Classical music may promote calmer, more stable fetal heart rhythms, study suggests

New research published in the journal Chaos provides insight into how music affects the developing fetus. By examining changes in fetal heart rate variability in response to classical music, scientists found that exposure to music led to more regular and predictable patterns of fetal heartbeats—suggesting a soothing effect on the fetal autonomic nervous system.

Previous work has suggested that music can stimulate fetal movements or heart rate accelerations, and some studies have hinted at long-term cognitive benefits. However, most studies have relied on conventional ways of measuring fetal heart rate that may miss more subtle changes. This new study aimed to go further by using a mathematical approach known as recurrence quantification analysis to examine the more complex, nonlinear patterns in fetal heart rate fluctuations.

“Our interest arose from a broader effort to understand how early sensory experiences shape autonomic and neurodevelopmental trajectories,” explained Eric Alonso Abarca‑Castro of Universidad Autónoma Metropolitana–Lerma and his co‑authors. “We had seen evidence in newborns that auditory stimulation can modulate heart rate variability, so we wondered whether similar effects could already be detected in utero, using advanced tools like Recurrence Quantification Analysis (RQA). While we cannot yet claim any direct effects on long‑term neurodevelopment, these preliminary findings open the door to future research into how prenatal sensory environments might influence the developing nervous system.”

The research team, based in Mexico, recruited 100 pregnant women in their third trimester from a maternal hospital in Toluca. After screening out cases with signal loss or pregnancy complications, they analyzed high-quality fetal heart data from 37 participants. Each fetus was exposed to two five-minute segments of classical music played through headphones placed on the mother’s abdomen.

The music included “The Swan” by Camille Saint-Saëns and “Arpa de Oro” by Abundio Martínez. The session was divided into four stages: five minutes before music (PRE), five minutes for the first song (STIM1), five minutes for the second song (STIM2), and five minutes after the music ended (POST).

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To assess how the music influenced fetal heart rhythms, the researchers used both traditional and advanced measures. Traditional metrics included average heart rate and standard deviation of heartbeat intervals. The more sophisticated recurrence quantification analysis looked at patterns in the timing between beats to assess regularity, complexity, and predictability. Specific measures included determinism, average and maximum line lengths, entropy, and trapping time—each capturing different aspects of the heart rhythm’s dynamics.

After the music ended, fetal heart rate patterns became more predictable and regular. There was a significant increase in determinism, line length, and trapping time from the PRE to POST stage, meaning that the heartbeats followed more stable patterns. Entropy, a measure of signal complexity, decreased after the music, suggesting that the heart rate dynamics became less chaotic. These changes suggest the music may have a calming effect on the fetal autonomic nervous system, which controls involuntary bodily functions such as heartbeat.

“Exposing a fetus to calm, classical music appears to make its heartbeat patterns more regular—and even slightly increases movement—during and immediately after the stimulus,” the researchers told PsyPost. “These changes suggest that simple, non‑invasive interventions like prenatal music might support healthy autonomic development, laying groundwork for better stress regulation after birth. Although we cannot assert that this will directly improve neurodevelopmental outcomes, our work invites further investigation into potential long‑term benefits.”

Interestingly, not all music appeared equally effective. The second piece, the traditional Mexican song “Arpa de Oro,” produced stronger changes in heart rate patterns than the first piece. During the STIM2 phase, the researchers saw increases in maximum line length and trapping time compared to the PRE phase, indicating a more stable and predictable response. The first song did not show statistically significant effects across these measures. This difference raises the possibility that musical characteristics—like melody, rhythm, or cultural familiarity—might influence how fetuses respond.

“Very few prior studies have applied detailed techniques such as RQA to fetal heart data, so it was striking to see clear, differential effects between two classical pieces—Saint‑Saëns’s ‘The Swan’ and Martínez’s ‘Arpa de Oro’—on the fetus’s heart‑rate dynamics,” the researchers said.

Despite the promising results, the study has some limitations. The final sample size was relatively small due to the strict requirements for signal quality. Additionally, the researchers did not assess the behavioral state of the fetus during the recordings, making it harder to link changes in heart rate variability to specific fetal actions like movement or sleep-wake cycles.

“Our sample was relatively small and limited to healthy, low‑risk pregnancies, and we only measured acute responses,” the researchers noted. “We cannot yet say whether these immediate changes translate into long‑term developmental improvements, nor how well they generalize across different populations or musical genres.”

Future studies are planned to explore whether different musical styles produce distinct responses and whether these early effects on heart rate are linked to later neurodevelopment. The team also hopes to follow infants over time to determine if prenatal exposure to music has lasting benefits for emotional or cognitive growth.

“We plan to conduct longitudinal follow‑ups comparing neurodevelopmental and autonomic outcomes in infants who received prenatal musical stimulation versus controls,” the researchers explained. “We also aim to explore a wider range of auditory environments—both soothing and potentially stressful—to map their developmental impacts more fully. Ultimately, we hope these studies will clarify whether and how prenatal music exposure can influence neurodevelopmental trajectories.”

“Beyond its applied implications, this research showcases how RQA can sensitively capture complex physiological responses in utero. We hope it encourages more interdisciplinary work combining psychophysiology, obstetrics, and musicology. While we make no claims about direct neurodevelopmental effects yet, our findings clearly open the door for future investigations into the role of prenatal sensory stimulation.”

The study, “Response to music on the nonlinear dynamics of human fetal heart rate fluctuations: A recurrence plot analysis,” was authored by José Javier Reyes-Lagos, Hugo Mendieta-Zerón, Migdania Martínez-Madrigal, Juan Carlos Santiago-Nuñez, Luis Emilio Reyes-Mendoza, Ximena Gonzalez-Reyes, Juan Carlos Echeverría, Eric Alonso Abarca-Castro, Ana Karen Talavera-Peña, Sara Avilés-Hernández, and Claudia Lerma.