Introduction

Recent studies and reviews indicate that pregnant women are more likely to are affected by severe illness and intensive care and mechanical ventilation^(1,2,3,4). Coronavirus disease-2019 (COVID-19) was associated with a substantial increase in maternal morbidity and mortality⁽⁵⁾. The maternal mortality rates varied widely from 1.35% to 12.3%^(6,7,8). Variants of concern have begun to be reported by the World Health Organization (WHO)⁽⁹⁾ and the pace of the pandemic has increased. Data on maternal mortality associated with the increasing waves of the pandemic have been accumulated recently^(7,10,11,12). As the pandemic progressed, new genetic variants of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) were identified in the second half of the 2020⁽⁵⁾. In May 2021, the Delta variant was identified as a variant of concern⁽⁵⁾, with research indicating that it was more transmissible and that patients with the Delta variant became ill faster and showed higher viral loads in the respiratory tract compared to the other variants⁽¹³⁾. Recently, Delta wave was related to a high maternal mortality rate, particularly for unvaccinated pregnant women⁽⁷⁾. Nowadays, the Omicron variant has taken the place of the Delta variant and it is identified as a more transmissible variant with decreased severity⁽¹⁴⁾.

Diagnosis of COVID-19 is mainly based on the symptoms of the patient, nasopharyngeal polymerase chain reaction (PCR) test results, and chest imaging tests^(9,15). For obstetricians, the lung ultrasound (LUS) is a rapid and safe technique for the triage, diagnosis and follow-up of pregnant women with COVID-19^(16,17). Performing LUS right after the fetal assessment for screening of COVID-19 is feasible until PCR results are acquired. It has the advantage of eliminating the ionizing radiation exposure from chest computed tomography (CT) and pregnant women’s concerns about ionizing radiation. LUS is a new thoracic imaging method that is becoming more widely used than other thoracic imaging modalities. Its usage to determine the pulmonary involvement in COVID-19 has increased recently⁽¹⁸⁾. Abnormal LUS findings were found relevant to early admission into intensive care units (ICU) or ICU and mortality in the pandemic^(16,18).

The data on maternal mortality rates during the latest variants of the COVID-19 pandemic needs to be updated. In this study, we aimed to investigate the COVID-19 related maternal mortality in connection to Delta and Omicron waves and the impact of LUS in determining disease severity-mortality in one of Turkey’s largest pandemic centers.

Results

Overall, there were 1.065 pregnant women hospitalized due to the COVID-19 infection between March 2020 and January 2022. Fifty-one (4.79%) of these patients had critical sickness, 96 (9.01 percent) of them had a severe illness, 62 (5.82 percent) of them were admitted to the ICU and 28 (2.63 percent) of the hospitalized pregnant women had died. Monthly data for the number of hospitalized patients and the maternal deaths between March 2020 and January 2022 are presented in Figure 1.

Of the 1,065 patients, 783 (73.52%) were hospitalized before the Delta wave with a maternal mortality rate of 1.28% (10/783), 243 were hospitalized during the Delta wave with a maternal mortality rate of 7% (17/243), and 39 (3.66%) patients were hospitalized during the Omicron wave with a maternal mortality rate of 2.56% (1/39) (p<0.001, chi-square=23.71532). There was a significant increase in maternal death with the impact of the Delta wave compared with pre-Delta period [relative risk (RR)=5.478, 95% confidence interval (CI) (2.54-11.8), z=4.342, p<0.001]. The count and the rates of maternal deaths, patients with ICU admission and with severe-critical disease during pre-Delta, Delta, and Omicron waves are summarized in Table 1. There were not any difference between demographic and obstetric characteristics of maternal deaths before and during the Delta wave and these are presented with characteristics of all maternal deaths in Table 1.