Posted on June 22nd, 2026.

Published by Comprehensive Pediatrics and Internal Medicine, LLC | Hoover, AL

Pregnancy is a time when every decision matters — not just for you, but for the growing life you are nurturing. As marijuana use becomes more widespread and legalization continues to expand across the United States, more expectant parents are asking whether cannabis or THC is safe to use during pregnancy. The honest answer, based on current research and the guidance of major medical organizations, is clear: THC use during pregnancy carries real risks, and no safe level of use has been established.

At Comprehensive Pediatrics and Internal Medicine, we believe that informed parents make the best decisions for their families. Here is what the science currently tells us.

What Is THC?

THC (tetrahydrocannabinol) is the primary psychoactive compound in cannabis — the ingredient responsible for the "high" associated with marijuana use. When a pregnant woman uses cannabis in any form — whether by smoking, vaping, eating edibles, or using concentrates — THC can cross the placenta and reach the developing fetus.

This is not a theoretical risk. It is a documented biological reality, and it is the foundation for all of the concerns outlined below.

How Does THC Affect the Developing Baby?

The fetal brain develops rapidly throughout all three trimesters of pregnancy. The body's natural endocannabinoid system plays a critical role in guiding that development — and THC, because it mimics and disrupts the endocannabinoid system, can interfere with this process.

According to the National Academies of Sciences, Engineering, and Medicine, there is substantial evidence that maternal cannabis smoking is associated with lower birth weight in newborns. Babies exposed to cannabis during pregnancy are more likely to weigh less at birth than unexposed babies, and lower birth weight is associated with a higher risk of health complications during infancy and beyond.

Emerging Research: THC and Fetal Heart Development

One of the most concerning areas of emerging research involves the effects of prenatal THC exposure on the developing heart. Epidemiological and experimental evidence increasingly suggests that THC exposure during pregnancy may raise the risk of congenital heart defects, including:

• Atrial Septal Defect (ASD) — commonly known as a "hole in the heart," this is an opening in the wall separating the two upper chambers of the heart
• Ventricular Septal Defect (VSD) — an opening in the wall separating the two lower chambers

Interference With Heart Formation

THC and other cannabinoids cross the placental barrier during critical windows of fetal heart development (cardiogenesis). Animal studies have shown that THC exposure can disrupt normal heart formation by causing abnormal thickening of heart tissue and reducing the activity of genes and transcription factors essential for healthy cardiac development.

What Population Studies Show

Large population studies and geospatial analyses conducted across the United States and Europe have found statistical associations between increased prenatal cannabis exposure and higher rates of congenital heart defects. Recent systematic reviews and meta-analyses suggest that babies exposed to cannabis during pregnancy may face a significantly elevated risk of cardiovascular malformations — some studies report the risk may be more than twice as high compared to unexposed pregnancies.

What Is an Atrial Septal Defect?

An ASD is a hole in the wall between the two upper chambers of the heart. Some small defects close on their own during early childhood, but larger defects may require ongoing monitoring, medical management, or surgical repair. While more research is needed to fully understand the connection between THC exposure and congenital heart defects, the findings to date are serious enough that they deserve the attention of every expectant parent and healthcare provider.

Effects on Newborns

Beyond birth weight and heart development, research has identified additional concerns for newborns exposed to cannabis before birth. Babies born to mothers who used cannabis during pregnancy may be more likely to require admission to a Neonatal Intensive Care Unit (NICU) following delivery.

A NICU admission does not necessarily indicate permanent health problems, but it does mean the baby requires additional monitoring and specialized care during a critical period — a stressful and often difficult experience for the entire family.

Pregnancy Complications for the Mother

Research has also explored possible links between cannabis use during pregnancy and adverse outcomes for the mother herself. While evidence in this area is still developing and complicated by factors such as tobacco use, alcohol use, and socioeconomic influences, the findings raise enough concern that cessation is recommended as the safest course of action.

Long-Term Effects: What We Know and What We Don't

Many parents wonder about the longer-term effects of prenatal THC exposure on a child's development, learning, and behavior. The honest answer is that the research is still catching up.

The National Academies concluded there is currently insufficient evidence to definitively determine whether maternal cannabis use causes outcomes such as:

• Sudden Infant Death Syndrome (SIDS)
• Difficulties with cognition or academic achievement
• Future substance use disorders in the child

It is important to understand that "insufficient evidence" does not mean THC is safe. It means that high-quality, long-term research has not yet been completed — and that the absence of proof is not proof of absence. Given that the fetal brain is developing rapidly and that THC crosses the placenta, waiting for certainty before acting is not a risk worth taking.

What the Major Medical Organizations Recommend

Because THC may affect fetal growth, brain development, and heart formation, the leading health organizations in the United States are unequivocal in their guidance:

• Centers for Disease Control and Prevention (CDC)
• American College of Obstetricians and Gynecologists (ACOG)
• March of Dimes

All of these organizations recommend complete cessation of cannabis and THC use during pregnancy and while breastfeeding. There is no known safe amount.

Using Cannabis for Nausea, Anxiety, or Sleep?

Some pregnant women turn to cannabis to manage symptoms like nausea, anxiety, pain, or difficulty sleeping. These are real challenges that deserve real solutions. If you are using cannabis for any of these reasons during pregnancy — or are considering it — please speak with your healthcare provider. Safer, evidence-based treatment options exist for all of these conditions, and your provider can help you find an approach that protects both you and your baby.

Never stop a prescribed medication without first consulting your healthcare provider.

The Bottom Line

Current evidence shows that THC exposure during pregnancy is associated with:

• Increased risk of lower birth weight
• Possible increased risk of pregnancy complications for the mother
• Greater likelihood of NICU admission for the newborn
• Potential disruption of fetal brain development
• Emerging evidence of an elevated risk of congenital heart defects, including atrial septal defects (ASD)

Because THC crosses the placenta and no safe level of use has been established, avoiding cannabis in all forms throughout pregnancy — and during breastfeeding — is the safest choice you can make for your baby's health and future.

If you have questions about cannabis use, pregnancy safety, or your child's health, our team at Comprehensive Pediatrics and Internal Medicine is here to help. We provide compassionate, evidence-based care for every stage of your family's life.

Request an Appointment: cpimalabama.com/contact-us Call Us: (205) 855-0357 Location: 430 Emery Drive, Suite 200, Hoover, AL 35244

References

• National Academies of Sciences, Engineering, and Medicine. The Health Effects of Cannabis and Cannabinoids: The Current State of Evidence and Recommendations for Research. Chapter 10: Prenatal, Perinatal, and Neonatal Exposure to Cannabis. Washington, DC: National Academies Press, 2017.
• American College of Obstetricians and Gynecologists (ACOG). Committee Opinion No. 722: Marijuana Use During Pregnancy and Lactation.
• Centers for Disease Control and Prevention (CDC). Cannabis and Pregnancy.
• March of Dimes. Marijuana Use During Pregnancy.
• PubMed. Studies on Prenatal THC Exposure and Fetal Heart Development.
• MDPI. Cannabis Exposure and Atrial Septal Defect Research.
• PubMed. Systematic Reviews and Meta-Analyses of Prenatal Cannabis Exposure and Congenital Heart Defects.