Getting infected with MRSA is more than three times more likely for pregnant women who have diabetes than it is for pregnant women without diabetes, according to a new study.

The study, featured in the July issue of the American Journal of Infection Control (AJIC), looked at more than 3.5 million delivery-related hospital admissions from the US Nationwide Inpatient Sample (NIS) between 2005 and 2008. The NIS accounts for 20% of community hospitals in the US, say the researchers.

MRSA (methicillin-resistant Staphylococcus aureus) infection was 3.4 times more likely to occur in women with diabetes than those without.

Of the 3,531,821 admissions, 5.3% (185,514) of women developed diabetes during pregnancy (gestational diabetes) and almost 1% (28,939) had diabetes pre-pregnancy.

The study found that pre-pregnancy diabetes appears to be a risk factor leading to invasive MRSA infection in the early period after birth. Pregnant women with gestational diabetes were found to potentially pose a higher risk of infection, but estimates were imprecise.

The study was carried out by Andrea M. Parriott from the Department of Epidemiology of the University of California, Los Angeles (UCLA) Fielding School of Public Health, and Onyenuchi A. Arah of the UCLA Center for Health Policy Research.

There were a total of 563 invasive MRSA infections diagnosed during hospitalization for delivery.

The researchers say they were unable to determine the exact way the MRSA infection was contracted in around half of the cases. In the other half of cases, around 30.9% of women contracted the infection via skin, 6.4% via urinary tract, 5.2% from other areas of the organ system, 3% from wound infections and 2% from septicemia.

MRSA is a strain of bacterium that develops a resistance to particular antibiotics within the body, including all penicillins and cephalosporins, a class of antibiotics derived from fungus, and carbapenems.

Delivery of infants is the most common reason for the hospitalization of patients in the US, say the study authors, with 4.3 million inpatient stays of pregnant women during 2006. The researchers add that because the number of inpatient stays are so highly made up of pregnant women admitted for labor and delivery, they make up a large proportion of the burden of MRSA infections within hospitals.

The researchers add that mothers with MRSA may also transmit the infection to their babies, potentially leading to severe disease and death in newborns, as well as hospital outbreaks.

The research concludes that although the data found is not sufficient in itself to conclude that pre-pregnancy diabetes is a direct cause of the risk of MRSA infection in pregnant women admitted to hospital, diabetes can increase susceptibility to the infection, most commonly in the skin, soft tissues and urinary tract.

The researchers say:

“When combined with previous research showing increased risk of certain infections in diabetic persons, it seems likely that diabetic women are at increased risk of MRSA infection compared with other women admitted for delivery of an infant. As we wait for further research on this topic, it might seem prudent for hospitals to be vigilant about possible MRSA risk among diabetic women in labor and delivery.”