最近這兩週每次去藥局買快孕隆黃體凝膠時，藥劑師都會一付很慎重其事地跟我警告"不可以服用孕婦維他命"！我一直覺得很奇怪，孕婦維他命不是特應該在懷孕初期補充嗎? 其中所含的葉酸正是幫助寶寶初期神經系統發育健全的重要元素。我實在無法裡解為何藥劑師叫我不要吃。這次忍不住就問了她為何吃孕婦維他命不好呢? 她回答說: 因為懷孕期間攝取過多維他命A會導致胎兒畸形。之前有人因為吃孕婦維他命，結果胎兒有水腦。她指了指旁邊的新寶納多，要我看它的維他命A成分。(Vitamin A (as Acetate)...1500 l.u. B-Carotene....1500 l.u.)   蝦咪??? 孕婦維他命我已經吃了好幾年了耶??? 只不過是吃不同牌子的~ (美國醫生也都建議計畫懷孕前三個月就要開始吃呀...這到底是怎麼回事?)
回家後立刻上網搜尋關於孕期補充維他命A的資料，多數中文資料也都是顯示懷孕期間要避免攝入過多的維他命A，否則會導致胎兒畸型比例提高。一般建議日攝取量在2500IU左右。
我趕緊拿起老公從美國買給我的孕婦維他命來看，驚訝的發現其中所含的維他命A高達5000IU。已經吃了好多年的我，心中超恐懼的。怎麼回事? 這瓶Rainbow Light是美國排名第一的孕婦維他命，怎麼會含有這麼高的維他命A呢? 趕緊開始查尋國外的資料。結果發現原來維他命A有兩種形式，一種是純天然的BETA胡蘿蔔素(較優的維他命A來源)，另一種是(retinoids or preformed vitamin A)天然合成的維他命A及其衍生物(例如A醇、A醛、A酯(維他命A丙酸酯、棕櫚酸維他命A、A酸等)。所有的retinoids經吸收後進入細胞，最終都會藉由化學反應變成A酸(retinoic acid)。目前的研究顯示這種天然合成的維他命A及其衍生物與胎兒畸形有正向關聯，而BETA胡蘿蔔素則沒有。
這瓶Rainbow Light上面有註明5000IU的Vitamin A 一半來自於BETA胡蘿蔔素，另一半來自於Paimitate)！天呀！這瓶粉貴且號稱第一的孕婦維他命竟然含有這麼高的合成為他命A? 還好到目前為止我吃的都是我之前回台自己帶回來的Nature Made牌！Nature Made這瓶還比較便宜說~ 裡面標示其維他命A 100%來自於BETA胡蘿蔔素！
原本著急萬分的我，這下子總算比較安心了~

所以結論是，選購孕婦維他命時，一定要看清楚其中的維他命A來源。千萬要買來自於BETA胡蘿蔔素的那種~ (還有，貴的牌子不一定比較好。Rainbow Light 是我老公在粉貴的有機超市WHOLEFOODS買的，一個月份60多元美金，結果成分還不如我在COSTCO 買的NATURE MADE 好，三個月份才20多元美金~~~ 不過我其實只比較了維他命A的部分，也許其他成分Rainbow light 比較好也不一定。) 還有，找到成分OK的孕婦維他命後，可以在記劃懷孕前三個月開始吃。根據美國醫生的說法是，這樣可以幫助將體內的環境先調整好，迎接寶寶到來。其中的葉酸對於寶寶初期前六週的神經系統發育相當重要。我也曾看到外國文獻說服用葉酸(孕婦維他命)可以增加受孕著床的機率。不知道可不可信就是啦~

 (一篇發表於新英格蘭醫學期刊的研究指出，婦女在準備懷孕或是懷孕初期，若能每天服用400～800微克的葉酸，則可有效的防止胎兒神經管缺陷的發生。)
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以下是我查到的英文資料: 解釋這兩種不同形式的維他命A對胎兒的影響，供大家參考~
Increasing your vitamin intake during pregnancy is a great idea; however, too much vitamin A has been linked to increased chances of birth defects. Be sure you're not getting too much!

Vitamin A Concerns During Pregnancy

Most Americans get an ample supply of vitamin A from their diet. Vitamin A is formed in our bodies from two types of compounds: retinoids (or preformed vitamin A) found in fortified cereals, fish, eggs, and meat, or carotenoids (such as beta-carotene) found in fruits and vegetables.

While you are pregnant, it is important to note how much vitamin A you get from which source. An excess of preformed vitamin A has been shown to cause birth defects. Birth defects have not been associated with excessive does of beta-carotene or other carotenoids.

 

Supplement Recommendations

Your prenatal vitamin probably contains some vitamin A, and that's good considering your increased need for vitamin A during pregnancy. Vitamin A helps with infection resistance and is important for the development of everything from your baby's eyes and heart to it's skin. For more information, see The Importance of Vitamin A and Vitamin D during Pregnancy.

Check the supplement facts label on your prenatal vitamin to determine the amount of vitamin A it contains. The label should state how much vitamin A comes from retinoid sources (such as retinyl palmitate) and carotenoid sources (such as beta-carotene). According to the Linus Pauling Institute at Oregon State University, which conducts micronutrient research, "no increase in the risk of vitamin A-associated birth defects has been observed at doses of preformed vitamin A from supplements below 3,000 mcg/day (10,000 IU/day). Since a number of foods in the U.S. are fortified with preformed vitamin A, pregnant women should avoid multivitamin or prenatal supplements that contain more than 1,500 mcg (5,000 IU) of vitamin A."

That said, your prenatal vitamin does not need to contain 100% of your daily requirement for vitamin A. In fact, it shouldn't. Since commonly eaten foods contain vitamin A, you will easily meet the remaining requirement from your diet. If your prenatal vitamin does contain 100% of your daily need for vitamin A determine that most of the vitamin A comes from beta-carotene, not a retinoid source.


Source: http://www.brighthub.com/health/diet-nutrition/articles/52467.aspx

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