How do pregnancy tests work? - Tien Nguyen

怀孕检测是如何运作的？- 提安·阮

翻译人员: Zhiting Chen 校对人员: Geoff Chen

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

最早的怀孕检测可以追溯到 公元前 1350 年的古埃及。

According to the Egyptians,

根据埃及的说法，

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

你只需要尿在小麦和大麦种子上， 然后等待。

If either sprouts, congratulations, you're pregnant!

如果其中任何一个发芽了， 恭喜，你怀孕了！

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

如果小麦发得快些，那就是女孩儿， 如果大麦发得快些，那就是男孩儿。

In 1963, a small study reproduced this test

在 1963 年，一个小研究 从新实践了这个实验

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

发现测孕的准确率高达 70% 。

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

尽管这个测试无法准确预知 孩子的性别。

Scientists hypothesized that the test worked

科学家们认为这个实验能够奏效

because pregnant women's urine contains more estrogen,

因为怀孕的女性尿液里 还有更高的雌性激素，

which can promote seed growth.

它能够使得种子更快发芽。

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

我们很容易觉得这个古老的方法 理所应当，

because modern pregnancy tests give highly accurate results within minutes.

因为现代怀孕测试能够在几分钟内 给出高准确度的结果。

So how do they work?

它是怎么运作的呢？

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

非处方的怀孕检测 都是设计为检测出一项指标：

a hormone called HCG.

一种叫 HCG 的荷尔蒙。

HCG is produced in the earliest stages of pregnancy

孕早期人体会产生 HCG

and starts a game of telephone

随后开始了电话游戏

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

告诉身体那个月 不要流出子宫内的薄膜。

As the pregnancy progresses,

怀孕的过程

HCG supports the formation of the placenta,

HCG 能够帮助形成胎盘，

which transfers nutrients from mother to fetus.

胎盘能够将母亲体内的 营养物质传送给胎儿。

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

怀孕测试开始 尿液覆盖露出来的试纸。

As the fluid travels up the absorbent fibers,

当尿液流到吸收剂纤维，

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

它将会跨越三个不同的区域， 每个区域都有很重要的任务。

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

当它到达反应区，

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

Y 字形状的蛋白质也就是抗体 会抓住任何识别到的 HCG。

Attached to these antibodies is a handy enzyme

贴在这些抗体上的 是一种容易取得的酶

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

这种酶能够激活染料分子， 这种染色分子在后面至关重要。

Then the urine picks up all the AB1 enzymes

然后尿液选择所有 AB1 酶

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

把它们带到测试区， 最终结果会出现在这里。

Secured to this zone are more Y-shaped antibodies

这个区域有更多的 Y 字抗体

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

在它的五个面都会黏住 HCG。

Scientists call this type of test a sandwich assay.

科学家们称这种测试为 三明治试验。

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

如果有 HCG，它会被夹在 AB1 酶和 AB2 酶之间，

and sticks to the test zone,

然后黏在测试区，

allowing the attached dye-activating enzyme to do its job

让附带着的染色激活酶发挥作用

and create a visible pattern.

创造一个可视的图案。

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

如果没有 HCG，尿液和酶 就这样流过去了。

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

最后，还有最后一站， 控制区。

As in any good experiment,

在每个成功地试验中，

this step confirms that the test is working properly.

这个步骤将会认定 前面的测试很好地完成了。

Whether the AB1 enzymes never saw HCG,

无论是 AB1 酶从未发现 HCG，

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

或者是在第一个反应区里 有太多的 AB1 酶了，

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

所有在反应区里带来的 AB1 酶 都应该在这里结束

and activate more dye.

刺激更多的染色反应。

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

因此，如果没有图案， 那就说明这个测试是失败的。

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

这些测试还是值得信赖的， 但也有可能失败。

For instance, false negatives can occur

比如说，错误的阴性反应可能会发生

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

如果 HCG 没有足够多以至能被检测出来。

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

移植后，HCG 水平每两到三天就会双倍增长，

so it may just be too early to tell.

所以也可能是过早了。

And beverages can dilute the urine sample,

同时，饮料也会冲淡尿液样本，

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

这就是为什么医生建议 早上一起床就做这个测试。

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

另一方面，错误的阳性反应也可能 来源于其它的 HCG，

like IVF injections, ectopic pregnancies,

像是试管受精针剂、怀孕异位，

or certain cancers such as uterine cancer or testicular cancer,

或是某种癌症像是子宫癌 或是睾丸癌，

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

这种情况下这些测试会显示 某位男士怀孕了。

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

女士们想要确认怀孕最好的方法 是去看医生。

The doctors are also looking for HCG,

医生也在寻找 HCG，

but with tests that are more sensitive and quantitative,

但是医生用的测试会更加敏锐和量化，

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

他们能够判定你血液中 HCG 的准确水平。

A few minutes can feel like forever

当你等待怀孕测试结果的时候

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

短短几分钟感觉像是永恒。

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

但在那短暂的时间里， 你见证了医学的力量。

That one little stick lets you ask a question,

那个小小的试纸 让你问一个问题，

perform a controlled experiment,

实行一个制式化的实验，

and then analyze the results to check your original hypothesis.

分析结果 测试你的假设。

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

最好的是，你永远不用等待下一个丰收。