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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 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 hormones, FSH,
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which ripens a hand full
of follicles of the ovary
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that they release estrogen.
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Each folicle 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 prepartion 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 the 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 masterbation.
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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 qualify 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.