Key takeaways:

• The AAP recommends car seat tolerance screening for premature infants and those at risk for breathing issues.
• Natalie L. Davis, MD, MMSc, explains which risk factors pediatricians should look for.

Babies with Down syndrome may benefit from car seat tolerance testing before leaving the hospital, according to recent findings from researchers at the University of Maryland.

The car seat tolerance test involves monitoring babies in their car seats before leaving the hospital to ensure they can breathe properly. The test is typically administered by bedside nurses, but pediatricians determine which babies should be tested.

Derived from Davis NL, et al. Pediatrics. 2020;doi:10.1542/2019-3593.

“The goal is to try to identify babies who aren’t breathing well when they are in their car seat position, because it is not a normal position for babies to be in,” Natalie L. Davis, MD, MMSc, a neonatologist at University of Maryland Golisano Children’s Hospital, told Healio. “Generally, babies are on their back to sleep or upright when being fed. This semi-upright position is not the most natural for breathing, but it is the safest for crashes.”

Car seats are typically built for full-term babies, which can cause smaller, premature infants to slide around or end up with their necks in a position that prevents full breaths, Davis said. For this reason, the AAP issued guidance in 1991 recommending car seat tolerance screenings for premature babies before they are discharged from the hospital. However, Davis said the guidelines are vague, as they only recommend screening for premature infants and other babies that physicians deem at risk for breathing problems in car seats. The guidelines do not mention specific risk factors.

In a study published in Hospital Pediatrics in July, Davis and colleagues reviewed medical records for 75 infants with Down syndrome who were born at or admitted to Golisano Children’s Hospital from 2013 through 2022 and participated in a car seat tolerance screening. Overall, 8 infants (11%) failed their first test. Notably, none of these infants were born prematurely, so they could have been missed based on AAP guidelines.

Davis has dedicated her career to identifying which babies are at risk to help pediatricians determine who to test. Healio spoke with Davis about her research and what physicians should know about car seat tolerance screenings.

Healio: There is some controversy surrounding these tests. Can you explain why?

Davis: It is not a controversy in pediatrics that we think all babies should be safe in their car seat and that we need to find the right one that fits them correctly so they can breathe safely. The controversy comes from how we demonstrate that.

The car seat test was implemented with the best intentions, but there was not a lot of research to say, “If we put the baby in this [car seat] and observe them for a period of time, they are guaranteed safe.” There weren’t great data to say that. So, some groups say that since there aren’t data to show the test will guarantee babies’ safety, we shouldn’t do this test. Other groups say we should test every baby to identify problems before they go home.

Healio: What happens when a baby fails the car seat test?

Davis: This is part of the controversy, too, because there isn’t good guidance as far as what to do when the baby fails. If the baby fails, first, we make sure they are safe, whether that is repositioning them or taking them out of the car seat to make sure their breathing is OK. The next steps are to try to figure out why they were not breathing effectively.

At University of Maryland, we have a robust child passenger safety team made up of nurses and doctors who have extra training in car seat safety. You can get certified as a child passenger safety technician, which is a 40-hour course to learn how to appropriately fit babies for car seats. Generally, we consult our child passenger safety team and have the experts look at the baby after they fail.

Frequently, they don’t fit well in their car seats, because car seats are not one-size-fits-all. Sometimes, we identify when they fail the car seat test that they are having oxygen drops even when they are not in the car seat, or they have a heart condition that we find out when we do additional imaging. But frequently, what it involves is giving them some more time to mature and potentially trying a different car seat or a different position.

Healio: The AAP recommends screening every baby born prematurely and any babies with risk factors for breathing problems. Based on your research, which risk factors have you identified that may warrant a car seat test?

Davis: The big problem is that the AAP says, “Hey, we should test kids at risk,” but then they don’t give specific reasons that babies might be at risk. So, it’s left up to each individual hospital to decide. I did a couple of studies a number of years ago where we contacted NICUs and nurseries to ask who they were screening in addition to preemies, and we found a variety of different things. They were frequently testing babies who needed oxygen as they were going home and babies with lung issues or immature lung disease. The other big category was babies with tone issues, so those with low tone, meaning they are floppy, and high tone, meaning they are tight. Babies with Down syndrome are known for having low tone. Other babies they tested had neuromuscular disorders, a history of seizures, brain injuries, heart conditions or airway issues.

Healio: Your latest study focused on screening babies with trisomy 21, or Down syndrome. Why did you look at this specific population?

Davis: This is a controversial test. Do I think every baby needs it? No. But there are certain populations who could benefit, and the key is to figure out those populations. One of the more common reasons hospitals were testing babies was trisomy 21 or Down syndrome, given their increased risk for breathing issues, so I wanted to focus on that group. The AAP guidance on caring for babies with Down syndrome says they should be evaluated in their car seat before going home, but it has not universally been done. I wanted to give pediatricians concrete, evidence-based data.

Healio: What was the most surprising finding from your study?

Davis: I honestly was surprised at how few failed the test. Anecdotally, taking care of a lot of these babies, I expected it to be higher than the 11% we found. I think part of that is we have such a robust child passenger safety team. If we have a child we think is higher risk, we get them involved sooner. We often will have them assessed and look at the car seat before we even do the test. I was also surprised that none of the infants who failed were premature. I thought the premature babies who had trisomy 21 were going to be higher risk. But because they often stay longer in the hospital, they have more time to mature, and actually end up being less likely to fail.

Healio: What are the next steps in this research?

Davis: I would love to do a larger multi-state study that is not limited to our patient population. We looked at 10 years’ worth of babies born at or admitted to the University of Maryland, so this was the biggest study to date on this patient population. However, it would be nice to have a national database to look at kids all over the country.

I also want to focus on these high-risk groups. The next population we are looking at is babies with hypoxic birth injury or brain injury at birth to see if they are at a higher risk for breathing problems.

For more information:

Natalie L. Davis, MD, MMSc, is a neonatologist and faculty advisor for the Child Passenger Safety Program at the University of Maryland Golisano Children’s Hospital. She can be reached at pediatrics@healio.com.