Name: スーパーフェッティングあなたが妊娠するとき...すでに妊娠しているにもかかわらず (Superfetation: When You Get Pregnant... Even Though You're Already Pregnant)
Uploaded: 2021-01-14T10:37:48.000Z
Duration: 7 min 7 s
Description: VoiceTubeの動画で発音を聞きながら英語表現を覚えよう！学べる英語：

weird stuff happens that changes everything.

Two fertile people have sex, their egg and sperm meet,

Because rarely, after someone gets pregnant,

And no, I don't mean shortly after having a baby.

I'm talking about getting pregnant days or even weeks

after conceiving, and carrying both fetuses

at the same time—what scientists call superfetation.

In humans, superfetation is super rare, but also super real.

And scientists have been studying these strange cases

of twinning for insights into how reproduction works.

If sperm fertilizes that egg within about a 24 hour period,

As that happens, part of the ovary produces hormones

like progesterone which help prepare the uterus for implantation.

And then, if those hormones do their job, about six days later,

the quickly-growing clump of cells burrows into the thick layer

of tissue lining the uterus and implants.

After that, the body continues to suppress ovulation,

and the lining of the uterus changes to accommodate the growing fetus—

changes which also make it less receptive to implantation.

But the uterus isn't completely unreceptive for several weeks.

Finally, about a month after implantation,

the opening at the bottom of the uterus called the cervix

This protects the fetus from pathogens and prevents

sperm from coming in and fertilizing another egg.

Now, obviously, twins and other multiples are a thing,

so we know that more than one embryo can implant.

But that's typically because an embryo happens to split itself

into multiple identical copies at an early stage,

or because the person released multiple eggs to begin with.

That means multiples generally occur before

the suppression of ovulation, the decrease in uterine receptivity,

For superfetation to occur, allllll of these barriers

A women had a set of twins that consistently measured

Doctors working on the case ruled out other reasons

for this difference in size, like genetic conditions

We don't know exactly what happened in this case,

but her doctors suggested atypical levels of hormones

that could have encouraged her to ovulate after implantation.

Then, so long as some sperm managed to make it

past the cervix before the mucus plug locked them out,

the second embryo could have settled into

the uterine lining before receptivity was totally gone.

Or, the woman may have released more than one egg

during ovulation, both of which were successfully fertilized.

In that case, the only reason she didn't have normal twins

was that the second experienced delayed implantation.

Basically, the doctors thought it may have pressed pause

on its development and hung around in the uterus

for a few weeks before implanting, getting in just under the wire

Other known cases of superfetation have involved

people with uterus didelphys: a rare condition

and therefore, can become doubly pregnant.

One such case gave birth to two healthy babies

From what doctors can tell, it seems like the two uteri

can function independently—so implantation in one

doesn't prevent implantation in the other.

And sometimes, these uteri even connect to different vaginas,

from reaching the egg if the person ovulates!

Scientists also hypothesize that the use of assisted

reproductive technologies can make superfetation more likely.

Still really rare, but, you know, a little less so.

And this probably has something to do with

With in-vitro fertilization, the egg donor often receives hormones

to induce more than one egg to mature at the same time.

The mature eggs are then retrieved with a needle

Once fertilized, two or three of these embryos

are transferred into the uterus, often while the person

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スーパーフェッティングあなたが妊娠するとき...すでに妊娠しているにもかかわらず (Superfetation: When You Get Pregnant... Even Though You're Already Pregnant)

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