Normal gestation time for a human fetus is 40 weeks and any child born before 37 weeks of gestation is considered premature. Being born premature presents a whole host of complications for a newborn and puts them at risk for health problems that can have life-long implications.
Premature babies – affectionately known as preemies – can suffer from a variety of health issues, like apnea, intraventricular hemorrhage, and respiratory distress syndrome, which can keep them in the hospital for weeks or months after they are born. But did you know that preemies are also at risk for hearing loss?
According to researchers, nearly 2-4% of premature infants are at risk of sensorineural hearing loss compared to 0.1-0.3% of their full-term counterparts. Since premature birth can be coupled with immediately life-threatening conditions, the risk of hearing loss is often overlooked or unappreciated during initial care. That being said, hearing loss in preemies can have lifelong consequences so special attention to its causes and treatments is of the utmost importance.
The Cause Of Hearing Loss
When we think of the causes of hearing loss in preemies, many of us might assume that it is often due to underdevelopment of the sensitive – yet important – organs and structures within the ear. Contrary to popular belief, however, the overwhelming consensus amongst neonatal hearing experts is that hearing loss in preemies is due to the antibiotics so frequently used to help the infants fight off infections.
It turns out that 1 in 500 people inherit a gene variation from their mothers that increases the risk of severe and irreversible hearing loss in infants after they are exposed to the commonly used antibiotic gentamicin.
While the solution to this issue may seem simple (just stop administering this antibiotic), gentamicin is incredibly effective at treating a whole host of bacterial infections, such as pneumonia, sepsis, and endocarditis, so it can be critical in saving a newborn preemie’s life. Thus, the answer may lie not in avoiding gentamicin completely, but in knowing when the antibiotic many eventually cause irreversible hearing loss.
Preventing Preemie Hearing Loss
Luckily, many researchers have already dedicated themselves to this important task. A team at the Manchester Centre for Genomic Medicine at the University of Manchester have been searching for a way to screen newborns for the genetic variation that increases this risk for hearing loss and have been making significant progress toward their goal. So far, the team believes that they have developed a genetic test for the gene variant that does not adversely affect the newborn.
Using a simple cheek swab, the team believes that they can generate a genetic test result in 30 minutes or less that can inform physicians as to whether or not they can administer gentamicin to a preemie, all within the recommended first hour after admission.
Another group of researchers is focusing on the antibiotics themselves. At Stanford University, a research team led by Tony Ricci, Ph.D., are looking to create a new generation of aminoglycosides – a type of broad-range antibiotic, which includes gentamicin among their ranks. Although these antibiotics save lives, they have a nasty side-effect: they cause hearing loss in about 20% of patients, particularly in newborns and people who take repeated doses.
To combat this issue, the Stanford researchers have created three new aminoglycoside antibiotics, all of which have molecules that are simply too large to enter the ion channels of the inner ear. Thus, these new antibiotics can significantly lower the risk of hearing loss, especially in preemies.
While the research is still in its early stages, the work of countless research teams will likely have a lasting impact on the prevalence of hearing loss in premature infants. As our understanding of premature infant hearing loss expands and new technologies are developed, we can work toward a world where premature babies can grow up to live long, healthy lives free from hearing loss.