Freezing Maternal Breast Milk Didn't Cut CMV Transmission

Major Finding: Among extremely preterm infants whose mothers' breast milk contained cytomegalovirus, the rate of infection was 11% in those fed only freeze-thawed milk, compared with 6% in those fed both fresh and freeze-thawed milk, a nonsignificant difference.

Data Source: Randomized trial of 140 infants born at less than 28 weeks' gestation and their 127 mothers.

Disclosures: None was reported.

VANCOUVER, B.C. — Freezing and thawing maternal milk before feeding it to extremely preterm infants does not reduce either transmission of cytomegalovirus or the severity of infection when it occurs, according to the findings of a Swedish trial that is the first to look at this issue in a randomized fashion.

Overall, only 8% of infants whose mothers were producing breast milk testing positive for cytomegalovirus (CMV) became infected. The rate of infection in infants fed only freeze-thawed milk (11%) was no lower than that in infants fed both fresh and freeze-thawed milk (6%).

None of the infections was symptomatic, and the laboratory abnormalities observed were transient and equally common between groups.

“Today, in Sweden at least, we think the benefits of giving fresh maternal milk override the risks of CMV infection,” said lead investigator Dr. Soley Omarsdottir, a pediatrician at the Karolinska University Hospital in Stockholm.

“But of course we have to follow these infants and see the long-term consequences,” she added, noting that emerging data suggest that CMV infection can cause changes in the white matter of the brain that may become clinically important later in life.

Some Swedish neonatal units routinely freeze maternal breast milk before feeding it to extremely preterm infants because they believe it reduces CMV transmission, according to Dr. Omarsdottir.

Indeed, laboratory data have shown that freezing can reduce both the viral titer and viral activity in milk. And smaller, nonrandomized studies suggest that freezing may reduce transmission to infants.

At the same time, intake of fresh milk early in life may be important. “We think that it may have benefits for the baby to colonize the gut flora with maternal breast milk very soon after birth,” Dr. Omarsdottir said at the meeting.

She and her colleagues enrolled in the trial 140 extremely preterm infants born at less than 28 weeks' gestation and their 127 mothers. The infants were randomized in nearly equal numbers to be fed only freeze-thawed maternal milk or both freeze-thawed and fresh maternal milk until they were 32 weeks of age.

When milk was frozen, it was kept at −20° C for at least 3 days. If mothers did not produce enough milk, it was supplemented with banked milk that was pasteurized and therefore virus free.

The mothers provided blood for CMV serology testing and breast milk for CMV testing by polymerase chain reaction (PCR) and viral culture. The infants were monitored for CMV infection by urinary PCR and culture performed for the first 6–12 weeks post partum.

According to study results reported in a poster session at the meeting, the mean gestational age of infants was 26 weeks in the group fed only freeze-thawed milk and 26 weeks in the group fed both fresh and freeze-thawed milk. The mean birth weights were 846 g and 836 g, respectively.

Of the 140 infants, 37 of those fed only freeze-thawed milk and 34 of those fed both fresh and freeze-thawed milk had mothers who were producing CMV-positive milk. Overall, 8% of these infants became infected, with no significant difference between groups (11% vs. 6%).

“The numbers of babies are too small to say it is more risky to freeze the breast milk,” Dr. Omarsdottir commented in an interview, and the infection rate was unexpectedly low. “We thought it is not ethical to continue the study just to get enough power to really compare [outcomes] better.”

None of the CMV infections were symptomatic. In each group, half of infected infants had transient alterations in liver function.

From the maternal perspective, 33 mothers in the freeze-thawed milk group and 29 in the combined fresh and freeze-thawed milk group were producing CMV-positive milk (49% overall), and most of these women also had positive CMV serology. The percentage whose infants became infected was not significantly different (12% vs. 7%).

“In our study, we did not see that routine freezing of maternal breast milk could reduce the risk of CMV transmission,” Dr. Omarsdottir concluded.

Major Finding: Among extremely preterm infants whose mothers' breast milk contained cytomegalovirus, the rate of infection was 11% in those fed only freeze-thawed milk, compared with 6% in those fed both fresh and freeze-thawed milk, a nonsignificant difference.

Data Source: Randomized trial of 140 infants born at less than 28 weeks' gestation and their 127 mothers.

Disclosures: None was reported.

VANCOUVER, B.C. — Freezing and thawing maternal milk before feeding it to extremely preterm infants does not reduce either transmission of cytomegalovirus or the severity of infection when it occurs, according to the findings of a Swedish trial that is the first to look at this issue in a randomized fashion.

Overall, only 8% of infants whose mothers were producing breast milk testing positive for cytomegalovirus (CMV) became infected. The rate of infection in infants fed only freeze-thawed milk (11%) was no lower than that in infants fed both fresh and freeze-thawed milk (6%).

None of the infections was symptomatic, and the laboratory abnormalities observed were transient and equally common between groups.

“Today, in Sweden at least, we think the benefits of giving fresh maternal milk override the risks of CMV infection,” said lead investigator Dr. Soley Omarsdottir, a pediatrician at the Karolinska University Hospital in Stockholm.

“But of course we have to follow these infants and see the long-term consequences,” she added, noting that emerging data suggest that CMV infection can cause changes in the white matter of the brain that may become clinically important later in life.

Some Swedish neonatal units routinely freeze maternal breast milk before feeding it to extremely preterm infants because they believe it reduces CMV transmission, according to Dr. Omarsdottir.

Indeed, laboratory data have shown that freezing can reduce both the viral titer and viral activity in milk. And smaller, nonrandomized studies suggest that freezing may reduce transmission to infants.

At the same time, intake of fresh milk early in life may be important. “We think that it may have benefits for the baby to colonize the gut flora with maternal breast milk very soon after birth,” Dr. Omarsdottir said at the meeting.

She and her colleagues enrolled in the trial 140 extremely preterm infants born at less than 28 weeks' gestation and their 127 mothers. The infants were randomized in nearly equal numbers to be fed only freeze-thawed maternal milk or both freeze-thawed and fresh maternal milk until they were 32 weeks of age.

When milk was frozen, it was kept at −20° C for at least 3 days. If mothers did not produce enough milk, it was supplemented with banked milk that was pasteurized and therefore virus free.

The mothers provided blood for CMV serology testing and breast milk for CMV testing by polymerase chain reaction (PCR) and viral culture. The infants were monitored for CMV infection by urinary PCR and culture performed for the first 6–12 weeks post partum.

According to study results reported in a poster session at the meeting, the mean gestational age of infants was 26 weeks in the group fed only freeze-thawed milk and 26 weeks in the group fed both fresh and freeze-thawed milk. The mean birth weights were 846 g and 836 g, respectively.

Of the 140 infants, 37 of those fed only freeze-thawed milk and 34 of those fed both fresh and freeze-thawed milk had mothers who were producing CMV-positive milk. Overall, 8% of these infants became infected, with no significant difference between groups (11% vs. 6%).

“The numbers of babies are too small to say it is more risky to freeze the breast milk,” Dr. Omarsdottir commented in an interview, and the infection rate was unexpectedly low. “We thought it is not ethical to continue the study just to get enough power to really compare [outcomes] better.”

None of the CMV infections were symptomatic. In each group, half of infected infants had transient alterations in liver function.

From the maternal perspective, 33 mothers in the freeze-thawed milk group and 29 in the combined fresh and freeze-thawed milk group were producing CMV-positive milk (49% overall), and most of these women also had positive CMV serology. The percentage whose infants became infected was not significantly different (12% vs. 7%).

“In our study, we did not see that routine freezing of maternal breast milk could reduce the risk of CMV transmission,” Dr. Omarsdottir concluded.

Major Finding: Among extremely preterm infants whose mothers' breast milk contained cytomegalovirus, the rate of infection was 11% in those fed only freeze-thawed milk, compared with 6% in those fed both fresh and freeze-thawed milk, a nonsignificant difference.

Data Source: Randomized trial of 140 infants born at less than 28 weeks' gestation and their 127 mothers.

Disclosures: None was reported.

VANCOUVER, B.C. — Freezing and thawing maternal milk before feeding it to extremely preterm infants does not reduce either transmission of cytomegalovirus or the severity of infection when it occurs, according to the findings of a Swedish trial that is the first to look at this issue in a randomized fashion.

Overall, only 8% of infants whose mothers were producing breast milk testing positive for cytomegalovirus (CMV) became infected. The rate of infection in infants fed only freeze-thawed milk (11%) was no lower than that in infants fed both fresh and freeze-thawed milk (6%).

None of the infections was symptomatic, and the laboratory abnormalities observed were transient and equally common between groups.

“Today, in Sweden at least, we think the benefits of giving fresh maternal milk override the risks of CMV infection,” said lead investigator Dr. Soley Omarsdottir, a pediatrician at the Karolinska University Hospital in Stockholm.

“But of course we have to follow these infants and see the long-term consequences,” she added, noting that emerging data suggest that CMV infection can cause changes in the white matter of the brain that may become clinically important later in life.

Some Swedish neonatal units routinely freeze maternal breast milk before feeding it to extremely preterm infants because they believe it reduces CMV transmission, according to Dr. Omarsdottir.

Indeed, laboratory data have shown that freezing can reduce both the viral titer and viral activity in milk. And smaller, nonrandomized studies suggest that freezing may reduce transmission to infants.

At the same time, intake of fresh milk early in life may be important. “We think that it may have benefits for the baby to colonize the gut flora with maternal breast milk very soon after birth,” Dr. Omarsdottir said at the meeting.

She and her colleagues enrolled in the trial 140 extremely preterm infants born at less than 28 weeks' gestation and their 127 mothers. The infants were randomized in nearly equal numbers to be fed only freeze-thawed maternal milk or both freeze-thawed and fresh maternal milk until they were 32 weeks of age.

When milk was frozen, it was kept at −20° C for at least 3 days. If mothers did not produce enough milk, it was supplemented with banked milk that was pasteurized and therefore virus free.

The mothers provided blood for CMV serology testing and breast milk for CMV testing by polymerase chain reaction (PCR) and viral culture. The infants were monitored for CMV infection by urinary PCR and culture performed for the first 6–12 weeks post partum.

According to study results reported in a poster session at the meeting, the mean gestational age of infants was 26 weeks in the group fed only freeze-thawed milk and 26 weeks in the group fed both fresh and freeze-thawed milk. The mean birth weights were 846 g and 836 g, respectively.

Of the 140 infants, 37 of those fed only freeze-thawed milk and 34 of those fed both fresh and freeze-thawed milk had mothers who were producing CMV-positive milk. Overall, 8% of these infants became infected, with no significant difference between groups (11% vs. 6%).

“The numbers of babies are too small to say it is more risky to freeze the breast milk,” Dr. Omarsdottir commented in an interview, and the infection rate was unexpectedly low. “We thought it is not ethical to continue the study just to get enough power to really compare [outcomes] better.”

None of the CMV infections were symptomatic. In each group, half of infected infants had transient alterations in liver function.

From the maternal perspective, 33 mothers in the freeze-thawed milk group and 29 in the combined fresh and freeze-thawed milk group were producing CMV-positive milk (49% overall), and most of these women also had positive CMV serology. The percentage whose infants became infected was not significantly different (12% vs. 7%).

“In our study, we did not see that routine freezing of maternal breast milk could reduce the risk of CMV transmission,” Dr. Omarsdottir concluded.