Today I thought I'd clear up some of those long-standing myths. We're going to talk about how to properly read pregnancy tests and ovulation predictor kits (OPK's), what they're measuring, and what the differences are between them. They may physically appear to look the same, but they are interpreted and read very differently.
TYPES OF PREGNANCY TESTS
First of all, let's acknowledge that not all pregnancy tests look equal. Some are digital, others are merely itty bitty test strips; some have a "plus" sign for positive, others two lines; some use pink dye, while others use blue. Despite the myriad of forms a pregnancy test can take, they all measure the same thing: hCG, or Human Chorionic Gonadotropin. You can spend $15 on a digital test or (my personal favorite) --they will tell you the same results. True, some are more sensitive than others (we won't get into that here), but trust me when I tell you there is functionally NO difference between a fancy shchmancy digital test and the "buy in bulk" kind .
HOW DO PREGNANCY TESTS WORK?
On [non-digital] pregnancy tests, you'll have a control line and a test line. The Control line will show up regardless of positive or negative test results to give you something to compare; the Test line will only show up if the test is positive. Here is the catch with pregnancy tests: a line is a line. It doesn't matter if it's the faintest of all lines, if it's there (and it's not an evap--see above), then it counts and you are in the early stages of pregnancy. It does not have to be as dark as the Control line, although if you were to keep testing for a few weeks you'd probably see it get even darker than the Control line as your hCG increases.
Typically, most women will see a faint line by 10 DPO (days past ovulation). If you are not charting with the Fertility Awareness Method, you may not know the exact date of ovulation. If you are charting, though, and you're wondering how early you can test, I would recommend starting no sooner than 9 DPO--preferably 12 DPO as you are more likely to get a clearer read.
If you see a line so faint that you think you might be seeing things (we jokingly refer to this as "line eye"), then wait two days, let your hCG increase, and test again.
TROUBLESHOOTING PREGNANCY TESTS
That means the test is invalid and defective. Throw it away and take a new test.
I took a pregnancy test and there was a strong Test line that showed up right away. I've taken three more over the course of a week and the Test line is fading. Why?
Unfortunately, this is usually the result of a chemical pregnancy, failed implantation, or early miscarriage. Basically, your body started producing hCG for a pregnancy, but instead of the levels rising higher and higher, they started to decrease instead. Depending on your circumstances, you may want to see your OB-GYN.
I'm 23 weeks and just took a pregnancy test for fun. It wasn't a very strong Test line, and definitely not as strong as my first tests I did when I found out I was pregnant. Should I be worried?
You shouldn't be worried on the basis of the test alone--it's completely normal for hCG production to slow down drastically at the end of the first trimester, as the placenta takes over production of progesterone. This means that pregnancy tests when you're "more" pregnant may, ironically, show a fainter line. As long as you don't have any other concerns for your or your baby's health, it's absolutely nothing to worry about.
I took a pregnancy test and it was negative. My usual Luteal Phase length is 12 days, but I confirmed ovulation for this cycle and my current LP is 15 days! What could be going on?
This is more of a rare scenario that most people are unlikely to run into, and also one that almost everyone but a diehard FAM charter might miss. Usually, your LP is only sustained by pregnancy. If there's no pregnancy, your temperatures drop and menstruation starts. Sometimes, though, ovarian cysts can cause elevated temps and lengthened Luteal Phases. You'll want to get some testing done with your OB-GYN.
Hopefully this has helped clear up some pregnancy test confusion! Let's switch gears and talk about OPK's.
TYPES OF OPK'S
HOW DO OPK'S WORK?
HOW DO YOU READ AN OPK?
Considering the way an OPK works, that is actually to your benefit. Remember that you're trying to "catch" your LH surge before ovulation--typically, your OPK pattern in the few days before ovulation will be light, light, darker, darker, until BAM! POSITIVE right before ovulation, then lighter, lighter, gone. The tests are designed to show you the progression of the LH surge over the course of several hours or days.
So unlike pregnancy tests, where you'll likely only need to take one or two and they'll be a few days apart, you'll take OPK's daily (and sometimes several times a day) in the few days before ovulation. Of course, it's most helpful if you're charting so that you can pinpoint which days would be most useful to test for when you're nearing ovulation.
Also, keep in mind this important difference between pregnancy tests and OPK's: while a pregnancy test is a sure bet on the positive unless it's an invalid test or evap line, a positive progression of OPK tests does NOT guarantee that you ovulated. Tricky, I know. But technically, your body can produce LH surges in preparation for ovulation, or produce an LH surge without sufficient estrogen to actually tip the scale and release an egg. So while an OPK test set will tell you that you did indeed have an LH surge, it will not (and cannot) ever guarantee that you ovulated. That is why I recommend relying on your primary fertility signs (BBT and cervical fluid) to confirm ovulation first and foremost, and using OPK's as an additional confirmation--much like cervical position. Remember, they are called Ovulation Predictor Kits, not Ovulation Confirming Kits.
A word of advice for those who are using OPK's to time pregnancy efforts: keep in mind that by the time you see a positive OPK, it's likely that your egg has already been released or will be released within hours. The egg lives only 12-24 hours from the time of release, then dies if it has not been fertilized with sperm. What this means is that you should be looking to have sex in the few days before ovulation, as your test lines get darker and darker. Of course, it is way easier to pinpoint ovulation and fertile days if you learn to chart your fertility signs and not simply rely on OPK's.
Two common possibilities: you're not producing enough LH to trigger ovulation, or you're not testing at the right time in your cycle. If you're charting, I would recommend starting to use OPK's 2-3 days before expected ovulation, or when you start to see egg white cervical fluid. If you're not charting, wait a few days and try testing again.
I took some OPK's and got a light-dark-light test line progression over a couple days. But my temperature hasn't shifted yet, and it's still going up and down. Why?
Most likely, your body did have and LH surge but didn't ovulate. This can be a pretty common occurrence, especially if you have irregular or long cycles, are just coming off of hormonal birth control, just had a baby, or any number of other things that can disrupt your hormonal balance. Remember that OPK's cannot confirm ovulation, only predict when it is most likely to be happening.
MAIN DIFFERENCES BETWEEN PREGNANCY TESTS AND OPK'S