Reproductive Health Effects

Spontaneous Abortion, Stillbirth Rates

It is difficult to link spontaneous abortion and stillbirths directly to a specific environmental exposure since women often may not realize they are pregnant at critical developmental periods when they might be exposed.

A large percentage of all embryos are lost within the first trimester of pregnancy (30-50% of all conceptions going undetected.)

Up to 50% of early spontaneous abortions occur due to abnormal chromosome complement correlated with increasing age of mother (the exact factors causing this are not well understood. ) The vast majority of early spontaneous abortions are of unknown cause.

Toxic exposures are among several possible explanations for later fetal loss, although the fact that there are also other possible common causes (including maternal illness, immunological or genital tract abnormalities) poses a challenge to linking cause with any degree of certainty.21

PCBs. High rates of spontaneous abortion occurred in mothers accidentally exposed to PCB-contaminated oil in Taiwan and Japan.

Solvents. There is fairly solid evidence from a number of studies that risk of spontaneous abortion was two to four times greater in women occupationally exposed to organic solvents such as perclorethylene (PCE), trichloroethylene, glycol ethers and aliphatic solvents.22 Women working in the electronics industry, dry cleaning, laboratories, cosmetologists and hairdressers are all at risk of exposure to various organic solvents.

See also, "Motherisk update: Exposure to organic solvents. Does it adversely affect pregnancy?" by Kristen I. McMartin and Gideon Koren, July, 1999.

Disinfection by-products. A recent study of over 5,000 women showed a greater risk of spontaneous abortion occurring in women who drank five or more glasses of tap water per day where they were consequently exposed to levels of disinfection by-products as indicated by trihalomethanes in excess of 75 micrograms per liter total.23

Pesticides. Studies have found that women who work in agriculture or had environmental exposure to pesticides during pregnancy have higher risk of spontaneous abortion or stillborn babies, although there is inconsistency in these studies.24 The Ontario Farm Family Health Study has shown that there was increased risk of miscarriage and preterm delivery where fathers reported a combination of pesticide-handling activities along with the use of specific pesticides in the three months prior to conception.25 From a recent review of epidemiological studies, Health Canada researchers suggest that scientific data generally report higher reproductive risks from maternal as opposed to paternal exposures to pesticides.26

Lead. High exposure to lead (i.e., at levels above 15 mcg/dL), whether occupationally or environmentally, is associated with increased risks of spontaneous abortions and still births.

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