How do pregnancy tests work? - Tien Nguyen

譯者: Sherl H 審譯者: Harry Chen

The earliest known pregnancy test dates back to 1350 BC in Ancient Egypt.

最早的懷孕檢測可追溯回 西元前 1350 年的古埃及

According to the Egyptians,

根據古埃及人的做法

all you have to do is urinate on wheat and barley seeds, and wait.

你只要在小麥和大麥的 榖粒上小便以及等待就好

If either sprouts, congratulations, you're pregnant!

如果兩者發芽了－恭喜你懷孕了唷！

And if wheat sprouts faster, it's a girl, but if barley, it's a boy.

小麥比較早發芽的話這是個女孩 要是大麥先發芽就是個男孩

In 1963, a small study reproduced this test

在 1963 年時有個小研究 重啟了這項試驗

and found that it predicted pregnancy with a respectable 70% accuracy,

並且發現它預測懷孕有著 約 70% 的準確率

though it couldn't reliably tell the sex of the baby.

即便它無法可靠地辨別胎兒的性別

Scientists hypothesized that the test worked

科學家推測這個測驗之所以有用

because pregnant women's urine contains more estrogen,

是因為孕婦的尿液中含有較多的雌激素

which can promote seed growth.

能夠促進種子的生長

Now it's easy to take this ancient method for granted

現今很容易不把這古法當一回事

because modern pregnancy tests give highly accurate results within minutes.

因為現代的懷孕檢測在幾分鐘之內 就會給出非常準確的結果

So how do they work?

它們的原理究竟是什麼呢？

Over-the-counter pregnancy tests are all designed to detect one thing:

臨櫃販售的驗孕棒全都是 被設計來偵測一項東西：

a hormone called HCG.

稱為「HCG」的荷爾蒙

HCG is produced in the earliest stages of pregnancy

HCG 在懷孕最早的階段 就被製造出來了

and starts a game of telephone

並且展開了傳聲筒遊戲

that tells the body not to shed the inner lining of the uterus that month.

告訴身體當月不要讓子宮內膜剝落

As the pregnancy progresses,

在懷孕有所進展時

HCG supports the formation of the placenta,

HCG 有助於胎盤的形成

which transfers nutrients from mother to fetus.

胎盤將養分從母體輸往胎兒

The test starts when urine is applied to the exposed end of the strip.

驗孕在尿液接觸到 試紙露出來的尾端時就開始了

As the fluid travels up the absorbent fibers,

當尿液在會吸水的纖維往上遠行

it will cross three separate zones, each with an important task.

它會穿越三個不同的區域 各區域都有一個重要的任務

When the wave hits the first zone, the reaction zone,

當尿液到達第一個區域 － 反應區

Y-shaped proteins called antibodies will grab onto any HCG.

稱作抗體的 Y 型蛋白質 會抓住任何 HCG

Attached to these antibodies is a handy enzyme

依附在這些抗體上的是一種有用的酵素

with the ability to turn on dye molecules, which will be crucial later down the road.

帶有顯現出染色分子的能力 那在後面的旅程中是很關鍵的

Then the urine picks up all the AB1 enzymes

接著尿液帶走所有的酵素 AB1

and carries them to the test zone, which is where the results show up.

將它們運到測試區 那就是結果顯現的地方

Secured to this zone are more Y-shaped antibodies

把守這一區的是更多的 Y 型抗體

that will also stick to HCG on one of its five binding sites.

它們也會緊黏著 HCG 五個鏈結處的其中一個

Scientists call this type of test a sandwich assay.

科學家把這種測試叫作「三明治檢測法」

If HCG is present, it gets sandwiched between the AB1 enzyme and AB2,

如果 HCG 出現了 就會被酵素 AB1 和 AB2 包夾住

and sticks to the test zone,

並且固定住在測試區裡

allowing the attached dye-activating enzyme to do its job

依附其上的染色活化酵素 得以做好份內工作

and create a visible pattern.

產生可見的圖樣

If there's no HCG, the wave of urine and enzymes just passes on by.

如果沒有 HCG 的話 尿液和酵素只會嘯湧而過

Finally, there's one last stop to make, the control zone.

最後還有個終點要停留 － 控制區

As in any good experiment,

如同任何一個良好的實驗

this step confirms that the test is working properly.

這一步驟確認本測試正妥當地在運作

Whether the AB1 enzymes never saw HCG,

不論是酵素 AB1 不曾發現 HCG

or they're extras because Zone 1 is overstocked with them,

或是因為酵素 AB1 已經 塞滿第一區而逸出

all the unbound AB1 enzymes picked up in Zone 1 should end up here

所有從第一區帶來的未結合 酵素 AB1最後應該出現在這裡

and activate more dye.

而且活化更多染色因子

So if no pattern appears, that indicates that the test was faulty.

所以如果沒有圖樣浮現 表示測試出了差錯

These tests are pretty reliable, but they're not failproof.

這些測試相當可靠 但並非完全不會出錯

For instance, false negatives can occur

比方說如果 HCG 濃度 還不足以被檢測出來

if concentrations of HCG aren't high enough for detection.

就可能發生錯誤的陰性反應

After implantation, HCG levels double every two to three days,

受孕後 HCG 的濃度 每 2 到 3 天就會倍增

so it may just be too early to tell.

所以可能是太早了而檢測不到

And beverages can dilute the urine sample,

而且喝飲料會稀釋尿液樣本

which is why doctors recommend taking the test first thing in the morning.

這就是為什麼醫生會建議 早上起床第一要務就是做測試

On the other hand, false positives can come from other sources of HCG,

另一方面來講錯誤的陽性反應 可能是出自 HCG 的其他來源

like IVF injections, ectopic pregnancies,

像是排卵針注射、子宮外孕

or certain cancers such as uterine cancer or testicular cancer,

或者諸如子宮癌或睪丸癌等特定癌症

making it possible for one of these tests to tell a man he's pregnant.

使得這些測試有可能 告知一個男人說他懷孕了

The best way for a woman to find out for sure is at the doctor's office.

對一個要確保結果正確的婦女來說 最好的方法是在醫師的診間

The doctors are also looking for HCG,

醫師也是打算要找出 HCG

but with tests that are more sensitive and quantitative,

但會用更敏銳、更量化的測試

which means they can determine the exact level of HCG in your blood.

這表示他們能夠測出 你血液中 HCG 確切的含量

A few minutes can feel like forever

當你正在等待驗孕結果的時候

when you're waiting on the results of a pregnancy test.

短短幾分鐘能夠感覺就像永遠

But in that brief time, you're witnessing the power of the scientific method.

但在那短短的時間內 你正見證著科學方法的能耐

That one little stick lets you ask a question,

那根小小的棒子讓你有所求問

perform a controlled experiment,

執行制式的實驗

and then analyze the results to check your original hypothesis.

接著分析結果來確認你原先的假設

And the best part is you won't even have to wait until the next harvest.

最棒的是你根本不必等到下一次收割