The objective of this randomized controlled study was to demonstrate whether fetal hearing can be assessed in utero.

Unselected women at term of pregnancy (37-41 weeks of gestation) undergoing cardiotocography (CTG) according to routine clinical care and with a complete postnatal follow-up were consecutively recruited.

The two groups of women were selected in a random way, and it was an unblended randomization controlled trial (RCT), according to a list created by the website ww.randomization.com.

If the CTG was non-reactive for 10 minutes women who were eligible for the study were randomized into two groups.

An auditive stimulus was generated in group A. This stimulus was produced by hitting a diapason on an acoustic surface, at a distance of 2-3 cm from the mother's skin (in order to avoid mechanical vibration to reach the fetus) in the area near the fetus' head.

The same procedure was repeated three times, waiting 30 seconds between one stimulus and the following one. The total duration of stimulation was about 2 minutes. Cardiac accelerations on the CTG and fetal movements perceived by the mother were recorded in the ten minutes after the stimulus was produced.

No stimulation was produced in group B, but the CTG was prosecuted until the clinical criteria were satisfied. The total length of the CTG was variable from a minimum of 20 minutes to a maximum of one hour.

All the clinical variables were recorded in the Case Report Form (CRF) in particular the lapse of time needed for the first fetal cardiac acceleration and for the first fetal movement to occur.

A complete postnatal follow-up was obtained through the examination of medical records and parental interview.

A power analysis was carried out using Power Analysis Sample Size (PASS) software (Kaysville,UT,USA) and was conducted before the enrollment started. It was estimated that, for a survival comparison test (Log Rank), given the sample allocation ratio=1:1, 100 cases per group would be needed to validate a hazard ratio between group A and group B of 1.5 with a power of 80% and a Type I error of 5%.

Inclusion Criteria:

1. Understand the Italian language;
2. Informative consensus;
3. To be between 18 and 48 years old;
4. To be sure of their gestational age, included between 37 0/0 and 41 5/7 weeks;
5. Single fetus pregnancy in cephalic position;
6. CTG with normal frequency and variability, without cardiac acceleration for 10 minutes, and with no uterine contractions.

Excluding criteria:

1. BMI before pregnancy more than 30 kg/m2, and at the end of pregnancy more than 35 kg/m2;
2. Uterine fibromatosis;
3. Premature rupture of membranes or oligohydramnios;
4. Fetal pathology (malformation or genetic syndromes);
5. Infective illness contract in pregnancy (CMV, herpes virus, rubella, syphilis, toxoplasmosis);
6. Anomalous CTG, or with contractions
7. Gestational diabet with insulin therapy;

7) Cholestasis of pregnancy; 8) Use of corticosteroids within the last hours; 9) Use of prostaglandins for cervical ripening, within the last hours.