Risk factors associated with the vertical transmission of cytomegalovirus in seropositive pregnant women

Pre-existing maternal IgG antibodies as a protective factor against congenital cytomegalovirus infection: A mother-child prospective cohort study

Background

An understanding of the correlation between maternal immunity and congenital cytomegalovirus (CMV) infection is critical for informing the design and evaluation of an effective maternal vaccine. This study aimed to quantitatively measure the protective effect of pre-existing maternal immunity against congenital CMV (cCMV) infection.

Methods

A mother-child cohort study was conducted in three maternal and child health hospitals in China from 2015 to 2018. Pregnant women were consecutively enrolled, and anti-CMV pp150 IgG concentration at early, middle and late gestational ages were evaluated. Their newborns were screened for cCMV infection by CMV-DNA testing of saliva and urine.

Findings

In total, 6729 pregnant women were enrolled, and 6602 of them (98·11%) were positive for CMV IgG at their early gestational age visit (median time: 13 gestational weeks (GW); time range: 6–25 GW). In total, 6228 live newborns were born to seropositive mothers, and 48 (0·77%) of these infants were diagnosed with cCMV infection. The geometric mean concentration (GMC) of CMV IgG at an early gestational age in the women who delivered cCMV-positive newborns (i.e., the transmitters) was 8·54 IU/mL; this was significantly lower than the GMC in the non-transmitters (11·01 IU/mL; P=0·04). In early gestation, the risk of cCMV infection decreased as maternal IgG antibody levels increased (P=0·020); however, the same was not true in middle or late gestation (P>0·05). Using receiver operating characteristic analysis, a CMV IgG concentration of 12·83 IU/mL was established as the optimal diagnostic threshold. Compared to lower levels of CMV IgG (<12·83 IU/mL) in seropositive pregnant women, higher maternal CMV IgG levels (≥12·83 IU/mL) were associated with a 50% reduction in cCMV infection risk in infants (relative risk=0·50; 95% confidence interval: 0·27–0·93; P=0·028).

Interpretation

For seropositive women, a higher level of CMV IgG at an early gestational age is associated with a lower risk of cCMV infection in their newborns.

Funding

National Natural Science Foundation of China; Science and Technology Key Project in Fujian Province; Merck Sharp & Dohme Corp., Kenilworth, NJ, USA; Fieldwork Funds for graduate students of Xiamen University.

Manuscript title: Maternal CMV seroprevalence rate in early gestation and congenital cytomegalovirus infection in a Chinese population

BACKGROUND

Congenital human cytomegalovirus (CMV) infection remains largely unrecognized and underemphasized in medical practice. This study aimed to describe the maternal CMV seroprevalence rate in early gestation and congenital CMV infection in a Chinese population.

METHODS

This was a prospective cohort study that was conducted in three hospitals in China from 2015 through 2018. Pregnant women were enrolled in early gestation and followed up in middle and late gestation with serological testing. CMV serostatus was determined by IgG testing in serum during early gestation. Their newborns were screened and confirmed for cCMV infection by real-time PCR testing in both saliva and urine at two time points. The cCMV prevalence, maternal seroprevalence and associated factors were analyzed.

RESULTS

In China, the CMV seroprevalence was 98.11% (6602/6729, 95% CI: 97.76%-98.41%), and the cCMV prevalence was 1.32% (84/6350, 95% CI: 1.07%-1.64%). Over 98% of cCMV-positive newborns were from pregnant women who were seropositive in early gestation in China. The prevalence of cCMV infection in newborns from seropositive and seronegative pregnant women was similar (crude prevalence: 1.33% vs 0.82%, P=1.00; estimated prevalence: 1.29% vs 1.05%, P=0.42). Pregnant women who were under 25 years old or primiparous had a lower seroprevalence. Newborns from pregnant women under 25 years old or from twin pregnancies had a higher prevalence of cCMV infection.

CONCLUSION

In China, the cCMV prevalence was high, and the rates were similar in newborns from pregnant women who were seropositive and seronegative in early gestation. The vast majority of cCMV newborns were from seropositive mothers.Trial registration: ClinicalTrials.gov identifier: NCT02645396..