A study conducted in Boston-area hospitals found low prevalence of asymptomatic coronavirus disease 2019 (COVID-19) infections among pregnant women, while a systematic review concluded maternal transmission of the virus to neonates is uncommon.
Universal testing in labor and delivery units of 4 major hospitals affiliated with Massachusetts’s General Brigham Health found low prevalence of asymptomatic coronavirus disease 2019 (COVID-19) infections among pregnant women, according to a study published in Infection Control & Hospital Epidemiology.1
During the peak of COVID-19 infections in New York City, several hospitals began testing all women admitted to the labor and delivery units for COVID-19. Results showed 14% of asymptomatic women tested positive for the virus.
However, researchers note it is unclear “whether the high rate of asymptomatic infections in New York is a reflection of a particularly high prevalence of SARS-CoV-2 (COVID-19) during that time period in New York, or a more generalizable phenomenon applicable to other high-prevalence areas.”
In Boston, clinicians began administering universal tests of COVID-19 via nasopharyngeal swab on April 18 at 2 academic and 2 community hospitals. The 4 hospitals provide maternity care to roughly 14,750 women each year.
Researchers evaluated electronic medical records of 757 women tested (99.2% of 763 women admitted) through May 5, 2020, while records of women with positive tests were independently reviewed by 2 physicians to confirm symptom status. During physical screening, women were assessed for presence of fever, new cough, shortness of breath, sore throat, muscle aches, new rhinorrhea, or new anosmia.
Of the women tested, 139 presented with symptoms possibly consistent with COVID-19, while 11 (7.9%) tested positive for the virus. Among the remaining 618 asymptomatic women, 9 (1.5%) tested positive, marking a 45% incidence of asymptomatic patients among confirmed cases.
In the 2 academic hospitals, 2.7% and 1.5% of asymptomatic women tested positive while in the 2 community hospitals, prevalence was 1.8% and 0.6%. None of the positive asymptomatic women developed symptoms during delivery hospitalizations and all 9 newborns tested negative for COVID-19.
“The incidence of asymptomatic infection amongst women admitted to the labor and delivery units in greater Boston was substantially lower than that of New York City despite similar case counts per capita,” authors found. “Notably, the 1% to 2% incidence of asymptomatic infection in our population more closely mirrors asymptomatic infection rates in other areas.”
Lower prevalence of asymptomatic infection in Boston may be due to the fact that universal testing began more than 30 days after social distancing orders were mandated in the region, resulting in a decline in community transmission. Boston is also less densely populated than New York City while some hospitals in New York City “transiently stopped or considered stopping birth partners from attending deliveries, which could have led to some women underreporting symptoms."
Researchers recommend universal COVID-19 testing among women presenting for labor and delivery continue in order to reduce transmission within healthcare facilities, and expand knowledge on community prevalence of infection. Data collected may also guide decisions on mitigation vs. containment efforts in communities at different stages of the pandemic curve.
Investigators consider the practice a public health priority, “given the implications of SARS-CoV-2 on maternal and newborn care at the time of birth and during the postpartum and neonatal period.”
However, additional research revealed maternal transmission of COVID-19 to neonates during pregnancy is uncommon, according to a systematic review published in BJOG: An International Journal of Obstetrics and Gynaecology. 2
Based on previous accounts of coronavirus infections during pregnancy, and in an effort to protect the neonate from infection, “many early reports of COVID-19 in pregnancy described management by cesarean, isolation of the neonate from the mother at birth, and formula feeding,” authors write. Records show that during the SARS-CoV outbreak in 2002-2003, out of 12 pregnant women with the virus, 3 passed away, 4 women miscarried in the first trimester, and 2 neonates were growth restricted while 4 were delivered preterm, according to authors.
“Expert guidelines have cautiously recommended vaginal birth in the absence of maternal respiratory failure or fetal compromise,” as opposed to c-section, researchers said.
In the current review, researchers evaluated 49 studies which included mode of delivery and infant infection status of 666 neonates and 655 women. Only cases where mothers had confirmed COVID-19 based on a positive swab test, or a high clinical suspicion of COVID-19 (eg, symptomatic and radiographic evidence in an area with high COVID-19 prevalence) were included in the review.
Researchers caution reports may include the same or overlapping cases, however they “have attempted to disentangle duplicate reports.”
Extracted data revealed:
“Neonatal COVID-19 infection is uncommon, almost never symptomatic, and the rate of infection is no greater when the baby is born vaginally, breastfed or allowed contact with the mother,” researchers concluded.
In addition, only 28 cases where the possibility for vertical transmission to have occurred have been published to date. Definite vertical transmission can be detected from samples of umbilical cord blood, neonatal blood collected within the first 12 hours of birth, or amniotic fluid collected prior to rupture of membranes.
“While we have presented data from a robust search of the literature for 655 women and 666 neonates, this still only includes 28 infected neonates and COVID-19 is a new virus,” authors note. “We caution the reader to interpret the data in light of this.”