Marijuana use during pregnancy is a growing concern, especially with increasing legalization. This article explores the current scientific understanding of the relationship between cannabis use and miscarriage risk.
Understanding Miscarriage
Miscarriage refers to the unexpected loss of a pregnancy before 20 weeks of gestation. Most miscarriages occur during the first trimester. Between 10% and 20% of all known pregnancies end in miscarriage. Various factors can contribute to miscarriage, including chromosomal abnormalities, responsible for about 50% of first-trimester losses. Other causes include hormonal imbalances, infections, uterine issues, and certain health conditions.
Cannabis Use and Miscarriage Risk
Research on the direct link between cannabis use and miscarriage risk has yielded varied results, making definitive conclusions challenging. Some studies suggest an increased risk, while others have not confirmed this.
The complexity of studying this association arises from several factors. Many studies rely on inaccurate self-reported cannabis use. Pregnant individuals may also use other substances, like tobacco, making it difficult to isolate the effects of cannabis alone, as tobacco smoking is a known miscarriage risk factor. Despite these complexities, some analyses have found an association between marijuana use and an increased chance of miscarriage or stillbirth, even when accounting for tobacco use. One study even suggested that male partners’ frequent cannabis use (one or more times per week) before conception could double the risk of miscarriage for their partners, particularly in early pregnancy.
How Cannabis Might Impact Pregnancy
The main psychoactive component of cannabis, delta-9-tetrahydrocannabinol (THC), readily crosses the placenta, potentially affecting fetal development. Cannabinoid receptors are present in reproductive tissues, the placenta, and the fetal brain, suggesting cannabis can directly influence these systems. THC and other cannabinoids might interfere with early embryonic development by disrupting crucial signaling pathways. For example, research on mice showed that THC can alter the balance of natural signaling molecules in the reproductive system, which are important for embryo development and implantation in the uterus. This interference could lead to abnormal embryonic development or issues with embryo transport to the uterus, potentially contributing to miscarriage or ectopic pregnancy.
In vitro studies indicate that THC can disrupt oocyte maturation and early embryonic development, leading to decreased maturation rates and increased cell death in blastocysts at higher concentrations. Cannabinoid exposure may also affect placental development and function, which are important for supporting the growing fetus. Compromised placental development has been linked to fetal growth restriction, and studies have identified changes in placental vasculature and function in cannabinoid-exposed pregnancies. The endocannabinoid system, which cannabis components interact with, plays an important role in early pregnancy, and its disturbance by cannabis use could impact overall pregnancy health.
Important Considerations for Pregnancy
Given the potential risks and current limitations in conclusive safety data, medical and public health organizations advise against cannabis use during pregnancy. The safest approach for those who are pregnant or planning to conceive is to avoid all forms of cannabis. This recommendation extends to both recreational and medical cannabis, as no amount has been proven safe for use during pregnancy.
It is important for individuals to discuss any substance use, including cannabis, with their healthcare provider. Healthcare professionals can offer personalized advice and support to help manage symptoms or conditions without resorting to substances that may pose risks to the pregnancy. Open communication with a doctor allows for safer alternatives and ensures the best possible health outcomes for both the pregnant individual and the developing baby.