Adverse impacts of chronic or intermittent hypoxia on development, behavior, and academic achievement have been reported in many well-designed and controlled studies in children with CHD and SDB as well as in a variety of experimental studies in adults. This should be taken into account in any situation that may expose children to hypoxia. Because adverse effects have been noted at even mild levels of oxygen desaturation, future research should include precisely defined data on exposure to all levels of desaturation.

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To investigate the effects on infants of the use of marijuana and cocaine during pregnancy and to compare the importance of urine assays with that of interviews in ascertaining drug use, we prospectively studied 1226 mothers, recruited from a general prenatal clinic, and their infants. On the basis of either interviews or urine assays conducted prenatally or post partum, 27 percent of the subjects had used marijuana during pregnancy and 18 percent had used cocaine. When only positive urine assays were considered, the corresponding values were 16 percent and 9 percent, respectively. When potentially confounding variables were controlled for in the analysis, the infants whose mothers had positive urine assays for marijuana, as compared with the infants whose mothers were negative according to both interviews and urine assays, had a 79-g decrease in birth weight (P = 0.04) and a 0.5-cm decrement in length (P = 0.02). Women who had positive assays for cocaine, as compared with nonusers, had infants with a 93-g decrease in birth weight (P = 0.07), a 0.7-cm decrement in length (P = 0.01), and a 0.43-cm-smaller head circumference (P = 0.01). To compare our findings with those of other investigators who did not use urine assays, we repeated the analyses, considering only self-reported use of marijuana (23 percent) and cocaine (13 percent). There were no significant associations between such use as determined by interviews alone and any of the measures of outcome. We conclude that the use of marijuana or cocaine during pregnancy is associated with impaired fetal growth and that measuring a biologic marker of such use is important to demonstrate the association.

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It is often assumed that visual survey data provide more accurate fish counts than conventional extractive gear. As a result, use of underwater vehicles to assess the abundance and distribution of fishes has increased rapidly over recent years. However, a review of observations reported for 48 demersal marine fish taxa showed that almost all respond in some way to underwater vehicles. Whether or not movements or changes in behavior affect survey bias is more difficult to assess. A simple conceptual model is presented to evaluate relationships between stimulus intensity, distances from the vehicle where reactions occur, and survey bias. Largest bias is caused by attraction or avoidance that occurs outside the field of cameras or observers. While light level and vehicle speed have been explored experimentally in a few cases, much remains to be learned about how bias varies among species, age groups, different vehicles, and operating conditions. Given poor understanding of survey bias, we recommend that surveys be conducted with minimum possible variation in operations and that vehicle time is devoted to experimental evaluation of methods. There is no good substitute for direct observations on fish behavior, distribution, and abundance; and survey design can be improved through experimentation.

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