[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:06.57,0:00:12.74,Default,,0000,0000,0000,,The earliest known pregnancy test\Ndates back to 1350 BC in Ancient Egypt.
Dialogue: 0,0:00:12.74,0:00:14.83,Default,,0000,0000,0000,,According to the Egyptians,
Dialogue: 0,0:00:14.83,0:00:20.07,Default,,0000,0000,0000,,all you have to do is urinate on wheat \Nand barley seeds, and wait.
Dialogue: 0,0:00:20.07,0:00:23.67,Default,,0000,0000,0000,,If either sprouts, \Ncongratulations, you're pregnant!
Dialogue: 0,0:00:23.67,0:00:28.96,Default,,0000,0000,0000,,And if wheat sprouts faster, it's a girl,\Nbut if barley, it's a boy.
Dialogue: 0,0:00:28.96,0:00:32.40,Default,,0000,0000,0000,,In 1963, a small study \Nreproduced this test
Dialogue: 0,0:00:32.40,0:00:37.10,Default,,0000,0000,0000,,and found that it predicted pregnancy\Nwith a respectable 70% accuracy,
Dialogue: 0,0:00:37.10,0:00:40.75,Default,,0000,0000,0000,,though it couldn't reliably \Ntell the sex of the baby.
Dialogue: 0,0:00:40.75,0:00:43.40,Default,,0000,0000,0000,,Scientists hypothesized \Nthat the test worked
Dialogue: 0,0:00:43.40,0:00:46.56,Default,,0000,0000,0000,,because pregnant women's urine\Ncontains more estrogen,
Dialogue: 0,0:00:46.56,0:00:48.75,Default,,0000,0000,0000,,which can promote seed growth.
Dialogue: 0,0:00:48.75,0:00:52.09,Default,,0000,0000,0000,,Now it's easy to take \Nthis ancient method for granted
Dialogue: 0,0:00:52.09,0:00:57.14,Default,,0000,0000,0000,,because modern pregnancy tests give\Nhighly accurate results within minutes.
Dialogue: 0,0:00:57.14,0:00:59.05,Default,,0000,0000,0000,,So how do they work?
Dialogue: 0,0:00:59.05,0:01:03.23,Default,,0000,0000,0000,,Over-the-counter pregnancy tests\Nare all designed to detect one thing:
Dialogue: 0,0:01:03.23,0:01:05.89,Default,,0000,0000,0000,,a hormone called HCG.
Dialogue: 0,0:01:05.89,0:01:09.30,Default,,0000,0000,0000,,HCG is produced in \Nthe earliest stages of pregnancy
Dialogue: 0,0:01:09.30,0:01:10.87,Default,,0000,0000,0000,,and starts a game of telephone
Dialogue: 0,0:01:10.87,0:01:15.02,Default,,0000,0000,0000,,that tells the body not to shed \Nthe inner lining of the uterus that month.
Dialogue: 0,0:01:15.02,0:01:16.65,Default,,0000,0000,0000,,As the pregnancy progresses,
Dialogue: 0,0:01:16.65,0:01:19.80,Default,,0000,0000,0000,,HCG supports the formation\Nof the placenta,
Dialogue: 0,0:01:19.80,0:01:23.65,Default,,0000,0000,0000,,which transfers nutrients \Nfrom mother to fetus.
Dialogue: 0,0:01:23.65,0:01:28.09,Default,,0000,0000,0000,,The test starts when urine is applied\Nto the exposed end of the strip.
Dialogue: 0,0:01:28.09,0:01:30.85,Default,,0000,0000,0000,,As the fluid travels up \Nthe absorbent fibers,
Dialogue: 0,0:01:30.85,0:01:35.37,Default,,0000,0000,0000,,it will cross three separate zones,\Neach with an important task.
Dialogue: 0,0:01:35.37,0:01:38.100,Default,,0000,0000,0000,,When the wave hits the first zone,\Nthe reaction zone,
Dialogue: 0,0:01:38.100,0:01:44.99,Default,,0000,0000,0000,,Y-shaped proteins called antibodies\Nwill grab onto any HCG.
Dialogue: 0,0:01:44.99,0:01:47.81,Default,,0000,0000,0000,,Attached to these antibodies\Nis a handy enzyme
Dialogue: 0,0:01:47.81,0:01:53.62,Default,,0000,0000,0000,,with the ability to turn on dye molecules,\Nwhich will be crucial later down the road.
Dialogue: 0,0:01:53.62,0:01:56.59,Default,,0000,0000,0000,,Then the urine picks up \Nall the AB1 enzymes
Dialogue: 0,0:01:56.59,0:02:00.85,Default,,0000,0000,0000,,and carries them to the test zone,\Nwhich is where the results show up.
Dialogue: 0,0:02:00.85,0:02:03.88,Default,,0000,0000,0000,,Secured to this zone are more\NY-shaped antibodies
Dialogue: 0,0:02:03.88,0:02:08.88,Default,,0000,0000,0000,,that will also stick to HCG\Non one of its five binding sites.
Dialogue: 0,0:02:08.88,0:02:12.22,Default,,0000,0000,0000,,Scientists call this type of test\Na sandwich assay.
Dialogue: 0,0:02:12.22,0:02:19.07,Default,,0000,0000,0000,,If HCG is present, it gets sandwiched\Nbetween the AB1 enzyme and AB2,
Dialogue: 0,0:02:19.07,0:02:20.93,Default,,0000,0000,0000,,and sticks to the test zone,
Dialogue: 0,0:02:20.93,0:02:24.24,Default,,0000,0000,0000,,allowing the attached dye-activating\Nenzyme to do its job
Dialogue: 0,0:02:24.24,0:02:26.62,Default,,0000,0000,0000,,and create a visible pattern.
Dialogue: 0,0:02:26.62,0:02:31.62,Default,,0000,0000,0000,,If there's no HCG, the wave of urine\Nand enzymes just passes on by.
Dialogue: 0,0:02:31.62,0:02:36.45,Default,,0000,0000,0000,,Finally, there's one last stop to make,\Nthe control zone.
Dialogue: 0,0:02:36.45,0:02:38.40,Default,,0000,0000,0000,,As in any good experiment,
Dialogue: 0,0:02:38.40,0:02:41.62,Default,,0000,0000,0000,,this step confirms that \Nthe test is working properly.
Dialogue: 0,0:02:41.62,0:02:44.93,Default,,0000,0000,0000,,Whether the AB1 enzymes never saw HCG,
Dialogue: 0,0:02:44.93,0:02:48.74,Default,,0000,0000,0000,,or they're extras because Zone 1\Nis overstocked with them,
Dialogue: 0,0:02:48.74,0:02:53.63,Default,,0000,0000,0000,,all the unbound AB1 enzymes picked up\Nin Zone 1 should end up here
Dialogue: 0,0:02:53.63,0:02:55.74,Default,,0000,0000,0000,,and activate more dye.
Dialogue: 0,0:02:55.74,0:03:00.08,Default,,0000,0000,0000,,So if no pattern appears,\Nthat indicates that the test was faulty.
Dialogue: 0,0:03:00.08,0:03:03.45,Default,,0000,0000,0000,,These tests are pretty reliable,\Nbut they're not failproof.
Dialogue: 0,0:03:03.45,0:03:05.34,Default,,0000,0000,0000,,For instance, false negatives can occur
Dialogue: 0,0:03:05.34,0:03:09.64,Default,,0000,0000,0000,,if concentrations of HCG \Naren't high enough for detection.
Dialogue: 0,0:03:09.64,0:03:13.50,Default,,0000,0000,0000,,After implantation, HCG levels double\Nevery two to three days,
Dialogue: 0,0:03:13.50,0:03:16.45,Default,,0000,0000,0000,,so it may just be too early to tell.
Dialogue: 0,0:03:16.45,0:03:18.52,Default,,0000,0000,0000,,And beverages can dilute the urine sample,
Dialogue: 0,0:03:18.52,0:03:22.88,Default,,0000,0000,0000,,which is why doctors recommend taking\Nthe test first thing in the morning.
Dialogue: 0,0:03:22.88,0:03:27.37,Default,,0000,0000,0000,,On the other hand, false positives\Ncan come from other sources of HCG,
Dialogue: 0,0:03:27.37,0:03:30.46,Default,,0000,0000,0000,,like IVF injections, ectopic pregnancies,
Dialogue: 0,0:03:30.46,0:03:34.44,Default,,0000,0000,0000,,or certain cancers such as uterine cancer\Nor testicular cancer,
Dialogue: 0,0:03:34.44,0:03:39.48,Default,,0000,0000,0000,,making it possible for one of these tests\Nto tell a man he's pregnant.
Dialogue: 0,0:03:39.48,0:03:43.85,Default,,0000,0000,0000,,The best way for a woman to find out \Nfor sure is at the doctor's office.
Dialogue: 0,0:03:43.85,0:03:46.37,Default,,0000,0000,0000,,The doctors are also looking for HCG,
Dialogue: 0,0:03:46.37,0:03:49.80,Default,,0000,0000,0000,,but with tests that are more sensitive\Nand quantitative,
Dialogue: 0,0:03:49.80,0:03:54.53,Default,,0000,0000,0000,,which means they can determine\Nthe exact level of HCG in your blood.
Dialogue: 0,0:03:54.53,0:03:56.94,Default,,0000,0000,0000,,A few minutes can feel like forever
Dialogue: 0,0:03:56.94,0:04:00.21,Default,,0000,0000,0000,,when you're waiting on the results \Nof a pregnancy test.
Dialogue: 0,0:04:00.21,0:04:04.55,Default,,0000,0000,0000,,But in that brief time, you're witnessing\Nthe power of the scientific method.
Dialogue: 0,0:04:04.55,0:04:07.21,Default,,0000,0000,0000,,That one little stick \Nlets you ask a question,
Dialogue: 0,0:04:07.21,0:04:09.28,Default,,0000,0000,0000,,perform a controlled experiment,
Dialogue: 0,0:04:09.28,0:04:13.06,Default,,0000,0000,0000,,and then analyze the results\Nto check your original hypothesis.
Dialogue: 0,0:04:13.06,0:04:17.46,Default,,0000,0000,0000,,And the best part is you won't even\Nhave to wait until the next harvest.