Neurotoxicology and Teratology, Vol. 13, pp. 329-334.© Pergamon Press plc, 1991. Printed in the U.S.A. 0892-0362/91 $3.00 + .00 Prenatal Marijuana Use and Neonatal Outcome NANCY DAY,1 USHA SAMBAMOORTHI, PAUL TAYLOR, GALE RICHARDSON, NADINE ROBLES, YOUNG JHON, MARK SCHER, DAVID STOFFER, MARIE CORNELIUS AND DORCIE JASPERSE University of Pittsburgh School of Medicine Departments of Psychiatry, Pediatrics and Neurology and University of Pittsburgh Department of Mathematical Statistics Received 22 October 1990 DAY, N., U. SAMBAMOORTHI, P. TAYLOR, G. RICHARDSON, N. ROBLES, Y. JHON, M. SCHER, D. STOFFER, M. CORNELIUS AND D. JASPERSE. Prenatalmarijuana use and neonatal outcome. NEUROTOXICOL TERATOL 13(3) 329-334, 1991.--In a longitudinal study of marijuana and other substance use during pregnancy, women were interviewed at each trimester of pregnancy. Growth parameters, morphological abnormalities and gestational age were assessed for the 519 livebom singletons. There were few significant effects of marijuana use during pregnancy on birth weight, head or chest circumference, gestational age, or growth retardation after adjustment for covariates using a regression model for analysis. There was a small but significant nega- tive effect of marijuana use during the first two months of pregnancy on birth length and a positive effect of marijuana use during the third trimester on birth weight. Birth weight Marijuana Fetal growth retardation Infant Pregnancy Substance use THE most frequent age of marijuana use for women is also the age of childbearing. Fifty percent of 18- to 35-year-old women reported using marijuana at least once, and 8% reported using marijuana a minimum of 10 out of the past 30 days (3). However, surprisingly little is known about the teratogenic effects of mari- juana use and the few reports in the literature have been conflict- ing (6). Several studies found no effect of marijuana use during preg- nancy on neonatal growth and no increase in the risk of morpho- logical abnormalities (22,24), other studies reported that infants exposed to marijuana were smaller or had more minor physical anomalies (17,19), while another detected an effect of marijuana on birth length (28). Fried et al. (14) found a linear association between decreased length of gestation and marijuana use, al- though they did not report a higher rate of prematurity (defined as <37 weeks gestation). Gibson et al. (15) reported a higher rate of prematurity and Hatch and Bracken (17) reported a higher rate of prematurity and small-for-gestational age infants, but only among offspring of white mothers. One factor affecting the comparability of these results is the difficulty of obtaining accurate measures of substance use, partic- ularly when the substance is illegal. An earlier report from this study found that women under-reported marijuana use when asked to report retrospectively over the entire first trimester (10). This was due, in part, to the difficulty of reporting accurately a behav- ior that is changing over time. Other investigators have demon- strated that marijuana use was under-reported when interview data were compared to urine tests and conversely, that urine tests missed marijuana use that was reported on interview (29). Another factor leading to disparity in the results may be dif- ferences in measurement of marijuana use. Some studies assessed frequency of marijuana use but not quantity (17) or used very global categories of use (22). Also, women were interviewed at differing times during pregnancy (15, 17, 29) or after delivery (19,22), thus introducing memory errors over unequal periods of time. These biases affect not only the measurement of marijuana but of other covariates such as other illicit drugs, alcohol and to- bacco. These problems, combined with small numbers of heavy marijuana users during pregnancy and the infrequency of negative outcomes in a general sample of pregnancies, may explain the variability of results. This report is from a longitudinal study of the effects of mar- ijuana use during pregnancy. The effects of marijuana use during each trimester of pregnancy on growth, gestational age, and mor- phological characteristics at birth were assessed. Marijuana use was measured at defined time points during pregnancy for each woman, and specific techniques were developed to measure the use during each of the three months of the first trimester. An analysis of sleep and electroencephalographic data from a subsample of infants in this study has demonstrated an effect of marijuana on the sleep patterns of newborns (26) that is still present when the children are three years old (4). This project is a parallel study to one focused on alcohol use during pregnancy. In the alcohol study, we have shown significant effects of alco- hol use on growth and morphology of the offspring (5, 7, 9) us- ing the same study design and instruments. This study was carried out at the Magee-Womens Hospital, which houses the Department of Obstetrics and Gynecology and 1Requests for reprints should be addressed to Nancy L. Day, Ph.D., Western Psychiatric Institute and Clinic, Program in Epidemiology, 3811 O'Hara Street, Pittsburgh, PA 15213. 329