Couples provided written and verbal consent after being informed about the study. Pre-test data were collected using the Personal Information Forms (PIF-Female, PIF-Male), Antenatal Mother Attachment Scale (PAAS), Antenatal Father Attachment Scale (PAAS), the Richard Campbell Sleep Questionnaire (RCSQ), and the State Anxiety Inventory (SAI).

Couples listened to fetal heart sounds (angel sounds) each night before sleep for three consecutive nights, with each session lasting approximately 20 minutes. The researcher provided remote support via WhatsApp throughout the intervention period. Post-test data were collected on the fourth day using the same measurement tools.

Couples provided written and verbal consent after being informed about the study. Pre-test data were collected using the same tools as the FHS group. Couples were sent audio recordings prepared using guided imagery scripts, and instructed to listen each night before sleep for three consecutive nights. The audio included calming suggestions to promote attachment and reduce anxiety.

On the fourth day, post-test data were collected using the same tools.

Couples in the control group received no intervention. Pre-test data were collected using the same measurement tools as the experimental groups. After three days without intervention, post-test data were collected on the fourth day.

Pregnant women and their partners listened to fetal heart sounds (also referred to as angel sounds) for 20 minutes before bedtime on three consecutive nights using a fetal heart rate monitoring device. The intervention aimed to enhance prenatal attachment and reduce anxiety by increasing awareness of the fetus through auditory stimulation.

Each item of The Maternal Antenatal Attachment Scale (MAAS), which has a total of 19 items, focuses on the pregnant woman's feelings, attitudes and behaviors towards the fetus. The scale is likert-type and each item is scored between 1 and 5 (5=represents very strong feelings towards the fetus; 1=represents the absence of feelings towards the fetus). A high score indicates a high degree of attachment. 11 items in the scale are scored in the opposite direction (1, 3, 5, 6, 7, 9, 10, 12, 15, 16, 18).

The Paternal Antenatal Attachment Scale are based on the fathers' experiences in the last two weeks and measure the father's feelings and thoughts towards the developing fetus in the mother's womb. Increasing score indicates higher degree of attachment. The scale is in 5-point Likert type and consists of 16 items and two sub-dimensions. Sub dimensions; "quality of attachment [2, (3), (7), 9, 11, (12), (15), 16]" in which the emotional experience of the father is measured while thinking about the baby in the womb, "time spent on attachment [( 1), 4, (5), (6), (8), 10, (13), 14]". 9 items are reverse scored in the scale. Cronbach's alpha reliability coefficient of the scale was 0.82; the Cronbach's alpha of the quality of attachment sub-dimension was 0.80; The alpha of the time spent connecting sub-dimension is 0.67.

This scale is a 6-item scale that measures the depth of night sleep, the time to fall asleep, the frequency of awakening, the time to stay awake when awakened, the quality of sleep, and the noise level in the environment. Each of the items is evaluated on a chart with numbers from 0 to 100. According to the scale scoring, "0-25" points indicate very bad sleep, while "76-100" points indicate very good sleep. The 6th item, which evaluates the noise level in the environment, is excluded from the scale total score evaluation, and the total score is evaluated over 5 items. As the score of the scale increases, the sleep quality of the patients also increases. The scale's Cronbach α value is 0.91.