一位懷孕6週的23歲女性來到門診進行產前照護。她展示了幾種非處方補充劑並問護理師：「每個人都告訴我葉酸現在非常關鍵，但我真的不知道為什麼，也不知道該吃多少。你能解釋一下嗎？」關於懷孕期間葉酸的補充，護理師應提供何項最準確的資訊？
A 23-year-old female at 6 weeks' gestation visits the clinic for prenatal care. She displays several over-the-counter supplements and asks the nurse, "Everyone tells me folic acid is crucial right now, but I don't really know why or how much to take. Can you explain it?" What is the most accurate information the nurse should provide regarding folic acid supplementation during pregnancy?
- A“You only need to take folic acid if your family has a history of Down syndrome, provided you eat plenty of green leafy vegetables.”「只有當您的家族有唐氏症病史，且您攝取大量綠色葉菜時，才需要補充葉酸。」
- B“Folic acid primarily prevents severe maternal anemia and should be taken at a dose of 4,000 mcg daily starting in the third trimester.”「葉酸主要用於預防嚴重的孕婦貧血，應從第三孕期開始，每日服用 4,000 mcg。」
- C“Folic acid significantly reduces morning sickness and should be taken along with high doses of Vitamin A to support fetal eye development.”「葉酸能顯著減輕晨吐，應與高劑量的維生素 A 一起服用，以支持胎兒的眼睛發育。」
- D“A daily intake of 400 mcg of folic acid is essential to prevent permanent neural tube defects, such as spina bifida, in your baby.”✓ 正解「每日攝取 400 mcg 的葉酸對於預防寶寶永久性神經管缺陷（如脊柱裂）至關重要。」
本題測驗產前營養學。葉酸（Folic acid / Vitamin B9）是所有懷孕及備孕期（Preconception）婦女最關鍵的單一維生素。它直接參與細胞的 DNA 合成。在受孕後的前 28 天（約第 4 週），胚胎的「神經管（Neural Tube）」會進行閉合。若此時母體極度缺乏葉酸，胎兒將發展出嚴重的神經管缺損（NTDs），如脊柱裂（Spina bifida，脊椎未能閉合）或無腦兒（Anencephaly，無大腦發展）。所有具備生育能力的婦女，公定建議劑量皆為每日攝取 400 mcg (微克) 或 0.4 毫克（選項D正確）。選項B錯誤，預防母體貧血的主要是鐵劑，且 4000 mcg (4 毫克) 僅針對生過神經管缺陷嬰兒的高危險特殊產婦。選項C錯誤且致命，高劑量維生素A（視黃醇衍生物如 B 酸）是一級致畸胎性物質（Teratogenic），會導致嚴重心血管與臉部畸形，孕期絕對禁忌高劑量。選項A錯誤，唐氏症是染色體異常而與葉酸無直接關聯，且無論飲食如何，保健食品額外補充是統一標準。
This question tests prenatal nutrition. Folic acid (Vitamin B9) is the single most critical vitamin for all pregnant women and women in the preconception period. It is directly involved in cellular DNA synthesis. During the first 28 days after conception (approximately the fourth week), the embryonic neural tube closes. If the maternal folate deficiency is severe at this time, the fetus may develop severe neural tube defects (NTDs), such as spina bifida (failure of spinal column closure) or anencephaly (lack of brain development). For all women of childbearing potential, the standard recommended dose is 400 mcg (micrograms), or 0.4 mg per day (option D is correct). Option B is incorrect; the primary prevention for maternal anemia is iron supplementation, and 4,000 mcg (4 mg) is reserved only for high-risk women who have previously had a child with a neural tube defect. Option C is incorrect and dangerous, because high-dose vitamin A (retinoid derivatives such as isotretinoin) is a first-class teratogen and causes severe cardiovascular and facial malformations; high doses are strictly contraindicated in pregnancy. Option A is incorrect, as Down syndrome is a chromosomal abnormality and is not directly related to folic acid, and regardless of diet, supplemental folic acid is a universal standard.
葉酸 400 mcg 預防神經管畸形的公版知識，是各國國民健康署/署立疾管局皆統一頒布的世界衛生組織常規。台美皆同。