Surveillance of pregnancy loss in human populations.

Surveillance of pregnancy loss as a way to detect hazardous exposures is attractive in principle. However, there are no established methods for monitoring pregnancy loss in humans. Surveillance is difficult because most loss occurs within the first 12 weeks of gestation, when pregnancy may not be documented or even recognized. Three possible approaches to surveillance of pregnancy loss are discussed here: direct surveillance of recognized loss, direct surveillance of unrecognized loss, and indirect surveillance of all loss. These approaches vary in cost, technique, power, and interpretability. While these surveillance methods appear potentially useful, their effectiveness in practice has not yet been determined.