Introduction: The prevalence of poor mental health during pregnancy is estimated at 10% and it appears to be associated with increased maternal and child morbidity. This pilot study aims to assess the impact on pregnant women, their mental health, and health care trajectory of early identification of poor mental health during pregnancy. Method: This interventional study was carried out in three districts of Paris and included two groups. The intervention group was composed of pregnant women whose screening for poor mental health consisted in systematically asking them, in the first trimester of pregnancy, a single question. The control group was composed of pregnant women monitored as usual. All of these women benefited from a telephone interview eight to twelve weeks after their recruitment in order to assess their mental health in the second trimester of pregnancy and describe their care pathway. Results: In the intervention group, women benefited from early prenatal interview more often and they felt that their medical care had improved their well-being during pregnancy more frequently (P < 0.05). Women in the control group found it harder to express their psychological difficulties, expressed them less frequently and had trouble with medical care follow-up when offered (P < 0.05). Conclusion: The early screening for poor mental health by a single question during pregnancy seems to positively change the care pathway of pregnant women with poor mental health. In addition, it could improve the well-being of pregnant women in the second trimester of pregnancy.