Although the actual number of pregnant women who abuse methamphetamine (MAP) in Japan remains unknown, it appears to be increasing [1]. Thus, rapid screening for MAP in newborns with on-site immunoassay devices is essential for protecting the health of both the mother and child. Urine is the most popular specimen of choice for drug testing, because it can usually be collected noninvasively in a large volume [2]. However, a special bag is required to collect urine from newborns. Sometimes this can be problematic, because skin dermatitis can be induced in newborns as a result of contact with adhesives used to fix the bag to the skin. As an alternative to urine specimens, meconium and hair can also be used for noninvasive drug testing in newborns [3–7]. However, use of these sample types requires liquid– liquid or solid-phase extraction before analysis for the drug via immunoassay devices or instruments such as a gas chromatograph–mass spectrometer or liquid chromatograph–mass spectrometer. Thus, these latter specimens are not practical for bedside drug testing. Moreover, interpretation of hair results can sometimes be confusing because of extreme contamination of the hair by external drug exposure [8]. However, visual demonstration of drugs by matrix-assisted laser desorption ionization time-of-flight mass spectrometry has been shown to be able to discriminate between deliberate drug use and passive exposure to drugs [9]. Recently, we developed a screening method for MAP in urine absorbed in a disposable diaper, with the analysis using the conventional immunoassay devices, Instant View M-1 (Alfa Scientific Designs, Poway, CA, USA) and Triage DOA (Biosite, San Diego, CA, USA) [10]. Our method makes it possible to quickly test newborns for MAP at the bedside. Our previous study results demonstrated that MAP could be completely recovered from disposable diapers, which means that MAP is not adsorbed nonspecifically onto the polymers (sodium polyacrylate) of the diapers. However, when urine is excreted into a disposable diaper, it is exposed to the infant’s body temperature until the diaper is exchanged for a new one. In addition, when the newborn continues to wear the same diaper, there is slight decomposition of the urine retained in the diaper due to proliferation of bacteria at body temperature. Nagata et al. [11] reported that MAP in bodily fluids and tissues was stable against decomposition at room temperature for a long period of time. However, the stability of urinal MAP in the polyacrylate environment of the diaper at body temperature has yet to be determined. Due to the metabolism of bacteria, putrefactive amines are produced in biological specimens left at room temperature [12]. In addition, there is a variable cross-reaction between the anti-MAP antibodies used for immunoassay devices and some putrefactive amines such as phenethylamine and tyramine, which is frequently problematic when screening for MAP in forensic autopsy cases [13]. Moriya et al. [14] reported that the anti-MAP antibodies used for the Triage DOA cross-react with phenethylamine at a concentration of 5000 ng/ml or higher in an aqueous T. Shiotsuki F. Moriya (&) Department of Nursing, Faculty of Health and Welfare, Kawasaki University of Medical Welfare, Matsushima, Kurashiki, Okayama 701-0193, Japan e-mail: moriyaf@mw.kawasaki-m.ac.jp