Recent clinical data suggest that pregnancy exacerbates SARS-CoV-2 complications. Expectant mothers face stressors to the immune system and to the lungs and heart that increase vulnerability to COVID-19 illness. “Pregnant patients most at risk to have a severe outcome during pregnancy are those with obesity, diabetes and hypertension. For lab specialists, it would be important to know if these pathologies are present,” David Baud, MD, PhD, an expert on emerging infectious diseases and pregnancy who heads the obstetric service department at Lausanne University Hospital in Switzerland, told CLN Stat.

Several factors may play a role in the virus’ pathophysiology and clinical course in pregnant women, said Baud. This includes an increased sensitivity to hypoxemia due to anatomical and physiological changes associated with pregnancy, risk of pulmonary (and placental) microvascular thrombosis, and an impaired immune function leading to a possibly unfavorable inflammatory response.

Pregnant women with the virus are at risk for experiencing pre-term births, according to a new BMJ report of 77 studies that included more than 11,000 pregnant and recently pregnant women admitted to the hospital and diagnosed with confirmed or suspected SARS-CoV-2. Infected pregnant women are also more likely to end up in the ICU, according to the BMJ report and others. One study that compared ICU admission rates between pregnant and non-pregnant infected patients in Sweden found that pregnant women and postpartum women had a nearly six-fold greater chance of admission, according to this news report. Similarly, the U.S. Centers for Disease Control and Prevention (CDC) reported that among more than 91,000 infected women of reproductive age, pregnant individuals had higher ICU admissions (1.5%) compared to nonpregnant women (0.9%). They also needed mechanical ventilation more often (0.5%) compared with 0.3% of nonpregnant women.

In calculating its data, CDC “didn’t divide out hospitalizations that would be expected for delivering a baby from hospitalizations related to illness,” noted Diana Bianchi, MD, in a recent Q&A with Francis Collins, MD, PhD, director of the National Institutes of Health (NIH). “But the report did show that pregnant women are at a higher risk of needing respiratory support and having serious illness, particularly if there is an underlying chronic condition, such as chronic lung disease, diabetes or hypertension,” added Bianchi, director of NIH’s Eunice Kennedy Shriver National Institute of Child Health and Human Development.

Compared to other upper respiratory illnesses such as H1N1 influenza, risk of ICU admission and mechanical ventilation remains low for pregnant women, the American College of Obstetricians and Gynecologists (ACOG) observed in its analysis of the CDC data. ACOG noted that Black or Hispanic women had a higher infection risk. Additionally, ICU admission was more common in non-Hispanic Asians (3.5%) compared to all pregnant women (1.5%). “ACOG is reviewing all of our clinical materials and patient resources related to COVID-19 in light of newly available information and will make any necessary revisions to recommendations,” said Christopher M. Zahn, MD, FACOG, ACOG’s vice president of practice activities in a statement.

ACOG has developed an algorithm to aid clinicians in treating and managing pregnant women exposed to, or showing symptoms of SARS-CoV-2. The algorithm recommends pathways for routine medical care or testing depending on the patient’s presentation. Clinicians should conduct an illness severity assessment in patients recommended for testing, to categorize these patients into additional risk categories.

In her interview with Collins, Bianchi mentioned that fetuses don’t appear to have a high risk of contracting the virus from mothers.  “Now, that’s based on the fact that available studies seem to suggest that the ACE2 receptor that the virus uses to bind to our cells, is not expressed in third trimester placental tissue. That doesn’t mean it’s not expressed earlier in gestation. The placenta is so dynamic in terms of gene expression,” Bianchi said in her interview with Collins.

Other studies suggest that in utero transmission is possible. A literature review of the clinical characteristics, obstetric outcomes and vertical transmission in pregnant women with SARS‐CoV‐2 infection, uncovered 19 cases in which neonates were diagnosed with the virus. “This contrasts with SARS, where no evidence of vertical transmission exists,” wrote the investigators. But unlike SARS, MERS or influenza, SARS-CoV-2 does not seem to pose a greater risk in pregnant women compared with non-pregnant women, the authors concluded. About 25% of the infants born to infected mothers in the BMJ study were admitted to a neonatal until, but few deaths and stillborn cases were reported.

The Pan American Health Organization (PAHO) believes enough of a risk exists to warrant close prenatal checks. “The current available data suggest that pregnant women are at a higher risk of developing a severe form of COVID-19; in some cases, this may lead to death.” In an epidemiological alert, PAHO recommends that all countries in the Americas ramp up efforts to ensure access to prenatal care services and preventive measures to reduce deaths and morbidly related to the virus. Health services should also “maintain communication with pregnant women in order to provide resources on whom to consult in case of an emergency and to coordinate virtual, face-to-face, or home check-ups if necessary.”