Home pregnancy test or ultrasound: what each one tells you

How home pregnancy tests work

A home test looks for human chorionic gonadotropin (hCG) in your urine. The placenta starts making it soon after the fertilized egg attaches to the lining of the uterus (Mayo Clinic). It appears in blood and urine as early as 10 days after conception (MedlinePlus). A standard home test is qualitative: it tells you whether your hCG is raised, not how much there is (FDA).

When a test can turn positive

Weeks of pregnancy are counted from the first day of your last period, so when your period is late you’re already about 4 weeks pregnant (Cleveland Clinic). Some tests can turn positive before then (FDA), but most over-the-counter tests won’t show a pregnancy until your period is late (MedlinePlus).

Even then, a negative isn’t final. On the first day of a missed period, the FDA says, 10 to 20 of every 100 pregnant women won’t detect their pregnancy. It explains why: many women have irregular periods, and may miscalculate when their period is due. For the most reliable result, it says, test 1 to 2 weeks after a missed period (FDA).

Biology sets a limit, too. In a North Carolina study from 1982 to 1986, 221 healthy women aged 21 to 42 who were planning a pregnancy gave first-morning urine samples, which a lab tested with an extremely sensitive hCG assay. Of 136 clinical pregnancies with data, 14 (10%) hadn’t implanted by the first day of the missed period: the day each woman expected her period, based on the usual cycle length she reported. So even an ideal hCG test would catch at most about 90% of these pregnancies that day, the authors estimated, and 97% a week later (Wilcox and colleagues, JAMA, 2001).

Reading the result

• Use first-morning urine, when it’s most concentrated, and don’t drink a lot beforehand (Mayo Clinic, Cleveland Clinic).
• Check the date, the timing and the control line. Don’t use an expired test or read it early. If the control line or symbol doesn’t appear, the test isn’t working (Mayo Clinic).
• A faint line can still be a positive. An evaporation line is different: it can appear if you check the test after the urine has dried (Cleveland Clinic).
• Unsure? Test again after several days. hCG rises quickly, so a later test may be positive (FDA). Still unsure after several tests? Call your doctor or midwife.

Some digital tests add an estimate of weeks since conception (Clearblue). How far along am I? explains what that reading counts.

How accurate are home pregnancy tests?

Many tests claim to be 99% accurate, but they differ in how well they find a pregnancy soon after a missed period (Mayo Clinic). MedlinePlus puts urine tests at 97% to 99% accurate a week or two after a missed period (MedlinePlus). The NHS sums it up: “A positive test result is almost certainly correct. However, a negative test result is less reliable” (NHS).

When a test says no, but you’re pregnant

Testing too early is the main reason for a false negative, says Cleveland Clinic: the placenta may not have made enough hCG yet (Cleveland Clinic, FDA). Dilute urine or reading the result too soon can also miss it (MedlinePlus, Mayo Clinic). If the negatives continue and your period still doesn’t come, see your doctor or midwife: a blood test may be more accurate, and some health problems can also cause missed periods (Mayo Clinic).

When a test says yes, but you’re not

That’s rare, say Mayo Clinic and Cleveland Clinic (Cleveland Clinic). Causes include fertility medicine that contains hCG, if you test soon after taking it, problems with the ovaries, and menopause. Most medicines, including antibiotics and birth control pills, don’t affect the result (Mayo Clinic). Rarely, a condition not related to pregnancy raises hCG (MedlinePlus, Cleveland Clinic).

A positive test, then a period

A positive test followed by a period can be a very early miscarriage, sometimes called a chemical pregnancy: a loss before the fifth week, before the pregnancy can be seen on an ultrasound. Cleveland Clinic calls these losses “very common” (Cleveland Clinic). The test wasn’t wrong; the pregnancy ended very early.

In the North Carolina study, lab tests of daily urine samples over 707 menstrual cycles found 198 pregnancies, and 22% ended before the pregnancy was detected clinically. Most of those losses would not have shown up on the less sensitive tests of earlier studies. Of the 40 women who had one, 95% became clinically pregnant within two years (Wilcox and colleagues, New England Journal of Medicine, 1988).

However early, it can be a real loss: “Each experience is valid,” says Cleveland Clinic. Tell your doctor or midwife about a positive test followed by bleeding. With heavy bleeding, severe pain, shoulder-tip pain or feeling faint, call 911 (999 in the UK) or go to the emergency room now. Postpartum Support International’s HelpLine, 1-800-944-4773, offers support and resources, and PSI runs online support groups, including for pregnancy loss (PSI). Pregnant again? Pregnant after a loss is written for you.

A positive test can’t show where the pregnancy is

In an ectopic pregnancy, the fertilized egg implants and grows outside the main cavity of the uterus, most often in a fallopian tube. “If you take a pregnancy test, the result will be positive,” says Mayo Clinic, though the pregnancy can’t proceed normally (Mayo Clinic). In the U.S., that’s 1% to 2% of pregnancies (AAFP, 2019). Locating it is a job for a medical ultrasound: NICE tells doctors in England not to use hCG blood results to work out where a pregnancy is (NICE).

In the UK, call 999 or go to A&E for any of these symptoms. The NHS in England says to call 999 or go to A&E for a combination of sudden, intense tummy pain, feeling very dizzy or fainting, feeling sick, or looking very pale (NHS). If you’re pregnant and bleeding, it says to call 999 for any of the symptoms in the box. For light bleeding or spotting with no or only mild pain, it points you to your maternity unit, an early pregnancy unit or NHS 111 (NHS).

What a blood test adds

A qualitative blood test gives a yes or no; a quantitative one measures the exact amount of hCG. Blood tests can find very small amounts and show a pregnancy before a missed period. But they aren’t commonly used just to check, because urine tests are cheaper, very accurate and quicker (MedlinePlus).

Their real use is following a pregnancy over time. When a test is positive but a medical scan can’t yet show where the pregnancy is, AAFP’s review recommends repeat quantitative hCG tests and ultrasound, with close monitoring of symptoms, for people who are stable (AAFP, 2019). Leave the sums to your doctor or midwife; No heartbeat on an early ultrasound explains this “pregnancy of unknown location” and how the repeat tests are timed.

What a medical ultrasound adds

A medical ultrasound, ordered by your doctor or midwife, answers questions a pregnancy test can’t. The U.S. practice guideline from radiology, obstetric and ultrasound societies lists first-trimester reasons for one, including (ACR–ACOG–AIUM–SMFM–SRU):

• Where the pregnancy is: confirming it’s in the uterus, or looking into a suspected ectopic pregnancy.
• A heartbeat: confirming cardiac activity.
• How many babies. Can you see twins at 6 weeks? explains when a scan can tell.
• How far along: ACOG calls first-trimester ultrasound measurement “the most accurate method to establish or confirm gestational age,” to within 5 to 7 days (ACOG Committee Opinion 700).
• Pain or bleeding: looking for the cause.

No scan checks for everything. Even the detailed screening scan offered in England, usually at 18 to 21 weeks, checks for signs of 11 conditions, and the NHS says it “cannot find all conditions” (NHS).

Doctors use “confirmed” with care. A 2024 lexicon from a multisociety panel convened by the Society of Radiologists in Ultrasound treats a yolk sac inside a sac in the uterus as “incontrovertible evidence of a pregnancy.” An empty sac is reported as a probable pregnancy (Society of Radiologists in Ultrasound, 2024).

Why a medical scan can’t confirm a pregnancy before about 5 weeks

On an internal scan, the lexicon says, the sac is “typically visualized at 5 weeks,” counted from the first day of your last period. The yolk sac follows at about 5½ weeks, and an embryo with a heartbeat typically at 6. A scan over the belly shows each about a week later (AAFP, 2009).

So can an ultrasound detect a pregnancy before a missed period? Usually not. A missed period comes at about 4 weeks, a week before a sac typically shows, and in the North Carolina study, 1 in 10 of the clinical pregnancies hadn’t even implanted by then. The hormone comes first. How early can an ultrasound see a pregnancy? goes week by week.

A scan that shows little or nothing after a positive test can simply mean it’s early. It can also be a sign of a problem, such as an early loss or an ectopic pregnancy, and only your doctor or midwife can tell which. Tell your doctor or midwife, even if you feel well.

Which to use, and when

If you feel well, this order works:

1. Take a home test from the first day of a missed period, or at least 21 days after unprotected sex if you don’t know when your period is due (NHS).
2. Positive? Call your doctor or midwife. You might need a blood test or a medical ultrasound to confirm the pregnancy (Mayo Clinic). In England, you can refer yourself to an NHS midwife (NHS).
3. Have the medical scan when it’s due. In the U.S., Cleveland Clinic says to expect your first prenatal visit at 8 to 10 weeks, and it may include an internal ultrasound (Cleveland Clinic). In England, a dating scan is offered at around 10 to 14 weeks (NHS). Why your first prenatal appointment isn’t until 8 to 12 weeks explains the wait.
4. Be seen sooner if there’s a reason. Pain and bleeding are listed reasons for a first-trimester medical scan (ACR–ACOG–AIUM–SMFM–SRU). So is a past ectopic pregnancy: the NHS advises telling your GP early, “so early scans can be carried out” (NHS).

With severe pain, heavy bleeding, shoulder-tip pain or feeling faint, skip these steps and follow the emergency box above.

Where an elective scan fits

An elective (keepsake) scan is one you book yourself, to see the pregnancy. It isn’t medical care.

They aren’t allowed everywhere: Connecticut requires a medical purpose and an order, and Germany has banned non-medical scans in pregnancy since January 2021. Can you get a pregnancy ultrasound without a doctor’s referral? has the sources and compares the two kinds of scan.

The FDA says ultrasound used only for non-medical reasons, such as keepsake videos, “has been discouraged,” and the American Institute of Ultrasound in Medicine (AIUM) “strongly discourages the nonmedical use of ultrasound” (FDA, AIUM). ACOG says ultrasound should be used only to answer a relevant clinical question or otherwise bring a medical benefit (ACOG Committee Opinion 723). Safety, in plain words has their statements, and Is an early ultrasound safe for the baby? weighs the evidence.

In the U.S., coverage turns on the medical reason. One Medicaid plan’s 2026 policy calls scans done only to learn the baby’s sex or to give parents photographs not medically necessary (Louisiana Healthcare Connections).

What each one costs

In the U.S., a home test costs from under $1 to about $15, GoodRx said in 2022, and Planned Parenthood says $1 to $15 (GoodRx, 2022, Planned Parenthood). GoodRx added that health departments, federally qualified health centers and family planning clinics may offer free tests. In England, sexual health services do (NHS). For scan prices, see what an early pregnancy ultrasound costs without insurance.

Seeing it for yourself, in Glendale

Confirming a pregnancy is your doctor or midwife’s job. Our Pregnancy Check is for seeing it: a short, private 2D ultrasound in the first 10 weeks, at our studio in Glendale, Los Angeles County. It takes a few minutes. On a big screen, we point out what you’re looking at and tell you what we could and couldn’t see. You leave with 8 black-and-white prints. It’s one price, $100, with no referral or insurance.

Call (818) 243-7010 first with the first day of your last period, and we’ll say whether it’s a good day to come. If it’s too early to see, you come back for a second look, almost always at no charge. Little or nothing on the screen can simply mean it’s early, but it can also be a sign of a problem, and only your doctor or midwife can tell which. Tell your doctor or midwife, even if you feel well. Same-day appointments are often available.

Our lead sonographer, Irina, has nearly two decades of experience and more than 30,000 pregnancy ultrasounds. We can’t diagnose, date a pregnancy, check on your health or replace prenatal care. See what a Pregnancy Check includes, or where to start after a positive test.

Got a due date, or an estimate? Try it in the planner: it lists the sessions ready for you now and the ones that open later, and keeps what you enter on your device.

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