A variety of environmental factors have been linked to both isolated and recurrent pregnancy loss. Exposure to three particular substances are of primary importance due to their common use, alcohol, cigarettes, and caffeine. As little as three alcohol drinks per week is associated with miscarriage. Cigarette smoking is also associated with both infertility and recurrent pregnancy loss which is not surprising since nicotine and its metabolic byproducts are concentrated in follicular fluid (fluid bathing the eggs within the ovary) and in uterine blood vessels. Consumption of coffee and other caffeinated beverages during early pregnancy is related to adverse pregnancy outcome including first trimester miscarriages.
Other life style choices may contribute to pregnancy loss. These include obesity, stress, recreational drugs, and use of nonsteroidal anti-inflammatory agents during pregnancy. Occupational exposure to heavy metals like lead or mercury, anesthetic gases, and organic solvents are associated with pregnancy loss. Prolonged exposure to ionizing radiation may also be a cause of miscarriage and is perhaps the reason why flight attendants and pilots have a higher incidence of loss. Prolonged standing and working long hours is not associated with miscarriage, but is associated with preterm labor and low birth weight babies. There is no evidence that mild to moderate exercise during pregnancy in healthy women is associated with miscarriage, however, no studies have been performed in those with a history of recurrent pregnancy loss. Exposure to electromagnetic fields from computer terminals is not associated with adverse reproductive outcome. Large studies of women without a history of recurrent pregnancy loss indicate that sexual intercourse during pregnancy is not associated with miscarriage, however, once again, these studies have not been performed in women with a history of recurrent loss.