Alcohol, Caffeine, Cannabis, and Vaping: What They Do to Fertility
How alcohol, caffeine, cannabis, and vaping affect fertility and conception. Evidence-based guidance for anyone with TTC substance questions.
The "can I still have one glass?" questions get asked constantly on TTC forums — and they deserve a straight answer. Here's what the evidence says on the four most commonly asked-about substances: alcohol, caffeine, cannabis, and vaping. No moralizing, just the clinical picture.
How does alcohol affect fertility when trying to conceive?
Heavy alcohol use — roughly 8 or more drinks per week — is associated with lower fecundability and altered cycle patterns. The picture for light drinking is less clear. Most reproductive endocrinologists recommend minimizing or stopping alcohol during active TTC, particularly in the luteal phase, when early pregnancy may already be present before a positive test.
Is it safe to drink alcohol while trying to get pregnant?
Once pregnancy is confirmed, the answer shifts: no safe threshold has been established. ACOG and the CDC both recommend zero alcohol during pregnancy. Fetal alcohol spectrum disorders have no established minimum dose. If you had a drink before you knew you were pregnant, that is common and rarely causes harm — the practical guidance is simply to stop now.
How much caffeine is considered safe when trying to conceive?
During pregnancy, keeping caffeine under 200 mg per day is the standard guidance — amounts above that are associated with miscarriage and low birth weight. In the TTC phase, the evidence is less clear; most clinicians consider 200 to 300 mg per day likely fine. Amounts above 500 mg per day have been associated with lower fecundability. Caffeine adds up across sources: coffee, tea, energy drinks, dark chocolate, pre-workout, and some medications all count.
Does smoking affect fertility?
Cigarettes, cigars, and hookah are unambiguous — stop. Smoking lowers AMH, brings menopause forward by an average of 1 to 4 years, reduces sperm quality, and doubles miscarriage risk. Quitting before trying to conceive has measurable fertility benefit, and that benefit shows up in markers within 2 to 3 months.
How does cannabis use affect fertility and conception?
Cannabis (THC) should be avoided during TTC and pregnancy. It impacts ovulation in people with ovaries and lowers sperm count and motility in sperm-contributing partners. THC crosses the placenta and is linked to neurodevelopmental effects. Being legal where you live is not the same as being safe in pregnancy. For CBD specifically, current guidance is to treat it the same as THC — it is unregulated and the fertility evidence is thin.
What does vaping do to fertility?
Nicotine vaping is as damaging to fertility as cigarettes — it reduces egg quality, lowers sperm parameters, and raises miscarriage risk. Nicotine-free vapes are unregulated and the flavoring chemicals are not well-studied. Stop vaping during TTC; resources exist to help with cessation.
How long before trying to conceive should you stop using alcohol or cannabis?
Two to three months is the meaningful window. Sperm regenerates on a roughly 74-day cycle, so behavior changes in a sperm-contributing partner show up in semen analysis results within that timeframe. The same general timeline applies to cycle patterns and other markers that respond to lifestyle changes. If TTC is serious, cutting back matters on both sides of the equation.