Background:
Fetal mortality is still insufficiently known, valued, and studied in different contexts.

Objectives:
This is a study protocol designed to identify a large and innovative number of epidemiologic and biological risk factors (demographic, social and environmental, maternal infections, placental alterations and angiogenic factors, gestational and fetal disorders, and prenatal care) and to understand their complex relationships, as well as factors related to fetal loss.

Methods:
This is a prospective case-control study with estimated 415 cases (stillbirths) and 415 controls (live-births) carried out in 15 public hospitals in São Paulo City, Brazil. Data is being collected for cases and controls from mother’s interviews, hospital records and antenatal cards. And from multiple genetic and serological analyses in samples of maternal and umbilical cord blood and the placenta. For a smaller number of cases traditional and non-invasive autopsies of the stillbirths are being performed and compared to imaging techniques. In a subsample of 100 women additional interviews and psychometric scales are being performed.

Results:
The Covid19 pandemic had a high impact on health services and on the research activities, a team offered constant field support and supervision to reduce case losses and technical and scientific meetings were offered. Until Nov-2022 269 cases and 269 controls were enrolled and carried out interviews, representing 64.8% of the defined sample. Data from antenatal cards and medical charts are being extracted of cases and controls. Placentas were obtained for 262 cases and controls and 265 maternal blood samples of cases and controls collected, 22.6% of the fetuses were referred for autopsy, and 93 (93%) interviews carried out with bereaved mothers.

Conclusion:
The results will enable us to develop multiple analyses of the complex relationships of social, environmental, biological risk factors and health services and participate in the efforts to reduce stillbirths and its impact.