Singapore study shows decline in CMV seroprevalence among pregnant women

There appears to be a downward trend in the prevalence of antibodies against cytomegalovirus (CMV) among pregnant women in Singapore, raising concerns about the potential increase in the proportion of this population who face increased susceptibility to primary CMV infection during pregnancy, as shown in a study.

In a cohort of 385 pregnant women (median age 32 years) receiving antenatal care at Singapore General Hospital, the overall percentage of CMV IgG positivity was 71.7 percent (95 percent confidence interval [CI], 067–0.76; p<0.001). This percentage increased with age, reaching 79 percent in the over-40 age group (p<0.012) and slightly decreasing to 72.5 percent in the 30–39 age group (p<0.001) and then to 68.3 percent in the 20–29 age group (p<0.001). [Trop Med Health 2024;52:67]

“This is the first study in over 2 decades to provide important epidemiological data on the seroprevalence of CMV amongst pregnant women in Singapore,” the investigators said.

They pointed out that the estimated seropositivity rate for CMV IgG in the current antenatal population is 15.3 percent lower than that reported in a 1998 study and supports the initial hypothesis that CMV IgG is likely to have fallen with improved hygiene and socioeconomic conditions in Singapore. [Singapore Med J 2000;41:151-155]

“A declining trend in CMV seropositivity in women of reproductive age is important from a public health standpoint … as [a] larger proportion of women will now be at risk of acquiring primary CMV infection during pregnancy,” the investigators noted. “[Nevertheless] it not necessarily translates to a rising incidence of congenital CMV. Lower seroprevalence is often associated with improved hygiene and higher socioeconomic condition, which are typically maintained throughout pregnancy.

“In countries where seropositivity is declining, the more critical factor is the shift in proportion of congenital CMV cases resulting from primary versus nonprimary infections… As more women enter pregnancy being seronegative, a higher proportion of congenital CMV cases arise from primary infections, which carry a greater risk of vertical transmission, having symptomatic infants at birth, and worse neurological sequalae compared with nonprimary infections,” they continued. [Maedica (Bucur) 2020;15:253]

Preventative measures such as hygiene interventions such as avoiding contact with infected bodily fluids (eg, saliva, tears and urine), hand hygiene, and regular cleaning of potential fomites such as diaper change areas and toys greatly help to reduce primary CMV infections. This is especially important for women living in households with young children, who can be a frequent source of CMV and can shed the virus for extended periods after infection, according to the investigators. [EBioMedicine 2015;2:1205-1210; https://cps.ca/en/documents/position/update-on-congenital-cytomegalovirus-infection-prenatal-prevention-newborn-diagnosis-and-management; Rev Med Virol 2011;21:240-255]

While the present study was limited by its single-centre nature, it remained representative of the national data, as participants were randomly selected and included the varying demographics of pregnant women in Singapore, the investigators said. They called for a multicentre cohort study with a larger number of participants to provide a better picture on the overall CMV seroprevalence in the antenatal population in Singapore.