Which pregnancy test is best for you?

No single test is best for everyone. The question of which pregnancy test is best has no brand name as its answer. What does differ per test: how sensitive it is, and how well you read the result. In a comparison of eight tests, two scored under 50 percent agreement.

That is the point most comparison lists leave out.

What actually separates one test from another

Every pregnancy test measures the same hormone: hCG. That hormone only starts rising after implantation. So the difference is not what they measure, but from which level they can see it.

That threshold is called sensitivity and is given in mIU/ml. A test rated 10 mIU/ml responds earlier than one rated 25 mIU/ml. Something far more ordinary also counts: whether you read the result correctly.

Which pregnancy test is the most reliable?

In 2015, researchers tested eight over-the-counter kits. They used urine samples with known hCG levels of 0, 15 and 25 mIU/ml. Results were read by a technician and by 72 women. Neither group knew the expected answer.

The spread was wide.

Percentages show agreement with the result expected at that hCG level. The authors put it bluntly: many tests are not as accurate as their packaging claims.

One caveat belongs with it. The study was co-run by employees of the company that makes Clearblue. Clearblue came out on top. That does not make the measurements worthless, but it is worth weighing.

Something else appears on no packaging at all. There are no international standards for how home-test accuracy must be demonstrated. A CE mark therefore says little about measured sensitivity.

Is Clearblue better than a supermarket test?

In that study Clearblue scored higher than most other brands, mainly on readability. Dutch drugstore own-brand tests were not included, so it says nothing about those.

What you can take from it is this. A digital test showing "pregnant" or "not pregnant" leaves less room for doubt than two faint lines. If you are reading it with shaking hands, that matters.

What is the best day to take a pregnancy test?

The longer you wait, the more reliable any test becomes. That is down to implantation, not the test.

In a study of 221 women, hCG appeared in urine only 6 to 12 days after ovulation. In 84 percent it showed on day 8, 9 or 10.

That spread explains why early testing is so erratic. Test before implantation is complete and there is nothing yet to measure. The number of days you wait does more for certainty than the brand on the box.

An example. Two women test twelve days after ovulation, on the same morning. For one the embryo implanted on day 8, for the other on day 11. The first sees a clear line, the second sees nothing.

They are equally pregnant. Their hCG is simply a few days out of step. The first may already be above the 25 mIU/ml a standard test responds to. The second is still below it.

The day your period is late is a practical turning point. A week late, hCG in an ongoing pregnancy sits well above the threshold of any common test.

A faint line: are you pregnant?

A faint line counts as a positive result. The test is seeing hCG, just not much of it.

One exception causes a lot of confusion: the evaporation line. Look after half an hour and dried urine can leave a greyish mark. So read the result within the time the leaflet gives.

If you are unsure, testing again after two days usually settles it. hCG roughly doubles every two days at this stage, so a real line gets darker.

When a blood test shows more than a urine test

A urine test gives yes or no. A blood test measures how much hCG there is, as a number.

That matters when a further question sits underneath. For example how far along you are, or how a value is developing. Blood or urine: the difference covers when each adds something. hCG levels in early pregnancy explains what the numbers mean.

If you had light bleeding around your expected period, implantation bleeding or period helps place it. The marker itself is described at b-hCG, and the pregnancy blood test measures it in blood.

If the result is positive, Thuisarts.nl sets out the first steps. If a result leaves you unsure, discuss it with your GP or midwife.

If you ask us where most of the confusion comes from, it is not the brand. It is when someone tests, and how the line gets read afterwards.

Frequently asked questions

Which pregnancy test is the most sensitive?

Tests rated at 10 mIU/ml respond earliest. That threshold is printed on the box but is not independently verified. Read it as a claim.

Can you take a pregnancy test during the day?

You can. Urine is most concentrated in the morning, which helps if you are testing early.

How reliable is a test once your period is late?

From the day your period is late, any common test is sensitive enough in an ongoing pregnancy.

Can a test be negative while you are pregnant?

Yes, mainly with early testing or very dilute urine. If your period stays away after a negative test, contact your GP.

References

• Johnson S, Cushion M, Bond S, Godbert S, Pike J. Comparison of analytical sensitivity and women's interpretation of home pregnancy tests. Clin Chem Lab Med. 2015;53(3):391-402. PMID 25274958
• Gnoth C, Johnson S. Strips of Hope: Accuracy of Home Pregnancy Tests and New Developments. Geburtshilfe Frauenheilkd. 2014;74(7):661-669. PMID 25100881
• Wilcox AJ, Baird DD, Weinberg CR. Time of implantation of the conceptus and loss of pregnancy. N Engl J Med. 1999;340(23):1796-1799. PMID 10362823
• Thuisarts.nl, information on pregnancy and first steps

Every blood test result includes a professional assessment from a BIG-registered doctor. For treatment decisions, discuss your results with your GP.