Antibodies that guard against COVID-19 can transfer from mothers to babies while in the womb, according to a new study from Weill Cornell Medicine and NewYork-Presbyterian researchers. This discovery adds to growing evidence that suggests that pregnant women who generate protective antibodies after contracting the coronavirus often convey some of that natural immunity to their foetuses. The findings also lend support to the idea that vaccinating mothers-to-be may also have benefits for their newborns.
"Since we can now say that the antibodies pregnant women make against COVID-19 have been shown to be passed down to their babies, we suspect that there's a good chance they could pass down the antibodies the body makes after being vaccinated as well," said Dr Yawei Jenny Yang, an assistant professor of pathology and laboratory medicine at Weill Cornell Medicine and the study's senior author.
Yang and her team analysed blood samples from 88 women who gave birth at New York-Presbyterian/Weill Cornell Medical Centre between March and May 2020, a time when New York City was the global epicentre of the pandemic. All of the women had COVID-19 antibodies in their blood, indicating that they had contracted the virus at some point even though 58% of those women had no symptoms.
Furthermore, while antibodies were detected in both symptomatic and asymptomatic women, the researchers observed that the concentration of antibodies was significantly higher in symptomatic women. They also found that the general pattern of antibody response was similar to the response seen in other patients, confirming that pregnant women have the same kind of immune response to the virus as the larger patient population – something that hadn't previously been known for sure, since a woman's immune system changes throughout pregnancy.
In addition, the vast majority of the babies born to these women – 78% – had detectable antibodies in their umbilical cord blood. There was no evidence that any of the infants had been directly infected with the virus and all were COVID negative at the time of birth, further indicating that the antibodies had crossed the placenta – the organ that provides oxygen and nutrients to a growing baby during pregnancy – into the foetal bloodstream. Newborns with symptomatic mothers also had higher antibody levels than those whose mothers had no COVID symptoms.
This data implies that pregnant women could pass along vaccine-generated antibodies in the same way, potentially shielding both mother and child from future infection.
However, it is not yet known exactly how protective these antibodies might be, or how long that protection might last.
Dr Laura Riley, chair of the department of obstetrics and gynaecology at Weill Cornell Medicine, obstetrician and gynaecologist-in-chief at NewYork-Presbyterian/Weill Cornell and one of the study's co-authors, is still advising pregnant patients who decide to get vaccinated to continue to follow current safety guidelines to prevent the spread of the disease.
Riley, Yang and their colleagues are leading follow-up investigations that are currently enrolling pregnant women who receive the vaccine, as well as vaccinated mothers who are breastfeeding, to assess the antibody response in those groups after vaccination. That information could help guide maternal vaccination strategies moving forward.
"The $1m question is: Will the group of women who are now being vaccinated get the same type of protection? We don't know that yet," Riley said. "Getting those answers is going to be really important."
Study details
Severe acute respiratory syndrome coronavirus 2 serology levels in pregnant women and their neonates
Jeffrey M Kubiak, Elisabeth A Murphy, Jim Yee, Kristen A Cagino, Rachel L Friedlander, Shannon M Glynn, Kathy C Matthews, Magdalena Jurkiewicz, Ashley C Sukhu, Zhen Zhao, Malavika Prabhu, Laura E Riley, Yawei J Yang
Published in the American Journal of Obstetrics and Gynaecology on 22 January 2021
Abstract
Background
Pregnant women and their neonates represent 2 vulnerable populations with an interdependent immune system that are highly susceptible to viral infections. The immune response of pregnant women to severe acute respiratory syndrome coronavirus 2 and the interplay of how the maternal immune response affects the neonatal passive immunity have not been studied systematically.
Objective
We characterized the serologic response in pregnant women and studied how this serologic response correlates with the maternal clinical presentation and with the rate and level of passive immunity that the neonate received from the mother.
Study Design
Women who gave birth and who tested positive for immunoglobulin M or immunoglobulin G against severe acute respiratory syndrome coronavirus 2 using semiquantitative detection in a New York City hospital between March 22, 2020, and May 31, 2020, were included in this study. A retrospective chart review of the cases that met the inclusion criteria was conducted to determine the presence of coronavirus disease 2019 symptoms and the use of oxygen support. Serology levels were compared between the symptomatic and asymptomatic patients using a Welch 2 sample t test. Further chart review of the same patient cohort was conducted to identify the dates of self-reported onset of coronavirus disease 2019 symptoms and the timing of the peak immunoglobulin M and immunoglobulin G antibody levels after symptom onset was visualized using local polynomial regression smoothing on log2-scaled serologic values. To study the neonatal serology response, umbilical cord blood samples of the neonates born to the subset of serology positive pregnant women were tested for serologic antibody responses. The maternal antibody levels of serology positive vs the maternal antibody levels of serology negative neonates were compared using the Welch 2 sample t test. The relationship between the quantitative maternal and quantitative neonatal serologic data was studied using a Pearson correlation and linear regression. A multiple linear regression analysis was conducted using maternal symptoms, maternal serology levels, and maternal use of oxygen support to determine the predictors of neonatal immunoglobulin G levels.
Results
A total of 88 serology positive pregnant women were included in this study. The antibody levels were higher in symptomatic pregnant women than in asymptomatic pregnant women. Serology studies in 34 women with symptom onset data revealed that the maternal immunoglobulin M and immunoglobulin G levels peak around 15 and 30 days after the onset of coronavirus disease 2019 symptoms, respectively. Furthermore, studies of 50 neonates born to this subset of serology positive women showed that passive immunity in the form of immunoglobulin G is conferred in 78% of all neonates. The presence of passive immunity is dependent on the maternal antibody levels, and the levels of neonatal immunoglobulin G correlate with maternal immunoglobulin G levels. The maternal immunoglobulin G levels and maternal use of oxygen support were predictive of the neonatal immunoglobulin G levels.
Conclusion
We demonstrated that maternal serologies correlate with symptomatic maternal infection, and higher levels of maternal antibodies are associated with passive neonatal immunity. The maternal immunoglobulin G levels and maternal use of oxygen support, a marker of disease severity, predicted the neonatal immunoglobulin G levels. These data will further guide the screening for this uniquely linked population of mothers and their neonates and can aid in developing maternal vaccination strategies.
[link url="https://news.weill.cornell.edu/news/2021/02/researchers-learn-that-pregnant-women-pass-along-protective-covid-antibodies-to-their"]Weill Cornell material[/link]
[link url="https://www.ajog.org/article/S0002-9378(21)00053-3/fulltext"]American Journal of Obstetrics and Gynecology study (Open access)[/link]