How in vitro fertilization (IVF) works
-
0:07 - 0:09In 1978, Louise Brown became
-
0:09 - 0:14the world's first baby to be born
by in vitro fertilization, or IVF. -
0:14 - 0:18Her birth revolutionized
the field of reproductive medicine. -
0:18 - 0:21Given that approximately one in eight
heterosexual couples -
0:21 - 0:23has difficulty conceiving,
-
0:23 - 0:25and that homosexual couples
and single parents -
0:25 - 0:28often need clinical help to make a baby,
-
0:28 - 0:31the demand for IVF has been growing.
-
0:31 - 0:37IVF is so common, that more than 5 million
babies have been born through this technology. -
0:37 - 0:43IVF works by mimicking the brilliant
design of sexual reproduction. -
0:43 - 0:45In order to understand IVF,
-
0:45 - 0:50we first need to take a look
at the natural process of baby making. -
0:50 - 0:54Believe it or not,
it all starts in the brain. -
0:54 - 0:57Roughly fifteen days
before fertilization can happen, -
0:57 - 1:03the anterior pituitary gland secretes
follicle stimulating hormone, FSH, -
1:03 - 1:05which ripens a handful
of follicles of the ovary -
1:05 - 1:08that then release estrogen.
-
1:08 - 1:10Each follicle contains one egg,
-
1:10 - 1:14and on average,
only one follicle becomes fully mature. -
1:14 - 1:17As it grows and continues
to release estrogen, -
1:17 - 1:22this hormone not only helps coordinate
growth and preparation of the uterus, -
1:22 - 1:27it also communicates to the brain
how well the follicle is developing. -
1:27 - 1:29When the estrogen level is high enough,
-
1:29 - 1:35the anterior pituitary releases a surge
of luteinizing hormone, LH, -
1:35 - 1:37which triggers ovulation
-
1:37 - 1:42and causes the follicle to rupture
and release the egg. -
1:42 - 1:44Once the egg leaves the ovary,
-
1:44 - 1:49it is directed into the Fallopian tube
by the finger-like fimbriae. -
1:49 - 1:53If the egg is not fertilized
by sperm within 24 hours, -
1:53 - 1:55the unfertilized egg will die,
-
1:55 - 1:57and the entire system will reset itself,
-
1:57 - 2:02preparing to create a new egg
and uterine lining the following month. -
2:02 - 2:05The egg is the largest cell in the body
-
2:05 - 2:08and is protected by a thick,
extracellular shell of sugar -
2:08 - 2:12and protein called the zona pellucida.
-
2:12 - 2:17The zona thwarts the entry and fusion
of more than one sperm, -
2:17 - 2:20the smallest cell in the body.
-
2:20 - 2:23It takes a man two to three months
to make sperm, -
2:23 - 2:26and the process constantly renews.
-
2:26 - 2:32Each ejaculation during sexual intercourse
releases more than 100 million sperm. -
2:32 - 2:37But only 100 or so will ultimately
make it to the proximity of the egg, -
2:37 - 2:43and only one will successfully penetrate
through the armor of the zona pellucida. -
2:43 - 2:46Upon successful fertilization,
-
2:46 - 2:49the zygote immediately begins
developing into an embryo, -
2:49 - 2:52and takes about three days
to reach the uterus. -
2:52 - 2:54There, it requires
another three or so days -
2:54 - 3:00to implant firmly into the endometrium,
the inner lining of the uterus. -
3:00 - 3:03Once implanted, the cells that
are to become the placenta -
3:03 - 3:06secrete a hormone that signals
to the ovulated follicle -
3:06 - 3:09that there is a pregnancy in the uterus.
-
3:09 - 3:12This helps rescue that follicle,
now called the corpus luteum, -
3:12 - 3:18from degenerating as it normally would
do in that stage of the menstrual cycle. -
3:18 - 3:21The corpus luteum is responsible
for producing the progesterone -
3:21 - 3:26required to maintain the pregnancy
until six to seven weeks of gestation, -
3:26 - 3:28when the placenta develops
and takes over, -
3:28 - 3:32until the baby is born
approximately 40 weeks later. -
3:32 - 3:36Now, how do you make a baby in a lab?
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3:36 - 3:38In patients undergoing IVF,
-
3:38 - 3:42FSH is administered at levels
that are higher than naturally occuring -
3:42 - 3:46to cause a controlled
overstimulation of the ovaries -
3:46 - 3:50so that they ultimately
produce multiple eggs. -
3:50 - 3:53The eggs are then retrieved
just before ovulation would occur, -
3:53 - 3:56while the woman is under anesthesia,
-
3:56 - 4:00through an aspirating needle
that is guided by ultrasound. -
4:00 - 4:05Most sperm samples are produced
by masturbation. -
4:05 - 4:10In the laboratory, the identified eggs
are stripped of surrounding cells -
4:10 - 4:14and prepared for fertilization
in a petri dish. -
4:14 - 4:17Fertilization can occur
by one of two techniques. -
4:17 - 4:20In the first, the eggs are incubated
with thousands of sperm -
4:20 - 4:25and fertilization occurs naturally
over a few hours. -
4:25 - 4:28The second technique maximizes
certainty of fertilization -
4:28 - 4:32by using a needle
to place a single sperm inside the egg. -
4:32 - 4:37This is particularly useful when there is
a problem with the quality of the sperm. -
4:37 - 4:42After fertilization, embryos can be
further screened for genetic suitability, -
4:42 - 4:44frozen for later attempted pregnancies,
-
4:44 - 4:49or delivered into the woman's uterus
via catheter. -
4:49 - 4:54Common convention is to transfer
the embryo three days after fertilization, -
4:54 - 4:57when the embryo has eight cells,
-
4:57 - 5:01or on day five, when
the embryo is called a blastocyst, -
5:01 - 5:04and has hundreds of cells.
-
5:04 - 5:09If the woman's eggs are of poor quality
due to age or toxic exposures, -
5:09 - 5:11or have been removed due to cancer,
-
5:11 - 5:14donor eggs may be used.
-
5:14 - 5:19In the case that the intended mother
has a problematic uterus, or lacks one, -
5:19 - 5:23another woman, called
the gestational carrier or surrogate, -
5:23 - 5:26can use her uterus to carry the pregnancy.
-
5:26 - 5:28To increase the odds of success,
-
5:28 - 5:32which are as high as 40%
for a woman younger than 35, -
5:32 - 5:37doctors sometimes transfer
multiple embryos at once, -
5:37 - 5:40which is why IVF results
in twins and triplets -
5:40 - 5:43more often than natural pregnancies.
-
5:43 - 5:48However, most clinics seek to minimize
the chances of multiple pregnancies, -
5:48 - 5:52as they are riskier
for mothers and babies. -
5:52 - 5:56Millions of babies, like Louise Brown,
have been born from IVF -
5:56 - 6:00and have had normal, healthy lives.
-
6:00 - 6:03The long-term health consequences
of ovarian stimulation -
6:03 - 6:06with IVF medicines are less clear,
-
6:06 - 6:10though so far, IVF seems safe for women.
-
6:10 - 6:12Because of better genetic testing,
-
6:12 - 6:14delayed childbearing,
-
6:14 - 6:17increased accessibility
and diminishing cost, -
6:17 - 6:23it's not inconceivable that artificial
baby making via IVF and related techniques -
6:23 - 6:27could outpace natural reproduction
in years to come.
- Title:
- How in vitro fertilization (IVF) works
- Speaker:
- Nassim Assefi and Brian A. Levine
- Description:
-
Infertility affects 1 in 8 couples worldwide. But in the last 40 years, more than 5 million babies have been born using in vitro fertilization (IVF). How does it work? Nassim Assefi and Brian A. Levine detail the science behind making a baby in a lab.
- Video Language:
- English
- Team:
- closed TED
- Project:
- TED-Ed
- Duration:
- 06:43
Michelle Mehrtens edited English subtitles for How in vitro fertilization (IVF) works | ||
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Jessica Ruby accepted English subtitles for How in vitro fertilization (IVF) works | ||
Jessica Ruby edited English subtitles for How in vitro fertilization (IVF) works | ||
Jessica Ruby edited English subtitles for How in vitro fertilization (IVF) works | ||
Jessica Ruby edited English subtitles for How in vitro fertilization (IVF) works | ||
Jennifer Cody edited English subtitles for How in vitro fertilization (IVF) works | ||
Jennifer Cody edited English subtitles for How in vitro fertilization (IVF) works |