ABSTRACT: Marijuana, also known as cannabis sativa, is the most common illicit drug used during pregnancy. According to most studies, marijuana use during pregnancy is reported as being between 2% and 5%. Growing numbers of states have legalized marijuana for recreational or medicinal purposes. This could lead to even greater use by pregnant women. Women who are pregnant or considering becoming pregnant should stop using marijuana. There are concerns about impaired neurodevelopment as well as maternal and fetal exposure. Obstetrician-gynecologists should be discouraged from prescribing or suggesting marijuana for medicinal purposes during preconception, pregnancy, and lactation. Women who are pregnant or planning to become pregnant should be advised not to use marijuana for medicinal purposes. Better safety data are available for pregnant women. Insufficient data is available to assess the effects of marijuana on infants during breastfeeding and lactation. Therefore, it is recommended that marijuana use be discouraged.
Recommendations
The American College of Obstetricians and Gynecologists recommends that you use
- All women should be asked about their use and habits of alcohol, tobacco, and marijuana before and during pregnancy.
- Pregnant women who use marijuana should be counseled regarding potential health risks.
- Pregnant or considering becoming pregnant women should stop using marijuana.
- Women who are pregnant or planning to become pregnant should be advised not to use marijuana medicinally. There are better safety data for pregnant women.
- Insufficient data exists to assess the effects of marijuana on infants while they are breastfeeding and lactating.
Introduction
Marijuana, also known as cannabis sativa, is the most common illicit drug used during pregnancy. Self-reported marijuana use during pregnancy is between 2% and 5% according to most studies. However, it rises to 15-28% in urban women who are socioeconomically disadvantaged 1 2 3 4 5. Because some users might not seek prenatal care, higher rates of marijuana use can be found at the time of birth than at prenatal visits. Notably, between 3-40% of marijuana users continue using it during pregnancy. Many women believe that it is safe and more affordable than tobacco, 3-4 67. Recent research found that 18.1% of pregnant women who reported marijuana use over the past year met the criteria to be considered either dependent or abusive marijuana users. 8. An increasing number of states have legalized marijuana for recreational or medicinal purposes. This could lead to increased use by pregnant women.
Cannabinoids are responsible for the medicinal and psychoactive effects of marijuana. They are absorbed through the lungs when it is smoked, or the gastrointestinal tract when it is ingested. Tetrahydrocannabinol, also known as THC, is a small, highly lipophilic compound that quickly gets to the brain and fat. THC is metabolized by the liver and has a half-life that ranges from 20-36 hours for occasional users to 4-5 day for heavy users. It may take up to 30 days to get rid of all its contents. In animal models, THC crossed the placenta and produced plasma levels approximately 10% higher than maternal levels after acute exposure. Repetitive exposures resulted in significantly higher fetal concentrations. There are limited human data suggesting that THC may also be present in breast milk.
It is not possible to know the exact effects of marijuana use on pregnancy and the developing foetus. This is partly due to the fact that users often also use other drugs such as tobacco, alcohol or illicit drugs. Many of the same carcinogenic and respiratory disease-causing toxins found in marijuana smoke are also present in tobacco smoke. These toxins can be several times higher than those in tobacco smoke. Negative socioeconomic conditions such as poverty or malnutrition may also contribute to adverse outcomes that could be attributed to marijuana. One population-based study found that marijuana users who were pregnant were less likely than nonusers to be underweight, have lower education levels, and are more likely to take folic acid supplements. Another study showed that women who have been exposed to marijuana are more likely than nonusers to suffer from intimate partner violence. This is another risk factor for poor pregnancy outcomes. These confounders are often accounted for in studies evaluating marijuana use during pregnancy. Potential recall bias and reporting issues can affect studies of marijuana use during pregnancy. These studies often depend on self-reported behaviors, such as frequency, timing and amount. Other confounding factors may be caused by marijuana potency that has increased over time.
Marijuana use during pregnancy
Cannabinoids can be either plant-derived or endogenous and exert their central nervous system effects through the cannabinoid receptor. Animal models show that endocannabinoids play a key role in normal fetal brain growth, including neurotransmitter system and neuronal proliferation and differentiation. Human fetuses show a central nervous system cannabinoid type 1 at 14 weeks gestation. This receptor density increases with increasing gestational age and suggests a role of endocannabinoids 15 16.
Exogenous cannabinoid in utero exposure has been shown to disrupt normal brain function and development, according to laboratory animal studies. In utero cannabinoid exposure may cause impaired cognition or increased sensitivity to abuse drugs. Supraphysiologic fetal cannabisnoid exposure can increase brain susceptibility for the apoptotic effects ethanol 18. This raises concerns about poly-substance abuse. It also suggests that exogenous cannabinoids may negatively impact brain development. Research has shown that children who were exposed in utero to marijuana had lower scores in visual problem solving, visual motor coordination, and visual analysis tests than those who were not. Prenatal marijuana exposure is associated also with behavioral problems and decreased attention span, and can be used as a predictor for marijuana use at the age of 14 years. 23-24 25 Prenatal marijuana exposure has less impact on school performance. One longitudinal study showed no effect on cognition or school performance in children between 5-12 years of age. 26 27 Another longitudinal investigation of predominantly urban children with lower socioeconomic status found poorer spelling and reading scores, and lower teacher perceptions of school performance.
There is no evidence to suggest that marijuana causes anatomical defects in human structure 29 3031. One large study found that the adjusted odds ratio of marijuana users giving birth to babies with major congenital disabilities was not statistically significant. The study did not consider the timing of marijuana use during pregnancy 29. Later studies identified marijuana use in the month preceding or during the first three months after pregnancy. Nonusers were used as controls. The adjusted odds of 20 major anomalies were not significantly different between users and nonusers. The odds of having anencephaly in the offspring from users increased significantly to 2.5 (95% confidence interval [CI],1.3-4.9] 30). However, this analysis only considered marijuana use during the first month. This finding could be confounded by another observation: marijuana users are less likely than nonusers 2 to take supplemental folate.
The evidence currently available does not support a link between marijuana use during pregnancy and perinatal death. However, stillbirths may be slightly more common 31 32. A meta-analysis of 31 case-control and observational studies that compared neonatal outcomes for marijuana users and non-users looked at stillbirth and perinatal deaths as secondary outcomes. Comparatively to nonusers, marijuana users had similar rates of perinatal deaths (relative risk [RR], 1,09; 95%CI. 0.62-1.91), but higher stillbirth rates (1.74; 95%CI. 1.03-2.93). This latter finding should not be taken as a recommendation for smoking cessation. When adjusted estimates were combined, statistically significant associations between marijuana and adverse outcomes became statistically insignificant. A meta-analysis report that showed that THC was associated with stillbirths at or above 20 weeks gestation supports this interpretation. The effect of smoking 33 was somewhat confusing, however.
Numerous studies have evaluated the newborn birth weights as well as multiple biometric parameters following in utero cannabis exposure. Birth weight below 2,500g was the primary outcome. However, marijuana use was also considered to be a factor in birth outcomes. Women who used marijuana less frequently than once a week were not at higher risk (8.8% versus 6.7%;RR, 1.22; 95%CI, 0.91-1.644). Women who used marijuana regularly during pregnancy were more likely to give birth under 2,500g than women who did not use it weekly (11.2% versus 6.7%; 95%CI, 1.44-2.45). After adjusting for confounders such as tobacco users (21.2% versus 14.8%) and marijuana nonusers (20.2% versus 1.21; 95%CI, 1.00-1.45), a retrospective cohort study that was not part of the meta-analysis showed a slightly higher risk of birth weights below the 10th percentile in marijuana users. Numerous studies have shown that exposed offspring had shorter birth lengths, smaller head circumferences, and higher birth weights. These results were especially evident in women who used marijuana more frequently, especially during the first and second trimesters. These observations are not yet clinically relevant.
