Study reveals key infection pathways from mothers to premature newborns weighing less than 1.5kg

A research team at Samsung Medical Center has found infection pathways from mothers to extremely premature infants. This is the first study to analyze the transmission of infections in this vulnerable population, with implications for developing preventive antibiotic strategies.

The study, led by Professors Chang Yun-sil, Ahn So-yoon, Sung Se-in, Yang Mi-sun, and Hwang Ji-eun of the Department of Pediatrics, conducted between 2013 and 2020, analyzed 173 extremely premature infants—defined as weighing less than 1,500 grams at birth—born to mothers with confirmed infections.

The results identified the primary pathways of infection and the factors influencing the transmission from mother to child.

Premature infants are especially susceptible to bacterial infections due to their underdeveloped immune systems. In cases where there is a risk of premature birth or infection, antibiotics are often administered to the mother or the newborn to prevent severe complications such as sepsis.

However, the widespread use of antibiotics raises concerns, including antibiotic resistance in mothers and side effects in infants, such as necrotizing enterocolitis and neurodevelopmental disorders.

The research team divided the infants into two groups -- 45 who developed infections and 128 who did not – and analyzed the pathogens found in the mothers' blood, urine, and vaginal samples.

The result showed Escherichia coli (E. coli) as the most common pathogen, accounting for 30.6 percent of maternal infections, followed by Candida (29.5 percent), Group B Streptococcus (16.8 percent), Klebsiella (12.1 percent), and Enterococcus (11.6 percent). Similarly, in the infected infants, E. coli (35.6 percent) was the most prevalent, followed by Candida (20 percent), Group B Streptococcus (15.6 percent), Enterococcus (15.6 percent), and Klebsiella (8.9 percent).

The study identified the vaginal tract as the most common transmission route. Among infants infected with E. coli, 30.2 percent were infected via the vaginal route during childbirth. Notably, when E. coli was detected in the mother's blood, the transmission rate to the infant was 100 percent, indicating the need for heightened vigilance in such cases.

Further analysis revealed that certain maternal factors increased the likelihood of infection transmission.

These factors included elevated maternal white blood cell counts, a history of chorioamnionitis, and cervical cerclage.

Mothers with white blood cell count exceeding 15,000/µL had a 2.62-fold higher risk of transmitting infections to their infants, and the presence of chorioamnionitis increased the transmission risk by 10.54 times, and those who had undergone cervical cerclage faced a 4.44-fold higher risk.

Infants who contracted infections from their mothers had a threefold higher mortality rate and a sixfold higher risk of intraventricular hemorrhage compared to those who did not contract infections.

The research team concluded that antibiotic use should be considered based on maternal factors such as a history of premature rupture of membranes, chorioamnionitis, cervical cerclage, and elevated white blood cell counts.

“Even for extremely premature infants, antibiotics should be used cautiously after checking for bacterial cultures and signs of inflammation,” Chang said. “By avoiding the overuse of antibiotics and administering them only when necessary, we hope to protect these precious lives.”

The study's findings were published in the recent issue of Scientific Reports.