How soon can i test for pregnancy after missed period

If you’re trying to get pregnant, the best time to take a pregnancy test is one week after you’ve missed your period. Why? Because this is really the best way to prevent a false negative result (a negative test in someone who's actually pregnant) result.

Home pregnancy tests can be used as early as the first day after your first missed period in women with regular/predictable monthly menses. If you have irregular periods, you can administer a test 14 days after intercourse, since you likely can’t pinpoint your exact time of ovulation.

Pregnancy tests detect a hormone called human chorionic gonadotropin (HCG), which is produced in early pregnancy. The production of this hormone begins slowly and increases as the pregnancy grows. Standard urine pregnancy tests will detect the HCG level when it reaches 20-50 milliunits/milliliters.

If you take a test too soon (before you've missed your period), the levels of HCG may not be high enough to detect a pregnancy and it could cause a negative result, even though you're actually pregnant.

I advise my patients to wait at least one day after you miss your period. If you wait one week after a missed period, the chance of a false negative is very low if you have a normal monthly menstrual cycle.

Brand name versus generic pregnancy tests

Home pregnancy tests, both brand name and generic, are very accurate at detecting the HCG hormone and any positive result, even a faint line, can be considered positive. HCG is only produced by a pregnancy; any positive result indicates a pregnancy.

You don’t need a serum (blood) pregnancy test to confirm pregnancy. Both urine and blood detect HCG, although the blood test is more sensitive and can detect HCG levels at much lower levels than a urine test. In certain situations, your doctor may want to perform a blood HCG test but it’s not typically needed to confirm a pregnancy.

Although most tests advertise 99% accuracy, the ability of a particular brand to detect HCG at levels less than 50 ml may vary. Some brands may be better able to detect lower levels of HCG than others. If your HCG level is more than 50 ml, which is the detection rate of most tests, even generic tests will detect a pregnancy accurately.

How to prevent a false negative result

The number one cause of a false negative test is taking the test too soon after you conceive. Also, if you don’t follow the test instructions carefully, it could affect your result.

Urine, even in women who drink large amounts of water, should still yield a positive result. But urine shouldn’t be diluted with water before taking a test. A good time to take the test is in the morning when you first wake up.

If a test is negative in a woman who suspects she’s pregnant or if she has irregular cycles, she should repeat the test in one week.

Medications and test results

Medications don’t typically interfere with results, neither causing false positive nor false negative. Only a medication containing HCG would affect the result.

When to see your doctor

Although home tests can detect a pregnancy, it gives no information as to viability. It’s important to make an appointment with your doctor to confirm your pregnancy and to detect a fetal heart rate through an ultrasound (usually at six to 10 weeks). If you have a positive pregnancy test, your obstetrician can provide information about warning signs of an abnormal or worrisome pregnancy and can advise you on when to make an appointment to confirm your pregnancy.

Since the earliest recorded history, women have had a strong desire to know whether they are pregnant as early as possible. The body goes through countless changes in the first trimester, and one of the first indicators is a change in the hormones that leave the body through urine.

Ancient Egyptians relied on a form of urine testing to determine pregnancy status way back in 1350 BCE. A woman urinated daily on wheat or barley seeds and if the plants grew, it meant she was pregnant. Modern-day validation suggests that test was about 70% accurate in detecting human chorionic gonadotropin (hCG), a hormone produced by a woman’s body soon after implantation of a fertilized egg inside the uterus.

Thankfully, urine-based pregnancy tests have evolved substantially. Women now have access to advanced tests that can detect a pregnancy as early as eight days after ovulation. But while many home pregnancy tests are marketed as simple and effective, getting accurate results comes down to how early in your ovulation cycle you take the test.

Ovulation generally occurs around day 15 of a 28-day cycle. In a normal pregnancy, an egg is fertilized in the fallopian tube and then travels into the uterus, where it implants in the uterine wall. After implantation, production of hCG starts from cells in the developing placenta (tissue that will feed the fetus). Trace levels of hCG can be detected as early as eight days after ovulation.

That means you could get positive results several days before you expect your period to start. However, the first part of your cycle is more variable than the second, making it tricky to determine the best time for an early test.

“Thankfully, pregnancy tests have evolved substantially since the 20th century. Women now have access to advanced tests that can detect a pregnancy as early as eight days after ovulation.”

When to take a home pregnancy test

The length of time from the first day of a period to ovulation can vary by several days from month to month. Sexual activity around ovulation leads to the possibility of fertilization of an released egg by sperm. But even then, the time frame for a fertilized egg to implant can vary. And hCG isn’t produced until after implantation has occurred.

For the most accurate results, we recommend testing in the morning on the day you expect your period to start. This allows for variability in the timing of ovulation, fertilization, and implantation. Testing in the morning provides a more concentrated urine sample.

Follow the directions carefully to get the best results. Before you take the test, make sure you understand what the readout for “pregnant” and “not pregnant” will be. Some tests still use two lines to indicate you are pregnant and one to indicate that you aren’t. However, many tests have switched to words such as “yes” and “no”, or “pregnant” and “not pregnant” for additional clarity.

Related reading: Is it OK to use a hot tub during early pregnancy?

Pregnancy test accuracy

Each type of pregnancy test is designed to detect a set minimum level of hCG. This is why pregnancy test manufacturers advertise the way they do: “Know four days sooner,” or “Accurate up to six days before a missed period.” However, while home pregnancy tests are quite accurate – many boast a 99% detection rate based on laboratory testing results – marketing claims can be misleading.

For example, a 99% detection rate means a test can detect hCG 99% of the time on the day you miss your period. These statistics also assume that women are testing at the optimal time and following all instructions correctly.

Many home pregnancy tests available today are midstream urine dip tests, which are the traditional “pee-on-a-stick” tests and are fairly easy to use. There also are tests in which you pee into a cup and dip a test strip into the urine. The New York Times published a story ranking the best home pregnancy tests, citing a midstream test with an ergonomic grip as the easiest to use and most accurate.

Research has shown that average test results when women used the dip tests matched lab test results just 70% of the time, whereas 99% of women typically can get an accurate reading from a midstream test.

False positive and negative results

When a test result is inaccurate, it’s either a false negative (the test says you are not pregnant, but you are) or a false positive (the test says you are pregnant, but you aren’t). Several factors can cause false negative results:

• Having too dilute urine after drinking a lot of water or testing later in the day.
• Testing too soon when there has not been enough time for a fertilized egg to implant and start hCG production.
• Using a pregnancy test that doesn’t detect lower levels of hCG. You can check the package insert for more information about the level at which the test will be positive.

Sometimes an egg will implant briefly but will not be sustained. This is also called a chemical pregnancy – hCG is produced, but the pregnancy doesn’t continue. A test performed several days before an expected period can show a positive result, but the woman still gets her period soon or on time. Rarely, certain tumors can produce hCG, causing a pregnancy test to be positive even when a woman is not pregnant.

Related reading: It's not your fault: Understanding miscarriage

When to see a doctor

Most women who have a positive pregnancy test should wait a week or two before calling the Ob/Gyn office for a pregnancy blood test or ultrasound to confirm the pregnancy. We suggest waiting because the rate of early pregnancy loss is high, and it’s possible that you might have had a chemical pregnancy.

However, women with a history of ectopic pregnancy or current abdominal pain should call the doctor right away to be examined. Ectopic pregnancies implant outside of the uterus and produce hCG, resulting in positive pregnancy tests. However, these pregnancies can cause abdominal bleeding and prompt medical care is necessary. Women who have congenital heart defects or other chronic physical or mental health conditions should also see a doctor right away because treatment plans or medications might need to be altered to protect the woman and the fetus.

Advances in home pregnancy tests give women greater insight into what’s going on in their bodies sooner than ever before. No matter what your childbearing plans might be, it’s essential to get quick, accurate results at home to plan your next steps accordingly.

To visit with an Ob/Gyn, call 214-645-8300 or request an appointment online.