Either way, if you think you might be pregnant , you need to know for sure. But what are the odds a positive pregnancy test might be wrong? When you get pregnant, your body produces a hormone called human chorionic gonadotropin, or hCG. Home pregnancy tests look for that hormone in your urine. If hCG is present, you should get a positive test result when you pee on a stick.
But hCG levels start out very low and increase over time. Emery says. Some potential causes include:. You took a pregnancy test and got two lines. But a few days later, your period arrived in force. What gives? The most common reason this happens is an early pregnancy loss , also known as a chemical pregnancy. During the first trimester, they may feel more fatigued than usual.
Some may experience nausea and vomiting, and mood swings are also common in the first trimester. During pregnancy, women no longer have their periods, but it is generally only within the second trimester that the belly will begin to enlarge. Women experiencing the hook effect in their pregnancy tests may still not see positive results despite their pregnancy becoming more noticeable through these changes. When evaluating the results of a pregnancy test, doctors should consider all of the clinical signs and the laboratory and medical imaging tests.
Relying on pregnancy test results may cause missed or delayed diagnoses and delayed prenatal care, which can harm both the woman and the growing fetus. The hook effect in pregnancy occurs when a person has high concentrations of hCG, the pregnancy hormone for which both urine and blood pregnancy tests check. High levels of hCG can overwhelm the antibodies that pregnancy tests use.
When too much hCG is present in a sample, the antibodies may fail to bind, and the test will appear negative. The hook effect may occur when levels of hCG reach , milli-international units per milliliter.
Certain medical conditions, such as cancer and pregnancy-related diseases, may cause high levels of hCG. Women having twins or triplets may also have high levels of this hormone, which can be difficult for a pregnancy test to detect.
Although the hook effect occurs very rarely, the medical implications of a false-negative result can be serious. Doctors relying on blood and urine pregnancy tests may falsely assume that the woman is not pregnant. As a result, the woman may not receive proper prenatal care until an ultrasound confirms the pregnancy. Prenatal care involves routine follow-up visits with doctors, as well as laboratory and medical imaging tests.
Some people require vitamin and mineral supplements, and others may need to stop taking certain medications. Doctors also advise making specific lifestyle changes, such as avoiding alcohol, smoking, and illicit drugs. Delaying prenatal care can be dangerous for both the woman and child. Doctors may find it challenging to identify the hook effect in laboratory tests.
Often, laboratory technicians will test undiluted and diluted samples to detect the hook effect. Although this approach can detect the hook effect in undiluted samples, it is expensive because it requires additional labor and materials. Experts suggest that the sample pooling method can help prevent the hook effect at a much lower cost. This method involves testing a pooled sample and a fold dilution of the pool. The technician pools 10 samples from 10 people. The other samples in the batch dilute each sample fold.
The laboratory worker then dilutes a portion of the pooled sample by fold. The technician now has a sample that is fold diluted, which they can test and compare with the pooled sample. Doctors can detect the hook effect if the fold dilution sample gives a higher result than the pooled sample. Rarely, certain medical conditions can cause a home pregnancy test to give a false positive. These include:. Your doctor may give you a urine or blood test to confirm the results and monitor your hCG levels.
You may also get a transvaginal ultrasound to look for the gestational sac as confirmation that the pregnancy is proceeding normally. But if you were excited by your early results, it can be very upsetting.
There are also support groups where you can find inspiration and obtain knowledge from women who have been through the same thing. Working one-on-one with a therapist, family member, or trusted friend can also be beneficial. What are the telltale early symptoms of pregnancy?
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Chemical pregnancy. It may be the result of issues within the uterus, such as: fibroids scar tissue a congenital uterine anomaly that causes an irregular-shaped uterus Low amounts of certain hormones, such as progesterone, can reduce the likelihood of implantation and embryo growth.
Some causes of chemical pregnancy are unknown.
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