When you take a pregnancy test, be it in blood or urine, you might aks yourself if it can be negative if you’re pregnant, that is, if there can be a fals negative.
Doubts about the reliability of this test are common, especially if pregnancy symptoms are present.
The different sections of this article have been assembled into the following table of contents.
Pregnancy tests measure the hormone hCG (human chorionic gonadotropin) that is characteristic of pregnancy. Beta-hCG is usually not detected until at least 14 days after the date of conception.
This hormon will be secreted by the embryo in large quantities from the sixth day of pregnancy. The increase in levels of this hormone is responsible for the typical pregnancy symptoms and its main function is to prevent the disintegration of the corpus luteum in the ovary. It also intervenes in immune tolerance during pregnancy, protecting the early fetus from immune rejection.
At 2-3 months of pregnancy, the placenta begins to secrete hormones on its own and the secretion of hCG decreases. Thus, due to the drop in this hormone as pregnancy progresses, a pregnancy test during the second or third trimester could give a false negative. Can there be a false negative in the first pregnancy weeks, too?
False negatives in pregnancy tests
The blood pregnancy test is more sensitive than the test that detects this hormone in urine, so the chance of a false negative is lower. Precisely because this test is more reliable, many women, as well as fertility centers, choose to detect the hormone hCG in blood.
A result of more than 10 mIU/ml is generally considered positive, although if the result is just at the limit it is recommended to repeat the test about 5 days later and see how it evolves to rule out a biochemical pregnancy.
The causes for a false-negative pregnancy test are as follows:
- The test was done too early: if at least 12 days have not passed since ovulation or there is no delay in menstruation it is very possible that hormone levels are not high enough to be detected by the test.
- The test has not been done with the morning urine: if you do a urine pregnancy test it is important to do it with the morning urine, which is the one that has the highest concentration of the hormone hCG.
- The woman is taking or has taken any medication that may affect the outcome.
- The chosen test has low sensitivity, i.e. it detects pregnancy hormone levels above 20 mIU/ml, so it is not able to detect pregnancy at an early stage.
- Pregnancy has been lost early.
- The test has expired or is damaged.
In the event of any of these situations, the best way to check whether or not there really is a pregnancy is to repeat the test about five days later to confirm the result.
Why do I feel pregnant if I'm not?
As we have said, you can feel pregnant under many conditions and only get negative results on pregnancy tests. However, if the symptoms persist and you are in doubt, you should consult your doctor.
The doctor will order a blood hCG test to confirm whether or not there really is a pregnancy and a transvaginal ultrasound to look directly inside the uterus for a gestational sac and embryo. You will also need to do a physical exam, and check the size of your uterus.
If the doctor rules out pregnancy, you may be facing a false pregnancy. The causes can be diverse, such as a woman having a very strong desire to be a mother or an atrocious fear of pregnancy.
Among the symptoms of false pregnancy, there are:
- Disappearing menstruation (amenorrhea)
- Increased size of the breasts, the aureole and its pigmentation
- Skin darkening
- Adominal enlargement
- Significant weight gain, more than in a normal pregnancy, and a strong increase in appetite
- Nausea and gastric problems such as heartburn
- Sleep disorders
Your doctor may order some tests to prove that these symptoms are not due to some other disorder and be able to confirm that this is really a false pregnancy.
If the doctor confirms a false pregnancy, the woman will need to do psychological therapy, which may be accompanied by medication if the professional considers it necessary for the specific case, as well as working at home with the couple to overcome it.
Other causes of period delay
A late period make us think of irregularity in the menstrual cycle, and these irregularities can occur in all women at some point in their lives. The causes are usually very varied, very few women have a 28 day cycle.
Once the possibility of pregnancy is excluded, the causes of menstrual delay can be:
- Polycystic Ovaries
- women with polycystic ovary syndrome may have infrequent or prolonged menstrual periods, have excessive levels of male hormone (androgen) and their most frequent symptoms are hirsutism (excess hair), abdominal obesity, and menstrual irregularity. It is one of the most common disorders in women and its prevalence is estimated between 5 and 20%.
- Changes in habits
- time shifts can influence the hormonal cycle, women who make drastic dietary changes, severe exercise, or a major emotional life change may be responsible for irregular cycles. It is therefore important to maintain an adequate and balanced eating habit.
- is one of the main enemies because it affects the production of cortisol, increasing its levels which are reflected in the production of estrogen and progesterone later, again explaining menstrual delays and the presence of nausea.
- Thyroid hormone alterations
- excess (hyperthyroidism) or defect (hypothyroidism) of thyroid hormones results in problems achieving pregnancy or carrying a pregnancy to term, miscarriages, problems in pregnancy and premature birth. In addition, they are associated with anovulation and abnormal menstrual cycles.
- the ingestion of certain medications can cause amenorrhea (absence of menstruation), antipsychotics, antidepressants and a bad ingestion of oral contraceptives are examples of this.
- Assisted Reproduction Treatments
- Among these patients the use of vaginal progesterone sometimes delays menstrual bleeding, and can cause a delay in intestinal emptying, causing nausea and emotional changes, which are often confused with pregnancy symptoms.
As we have just seen, there are many causes that can cause a delay in menstruation after an assisted reproduction treatment, so if you have any doubt, do not hesitate to see your specialist, he will surely clarify all your doubts.
FAQs from users
Can a pregnancy test fail?
Yes, the negative result can be wrong. The main reason is usually that the pregnancy test has been done too soon, but, as indicated in the article, it can happen because the test is in poor condition, because it is not highly sensitive or because there has been an early abortion, among other things.
I think I'm pregnant but the test is negative, what's wrong with me?
Don't worry, everything is fine with you. Just repeat the test in about a week to confirm the result. If it's still negative, it's very likely that the symptoms you notice are due to another reason, not a pregnancy. If you are in doubt, it is best to contact your doctor for an ultrasound and an exploration, although if the pregnancy is very early you will not be able to see anything on the ultrasound and you should wait a few weeks.
How do I know if I'm pregnant if my test shows negative?
The first thing would be to repeat the pregnancy test after about 5 days. If the test continues to be negative, it is more likely that your period will come soon, but if it does not, it is best to consult your doctor.
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