Adding Marijuana to Tobacco During Pregnancy Did Not Worsen Birth Outcomes | Research

The takeaway

In a retrospective study of pregnant women who used tobacco, adding marijuana to tobacco use did not produce additional adverse birth outcomes beyond what tobacco alone caused, though both groups had high rates of adverse outcomes.

Obstetricians, neonatologists, and pregnant individuals who use both substances

No additional adverse birth outcomes from marijuana beyond tobacco effects

What the researchers found

There were no significant differences in any birth outcome (APGAR scores, respiratory distress, NICU admission, growth restriction, birth weight, length, head circumference, gestational age, hospital stay) between tobacco-only users (n=71) and tobacco-plus-marijuana users (n=127). However, rates of adverse outcomes were high in both groups compared to expected rates in unexposed pregnancies.

Why it matters

Many pregnant women who use tobacco also use marijuana. This study suggests that in the context of tobacco use, marijuana does not add measurable risk, implying that tobacco may be the primary driver of the adverse birth outcomes seen in polysubstance-using pregnancies.

The numbers in context

71 tobacco-only, 127 tobacco + marijuana. No significant differences in: APGAR scores, respiratory distress, NICU admission, growth restriction, birth weight, birth length, head circumference, gestational age, or hospital stay.

How the study worked

Retrospective chart review of pregnant women identified via self-report or biochemical testing who used tobacco alone (n=71) or tobacco and marijuana simultaneously (n=127) at any point during pregnancy. Outcomes compared using linear regression and odds ratio analysis.

What this study cannot tell us

Small sample sizes limit statistical power to detect small differences. Retrospective design with chart review. Self-report and biochemical testing may not capture all exposure. No unexposed comparison group. Cannot determine dose, frequency, or timing of either substance.

How to read the evidence

Retrospective chart review with small sample, no unexposed controls, and potential underreporting of substance use.

When this study was published

2024 study

The bigger picture

This finding is consistent with the earlier study (RTHC-05710) showing cannabis co-exposure did not worsen tobacco's cognitive effects on children. The pattern suggests tobacco's effects may dominate the prenatal harm picture when both are used.

Questions still open

Would marijuana use alone (without tobacco) show different birth outcomes? Is the null finding due to marijuana truly having no additional effect, or due to insufficient power? Would larger studies with biomarker-confirmed exposure change the conclusions?

Common questions

Does marijuana make tobacco's effects on pregnancy worse?

In this study, no. Pregnant women who used both tobacco and marijuana had similar birth outcomes to those who used tobacco alone. However, both groups had high rates of adverse outcomes compared to unexposed pregnancies.

Which is worse for pregnancy, tobacco or marijuana?

This study suggests tobacco may be the primary driver of adverse birth outcomes in women who use both. Tobacco-only and tobacco-plus-marijuana groups had similarly poor outcomes, with no additional risk from adding marijuana.

Read the original research

Birth outcomes following in utero co-exposure to tobacco and marijuana.

Birth defects research, 116(1), e2272

View on PubMed ↗Publisher’s paper ↗

Citation

Waddell, Madison L; Dickson, Samantha A; Dodge, Phoebe A; Kopkau, Haley E; Nadolski, Katherine N; Zablocki, Victoria; Forrestal, Kaya M; Bailey, Beth A. (2024). Birth outcomes following in utero co-exposure to tobacco and marijuana.. Birth defects research, 116(1), e2272. https://doi.org/10.1002/bdr2.2272