A history of spontaneous (i.e., miscarriage) or surgical abortion has been associated with a small increase in the risk of preterm birth, with an increased risk with increased number of abortions, although it is unclear whether the increase is caused by the abortion or by confounding risk factors (e.g., socioeconomic status).[39] Increased risk has not been shown in women who terminated their pregnancies medically.[40] Pregnancies that are unwanted or unintended are also a risk factor for preterm birth.[41]