WEBVTT

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In 1978, Louise Brown became 


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the world's first baby to be born
by in vitro fertilization, or IVF.

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Her birth revolutionized 
the field of reproductive medicine.

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Given that approximately one in eight
heterosexual couples

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has difficulty conceiving,

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and that homosexual couples
and single parents

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often need clinical help to make a baby,

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the demand for IVF has been growing.

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IVF is so common, that more than 5 million
babies have been born through this technology.

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IVF works by mimicking the brilliant
design of sexual reproduction.

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In order to understand IVF,

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we first need to take a look 
at the natural process of baby making.

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Believe it or not, 
it all starts in the brain.

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Roughly fifteen days 
before fertilization can happen,

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the anterior pituitary gland secretes
follicle stimulating hormone, FSH,

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which ripens a handful 
of follicles of the ovary

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that then release estrogen.

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Each follicle contains one egg,

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and on average, 
only one follicle becomes fully mature.

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As it grows and continues 
to release estrogen,

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this hormone not only helps coordinate
growth and preparation of the uterus,

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it also communicates to the brain
how well the follicle is developing.

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When the estrogen level is high enough,

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the anterior pituitary releases a surge
of luteinizing hormone, LH,

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which triggers ovulation

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and causes the follicle to rupture
and release the egg.

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Once the egg leaves the ovary,

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it is directed into the Fallopian tube
by the finger-like fimbriae.

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If the egg is not fertilized 
by sperm within 24 hours,

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the unfertilized egg will die,

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and the entire system will reset itself,

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preparing to create a new egg
and uterine lining the following month.

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The egg is the largest cell in the body

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and is protected by a thick, 
extracellular shell of sugar

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and protein called the zona pellucida.

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The zona thwarts the entry and fusion
of more than one sperm,

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the smallest cell in the body.

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It takes a man two to three months
to make sperm,

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and the process constantly renews.

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Each ejaculation during sexual intercourse
releases more than 100 million sperm.

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But only 100 or so will ultimately
make it to the proximity of the egg,

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and only one will successfully penetrate
through the armor of the zona pellucida.

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Upon successful fertilization,

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the zygote immediately begins 
developing into an embryo,

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and takes about three days
to reach the uterus.

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There, it requires 
another three or so days

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to implant firmly into the endometrium,
the inner lining of the uterus.

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Once implanted, the cells that 
are to become the placenta

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secrete a hormone that signals
to the ovulated follicle

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that there is a pregnancy in the uterus.

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This helps rescue that follicle,
now called the corpus luteum,

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from degenerating as it normally would
do in that stage of the menstrual cycle.

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The corpus luteum is responsible
for producing the progesterone

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required to maintain the pregnancy
until six to seven weeks of gestation,

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when the placenta develops
and takes over,

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until the baby is born 
approximately 40 weeks later.

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Now, how do you make a baby in a lab?

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In patients undergoing IVF,

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FSH is administered at levels
that are higher than naturally occuring

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to cause a controlled 
overstimulation of the ovaries

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so that they ultimately 
produce multiple eggs.

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The eggs are then retrieved 
just before ovulation would occur,

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while the woman is under anesthesia,

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through an aspirating needle
that is guided by ultrasound.

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Most sperm samples are produced
by masturbation.

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In the laboratory, the identified eggs
are stripped of surrounding cells

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and prepared for fertilization 
in a petri dish.

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Fertilization can occur 
by one of two techniques.

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In the first, the eggs are incubated
with thousands of sperm

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and fertilization occurs naturally
over a few hours.

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The second technique maximizes
certainty of fertilization

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by using a needle 
to place a single sperm inside the egg.

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This is particularly useful when there is
a problem with the quality of the sperm.

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After fertilization, embryos can be 
further screened for genetic suitability,

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frozen for later attempted pregnancies,

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or delivered into the woman's uterus
via catheter.

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Common convention is to transfer
the embryo three days after fertilization,

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when the embryo has eight cells,

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or on day five, when
the embryo is called a blastocyst,

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and has hundreds of cells.

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If the woman's eggs are of poor quality
due to age or toxic exposures,

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or have been removed due to cancer,

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donor eggs may be used.

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In the case that the intended mother
has a problematic uterus, or lacks one,

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another woman, called 
the gestational carrier or surrogate,

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can use her uterus to carry the pregnancy.

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To increase the odds of success,

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which are as high as 40%
for a woman younger than 35,

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doctors sometimes transfer
multiple embryos at once,

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which is why IVF results 
in twins and triplets

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more often than natural pregnancies.

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However, most clinics seek to minimize
the chances of multiple pregnancies,

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as they are riskier 
for mothers and babies.

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Millions of babies, like Louise Brown,
have been born from IVF

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and have had normal, healthy lives.

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The long-term health consequences
of ovarian stimulation

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with IVF medicines are less clear,

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though so far, IVF seems safe for women.

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Because of better genetic testing,

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delayed childbearing, 


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increased accessibility
and diminishing cost,

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it's not inconceivable that artificial
baby making via IVF and related techniques

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could outpace natural reproduction
in years to come.