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irth. These effects are small by comparison with those caused by tobacco use during
pregnancy, and have not been observed in all studies.
— The health and psychological effects of cannabis use, Hall (2001) [4]
En metaanalys från 1997 där 10 studier med totalt 32483 födslar ingick undersöktes ledde till
slutsatsen att man inte kan bevisa att cannabis leder till låg födelsevikt. Professor English anser bl.a att
tidigare studier som visat samband inte tagit hänsyn till tobaksanvändning, något som är relevant då
cannabis ofta intas tillsammans med tobak. Studierna i fråga är Greenland (1983), Witter & Niebyl
(1990), Hayes (1991), Castro (1993), Yawn (1994), Singer (1994) English noterar även att studierna
inte viar något samband mellan brukets omfattning och vikten, dvs. att mer THC för modern ger lägre
vikt hos barnet.
SETTING:From the Medline database, we identified 10 studies in which the results
were adjusted for cigarette smoking. In seven studies, information on cannabis use
was collected prenatally. Five studies reported results for differences in mean birth
weight associated with maternal cannabis use.
PARTICIPANTS: 32,483 women giving birth to live-born infants.
“
MEASUREMENTS: Mean birth weight and odds ratio for low birth weight.
FINDINGS: Three analyses of the studies on mean birth weight were conducted to
avoid double-counting women from one study. The largest reduction in mean birth
weight for any cannabis use during pregnancy was 48 g (95% confidence interval
(CI) 83-14 g), with considerable heterogeneity among the five studies. Mean birth
weight was increased by 62 g (95% CI 8 g reduction-132 g increase; p heterogeneity
0.59) among infrequent users (< or weekly) whereas cannabis use at least four times
per week had a 131 g reduction in mean birth weight (95% CI 52-209 g reduction; p
heterogeneity 0.25). From the five studies of low birth weight, the pooled odds ratio
for any use was 1.09 (95% CI 0.94-1.27, p heterogeneity 0.19).
CONCLUSIONS: There is inadequate evidence that cannabis, at the amount typically
consumed by pregnant women, causes low birth weight.
— Maternal cannabis use and birth weight: a meta-analysis, English (1997) [30]
”
Det finns även en stor studie från 1999 som inte nämns. Danska forskare kontrollerade data för nästan
13000 födslar där mammorna hade fått fylla i hälsoformulär och man kunde först se att nyfödda vägde
mindre och var kortare hos cannabisrökande kvinnor. När man justerade för alkoholanvändning så
fanns avvikelsen kvar, men när man justerade för tobak så försvann den. Det visar att sambandet
mellan cannabis och låg födelsevikt inte enbart kan skyllas på cannabis utan andra, tidigare förbisedda
faktorer, men i flera fall just tobak.
“
In two Copenhagen University hospitals 12,885 pregnant women, seen during the
period 1.8.1992 to 30.04.1995, answered questionnaires regarding consumption of
alcohol, tobacco, cannabis and other drugs. The prevalence of cannabis use was 0.8%.
Women using cannabis but no other illicit drugs were each retrospectively matched
with four randomly chosen pregnant women in the same period and the same age
group and with same parity. Eighty-four cannabis users were included. These women
were socioeconomically disadvantaged and had a higher prevalence of present and
past use of alcohol, tobacco and other drugs. No significant difference in pregnancy,
delivery or puerperal outcome was found. Children of women using cannabis were
150 g lighter, 1.2 cm shorter and had 0.2 cm smaller head circumference than the
control infants. Controlling for the child's sex and maternal use of alcohol did not
eliminate the significant differences in birthweight and length; however, they were
eliminated by controlling for maternal tobacco smoking. It is concluded, that the use
of cannabis is not a major prognostic factor regarding the outcome of pregnancy, but
is an indicator of low socioeconomic status and use of other substances.
— Cannabis and pregnancy av Balle J, Olofsson MJ, Hilden J (1999) [31]
”
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