What causes pregnancy loss? Preexisting mental illness as an independent risk factor

Maternal mental health disorders in pregnancy are common and are associated with prematurity, low birth weight and delivery complications. We explored whether existing mental illness was associated not just with fetal complications but also with fetal death.

We conducted a retrospective cohort analysis using data from the National Comorbidity Survey (NCS). The NCS is a nationally representative multistage probability study of the prevalence of psychiatric disorders in the United States. We analyzed the association between a prepregnancy mental health diagnosis and subsequent miscarriage or stillbirth, using multivariable logistic regression to control for maternal age, race, health risks and other independent risk factors for fetal death.

Patients with any mental health disorder prior to pregnancy [odds ratio (OR)=1.8], specifically those with affective disorders (OR=1.6) or substance use disorders (OR=1.4), were at significantly higher risk for fetal mortality in pregnancy. This risk remained significant even when controlling for health and behavioral risk factors that cause fetal loss.

These results are consistent with studies showing mental health to be independently associated with morbidity and mortality in heart disease, stroke and cancer. The etiology remains poorly understood, but may include neuroendocrine, behavioral and genetic mediators.