She passed the entrance exam of the "Internat des hôpitaux de Paris" and spent the next four years as an intern gaining clinical experience in pediatrics.

She was accompanied by Jean Aicardi and Jacques Couvreur, both Fulbright scholars, and the three became the first interns of the Hôpitaux de Paris to be awarded scholarships for the US.

Gautier had recently joined the pediatrics group he headed at the Armand-Trousseau Hospital, and she offered to attempt this, since she had been trained in both cell culture and tissue staining techniques in the United States.

[4] In order to count the chromosomes, Gautier worked on fibroblasts derived from connective tissue, which were easier to obtain under local anesthesia.

Although the principle of cell culture is simple, there were many practical obstacles to getting it to work under the primitive conditions available to Gautier, who was forced to use a personal loan to purchase laboratory glassware and, at times, her own blood as a source of human serum.

She used the "hypotonic shock" method[5] followed by drying the slide after attachment in order to disperse the chromosomes of dividing cells and make them easier to count.

Gautier entrusted her slides to Jérôme Lejeune, a fellow researcher at CNRS, who offered to take pictures in another laboratory better equipped for this task.

The Jérôme Lejeune Foundation obtained authorisation from the Bordeaux Tribunal de Grande Instance for bailiffs to be sent to film this session.

At the last minute, concerned that the recording might be used in legal proceedings it could not afford to defend, the congress organizers decided to cancel her presentation and she received her award privately instead.

[18] After the trisomy discovery Gautier left Turpin's team and applied for a position in public health care to dedicate herself to cardio-pediatrics.