Cigarettes, Alcohol and Marijuana: Varying Assoociatons with Birthweight

International Association of Epidemiology, Vol. 16, No. 1 1987

Jennie Kline, Zena Stein and Michelle Hutzler


The relations of cigarette smoking, alcohol drinking and marijuana use
during pregnancy to birthweight were examined in two prospectively studied
pregnancy cohorts (Phases I and II). After analytic adjustment in
ordinary least squares regressions for other factors that influence
birthweight, cigarette smoking during at least half the pregnancy was
associated with a significant decrease in mean birthweight (159 grams in
Phase I, 202 grams in Phase II) In Phase II only, beer drinking was
associated with a significant decrement of 8.4 grams in estimated
birthweight per ounce of absolute alcohol per month. Neither wine nor
liquor drinking in the Phase II data nor any of the three beverages in the
Phase I data was associated with significant decrements in predicted
birthweight. Furthermore, with one exception (drinking once a week in
Phase II only), alcohol drinking, defined as the number of occasions per
month on which any alcoholic beverage was consumed, was not associated with
a change in birthweight. Regarding marijuana use, the data are not
consistent between the two phases. In the Phase I data, no coherent trend
in association with birthweight was observed. In the Phase II data,
marijuana use 2-3 times per week, 4-6 times per week and daily was
associated with increasing decrements in estimated birthweight: 127 g, 143
g, and 230g respectively. The inconsistent findings for alcohol drinking
and marijuana use between phases stand in marked contrast to the consistent
findings for cigarette smoking. The evidence regarding marijuana use and
birthweight is sparse, with one study reporting a positive association (15)
and another no association. (16)

The greatest degree of inconsistency between the two phases was
observed for daily use of marijuana. In Phase I, use 2-4 times per month
was associated with a significant increase in birthweight; in Phase II,
daily use was associated with a decrease in birthweight, with lesser
decrements for use 2-3 and 4-6 times per week. The questions asked in the
two phases were not directly comparable, although one would have thought
the modification too slight to explain the differences. The proportion of
daily users is higher in Phase II, an observation that might have resulted
from the change in the questionnaire. One suggestion is that the
composition of the substance has changed, or perhaps that it was subjected
to a contaiminant or herbicide over the second phase. Certainly marijuana,
unlike the other two exposures, is unstandardized and likely to vary. It
is also possible that the amount smoked on each occasion could be higher in
Phase II than in Phase I, but we have no information on this point.
Finally, we thought that marijuana users in more recent times might be
taking cocaine or other drugs as well as marijuana. This proved to be the
case, but among women not using cocaine, a decrement in birthweight of
borderline significance persists for Phase II women who smoke marijuana
daily.

}}}### (In other words remove the paraquat and cocaine and a decrement in
birthweight of only borderline significance exists!!)

(15) Hingson R, et al: Effects of maternal drinking and marijuana use on
fetal growth and development. "Pediatrics" 1982; 70: 539-46

(16) Linn S, Schoenbaum S C, et al: The association of marijuana use with
outcome of pregnancy. AJPH 1983; 73: 1161-4.

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