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Postnatal CMV Infection in Premature Infants

By March 16, 2015Cytomegalovirus ("CMV")

A new study led by German researchers suggests that very preterm infants may suffer long-term cognitive impairment – especially later in life – if infected with cytomegalovirus (“CMV”) following birth.

Preterm infants are particularly vulnerable to CMV infection because of their immature immune systems. Strategies to reduce CMV transmission in this at-risk population are being carefully considered by the research community, with no clear consensus yet reached.

Effects of Postnatal CMV Infection in Very Preterm Infants

In 2012, there were 56,252 very low birth weight (“VLBW”, defined as having a weight at birth of < 1,500 g) infants born in the U.S., representing approximately 1.4% of all live births. These preterm infants are at increased risk of neonatal complications from a variety of causes – and consequently as many as 25% to 30% of VLBW infants may suffer long-term neurodevelopmental impairment. Physicians have long sought to identify risk factors in an effort to improve patient treatment strategies and outcomes.

Research conducted at the University Children’s Hospital in Tübingen, Germany indicates that postnatal CMV infection may be one such risk factor. In the study, which has been ongoing since 1995, researchers assessed, at regular intervals, the cognitive abilities of very preterm infants (defined as having a gestational age < 8 months or weighing < 1,500 g) infected with CMV within three months of birth. Infants infected before birth were excluded.

The researchers found that study participants with postnatal CMV infection scored significantly below a control group without CMV infection in tests examining general intelligence. Critically, the effects of postnatal CMV infection were only detectable later in childhood.

Researchers found no effects of postnatal CMV infection in infants between the ages 2 and 4.5 years old. However, significant difference in cognitive abilities became detectable between the ages of 6 and 8 years old. This finding shows that CMV infection of preterm infants may affect more complex, higher-level cognitive functions that may necessitate long-term follow up to fully measure.

If confirmed by other research, the study’s authors suggest that their results would support the implementation of methods to prevent CMV transmission in this at-risk preterm population – including pasteurization of breast milk from CMV-positive mothers.

Breast Milk for Premature Infants: To Pasteurize or Not to Pasteurize

In a previous post, we highlighted a recent study that examined breast milk as a potential CMV transmission source. Breast milk is believed to be optimal for the nutrition and health of infants, but in CMV-seropositive mothers of preterm infants it may also be a source of postnatal CMV infection. To date, there has been no clear consensus on how to treat breast milk, and specifically, whether the benefits of pasteurization outweigh the costs.

A new study conducted at the Innsbruck Medical University in Austria found that feeding preterm infants pasteurized breast milk dramatically decreased the rate of postnatal CMV infection – 11 out of 28 infants fed unpasteurized breast milk in the study developed CMV while only 1 of 24 did when fed pasteurized breast milk.

While pasteurization of human breast milk eliminates CMV, it also reduces the activity of immunological components including growth factors, lysozymes, and maternal antibodies. Pasteurization also impacts the antibacterial properties of breast milk.

Indeed, in the Austrian study, there was a nonsignificant trend to an increased rate of necrotizing enterocolitis in the pasteurized group. Necrotizing enterocolitis is the most common gastrointestinal emergency in premature infants in neonatal intensive care units.

Other studies have also shown that feeding premature infants fresh, unpasteurized milk reduces the risk of necrotizing enterocolitis, late-onset sepsis, and even neurodevelopmental impairment.

Additional Research is Required

CMV is a complex, multi-symptom disease with lasting sequelae. Additional research is needed to better understand the long-term impact of postnatal CMV infection in preterm infants. Also needed are larger studies examining the benefits and costs of breast milk pasteurization so that healthcare providers can create the best possible treatment approach for infants at risk.