was not available) prepregnancy weight reported in the medical record, and major medical comorbidity including any of the following: asthma of any severity or chronic obstructive pulmonary disease, chronic hypertension, or pregestational diabetes. Models for the primary outcome also included obstetric history, categorized as no prior deliveries after 20 weeks of gestation, prior delivery with hypertensive disorder or preterm birth, or prior delivery without hypertensive disorder or preterm birth. The model for cesarean birth included history of cesarean birth (categorized as no prior pregnancy 20 weeks of gestation or longer, history of only vaginal births, or any prior cesarean birth) in addition to the baseline demographic variables previously described.
To account for the random sampling of individuals, weighted analyses were performed. For maternal outcomes, Poisson regression models were used to estimate relative risks (RRs) and 95% CIs. To account for patients with twin gestations, models based on a generalized estimating equations framework with exchangeable correlation structure were used to estimate RRs for neonatal outcomes. For skewed continuous variables, medians were presented for descriptive purposes and the natural log-transformed value was used in the regression model to estimate differences in the means of the log-transformed values.
A planned sensitivity analysis was performed in which patients with documented SARS-CoV-2 infection (positive nucleic acid or antigen test result in the outpatient or inpatient setting) at any time during pregnancy through 42 days postpartum were excluded from the analysis. An additional sensitivity analysis was performed in which missing BMI values were imputed based on a generalized linear model. The imputation modeled the natural-log scale BMI with the linear, quadratic, and cubic natural-log scale BMI at delivery calculated from the most recent pregnancy weight before delivery. For patients with BMI at delivery and without prenatal (or prepregnancy) BMI available, imputed BMI values were the back-transformed predicted values based on the model.
Subgroup analyses were conducted by race and ethnicity, parity, and insurance status to determine whether the association or lack thereof prevailed throughout particular subgroups of patients. Race and ethnicity was evaluated given the known association between maternal race and morbidity.9 Likelihood ratio tests were used to evaluate interactions between the exposure and a prespecified subgroup. For each subgroup, stratified analyses were conducted for outcomes only if there was evidence of significant effect modification.
Nominal two-sided P-values are reported; P<.05 was considered statistically significant. No adjustment was made for multiple comparisons. Statistical analyses were performed using SAS 9.4.
During the pandemic in 2020, 12,133 patients gave birth to 12,407 neonates on randomly selected delivery dates. Of those individuals, 3.1% (n=381/12,133, 95% CI 2.8–3.5%) had documented SARS-CoV-2 infection during pregnancy through 42 days postpartum (Fig. 1). The proportion of patients with SARS-CoV-2 infection from March through December 2020 varied consistent with surges in infection rates across the MFMU (Fig. 2). Before the pandemic in 2019, 9,709 patients gave birth to 9,938 neonates on randomly selected delivery dates. Demographic characteristics are shown in Table 1.
Table 1. -
Demographics and Baseline Characteristics
|During Pandemic (n=12,133)
||Before Pandemic (n=9,709)
||26.6 (23.0–32.0) (n=11,008)
||26.6 (22.9–32.1) (n=8,604)
|Race and ethnicity
| American Indian/Alaskan Native
| Native Hawaiian/Pacific Islander
| Non-Hispanic Black
| Non-Hispanic White
| More than 1 race
|No prior pregnancy 20 wk or longer
|Previous preterm birth (20–less than 37 wk)
|Previous cesarean birth
|Smoked during this pregnancy
|Any substance use during this pregnancy
|Asthma or COPD
|Chronic cardiovascular disease
|Chronic renal disease
|Chronic liver disease
|Inflammatory bowel disease
BMI, body mass index; HDP, hypertensive disorder of pregnancy; COPD, chronic obstructive pulmonary disease.
Data are mean±SD, median (quartile 1–quartile 3), n (%), or n/N (%) unless otherwise specified.
*Asthma or COPD, pregestational diabetes, chronic hypertension
During the pandemic in 2020, there were modifications to hospitals, health care systems, and community-level risk-mitigation strategies for SARS-CoV-2, which peaked from March through June 2020 (Fig. 3).
The incidence of the primary composite outcome was 9.3% (95% CI 8.8–9.8) during the pandemic and 8.9% (95% CI 8.3–9.5) before the pandemic. Giving birth during the pandemic was not associated with the primary composite of maternal death or serious morbidity (9.3% vs 8.9%, adjusted relative risk [aRR] 1.02, 95% CI 0.93–1.11) (Fig. 4 and Table 2). There were no maternal deaths in either group, which precluded comparison for this component of the primary outcome. In sensitivity analyses that excluded those with either a positive SARS-CoV-2 test result or imputed BMI, the results were unchanged (Appendices 3 and 4, available online at https://links.lww.com/AOG/C932).
Table 2. -
Primary and Secondary Maternal and Neonatal Outcomes*
||RR (95% CI)
||aRR (95% CI)
|During Pandemic (n=12,133)
||Before Pandemic (n=9,709)
|Primary composite of maternal death or serious morbidity from common obstetric complications
| Postpartum hemorrhage
|Secondary maternal outcomes
| Cesarean birth
| ACOG- and SMFM-defined severe morbidity
| ICU admission
| No. of ICU days
||−0.1 (−0.2 to 0.1)†
||−0.15 (−0.30 to 0.00)†
| Venous thromboembolism (DVT or PE)
| Superficial or deep incisional SSI
| No. of inpatient hospitalization days
||−0.1 (−0.1 to −0.1)†
||−0.09 (−0.11 to −0.08)†
| Length of stay (d)
||−0.1 (−0.1 to −0.1)†
||−0.09 (−0.11 to −0.08)†
| Stillbirth at 20 wk or later
| Neonatal death
| Live births or stillbirth 20 wk or later
| Perinatal preterm composite
| Perinatal term composite
| Live births
| NICU admission
| No. of NICU days
||0.01 (−0.07 – 0.09)†
||0.04 (−0.04 – 0.12)†
RR, relative risk; aRR, adjusted relative risk; HDP, hypertensive disorder of pregnancy; ACOG, American College of Obstetricians and Gynecologists; SMFM, Society for Maternal-Fetal Medicine; ICU, intensive care unit; DVT, deep vein thrombosis; PE, pulmonary embolism; SSI, surgical site infection; NICU, neonatal intensive care unit.
Data are n (%) or median (interquartile range), unless otherwise specified.
*Model for primary composite of maternal death or serious morbidity adjusted for Maternal-Fetal Medicine Units (MFMU) site, maternal age, body mass index (BMI), any comorbidity (asthma or chronic obstructive pulmonary disease [COPD], pregestational diabetes, chronic hypertension), and obstetric history (no prior pregnancy, prior pregnancy without preterm birth [PTB] or preeclampsia, prior pregnancy with PTB or preeclampsia). Model for cesarean birth adjusted for MFMU site, maternal age, BMI, any comorbidity (asthma or COPD, pregestational diabetes, chronic hypertension), and prior delivery route (no prior pregnancy, vaginal delivery only, cesarean delivery). All other models adjusted for MFMU site, maternal age, BMI, and any comorbidity (asthma or COPD, pregestational diabetes, chronic hypertension).
†Difference in means of the natural-log transform.
Giving birth during the pandemic was not associated with cesarean birth (32.4% vs 31.3%, aRR 1.02, 95% CI 0.97–1.07). American College of Obstetricians and Gynecologists– and Society for Maternal-Fetal Medicine–defined severe morbidity,7 which includes ICU admission (1.4% vs 1.9%, aRR 0.69, 95% CI 0.56–0.84), as well as ICU admission alone (1.2% vs 1.7%, aRR 0.67, 95% CI 0.53–0.83) were less frequent during the pandemic than before the pandemic. Among individuals admitted to the ICU, there was no difference in number of ICU days (median 2 days vs 2 days, adjusted mean difference of log-transform −0.15, 95% CI −0.30 to 0.0). Overall length of hospital stay was shorter during the pandemic than before the pandemic (median 2 days vs 3 days, adjusted mean difference of log-transform −0.09 days, 95% CI −0.11 to −0.08).
Neonatal outcomes did not differ for those who gave birth during the pandemic compared with those who gave birth before the pandemic (Table 2). In sensitivity analyses that excluded those with either a positive SARS-CoV-2 test result or imputed BMI, the results were unchanged (Appendices 3 and 4, https://links.lww.com/AOG/C932).
There was no significant interaction between race and ethnicity or insurance status and giving birth during the pandemic for the primary outcome. Parity had a significant interaction with giving birth during the pandemic for the American College of Obstetricians and Gynecologists– and Society for Maternal-Fetal Medicine–defined severe morbidity outcome (no prior pregnancy 20 weeks or longer: aRR 0.84, 95% 0.64–1.09; prior pregnancy 20 weeks or longer: aRR 0.51, 95% CI 0.36–0.71), meaning that parous individuals were significantly less likely to experience the outcome than nulliparous individuals during compared with before the pandemic. Similarly, there was a significant interaction between parity and giving birth during the pandemic for ICU admission (no prior pregnancy 20 weeks or longer: aRR 0.80, 95% 0.60–1.06; prior pregnancy 20 weeks or longer: aRR 0.50, 95% CI 0.35–0.72), meaning that parous individuals were significantly less likely to experience an ICU admission than nulliparous individuals during compared with before the pandemic (Appendices 5–7, available online at https://links.lww.com/AOG/C932).
In a multicenter U.S. cohort, we found no association between giving birth during the early COVID-19 pandemic and a composite outcome of maternal death or serious morbidity from common obstetric complications overall when compared with a historical control group.
In a prior publication from the NICHD MFMU GRAVID study, SARS-CoV-2 infection in pregnancy was associated with our primary composite outcome of death or serious morbidity.5 It is reassuring to find that, in the population overall, similar effects were not observed. The current study included patients with a positive SARS-CoV-2 test result who gave birth on randomly selected days in 2020; these individuals accounted for approximately 3% of the cohort who gave birth during the pandemic. Results did not differ when these patients were excluded in sensitivity analyses.
We hypothesized that giving birth during the early COVID-19 pandemic would be associated with serious morbidity from common obstetric complications due to changes in health care delivery, delays in presentation to care, and delays in timely intervention in the hospital. Other studies have demonstrated increased rates and severity of diabetic ketoacidosis in children.10,11 Within obstetrics and gynecology, the COVID-19 pandemic has been associated with increased rates of rupture of ectopic pregnancy and lower rates of obstetric and gynecologic emergency department visits early in the pandemic.12,13 It could be that our observed lack of association with serious morbidity and mortality in the obstetric population speaks to the necessity of continuing to operate labor and delivery units with relatively normal function even during a pandemic.
The observed lower prevalence of ICU admission in the obstetric population early in the COVID-19 pandemic may reflect decreased ICU bed availability for those with serious illness other than COVID-19. However, we do not have detailed data regarding hospital bed shortages at the individual sites. The association between giving birth during the COVID-19 pandemic and shorter hospital stays has been observed in other studies.14 We followed patients through 42 days postpartum, so any increased risk for mortality or serious morbidity associated with these shorter hospital stays would have been identified.
Notably, there were no maternal deaths in our cohort on the randomly selected delivery dates through 42 days postpartum. Given that maternal death is a rare outcome, we did not have a sufficient sample size to examine this component of the composite individually. Larger studies are required to examine maternal mortality at the population level, because there are initial concerning findings for an increase in maternal mortality during the pandemic.2,15 Our study also does not examine pregnancy-related deaths through 1 year postpartum as recommended by the Centers for Disease Control and Prevention16; there are cases in which pregnancy initiates a chain of events resulting in death later than our examined window of 42 days postpartum.
Strengths of this study include manual medical record abstraction to evaluate serious morbidity beyond what can be ascertained from billing or diagnostic codes; representation from multiple hospital sites, which increases generalizability; and the ability to evaluate rare but serious obstetric complications that are clinically meaningful. We were also able to describe the care modifications that occurred during the pandemic across the sites. Finally, we performed sensitivity analyses and demonstrated that our results were robust even when excluding patients affected directly by SARS-CoV-2 infection.
This study has several limitations. First, these data were collected early in the pandemic (March–December 2020), and we could not evaluate whether there were differences in outcomes for obstetric patients during subsequent surges of infection in the United States. However, this was the phase of the most drastic health care and community-level modifications across the country, and no difference was detected. Second, although the sample size was sufficient for our primary outcome, differences in rare but important outcomes such as maternal death could not be evaluated. Third, most of the participating hospital sites were academic medical centers, which limits generalizability. Similarly, most of the MFMU centers are in the Northeast, and these hospitals may have experienced more disruption to care early in the pandemic when little was known about SARS-CoV-2 transmission. However, we hypothesize that this would have increased the likelihood of finding an increase in maternal morbidity, and we did not find one. Finally, the baseline rate of morbidity was higher than anticipated. The study was initially powered to detect a relative 30% increase from a baseline rate of 3%. With the higher baseline rate of 8.9%, with an alpha of 0.05 and our available sample size, we had 90% power to detect a relative increase of 15% (to 10.2%) or an RR of 1.15.
In summary, no association was found between giving birth during the pandemic and serious maternal morbidity from common obstetric complications. These data are reassuring in that, even during a health care crisis, outcomes for individuals giving birth remained similar to those before the early COVID-19 pandemic. Nonetheless, investigation of maternal morbidity and mortality during the COVID-19 pandemic in settings outside of the United States or in regions of the country that are under-represented in this cohort, including more rural settings, remains critical as we learn from our initial response to COVID-19 globally.
Authors' Data Sharing Statement
- Will individual participant data be available (including data dictionaries)? Yes
- What data in particular will be shared? De-identified study data will be shared through NICHD Data and Specimen Hub (DASH) following reasonable request within 1 year of study publication.
- What other documents will be available? None
- When will data be available (start and end dates)? Within 1 year of manuscript publication
- By what access criteria will data be shared (including with whom, for what types of analyses, and by what mechanism)? Access to data will follow requirements in place through DASH.
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