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In recent years, the evaluation of in utero exposure to drugs of abuse has been achieved by testing biological matrices (substances from the body) coming from the fetus or newborn (eg, meconium – the first faeces from the newborn, fetal hair, cord blood, neonatal urine), the pregnant or nursing mother (eg, hair, blood, oral fluid, sweat, urine, breast milk), or from both the fetus and the mother (eg, placenta, amniotic fluid – the fluid inside the pregnant uterus).

Overall, these matrices have the advantage of noninvasive collection (with the exception of amniotic fluid) and early detection of exposure from different gestational periods. Matrices such as amniotic fluid, meconium, fetal hair, and maternal hair provide a long historical record of prenatal exposure to certain drugs and can account for different periods of gestation: amniotic fluid from the early pregnancy, meconium for the second and third trimester of gestation, fetal hair for the third, and finally maternal hair (when long enough) for the whole pregnancy. Placenta may reveal the passage of a substance from the mother to the fetus. Cord blood and neonatal urine are useful for determining acute exposure to drugs of abuse in the period immediately previous to delivery. Drug detection in maternal blood, oral fluid, and sweat accounts only for acute consumption that occurred in the hours previous to collection and gives poor information concerning fetal exposure.

Different immunoassays were used as screening methods for drug testing in the above-reported matrices or as unique analytical investigation tools when chromatographic techniques coupled to mass spectrometry were not commonly available. However, in the last decade, both liquid and gas chromatography-mass spectrometric methodologies have been routinely applied after appropriate extraction of drugs and their metabolites from these biological matrices.

The fetal, neonatal, and occasionally maternal matrices are, to varying degrees, repositories of drugs to which the fetus is exposed in utero. An accurate assessment of fetal exposure to drugs of abuse through the analysis of these matrices is important in identifying infants at risk and for providing treatment and follow-up.

Although currently available analytic methods are specific and sensitive to allow the detection up to minute amounts of parent drugs and their metabolites in these various biological matrices, further studies are needed to translate the information into clinical practice.Finally, the mechanism of fetoplacental passage of drugs, drug metabolism, and the potential adverse effects of drugs on developing organisms have to be further ascertained in animal and human studies.