And if that's not bizarre enough for you at face value, the way it all shakes out will be.

如果從表面上看這還不夠離奇，那麼這一切的結局會讓你覺得離奇。

See, cancer risk can go one of two ways.

癌症風險有兩種可能。

You can become more likely to develop cancer, or less likely.

你可能更容易患上癌症，也可能更不容易患上癌症。

But in this case, it's both.

但在這種情況下，兩者兼而有之。

The same person can have an increased and decreased risk of developing breast cancer after childbirth.

同一個人在分娩後患乳腺癌的風險可能增加，也可能減少。

Confused?

困惑？

I'll explain.

我來解釋一下。

Hopefully by the end, the baby will be the only thing keeping you up at night.

希望到最後，只有孩子會讓你徹夜難眠。

INTRO

導言

A lot of things are in flux during pregnancy.

懷孕期間，很多事情都在變化。

Hormones are changing your body, from your joints to your blood flow.

荷爾蒙正在改變你的身體，從關節到血液流動。

And it turns out that those changes are related to a new risk of developing breast cancer later in life.

而事實證明，這些變化與日後罹患乳腺癌的新風險有關。

Great.

好極了

Now, some of the trends researchers have observed in the relationship between childbirth and breast cancer risk are also true for ovarian and endometrial cancers.

現在，研究人員在分娩與乳腺癌風險之間的關係中觀察到的一些趨勢也適用於卵巢癌和子宮內膜癌。

But most of the research is focused on breast cancer as one of the most common cancers in women.

但大部分研究都集中在乳腺癌上，因為乳腺癌是女性最常見的癌症之一。

So this video is about your risk of developing breast cancer, but know that what I'm saying may also be relevant for other cancers.

這段部影片是關於您罹患乳腺癌的風險，但要知道，我所說的內容也可能與其他癌症有關。

Also, you don't have to be a woman to get pregnant or have breast cancer, but the research says women, so we're going to say women.

另外，懷孕或罹患乳腺癌並不一定非得是女性，但研究表明是女性，所以我們就說是女性。

You get it.

你懂的。

And since we're talking about breast cancer, let's just start by addressing the melons in the room.

既然說到了乳腺癌，那就先說說這個房間裡的 "瓜 "吧。

In pregnancy, your breasts may get bigger as early as the first trimester to get ready to feed your baby.

早在懷孕前三個月，您的乳房就可能會變大，為哺育寶寶做好準備。

Throughout pregnancy, you ramp up development of small, branching ducts that will eventually produce milk.

在整個孕期，您的乳腺小導管都在加速發育，這些小導管最終會分泌乳汁。

And for that to happen, a lot of cells need to change and move around.

而要做到這一點，很多細胞都需要發生變化和移動。

Some cells specialize to make and secrete the milk, some make up the lining of the newly formed ducts, and others form new capillaries that feed the fresh tissue with blood.

一些細胞專門製造和分泌乳汁，一些細胞構成新形成的導管內壁，還有一些細胞形成新的毛細血管，為新鮮組織供血。

And that's probably all happening thanks to the hormones that you might have noticed when you accidentally came home from the market with almond milk instead of oat milk and burst into tears.

而這一切可能都要歸功於荷爾蒙的作用，當你不小心從市場買了杏仁牛奶而不是燕麥牛奶回家時，你可能就已經注意到了，並且淚流滿面。

A peer-reviewed publication from 2019 found that the relationship between pregnancy and some of the changes in breast cancer risk mainly comes from a specific type of breast cancer, which also happens to be the most common type, called estrogen receptor-positive breast cancer.

2019 年的一份經同行評審的出版品發現，懷孕與乳腺癌風險的一些變化之間的關係主要來自於一種特定類型的乳腺癌，這種類型的乳腺癌也恰好是最常見的類型，叫做雌激素受體陽性乳腺癌。

So that's one reason researchers think hormones like estrogen are to blame.

研究人員認為雌激素等荷爾蒙是罪魁禍首的原因之一。

It's also because of just how intertwined they are with the processes that could promote tumor growth.

這也是因為它們與可能促進腫瘤生長的過程交織在一起。

See, your pregnant body makes more hormones like prolactin that encourage your epithelial cells to build out your ducts.

懷孕的身體會分泌更多的催乳素等激素，這些激素會促進上皮細胞形成導管。

Estrogen and progesterone also trigger those breast cells to multiply.

雌激素和孕激素也會促使這些乳腺細胞增殖。

Which is a good thing, because you need to feed your baby!

這是好事，因為你需要餵養寶寶！

But some scientists think that this increase in reproductive hormones also increases your risk of cancer, because they stimulate the growth of cells that were already poised to head down a cancerous path.

但一些科學家認為，生殖激素的增加也會增加患癌症的風險，因為它們會刺激已經準備好走向癌症道路的細胞生長。

With so many growing, moving, and replicating cells, any DNA that was damaged before or during that process can duplicate and spread with every cell division.

在如此多的細胞生長、移動和複製過程中，任何在此之前或過程中受損的 DNA 都會隨著每次細胞分裂而複製和擴散。

So it might have been a small problem that never turns into anything, starts showing up all over the place, and becomes a big red flag.

這可能是一個小問題，但從來沒有變成任何東西，開始出現在所有地方，成為一個大紅旗。

At the end of the day, lots of genetic damage can lead to tumors.

歸根結底，大量的基因損傷會導致腫瘤。

And that doesn't just come from pregnancy, but also extends to your postpartum body.

這不僅來自於懷孕，還包括產後的身體。

Even when lactation ends, the remodeling that takes place in breast tissue to stop making breast milk could likewise create just the right environment to grow tumors.

即使哺乳期結束，乳腺組織也會因停止分泌乳汁而發生重塑，這同樣會為腫瘤的生長創造適宜的環境。

Researchers say your cancer risk reaches a high point relatively soon after pregnancy.

研究人員說，懷孕後不久，患癌症的風險就會達到一個高點。

They call it a short-term risk, but when they say short-term, they're talking about a peak risk around four or five years after childbirth.

他們稱之為短期風險，但他們說的短期風險是指分娩後四五年左右的高峰風險。

If you've raised a kid, maybe you feel like you've blinked and all of a sudden your infant is a full-fledged kindergartner.

如果你已經養育了一個孩子，也許你會覺得一眨眼的功夫，你的嬰兒就變成了一個成熟的幼兒園小朋友。

But an increased risk of developing breast cancer for multiple years isn't usually what I think of as a short-term health situation.

但是，多年來罹患乳腺癌的風險增加通常並不是我認為的短期健康狀況。

Especially when you find out that it may be a peak risk at five years, but your risk is still high and maybe slowly returning to baseline over a period of more than 20.

尤其是當你發現五年後風險可能達到峰值，但你的風險仍然很高，而且可能在 20 多年的時間裡慢慢恢復到基線。

You don't even have a kid at home anymore, and they're still calling it a short-term effect of childbirth.

你家裡都沒有孩子了，他們還說這是分娩的短期影響。

In any case, after pregnancy, your chances of getting cancer go up.

無論如何，懷孕後患癌症的機率都會增加。

But then they drop, and after a while, they end up lower than someone your age who has never given birth.

但隨後就會下降，過一段時間後，就會比你這個年齡段從未生育過的人還要低。

This SciShow video is supported by Brilliant, the online learning platform with thousands of lessons in computer science, math, and science.

本 SciShow 影片由 Brilliant 在線學習平臺提供支持，該平臺提供數千節計算機科學、數學和科學課程。

Brilliant is here for learners of every level.

這裡的輝煌適合各種水準的學習者。

Whether you want to dip a toe into math to learn some visual problem-solving techniques, or build on your solid foundation in computer programming to build a bot that filters your matches on dating apps.

無論你是想涉足數學，學習一些可視化的解題技巧，還是想在紮實的計算機編程基礎上構建一個機器人，在約會應用程序上篩選你的匹配對象。

You can do anything with knowledge on your side, and Brilliant helps you gain a little knowledge every day in just a few minutes.

有了知識，你可以做任何事情，而 Brilliant 可以幫助你每天在短短几分鐘內獲得一點知識。

For interactive learners who want to gain knowledge you can use in your daily life,

適合希望獲得日常生活知識的互動學習者、

Brilliant is the full package.

輝煌是全套的。

And to get started, head over to Brilliant.org slash SciShow, or the link in the description.

要開始學習，請訪問 Brilliant.org slash SciShow 或描述中的鏈接。

That link will also give you 20% off an annual Premium Brilliant subscription, and you'll get your first 30 days free.

通過該鏈接，您還可以以 20% 的折扣訂購年度 Premium Brilliant，而且前 30 天免費。

In pregnancy, you have a lot of cells growing and changing, which contributes to your unstable, cancer-prone situation.

在懷孕期間，有大量細胞在生長和變化，這就造成了不穩定、易患癌症的狀況。

But it's also making things way more stable in the long run by increasing the number of new, healthy breast cells.

但從長遠來看，它還能增加新的、健康的乳腺細胞的數量，從而使情況更加穩定。

These new cells used to be stem cells, and stem cells are more easily swayed to become other kinds of cells.

這些新細胞曾經是幹細胞，而幹細胞更容易被改造成其他類型的細胞。

So while they're very handy when tissues need to grow and differentiate, they're more vulnerable to the kinds of damage that breed cancer.

雖然它們在組織需要生長和分化時非常方便，但它們更容易受到滋生癌症的各種損害。

Cells in a stable, differentiated form are less susceptible to cancer, hence the lower risk well after a full-term pregnancy.

處於穩定分化狀態的細胞不易發生癌變，所以在足月妊娠後發生癌變的風險較低。

So there are scientific explanations for why your risk of developing cancer changes after childbirth, but it's not just based on hormone and cell studies.

產後罹患癌症的風險發生變化是有科學依據的，但並不只是基於激素和細胞研究。

There's a real link between childbirth and cancer that comes from massive longitudinal studies where researchers document the outcomes of tens of thousands of people for decades.

研究人員通過大規模的縱向研究，記錄了數以萬計的人數十年來的結果，從而得出分娩與癌症之間確實存在聯繫。

And they factor in things like family history to control for a generally elevated breast cancer risk.

他們還將家族史等因素考慮在內，以控制乳腺癌風險的普遍升高。

A collaboration of researchers in Sweden, the US, and Italy combed through the cancer registry and fertility registry in Sweden, looking at more than 12,000 cancer patients and more than 62,000 people of the same age who had not been diagnosed with cancer.

瑞典、美國和意大利的研究人員合作，對瑞典的癌症登記處和生育登記處進行了梳理，調查了 1.2 萬多名癌症患者和 6.2 萬多名未確診癌症的同齡人。

They separated out the data based on if and when everyone gave birth, and found an increase in breast cancer among people who had given birth for about 15 years after the event, but then a decrease after that.

他們根據每個人是否生育以及何時生育對數據進行了分類，發現生育後 15 年內，乳腺癌發病率有所增加，但之後又有所下降。

And that effect is not short-term.

而且這種影響不是短期的。

In fact, the protective benefit of a previous birth seems to compound when you give birth to more babies after that first pregnancy.

事實上，在第一次懷孕後，如果您生育了更多的嬰兒，前一次分娩的保護性益處似乎會更加明顯。

Researchers think that because hormones are key players in this whole childbirth-cancer relationship, by spending more time pregnant, you're reducing your long-term cancer risk levels.

研究人員認為，由於荷爾蒙是整個分娩與癌症關係中的關鍵因素，所以多花點時間懷孕，就能降低長期的癌症風險水準。

Every period of full-term pregnancy and longer lactation reduces the overall number of menstrual cycles and your lifetime exposure to hormones.

每個足月妊娠期和較長的哺乳期都會減少月經週期的總次數，也會減少你一生中接觸荷爾蒙的機會。

But there's another twist.

但還有一個轉折。

The decreased cancer risk tends to only exist if you have your first baby before around age 35.

只有在 35 歲左右生育第一胎時，癌症風險才會降低。

After that, you're entering years when people tend to have more cancers in general, so you can't take advantage of that decreased risk.

在此之後的幾年裡，人們患癌症的機率會普遍增高，所以無法利用降低的風險。

In that case, your risk is higher than someone your age who never gave birth.

在這種情況下，您的風險比從未生育過的同齡人要高。

To put it all together, pregnancy initially increases your risk of breast cancer, then eventually lowers it, but only if your first pregnancy was before the age of roughly 35.

綜上所述，懷孕最初會增加罹患乳腺癌的風險，但最終會降低風險，但前提是第一次懷孕必須在 35 歲左右。

If you're in your 30s, watching this video, and worrying about your impending breast cancer diagnosis because you haven't given birth before, know that you're probably not growing breast cancer right now.

如果你現在 30 多歲，正在觀看這部影片，並且因為沒有生育過而擔心自己即將被診斷出乳腺癌，那麼你要知道，你現在可能並沒有患上乳腺癌。

As a general rule, breast cancer isn't terribly common in women of reproductive age with or without babies.

一般來說，無論是否生育，乳腺癌在育齡婦女中並不常見。

And there are things you might be able to do, like breastfeeding for a year, that helped to decrease breast cancer risk by over 4% in a 2022 meta-study.

有些事情你也許可以做到，比如母乳餵養一年，在 2022 年的一項薈萃研究中，母乳餵養有助於將乳腺癌風險降低 4% 以上。

More importantly, we're talking about risks and percentages, not a sure thing.

更重要的是，我們談論的是風險和百分比，而不是確定的事情。

If having a kid is in the cards for you, then great.

如果有了孩子，那就太好了。

And if not, also great.

如果沒有，也很好。

But please don't get pregnant just to try to avoid breast cancer, because you might only reduce your risk of breast cancer by a little bit, but increase your chance of having a baby by a lot.

但請不要為了避免乳腺癌而懷孕，因為你可能只降低了一點患乳腺癌的風險，卻增加了很多生孩子的機會。