Recent Study Shows Connection Between Low Birth Vitality Score (APGAR) and Cerebral Palsy

BabyIn the excitement of delivery, many parents fail to understand the myriad of tests their babies go through immediately following birth - and the implications these tests hold not only for their children's immediate health, but also for their risk of suffering a variety of conditions later in life. The risk of cerebral palsy, in particular, may be evident based on an important quantifier known as the Apgar score. While the Apgar score's importance has been understood for decades, researchers are now realizing that it's even more indicative of future trouble than they initially believed.

What is the Apgar Score?

Developed by anesthesiologist Virginia Apgar in 1952, the Apgar score determines the extent to which obstetric anesthesia impacts newborns. The score takes a variety of factors into account, including skin color, response to stimulation, pulse, and more. These elements have been assigned letters to form the acronym APGAR: appearance, pulse, grimace, activity, and respiration. Each of these factors receives a score between 0 and 2, with 0 denoting unhealthy, 2 inferring good health, and 1 assigned to newborns somewhere in between. The five scores are added together to determine a final score somewhere between 0 and 10.

Typically, newborns are tested and assigned an Apgar score just a few minutes after birth. If their initial score is low, they may be subject to continued testing at five or ten-minute intervals. Research indicates that scores can differ considerably after just a few minutes, so regular testing is essential.

The Link Between Apgar Score and Cerebral Palsy

During the last several years, several studies have revealed a link between various Apgar scores and the later development of disabilities such as cerebral palsy or epilepsy. While a low Apgar score does not automatically mean that a given newborn is likely to develop these conditions, clear large-scale trends suggest an association. For example, a notable study of over 500,000 babies in Norway revealed that just 0.1 percent of newborns with an Apgar score of 10 developed CP, versus 10 percent of those with an Apgar score of 3 or less.

While past studies have largely focused on dangerously low Apgar scores, experts believe that even modest changes can have a significant impact. For example, a 2018 study published in The BMJ revealed that the hazard risk of cerebral palsy increased rapidly as the Apgar score decreased. The study involved an analysis of Medical Birth Registry data surrounding over 1.2 million babies born between 1999 and 2012 at full term. Over 1,200 of these children were identified as having cerebral palsy. From there, researchers calculated the risk of developing the condition based on each level of the Apgar scale. This data was analyzed for tests conducted both five and ten minutes after birth.

At five minutes, those with an Apgar score of 0 suffered a 280-fold risk of eventually developing cerebral palsy. This came as little surprise based on previous research, but in this study, researchers also found a doubled risk of CP for those with an Apgar score of 9 instead of 10. The risk of developing CP increased further when problematic Apgar scores persisted after a full ten minutes, but an increased score between five and ten-minute intervals didn't necessarily decrease the risk of CP. For example, babies with a score of 7 at five minutes and a higher score at ten minutes were more likely to suffer CP than those who scored 10 both times.

Why are Low Apgar Scores and Cerebral Palsy Linked?

While no definitive explanation is available to clarify the alarming link between low Apgar scores and later CP diagnosis, experts believe that oxygen deprivation may play a role. Newborns deprived of oxygen are more likely to exhibit low Apgar scores, and in select cases, oxygen deprivation may also increase the likelihood of CP. That being said, experts at the Centers for Disease Control (CDC) maintain that oxygen deprivation is only responsible for a small number of CP cases.

A myriad of other factors can also prompt CP, including premature labor, low birth weight, and infections during pregnancy. Low Apgar scores may be correlated with these issues; research suggests that low scores in premature babies are associated with gestational age and birth weight. For example, in the aforementioned Norwegian study, researchers found that just 4 percent of infants with a low birth weight but a high Apgar score were later diagnosed with CP, compared to 17 percent of low birth weight babies with low Apgar scores.

Multiple population studies make it clear: the vast majority of newborns with low Apgar scores will not develop cerebral palsy. Still, the link cannot be denied, even when considering modest score reductions. Hopefully, these findings will help health care professionals identify and address cases of high cerebral palsy risk early on.