Incidence and maternal-fetal risk factors of stillbirth. A population-based historical cohort and a nested casecontrol study.

BACKGROUND

For parents, stillbirth is a tragic experience; thus, identifying the associated risk factors can be beneficial in order to prevent this event. This study aimed to investigate the incidence and risk factors associated with stillbirth.

METHODS

In this historical cohort study, a total of 18,129 birth records were investigated. The outcome variable was having or not having stillbirth. For each case of stillbirth, three live birth infants on the same day and same hospital were selected as controls, which were matched for gestational age. The data were collected using a researcher-made checklist. Finally, data were analyzed using STATA, 13.0 with Cox proportional hazards regression model at the significance level of 0.05.

RESULTS

The cumulative incidence of stillbirth was 9.48 per 1,000 live births. Based on multivariate Cox regression model, five risk factors for stillbirth were identified, including male gender, fetal diseases, gestational hypertension, gestational diabetes, and maternal hypothyroidism, (all hazard ratios > 1 and p<0.05), and - for the first time in Iran - maternal hypothyroidism, oligohydramnios, and polyhydramnios were shown as risk factors for stillbirth, which were not evaluated in any previous study.

CONCLUSION

The findings of this study suggest that some maternal and fetal risk factors can be recognized as predictors of stillbirth, which might help to detect and prevent high-risk parents at early stages in order to avoid adverse health consequences in the mother and her neonate.