Matcha is generally considered fine in small amounts during pregnancy, but it needs watching. It is concentrated green tea, so its caffeine counts toward the daily limit that ACOG and the NHS advise (under 200mg). Most guidance points to roughly one cup a day, and to being mindful of a possible effect on folate absorption early on.
Matcha is green tea leaves ground into a fine powder that you whisk into water or milk. Because you drink the whole leaf rather than a steeped infusion, matcha is more concentrated than a regular cup of green tea. That means more caffeine and more of the plant compounds called catechins per serving. A typical cup of matcha has roughly 60 to 80mg of caffeine, though this varies by brand and how strongly it is made.
The main reason is caffeine. ACOG and the NHS advise keeping total caffeine under about 200mg a day in pregnancy, because higher intakes have been linked to lower birth weight and miscarriage. One matcha can use up a third to nearly half of that budget, and coffee, tea, cola and chocolate all add up too. Matcha's catechins (especially EGCG) may also slightly reduce how much folate your body absorbs, which matters most in the first trimester when folate protects against neural tube defects. The effect is small for people taking a prenatal vitamin, but it is why we lean cautious rather than giving a clear all-clear.
Track your total daily caffeine from all sources, not just matcha, and try to stay under 200mg. Keeping to about one cup a day fits most people within that limit. Take your prenatal or folic acid tablet at a different time from your matcha, ideally between meals, so the two do not compete. If you would rather avoid the caffeine entirely, decaffeinated green tea, rooibos, ginger or most fruit teas are caffeine-free options; the NHS notes that not all herbal teas are studied in pregnancy, so check individual ingredients.