bNumber of couples participating. Paternal exposure was reported.
cNumber of men reporting exposure to solvents during pregnancies of their spouses.
dNumber of births.
A number of adverse outcomes of pregnancy have been studied for possible associations with exposure to insecticides or solvents. Many of the studies have focused on the risk of fetal loss prior to normal gestation of 40 weeks. Spontaneous abortion (miscarriage) refers to the loss of a fetus prior to 20 weeks of development; after 20 weeks gestation, fetal loss is termed a stillbirth. A birth at less than 37 weeks is referred to as a preterm delivery or premature birth. The overall incidence of spontaneous abortion is estimated to be as high as 43%, with the majority occurring in the 14 days after conception when most pregnancies would not have been detected (Bennett, 1992; Smith and Suess, 1998). About 10% of clinically recognized pregnancies end in spontaneous abortion, usually between 7 and 12 weeks of gestation (NLM, 2002). Completeness of ascertainment is thus a great challenge in epidemiology studies of spontaneous abortion.
The most common identified cause of spontaneous abortion is a genetic abnormality of the embryo. Risk factors for spontaneous abortion include age, maternal illness, cigarette smoking, alcohol use, taking of medications, and having a previous spontaneous abortion. The risk of pregnancy loss is known to increase with increasing maternal age, especially after the age of 30 or 35, and is also high for women under the age of 18. In women who have had one previous spontaneous abortion, the probability of a second is estimated to be 13–26%, and the probability of another increases with successive spontaneous abortions (Smith and Suess, 1998). Several maternal occupational exposures have been associated with the risk of spontaneous