Maternal Lifestyles Study (MLS) 

 Prenatal substance abuse continues to be a major public health problem that affects millions of children and places both financial and social burdens on society. The most recent report from the National Household Survey on Drug Abuse estimated that, in 1999, the rate of drug use among pregnant women was 3.4 percent for illicit drugs, 17.6 percent for tobacco, and 13.8 percent for alcohol.

The MLS, another PPB-supported effort, began in the early 1990s as an interagency, longitudinal study against a backdrop of debate and controversy about the effects of prenatal cocaine exposure on child outcomes. Through the NRN, researchers could access a large, multisite population of newborn infants and their mothers, allowing an in-depth, prospective study of mothers and children in utero exposed to cocaine. The collaborative nature of the NRN provided access to a multicultural, multiethnic, socioeconomically and demographically varied population in which widespread use of drugs was previously demonstrated.

Now in its eleventh year, the MLS is the largest clinical, prospective, longitudinal study of prenatal drug exposure and child outcomes to date. It is conducted at four NRN sites at the University of Miami, the University of Tennessee at Memphis, Wayne State University, and Brown University. The cohort includes 658 exposed and 730 comparison mother/child dyads. In addition to PPB support, the National Institute on Drug Abuse has consistently co-funded the MLS effort since it began.

In Phase I of the MLS, 19,079 pregnant mothers were recruited just before or immediately after they gave birth. Of these, 16,988 (89 percent) met basic eligibility criteria, and 11,811 (70 percent) of these agreed to participate in the study. Drug use was confirmed by an interview with the mother and by gas chromatography/mass spectroscopy for cocaine/opiate metabolites in the meconium of the infant. Based on this information, 1,185 infants (10 percent) were exposed to either cocaine or opiates during pregnancy. A total of 7,442 infants (63 percent) were confirmed as not having been exposed to either cocaine or opiates; the exposure status of 3,184 infants (27 percent) was not confirmed. The use of alcohol, tobacco, and/or marijuana by the mother occurred in all three of these groups.

Phase II of the study tracked the development of infants who had been exposed to illicit drugs, comparing the results to infants whose mothers had not used illicit drugs. A total of 1,388 subjects were recruited for this phase of the MLS. Of these, 658 infants were exposed to cocaine, opiates, or both in utero, while 730 infants had been exposed to neither. All of these infants were initially assessed at one month of age; mothers or caretakers were encouraged to participate in visits at four, eight, 10, 12, 18, 24, 30, and 36 months of age. During these visits, the children participated in a variety of assessments that noted both their medical and developmental outcomes over time. Researchers also asked mothers and caretakers questions about the infant and the environment.

Mother/child dyads have continued their involvement in the MLS through subsequent phases. Phase III assessed children during visits that occurred when they were ages four through seven. Phase IV, which is now under way, includes children between the ages of eight and 11.

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