Pregnant women in the obstetrical unit at one St. Louis hospital this spring and summer were nearly 16 times more likely to have asymptomatic COVID-19 than all other surgical patients put together.

Obstetrics patients at the Barnes-Jewish Hospital in St. Louis were tested for the SARS-CoV-2 virus before planned procedures, including deliveries, according to a new study published in the September issue of the American Journal of Obstetrics and Gynecology .

All surgical patients admitted there are generally tested for COVID-19 before surgery, according to safety protocols that most hospitals follow. If the surgery is planned, the test is done within three days via an RT-PCR assay. If the surgery is urgent, a rapid test is performed.

Researchers in the Department of Obstetrics and Gynecology at Washington University School of Medicine in St. Louis looked at 5,543 preprocedural tests conducted between May 28 and July 22. About 10% of the tests, or 532, were of obstetrics patients; the other 90.4%, or 5,011, were all other surgical unit patients.

What the study said

The study was conducted after the hospital had resumed elective surgeries (tonsils, hernia, cataract surgery, dental implants, kidney donation, etc.). These procedures were put on hold when the pandemic started since they were not urgent.

Among the pregnant women, 25 asymptomatic COVID-19 cases were found upon hospital admission. Of the other 5,011 surgical patients undergoing orthopedic, ophthalmology and other critical care treatments, 14 tested positive for asymptomatic infection. The rate of infection was 4.7% among obstetrics patients versus 0.3% among the other surgical patients.

Universal testing does not include obstetrical units

Earlier this year, on March 14, the US Surgeon General Jerome Adams, MD, recommended that hospitals temporarily halt and postpone elective procedures to prioritize hospital resources. The American College of Surgeons endorsed that recommendation in April and advised hospitals across the US to screen surgical patients beforehand. In most cases, patients are tested 48 to 72 hours prior to their surgery and are quarantined until the test results arrive.

A review of 29studies through April 4 found that SARS-CoV-2 tests were generally only recommended for patients who needed high-risk surgeries, such as lung surgeries or transplants. The rule often did not apply to pregnant women prior to giving birth, according to the review, which gravely concerned the researchers. They recommend that pregnancy and childbirth should be seen on a par with other emergency medical procedures that require patients to be tested for the novel coronavirus.

“The obstetrical units are sometimes forgotten as a surgical unit that must continue to operate whether there is a pandemic or not; pregnancy and birth are medical events that don’t follow plans well. So, we can’t think that just because these are young and healthy patients, we don’t need to worry about COVID in obstetrics,” Jeannie C. Kelly, MD, lead author of the Missouri hospital study, told Medical Daily in an interview. Dr. Kelly is assistant professor in the Department of Obstetrics and Gynecology at Washington University.

“If your baseline population rate of infection is high enough that you think you need to universally test all surgical patients, you must include the obstetric patients as well because they seem to have actually a higher rate of asymptomatic infection than anyone else,” Dr. Kelly said.

Some hospitals have taken on this duty by themselves, as they are aware that women in labor need not display symptoms to be COVID-19 positive. One of them is Massachusetts General Hospital.

Why do pregnant women present more asymptomatic COVID-19 cases?

Dr. Kelly told Medical Daily t hat she does not have the answer to what might make pregnant women more susceptible to the infection. She noted that this study only compared asymptomatic cases.

“It’s an important area that needs more research. Pregnant women tend to be younger and healthier than the surgical population. This may make their disease course less severe. Also, the immune system also changes during pregnancy. It may be that some of these changes from pregnancy itself alters the severity of disease, too,” Dr. Kelly said.

Healthcare workers at risk while assisting childbirth

Healthcare workers are three times more at risk for COVID-19 than other people, despite wearing personal protective equipment (PPE), a study led by King’s College in London reported in August.

For example, a risky exchange could happen while placing a patient on a ventilator, as someone struggling to inhale and exhale could propel infectious air particles into the air.

The usual aerosol-generating procedures, like intubation, fortunately happen rarely on obstetrics floors, though when they do happen, they are “extremely urgent,” Dr. Kelly said.

However, the environment is infectious and unsafe for medical personnel on board, she said. "Labor itself, especially when a woman is in the second stage and pushing – can be argued is an aerosol-generating procedure. There is coughing, screaming, wailing, vomiting, and extremely hard and heavy breaths taken – sometimes for 3-4 hours – all with medical personnel in the room with the patient in extremely close quarters for the entire duration,” Dr. Kelly explained.

Despite not using equipment to support breathing, the high infection rate among pregnant women in the hospital setting was demonstrated earlier this year. In one study, 14% of obstetrical patients tested positive for asymptomatic infection upon admission at the New York–Presbyterian Allen Hospital and Columbia University Irving Medical Center. "Deliveries are a multidisciplinary team effort that includes nurses, anesthesiologists, pediatrics, and obstetrics, putting all of them at risk," Dr. Kelly said.

The take-home

A study published by the Journal of Korean Medical Science pointed out the policy of testing all individuals prior to surgeries, known as universal testing, was not cost-effective. Researchers said the percentage of people who tested positive was less than 1%, indicating that resources such as testing kits and PPE could be put to better use.

Dr. Kelly disagrees. She argued that the rate is higher in her department than the one cited in this paper and has been rising, reflecting the trend in the rest of the state. Besides, it is hard to perform a comprehensive cost-effective study on something like this, she added.

"Our patients have a baby to take home, and usually when a baby is born, family comes to visit. If a mom is positive and infectious, but doesn’t know it, she could transmit the disease to her baby. The cost of that is insurmountable," she said.

Seema Prasad is a freelance health reporter based in Bengaluru, India. She tweets @SeemaPrasad_me