Researchers suggest that brain changes associated with preterm birth may start in the womb.
Preterm birth is defined as the birth of an infant prior to 37 weeks of pregnancy. In the United States, around 1 in every 10 infants born in 2015 were preterm.
According to the Centers for Disease Control and Prevention (CDC), a baby's brain develops the fastest toward the end of pregnancy. Therefore, when a baby is born too early, their brain has not had time to fully flourish.
Study co-author Dustin Scheinost - of the Department of Radiology and Biomedical Imaging at Yale School of Medicine in New Haven, CT - and colleagues note that previous research has identified numerous alterations in brain circuitry that are present in preterm babies at, or just after, birth.
While the discovery of such alterations has provided important insight into the brain implications of preterm birth, the team points out that any brain changes that might occur prior to preterm birth remain unclear.
"[...] examinations of human brain networks at or after preterm birth are confounded by potential insults conferred both by the absence of neuroprotective elements and addition of neurotoxic influences, which are inherent conditions of early delivery," say the researchers.
"Studies of functional neural connectivity prior to preterm birth are needed to isolate processes that begin in the womb," they add. "If functional connectivity is altered in the preterm brain in utero, the untoward influences of extrauterine factors cannot be the source of those differences."
Weaker activity in pre-language brain regions for fetuses born preterm
For their study, Scheinost and colleagues enrolled 36 pregnant women with an average age of 25.3 years, of whom half were at a high risk of early delivery.
Between 22 and 36 weeks of pregnancy, the team used resting-state functional MRI in order to analyze the brain activity of each woman's fetus.
The final study sample consisted of 32 human fetuses. Of these, 14 were delivered preterm - between 24 and 35 weeks of pregnancy - while the remaining fetuses were born full term with no complications.
Compared with babies that were born full term, the researchers found that those born preterm had shown weaker neural activity in utero. This weaker activity was localized to regions of the brain's left hemisphere that are later involved in language processing.
"It was striking to see brain differences associated with preterm birth many weeks before the infants were prematurely born," says Scheinost. "Preterm infants are known to have brain changes in language regions, and we were particularly surprised that the fetal differences we detected were in these same language regions."
Overall, the researchers say that their findings indicate that brain changes related to preterm birth begin in the womb, independent of the effects of early delivery.
The team concludes:
"[...] we provide the first evidence that neural pathways are likely to be altered prior to preterm delivery. This discovery suggests that factors influencing early delivery may also impact development of the human brain, which has implications for life-long health.
Future work will address sources such as infection and inflammation that may play a causal role in altering these parallel pathways, bringing us closer to understanding both the primary neurological injury and the optimal timing for early intervention."
The researchers say that they will continue to follow up the children in this study in order to monitor their long-term health outcomes.