The effect of abused substances on antenatal and intrapartum fetal testing and well-being.

Recognition that use and abuse of substances by pregnant patients perpetuates, despite ongoing efforts to educate the public, necessitates clinicians to integrate understanding of potential effects on antepartum and intrapartum fetal testing into their interpretation and implementation of clinical findings. This includes acknowledging some anticipated alterations in results and selecting the appropriate type and frequency of testing methods and interventions. Certain substances are well documented in terms of expected variations in test results; others are not as clearly defined. An overview of information that may be helpful to the clinician is presented to promote understanding of fetal evaluation performed through common tests such as contraction stress test, the nonstress test, the biophysical profile, the modified biophysical profile, fetal movement counting, and Doppler velocimetry. What evidence is available should be used to assist in defining the actual status of the fetus as best as possible, even when the effects of substances may be unknown or have obscure results.