Two Reasons Coffee is Terrible When Trying For a Baby

Coffee, caffeine, and fertility

If you're anything like 62% of women, coffee is a big part of your daily routine. One cup contains about 100mg of caffeine -- not a lot, but enough to get most people's engine running. Caffeine is probably the most-studied dietary factor in fertility research; a 1970s study first suggested high doses could hurt pregnancy rates in mice, and dozens of studies since have ranged from "caffeine is detrimental" to "caffeine doesn't matter at all." The proposed mechanism involves caffeine interfering with estrogen levels via phytoestrogen-like compounds in coffee. Let's separate the two very different questions: does it affect your odds of conceiving, and does it affect your odds of a healthy pregnancy once you do?

The case for coffee being fine

Many studies, large and small, have looked at whether caffeine lowers natural conception odds, and the evidence mostly says no. A large 2017 review spanning several decades and dozens of studies found no evidence caffeine intake affects the odds of becoming pregnant, and found caffeine consumers just as likely to conceive within 12 months as non-consumers -- though slightly less likely within a 6-month window specifically. In other words: it might take a bit longer, but you're not worse off overall.

Coffee and IVF

Several IVF studies asked the same question in a more controlled setting. Of five studies to date, one found lower estrogen levels linked to caffeine intake, but none found a link to eggs retrieved, embryo quality, implantation, or pregnancy rates. One early 2002 study did find a link between preconception caffeine and lower live birth rates specifically (not pregnancy rates) -- meaning women could still get pregnant, but had a slightly higher miscarriage chance. Taken together: low-to-moderate caffeine is very unlikely to hurt your odds of conceiving, but that one finding does point toward the more important question.

Does caffeine increase miscarriage risk?

Several studies find a dose-dependent link between caffeine and miscarriage, and this matters because many miscarriages happen very early, often before you'd even know. At 100mg of caffeine a day (about one 8oz cup), risk is roughly 10% higher than for non-consumers. Recent reviews pooling decades of high-quality studies found risk about 37% higher at 300mg, and more than double at 600mg. For context, an 8oz cup has about 100mg -- but a Starbucks Grande has around 330mg on its own. So limiting coffee to a maximum of about 2 cups a day, or switching to decaf, is a reasonable target -- and this matters for early pregnancy specifically, not just once you're confirmed pregnant.

Should I quit coffee when trying to conceive?

Several studies spanning 30 years find pre-pregnancy coffee intake linked to slightly higher miscarriage rates once pregnancy occurs. The largest, a 2018 Harvard study of over 11,000 women from the Nurses' Health Study, found a 20% higher miscarriage chance for women drinking 4+ servings a day before pregnancy, versus none. Interestingly, total caffeine (including tea and soda) was only weakly linked -- suggesting something more specific to coffee itself. But there's a real methodological wrinkle here: women who drink more coffee before pregnancy are much more likely to keep drinking it in the earliest weeks after conception too, often before they even know they're pregnant. So these studies may be partly capturing early-pregnancy caffeine exposure, not purely pre-conception exposure. Given that ambiguity, switching to decaf once you're actively trying is a low-cost way to sidestep the question entirely -- you likely won't notice much difference, and you remove the risk either way.

Say no to energy drinks

Energy drinks deserve a specific mention: they pack a lot of caffeine plus other stimulant ingredients. A can of Red Bull has about 80mg (similar to two cans of Coke), but a tiny bottle of 5-Hour Energy and similar products can exceed 200mg -- 5-Hour Energy itself warns against use during pregnancy or nursing.

The bottom line on coffee

Low-to-moderate caffeine intake is unlikely to hurt your chances of conceiving in the first place. But there are two real reasons coffee is worth limiting once you're actively trying: it may somewhat raise miscarriage risk in early pregnancy (and possibly just before), and it crosses the placenta once you are pregnant, reaching the fetus directly. If quitting cold turkey feels like too much, one cup a day is unlikely to move the needle much -- but switching to decaf is the safest option if you want to optimize as much as possible.

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