Posttraumatic stress disorder (PTSD) is relatively common among pregnant and postpartum women. The lifetime prevalence of PTSD for women is about 10%, with one-third of episodes lasting more than five years. Given the relatively high prevalence of PTSD in young women and the chronic nature of the illness, many women may experience PTSD symptoms during pregnancy.

Past studies have suggested that stressful life events and PTSD may be associated with an increased risk of preterm birth; however, the findings have been inconsistent. One of the factors which has complicated the interpretation of these studies is that many women with PTSD are taking psychotropic medications – typically antidepressants or benzodiazepines – which may also modulate risk for preterm birth. A recent study has looked more closely at the link between PTSD symptoms and preterm birth, attempting to parse out the effect of medication on outcomes.

Women with a diagnosis of PTSD had an increased risk of preterm birth (odds ratio [OR] 1.22); however, it seems that this risk was even higher when PTSD occurred with a diagnosis of major depression. Women with diagnoses of both PTSD and a major depressive episode had a 4-fold increased risk of preterm birth; this risk is greater than, and independent of, antidepressant and benzodiazepine use. The researchers observed a dose-dependent effect; for each point increase on the Modified PTSD Symptom Scale (range, 0-110), the risk of preterm birth increased by 1% to 2%.

The authors hypothesize that stress and stress-related disorders may increase the risk of preterm birth through stimulation of the hypothalamic-pituitary-adrenal (HPA) axis. In response to stress, individuals with PTSD have elevated levels of corticotrophin-releasing hormone (CRH). During pregnancy, the placenta is an important peripheral source of CRH. Throughout pregnancy, the levels of CRH gradually increase and determine the timing of childbirth. If stress elevates maternal levels of CRH, this may result in preterm birth.

Ruta Nonacs, MD PhD

Yonkers KA, Smith MV, Forray A, Epperson CN, et al. Pregnant Women With Posttraumatic Stress Disorder and Risk of Preterm Birth. JAMA Psychiatry. 2014 Jun 11.