Pregnancy Test

At the beginning of the s, Hillel Shapiro and Harry Zwarenstein, who were researchers at the University of Cape Town, discovered that if urine from a pregnant female was injected into the South African Xenopus toad and the toad ovulated, this indicated that the woman was pregnant.

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This test was used throughout the world from the s to s, with Xenopus toads being exported live in great numbers. The test for pregnancy which can give the quickest result after fertilisation is a rosette inhibition assay for early pregnancy factor EPF. EPF can be detected in blood within 48 hours of fertilization. Most chemical tests for pregnancy look for the presence of the beta subunit of human chorionic gonadotropin hCG in the blood or urine.

Most home pregnancy tests are based on lateral-flow technology.

With obstetric ultrasonography the gestational sac sometimes can be visualized as early as four and a half weeks of gestation approximately two and a half weeks after ovulation and the yolk sac at about five weeks' gestation. The embryo can be observed and measured by about five and a half weeks. The heartbeat may be seen as early as six weeks, and is usually visible by seven weeks' gestation. A systematic review published in showed that home pregnancy test kits, when used by experienced technicians, are almost as accurate as professional laboratory testing Improper usage may cause both false negatives and false positives.

False negative readings can occur when testing is done too early. Quantitative blood tests and the most sensitive urine tests usually begin to detect hCG shortly after implantation, which can occur anywhere from 6 to 12 days after ovulation. Menstruation occurs on average 14 days after ovulation, so the likelihood of a false negative is low once a menstrual period is late.

Ovulation may not occur at a predictable time in the menstrual cycle , however. A number of factors may cause an unexpectedly early or late ovulation, even for women with a history of regular menstrual cycles. Using ovulation predictor kits OPKs , or charting the fertility signs of cervical mucus or basal body temperature give a more accurate idea of when to test than day-counting alone.

The accuracy of a pregnancy test is most closely related to the day of ovulation, not of the act of intercourse or insemination that caused the pregnancy. It is normal for sperm to live up to five days in the fallopian tubes , waiting for ovulation to occur. False positive test results may occur for several reasons, including errors of test application, use of drugs containing the hCG molecule, and non-pregnant production of the hCG molecule.

Urine tests can be falsely positive in those that are taking the medications: Spurious evaporation lines may appear on many home pregnancy tests if read after the suggested 3—5 minute window or reaction time, independent of an actual pregnancy. False positives may also appear on tests used past their expiration date. A woman who has been given an hCG injection as part of infertility treatment will test positive on pregnancy tests that assay hCG, regardless of her actual pregnancy status.

However, some infertility drugs e. Some diseases of the liver , cancers , and other medical conditions may produce elevated hCG and thus cause a false positive pregnancy test [14]. These include choriocarcinoma and other germ cell tumors , IgA deficiencies , heterophile antibodies , enterocystoplasties, gestational trophoblastic diseases GTD , and gestational trophoblastic neoplasms [15].

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Pregnancy tests may be used to determine the viability of a pregnancy. Serial quantitative blood tests may be done, usually 3—4 days apart.

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Failure to increase normally may indicate an increased risk of miscarriage or a possible ectopic pregnancy. Ultrasound is also a common tool for determining viability.

Pregnancy 101: How Pregnancy Tests Work

A lower than expected heart rate or missed development milestones may indicate a problem with the pregnancy. Inaccurate estimations of fetal age and inaccuracies inherent in ultrasonic examination may cause a scan to be interpreted negatively.



If results from the first ultrasound scan indicate a problem, repeating the scan 7—10 days later is reasonable practice. Records of attempts at pregnancy testing have been found as far back as the ancient Greek and ancient Egyptian cultures. The ancient Egyptians watered bags of wheat and barley with the urine of a possibly pregnant woman.

Your pregnancy and baby guide

The type of grain that sprouted was taken as an indicator of the fetus's sex. Hippocrates suggested that a woman who had missed her period should drink a solution of honey in water at bedtime: Avicenna and many physicians after him in the Middle Ages performed uroscopy , a nonscientific method to evaluate urine.

Selmar Aschheim and Bernhard Zondek introduced testing based on the presence of human chorionic gonadotropin hCG in If you don't know when your next period is due, do the test at least 21 days after you last had unprotected sex. Some very sensitive pregnancy tests can be used even before you miss a period, from as early as 8 days after conception.

It doesn't have to be in the morning. You can also buy pregnancy testing kits from pharmacists and some supermarkets. They can give a quick result and you can do the test in private. All pregnancy tests detect the hormone human chorionic gonadotrophin hCG , which starts to be produced around 6 days after fertilisation. Most pregnancy tests come in a box that contains 1 or 2 long sticks. You pee on the stick and the result appears on the stick after a few minutes. All tests are slightly different, so always check the instructions.

A positive test result is almost certainly correct.

Digital Pregnancy Tests vs. Non-Digital Pregnancy Tests

A negative result is less reliable. Speak to your GP if you get a negative result after a second test but your period hasn't arrived. Here are some signs that you should take a pregnancy test. Many women have a day menstrual cycle. Keep in mind that your period can sometimes be delayed or skipped due to stress , diet , exercise , or certain medical conditions.

Also pay attention to your flow if you suspect pregnancy. Take note of any difference in the color, texture, or amount of blood. Implantation can also produce a feeling similar to menstrual cramps. In early pregnancy, you may feel this discomfort and think your period is just around the corner, but then it never comes.

Your breasts may feel tender and appear bigger due to increased blood flow. Your nipples might hurt and the veins might look darker under the skin. As the weeks go on, these symptoms may get stronger before your HCG levels even out late in the first trimester. You know yourself, so pay attention to your body. Any unusual physical symptoms could prompt you to take a pregnancy test. Human error or defects can also result in unplanned pregnancy.

Birth control pills can be difficult to remember to take each day. Condoms can break and tear or otherwise be used incorrectly. According to Planned Parenthood, nearly 18 in every women relying on condoms for contraception get pregnant each year. According to Planned Parenthood, less than one out of every women using an IUD gets pregnant each year. Sexually active women in their reproductive years have a chance of pregnancy every month, even when using protection. There are certain signals your body might send that should prompt you to take a pregnancy test.

Test during your first morning bathroom visit, or hold it for several hours to increase the concentration of the HCG hormone that the test measures. Testing early helps to ensure that you get proper care for yourself and, if applicable, prenatal care for your baby. In the event of a positive result, contact your doctor as soon as possible to discuss your options and potential next steps. Home pregnancy tests HPTs are quite accurate.