How do pregnancy tests work? – Tien Nguyen

How do pregnancy tests work? – Tien Nguyen

The earliest known pregnancy test
dates back to 1350 BC in Ancient Egypt. According to the Egyptians, all you have to do is urinate on wheat
and barley seeds, and wait. If either sprouts,
congratulations, you’re pregnant! And if wheat sprouts faster, it’s a girl,
but if barley, it’s a boy. In 1963, a small study
reproduced this test and found that it predicted pregnancy
with a respectable 70% accuracy, though it couldn’t reliably
tell the sex of the baby. Scientists hypothesized
that the test worked because pregnant women’s urine
contains more estrogen, which can promote seed growth. Now it’s easy to take
this ancient method for granted because modern pregnancy tests give
highly accurate results within minutes. So how do they work? Over-the-counter pregnancy tests
are all designed to detect one thing: a hormone called HCG. HCG is produced in
the earliest stages of pregnancy and starts a game of telephone that tells the body not to shed
the inner lining of the uterus that month. As the pregnancy progresses, HCG supports the formation
of the placenta, which transfers nutrients
from mother to fetus. The test starts when urine is applied
to the exposed end of the strip. As the fluid travels up
the absorbent fibers, it will cross three separate zones,
each with an important task. When the wave hits the first zone,
the reaction zone, Y-shaped proteins called antibodies
will grab onto any HCG. Attached to these antibodies
is a handy enzyme with the ability to turn on dye molecules,
which will be crucial later down the road. Then the urine picks up
all the AB1 enzymes and carries them to the test zone,
which is where the results show up. Secured to this zone are more
Y-shaped antibodies that will also stick to HCG
on one of its five binding sites. Scientists call this type of test
a sandwich assay. If HCG is present, it gets sandwiched
between the AB1 enzyme and AB2, and sticks to the test zone, allowing the attached dye-activating
enzyme to do its job and create a visible pattern. If there’s no HCG, the wave of urine
and enzymes just passes on by. Finally, there’s one last stop to make,
the control zone. As in any good experiment, this step confirms that
the test is working properly. Whether the AB1 enzymes never saw HCG, or they’re extras because Zone 1
is overstocked with them, all the unbound AB1 enzymes picked up
in Zone 1 should end up here and activate more dye. So if no pattern appears,
that indicates that the test was faulty. These tests are pretty reliable,
but they’re not failproof. For instance, false negatives can occur if concentrations of HCG
aren’t high enough for detection. After implantation, HCG levels double
every two to three days, so it may just be too early to tell. And beverages can dilute the urine sample, which is why doctors recommend taking
the test first thing in the morning. On the other hand, false positives
can come from other sources of HCG, like IVF injections, ectopic pregnancies, or certain cancers such as uterine cancer
or testicular cancer, making it possible for one of these tests
to tell a man he’s pregnant. The best way for a woman to find out
for sure is at the doctor’s office. The doctors are also looking for HCG, but with tests that are more sensitive
and quantitative, which means they can determine
the exact level of HCG in your blood. A few minutes can feel like forever when you’re waiting on the results
of a pregnancy test. But in that brief time, you’re witnessing
the power of the scientific method. That one little stick
lets you ask a question, perform a controlled experiment, and then analyze the results
to check your original hypothesis. And the best part is you won’t even
have to wait until the next harvest.

Comments (100)

  1. What about 5000IU pure hcg powder dissolve in 1 ml water, and test such high concentration hcg water? What will happen?

  2. Of both wheat and barley grow at the same time, it's a gae..


  3. My favorite pregnancy test to use is “wait like 20wks and see if I get a baby bump”

  4. So women be making sandwiches even when they not

  5. I came to the wrong side of YouTube again :/

  6. Excellent delivery, pleasant animation….good job

  7. I’m not like pregnant or thinking I might be pregnant yet here I am

  8. Which seeds
    one is weat and other..?????

  9. Mr. Nguyen? Tien Nguyen is my Spanish teacher’s name. Is it him?

  10. Is Tien Nguyen a Vietnamese?


  12. I honestly didn't get the humor in the last sentence

  13. If i had my period, there's no way im pregnant right?

  14. So I can buy an ELISA test kit on walmart…cool

  15. 2:04 me when playing basketball

  16. Could’ve used this before my GCSE but whatever

  17. Hold on, why is the man taking a pregnancy test?


  19. why does it smell something funny on these parts?
    1:39 – 2:30
    do i have a problem with my "smellilatory" senses or is it just my brain?

  20. I thought In the thumbnail was a box cutter ?

  21. I can't say I have understood all the process in all honesty.

  22. I’m going to be sick after watching this video.

  23. Why does that doctor look so smug?

  24. wait so in the future what is the pregnancy test

  25. when you watch this on your period wishing you where pregnant

  26. I was srsly going to search this yesterday ?

  27. I wonder if an Egyptian would know what to do if you handed one a modern pregnancy test.

  28. Wait.. Why is a man taking a pregnancy test?!

  29. Where do you put it?

  30. They just take your baby and give you another one

  31. This is a big coincidence. My sister's classmate is named Tien Nguyen.

  32. I don’t know why I’m watching this, school taught us it for our exam

  33. If you had to wait to the next harvest for a pregnancy test, wouldn't you already know by then?

  34. Lesson by a Vietnamese person ?!!

  35. Why am I here and I'm not even teen yet.

  36. When I was pregnant, the doctor said that their tests don't differ that much from the over-the counter ones. I guess it varies

  37. 216 216 216!!!!!!!!

  38. I'm an 11 year old boy. Why did I get this in my recommended

  39. How to make sure it works

    Get a girfriend

  40. Well, ectopic pregnancies aren't false positives. They're pregnancies too.

  41. "Mom I'm pregnant."

    Mom: I'm so proud of you! Your father always wanted a 2nd child.

    Sweet Home Alabama

  42. Uhhhh…..Youtube…..?

  43. I actually never wondered about this till it popped up on my recommendations list lol

  44. maybe someone girlfriend is pregnant…..

  45. This video is excellent! It's exactly what the lecturers teach in med school, and public should also know about this

  46. Me: I live vloggers, conspiracy theories, Marvel cracks and let's plays.

    Youtube: So tHis Is hOw PrGNANcy TEsts wOrk

  47. 3:47 she shoved the blood inside her and said yup your pregnant

  48. H – Hello
    C -Creepy
    G – Grandma

  49. 3:40 oops I forgot my pants oh well

  50. Too think we men are always shed to tears whenever we hear that our wives are pregnant

  51. GIRLS u pee on it its more simple

  52. I thought you just put the white end in the mouth and wait

  53. I'm a boy/why am I here/why YouTube recommendation/??

  54. Still trying to white wash African Egyptian

  55. Yeah i surely need to know this.

  56. Who else though that thing on the thumbnail was a sharp cutter ti cut the bekky open and take out the baby? No, only me? Okay…

  57. I saw a Vietnamese name so I clicked

  58. Just imagine a guy gets a positive on a test

    "Mom, am i a girl?"

  59. I thought it said Teen Nyguyen.

  60. The person who invented pregnancy test should have won the noble prize that year, he probably didn't win it because he was a Chinese

  61. Dear YouTube,

    I watch the whole video you happy now?

  62. egyptians were really smart????

  63. Ok now i know everything

  64. I'm only 10, why am I watching dis? ???

  65. What ?? am?? I?? Watching?? Right?? Now?? ???

  66. Im.not pregnant or anything, but when they mentioned waiting I got nervous asf

  67. Why is this on my recommendation????

  68. Wow…thankyou…
    Making it easy! ?

  69. Here's a pregnancy text. Wait two month. No period means baby. Period means no baby

    This is obviously a joke and it doesn't always work that way

  70. What does it mean to have one stand in pregnancy kit

  71. There is nothing more dangerous then a pregnancy news

  72. I'm not married, I haven't even committed to any man…but I'm here, watching vids like these and excited to try a pregnancy test and get a positive ??

  73. Damn even the people back then were smarter then me ??

  74. That's my mom full name!

  75. Man takes pregnancy test. Results positive. Congrats you have testicular cancer!

  76. Who questions BC it means Before Christ

  77. There is a vision test on the wall..I didn't know that pregnancy affects vision.

  78. I thought the thumbnail was a knife.

  79. Me: " Yeah, I've performed a controlled experiment ? "
    Teacher: " Oh, what was it? "
    Me: " aha.. pregnancy test "

  80. Why am i watching this im a dude..

  81. After watching this HCG adventure i still don't understand this.. Anyways , if you're pregnant, you're pregnant . If you're not , you're not .

  82. 70% is huge !!!
    Props ancient Egypt


  84. Microbes in Ted Ed are so cute!!

  85. is there a reason all your videos are so fkn quiet TED-ed?

  86. Lily’s Gardan explains it all

  87. please translate into other langauges like hindi, aasami etc.

  88. Why is this recommended for me

  89. 3:37 best part???????

  90. Why am I watching this I’m 12

  91. Creativity gud concept …thanq madam

Comment here