Agreement of umbilical cord drug and cotinine levels with maternal self-report of drug use and smoking during pregnancy

Objective: We undertook this study to assess the agreement between fetal umbilical cord drug levels and maternal self-report. Study Design: Cord samples were collected from 103 placentas after delivery as a subproject of the larger Pacific Research Center for Early Human Development (PRCEHD) study. These cord samples were then processed to obtain cord lysates and enzyme-linked immunosorbent assay (ELISA) performed for cotinine and illicit drugs. Levels of each of these substances were compared with clinical information. Result: We found fair agreement between self-reported smoking and cotinine levels ( κ =0.26 (0.07 to 0.5)) as well as slight agreement with current drug use and positive drug levels ( κ =0.19 (−0.05 to 0.4)). Compared with maternal self-report, sensitivity of cotinine levels was 27% and specificity was 98%. Sensitivity of positive cord illicit drug levels was 32% and specificity was 85%. Conclusion: Umbilical cords provide another independent measure of maternal drug use and are readily available. To our knowledge, this is the first study to measure cotinine levels in the umbilical cord tissue.