Many are aware that fertility declines as you age

生育力都會隨著年齡增長而遞減

so when should you have kids,

所以應該何時生小孩

and is there anything you can do to beat your biological clock?

又是否有辦法扭轉生理上的劣勢呢？

A woman's first period is generally around age twelve or thirteen,

女性第一次的生理期大概會發生在十二、三歲時

but most ovaries don't start releasing eggs until a few years after this

但卵巢多半會在幾年後才開始釋放卵子

In fact, a woman's peak fertility

事實上，一位女性的生育力巔峰期

isn't actually until her early or mid twenties

大概落在二十歲出頭到二十幾歲中期

Unlike males who are constantly producing new sperm

不像男性隨時在製造新的精子

females have a finite number of eggs, but don't worry

女性所擁有的卵子數量是有限的，但不用擔心

By puberty you have around 300,000

在青春期你大概會有三十萬顆卵子

way more than the 300 to 400 you will release in your lifetime

數量遠遠超過一生會釋放的三百到四百顆卵子

However popular statistics show that after trying to conceive for one year,

然而人口數據顯示，在試圖懷孕的一年裡

A thirty-year-old woman has a 25% chance

一名三十歲的女性有百分之二十五的機率

of not conceiving a life birth

無法成功懷孕

This increases to a 44% chance at 35,

對三十五歲女性而言，機率增至百分之四十四

and 66% chance at 40 years old

到了四十歲則有百分之六十六的機率

But most of this data comes from a 2004 journal

但這些數據大多來自一篇 2004 年的期刊

looking at French birth records from 1670 to 1830

內容探討法國 1670 年至 1830 年期間的出生率

it's safe to say that a lot has changed

不可否認的是，相比那個時代沒有電力、

for the lives and health of women since before the age

抗生素和穩定的食物來源，現代女性的生活和健康

of electricity, antibiotics, and reliable food supply.

都已經改善許多

It also does an account for the amount of sex

另外，伴侶之間性行為次數也該納入考量

couples were having and the fact that sex drive tapers off as you age.

隨著年齡增長性慾望也會減少

Modern studies present a more optimistic look

現代研究結果顯示較為樂觀

with the percentage of women unable to conceive

二十七到三十四歲的女性

within a year of unprotected intercourse at 13% to 14%

在試圖懷孕的一年內

for women aged 27 to 34

失敗率僅為百分之十三至十四

and 18% for women aged 35 to 39.

三十五到三十九歲的女性懷孕失敗的幾率也才百分之十八

Still showing declining fertility but much better odds

隨著歲數的增長，生育力確實會降低

than the historical data suggest. Another study found that among

但已經比歷史數據顯示的好上許多。另一研究發現

38 and 39 year olds who have been pregnant before

從前已懷過孕的三十八、三十九歲女子

80% were able to become pregnant naturally within

其中有百分之八十都能夠在半年內自然懷孕

six months. And this points to another flaw in the studies

這也導向了此研究中的另一個瑕疵

Nearly half of all pregnancies in America are

在美國，將近一半的懷孕案例都是出自意外

unintended. This means highly fertile women are more

這意味著那些高生育力的女性

likely to become pregnant accidentally when they're younger,

較可能在年輕時意外懷孕

while those purposefully trying to have kids for the first time

而那些在三十歲過後才嘗試要次初懷孕的女性

in their late thirties are already disproportionately

不論是幾歲，生育力都已大大降低

less fertile regardless of age creating an overestimate

生理年齡對生育的影響

for the effect of biological aging.

因而顯得更加劇烈

However, older eggs may not fertilize normally and there is an increase

然而，較老的卵子或許無法自然受孕

of chromosomal abnormalities with age. A woman who is

隨著生育年齡的增長，染色體異常的情況也越可能發生

thirty has a 1 in 800 chance of having a baby with

三十歲女性有八百分之一的機率產下唐氏症寶寶

Down Syndrome, but the probability goes up to 1 in 100

四十歲時生產，機率則高達百分之一

when she's forty. Granted, that's still only

還好，那也只是百分之一的機率而已

a 1% chance. But what about men? Many assume

那對於男性來說呢？許多人認為男性生育能力並無受限

male fertility is limitless with some famous examples like

畢竟有許多知名案例，例如查理卓別林

Charlie Chaplin having kids up until his seventies.

到了高齡七十歲還仍然生得出孩子

And while men do continually make new sperm, the more cell divides

不過雖然男性隨時都在製造新的精子

the higher probability of genetic mutations.

細胞分裂次數越多，基因突變的機率也越高

By the time a man reaches 50, the cells that create his sperm

當一名男性臨屆五十歲，製造精子的細胞

have gone through over 800 rounds of division and replication.

早已經過了超過八百回的細胞分裂和複製

As a result, older fathers carry increased

因此高齡父親有較高機率生出患有先天疾病的嬰兒

risk of children with schizophrenia, autism, cancer

包含精神分裂症、自閉症、癌症、

a form of dwarfism, neurofibromatosis, and even skull and

侏儒症、神經纖維瘤病，甚至是顏面骨骼畸形

facial abnormalities. On top of this, even among young men

除此之外，就連在過去四十年內西方國家的

in the Western world, sperm counts have dropped over 50%

年輕男性精子數量都已經減少

in the last 40 years

超過百分之五十

The impact and importance of this

這會導致的結果

is yet to be determined though

還有待闡明

Of course, there's more to raising children than biology

不容置疑的是，有關生育孩童更多是在生物範疇之外的

anecdotal accounts points to younger parents having more energy, but

趣聞軼事表示年輕父母有更多的精力

older parents having more maturity and financial stability.

而年長父母則更加成熟，財務情況也較為穩定

Of course, more income does not mean better parents

有更多的收入不代表就是好父母，沒錯

but research has shown that higher family income is linked to higher

但是研究也指出高入學測驗成績往往來自有較高收入的家庭

SAT scores. Not to mention in low to middle

遑論在低收入到中低收入國家

income countries the risk of death per birth for women between

十五至十九歲的婦女分娩死亡案件

15 to 19 years old is 28% higher

比二十至二十四歲的婦女要高出百分之二十八

than for women 20 to 24 years old. Studies have

研究也發現

also found that in some Sub-Saharan African countries

在一些撒哈拉沙漠以南的非洲國家中

Up to 25% of girls and young women drop out of school

高達四分之一的女孩和年輕女性因為意外懷孕

because of unintended pregnancies.

而輟學

Preserving young female eggs by cryogenically freezing them

低溫冷凍儲存年輕女性卵子的做法也越來越常見

has also become more common but isn't a guarantee

但是並無法全然掛保證

with increasing age still affecting pregnancy success rates

因為年齡的遞增也會影響懷孕成功率

and researchers finding that the freezing process degrades

而且研究者也發現冷凍儲存會使卵子品質降低

the quality of the eggs. Additionally, this isn't a viable

再者，這對大多數女性來說不會是個選項

option for most women, as the cost of freezing alone

因為光是冷凍卵子就要花費一萬美元

is 10,000 dollars, and one round of in vitro fertilization

而一次的玻管受精過程就要

can cost upwards of 12,000 dollars.

花費高達一萬兩千美元

Overall, yes, conceiving a baby becomes more difficult

整體看來，當男女雙方年齡增長，生育會變得更加困難

as both men and women age, but it is not the level of

但也沒有嚴重到媒體經常報導的

baby panic that is so often discussed in the media.

高不孕程度

Individual fertility is very variable

基於基因和生活方式

based on genetics and lifestyle, and the best time to have kids

個體的生育力不一，決定何時適合生小孩是一件很私人的事

is a very personal decision as is having kids at all.

就如同養育孩子的方式也是

Special thanks to the Bill and Melinda Gates Foundation for supporting this episode.

特別感謝比爾及梅琳達蓋茲基金會對本集的贊助

Even though the world is on an incredible path of progress,

縱然世界正以驚人速度進步發展

it's important to remember that progress isn't inevitable.

必須記得這些進展並非理所當然

That's why the Gates Foundation has created a Goalkeepers Report

這正是為何蓋茲基金會創立了守門員記錄

which will help raise awareness, accountability, and drive action

喚起大眾的意識及責任感，並呼籲

for a better future.

為了一個更好的將來行動

Did you know that the number of mothers who die during childbirth

你知道在過去一個世代裡，因分娩致死的孕婦數量

has been halved in the past generation?

減少了一半嗎？

The Gates Foundation wants to ensure continued healthy lives

蓋茲基金會希望確保大眾的健康

and promote well-being for all ages.

與永續健全發展

Click the link in the description to read the report and see the progress being made.

按下底下描述中的鏈接，看看這項記錄

And subscribe for more weekly science videos every Thursday!

也要記得訂閱收看更多每週四釋出的科學影片！