A new study published in the American Journal of Obstetrics and Gynecology in September 2020 reports the impact of severe COVID-19 on pregnancy, making an important contribution to the management of the condition in this subgroup of patients.
Aim of the Study
The study was carried out in order to arrive at an accurate estimate of the risk that the pregnancy would have an adverse outcome in women who had COVID-19 during gestation and to understand the risk factors. It is known that respiratory viruses target pregnant women more often because of the immunological tolerance induced by pregnancy as well as other physiologic changes during this period.
Early reports from China and the US showed that there was no increased risk in pregnant women with severe COVID-19 compared to the general population.
However, a more recent study from the US Centers for Disease Control and Prevention (CDC) shows that pregnancy with COVID-19 is more often associated with hospitalization, the requirement for intubation and mechanical ventilation, and admission to an intensive care unit (ICU) than compared to the disease in non-pregnant women.
This report recommended telling pregnant women about the increased risk of complications. Still, notably, it did not differentiate admissions due to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection from those for other pregnancy-related reasons. There was no way to identify the actual increase in the risk of more intensive medical care and illness due to complications, if any, from either COVID-19 or pregnancy.
The current study uses a case-control approach to achieve a quantifiable assessment of the risks to the mother and child when a pregnant woman acquires COVID-19 and to understand the epidemiology of the infection and the risk factors for complications in this situation.
Risk Factors Identified
The researchers included 61 pregnant COVID-19-positive women and double the number of controls, matched by the delivery date. Of these, the overwhelming majority (~89%) had mild disease, while ~12% had a severe or critical disease. The case group had ~58% whites compared to only ~43% in the control group, while otherwise, they were well matched.
The severe/critical group had a higher percentage of Hispanics and Blacks than the controls, at ~57% and ~14% vs. ~26% and ~7%, respectively.
Most of the cases had no comorbidities. However, among those with severe or critical disease, the comorbidity incidence was higher (~43%) compared to ~25% in the control group. For individual comorbidities, too, the pattern was similar, with the incidence of diabetes being almost double in the severe/critical COVID-19, six-fold for chronic hypertension, (at ~30% each), 14-fold for renal disease, and ~5-fold for anemia.
The researchers found that over 60% of pregnant women with mild COVID-19 were asymptomatic. In the remainder, the most commonly reported symptoms of mild COVID-19 were fever, cough, and muscle pain.
However, in the group of severe/critical disease, all were symptomatic with cough, shortness of breath, and fever being reported most frequently. All patients with severe/critical disease were treated, but only in the mild group.
Laboratory results were similar in both controls and mild COVID-19 patients. Still, white cell counts, lymphocyte counts, and liver enzymes were elevated in those with severe/critical COVID-19, while platelet counts were low.
The clearly observed risk factors, therefore, include belonging to the Black and Hispanic races, being an older mother, obesity, having other chronic illnesses, and requiring hospitalization for COVID-19 before delivery. Again, the adverse outcomes of pregnancy are driven by severe or critical cases of COVID-19 at this time, since there is no observed difference in outcomes in mild cases.
Obstetrical and Neonatal Outcomes
Mild cases did not have a significant increase in adverse outcome compared to the controls, but those with severe/critical disease had a higher risk of preterm delivery, at a mean of 34 weeks compared to 38.7 weeks for controls. Overall, patients were more likely to deliver before 28, 34, and 37 weeks compared to controls.
The severe/critical COVID-19 group also had significantly more admissions unrelated to delivery, a higher cesarean rate, increased incidence of chorioamnionitis, pre-eclampsia and abnormal fetal heart patterns even with attempted intrauterine correction.
Neonates born to women with severe/critical COVID-19 in pregnancy had a higher risk of low birth weight, mostly due to early preterm delivery, of NICU admission, respiratory distress, and intraventricular hypertension. There was no difference between the neonatal outcomes in pregnant patients with mild COVID-19 versus controls.
The odds of adverse outcomes for mother and child in COVID-19 were 3.4 and 1.7 times higher, respectively, but since there was no significant difference in the odds for mild cases vs. controls, it is apparent that the higher risk is mostly due to the severe and critical cases.
With the increased detection of mild and asymptomatic cases of COVID-19, it is apparent that the majority of pregnant patients may be reassured as to the likelihood of a benign outcome. While the current study reported 64% asymptomatic infection with SARS-CoV-2 in pregnancy, others have reported much higher rates of ~90%.
It appears that the increased need for ICU admission and mechanical ventilation is chiefly limited to those pregnant patients with severe/critical COVID-19.
Another facet of this finding is the increased risk of transmission to the community as well as to healthcare workers, which emphasizes the need for more testing and greater precautions in the labor and delivery unit. While the babies may be treated as potentially infected patients to be investigated for the presence of the virus, requiring isolation and testing, they should not be separated from the mother unless with her consent.
In the current study, all babies were tested at 36 hours and were uniformly negative.
The increased risk of preterm birth is noted to be mostly due to deliveries initiated by medical staff, due to severe COVID-19 complications. The authors note that the study may show bias towards more severe disease, and more research at the community level may be needed to estimate this risk correctly.
The results of this study thus underpin the recommendation made by the CDC that pregnant women take extra care to avoid SARS-CoV-2 infection, given the increased risk of complications. However, these adverse outcomes are shown to be linked to identifiable risk factors.