Cannabis Use during Pregnancy and Risk of Adverse Birth Outcomes: A Longitudinal Cohort Study

Abstract

<b><i>Background:</i></b> With recent changes in legislation regulating recreational and medical cannabis use around the globe, increased use in pregnancy is to be expected. <b><i>Objectives:</i></b> To investigate the association between cannabis use during pregnancy and birth outcomes. <b><i>Method:</i></b> Data from the Norwegian Mother and Child Cohort Study (MoBa), a prospective pregnancy cohort, were used. Participants were recruited from all over Norway between 1999 and 2008: 9,312 women with 10,373 pregnancies who reported use of cannabis before or in pregnancy. Women reported on their illegal drug use before pregnancy and at pregnancy weeks 17/18 and 30 and at 6 months postpartum. Linear regression was used to estimate crude and adjusted effects of prenatal cannabis exposure on birth outcomes. <b><i>Results:</i></b> In 10,101 pregnancies, women had used cannabis before pregnancy but not during pregnancy. In 272 pregnancies, women had used cannabis during pregnancy, and among these, in 63 pregnancies, women had used cannabis in at least 2 periods. In adjusted analyses for potential confounders, only cannabis use during at least 2 periods of pregnancy showed statistically significant effects on birth weight. The effect was observed in the complete cohort (<i>B</i> = −228 g, 95% CI = −354 to −102, <i>p</i> < 0.001) and for the subgroup where information about the child’s father was available (<i>B</i> = −225 g, 95% CI = −387 to −63, <i>p</i> = 0.01). Our results may indicate that prolonged use causes more harm, whereas short-term use did not indicate adverse effects on birth outcomes. <b><i>Conclusions:</i></b> There was a statistically significant and clinically relevant association between the use of cannabis during pregnancy and reduced birth weight. Clinicians should screen not only for cannabis use but also for the length and intensity of use as part of a comprehensive substance use screening.

The Impact of Early Life Exposure to Cannabis: The Role of the Endocannabinoid System

“…Overall, reports about the effects of cannabis use during pregnancy in humans are conflicting [41]. While many researchers have demonstrated that prenatal cannabis use is associated with stillbirth [42,43], preterm birth [17,42,[44][45][46], small for gestational age [44,45,47,48], low birth weight [44,45,[49][50][51][52], and increased admission to neonatal intensive care units [45,48,52] (see Figure 1), others have reported no association between prenatal cannabis use and adverse pregnancy or neonatal outcomes [53][54][55]. Inconsistent conclusions from maternal cannabis studies in humans could be a result of confounding variables related to socio-demographics, sample size, maternal nutrition, poly-substance use, cannabis potency and frequency and duration of use; especially when much of this data relies on self-reported use.…”

The Effects of Cannabis on Female Reproductive Health Across the Life Course

“…In one of the earliest clinical studies on the topic, Mendelson et al performed time-course experiments in small groups of healthy female volunteers with self-reported ''normal menstrual cycles'' and no use of birth control medication or intrauterine devices to evaluate the effect of smoked cannabis on sex hormones. In the first such experiment, eight periovulatory participants each consumed a 1-g cannabis cigarette containing 1.8% THC and completed sex hormone testing at 15,20,25,30,45,60,90,120,150, and 180 min after smoking initiation. Cannabis smoking induced a statistically significant increase in LH and prolactin levels 20 min after smoking initiation ( p < 0.01 for both).…”

“…42 Finally, a retrospective cohort study (n = 24,874) conducted in Australia, found that the prevalence of lifetime cannabis use was 9.5% for Australian women and 2.6% in pregnancy. 38 Associations with perinatal outcomes Cannabis exposure during pregnancy has been implicated in a wide range of adverse perinatal outcomes (Table 2), including stillbirth, 3,43 preterm birth, 3,37,38,44 low birth weights 38,42,45 and other measures of fetal/ infant growth, [46][47][48] small for gestational age, 37,38,44 and increased admission to the neonatal intensive care unit (NICU). 38,44,47 A 2016 meta-analysis of 24 case-control, cross-sectional and cohort studies indicated that women who reported cannabis use during their pregnancy had higher odds of being anemic (pooled odds ratio [pOR] 1.36, 95% CI 1.10-1.69) compared with nonusers, and their infants more likely to have lower birth weight (pOR 1.77, 95% CI 1.04-3.01) and require transfer to NICU (pOR 2.02, 95% CI 1.27-3.21).…”

Prenatal Exposure to Delta-9-tetrahydrocannabinol (THC) Alters the Expression of miR-122-5p and Its Target Igf1r in the Adult Rat Ovary

“…Many researchers have demonstrated that prenatal cannabis use is associated with an increased risk of stillbirth [ 15 , 16 ], preterm birth [ 4 , 15 , 17 , 18 ], being small for gestational age [ 17 , 18 , 19 , 20 ], low birthweight [ 17 , 21 , 22 , 23 ], increased admission to neonatal intensive care units [ 18 , 20 ] and death within one year of birth [ 17 ]. In addition, prenatal exposure to cannabis may also result in long-term alterations in the offspring’s health [ 24 ].…”