On rare occasions, at-home pregnancy tests can produce a mistaken result - here's why it could happen.
At-home pregnancy tests are pretty damn
accurate. If you get a positive result you can almost certainly assume
you are pregnant, at which point you should visit your GP to confirm the
news, and then you can spend the next nine or so months cooking your
human child.
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But on some rare, and we mean very rare
occasions, your test might display a false result. This could either be
in the form of a 'false positive' - a test that says you're pregnant
when you don't actually have a viable pregnancy, or it could be in the
form of a 'false negative' - a negative result when you are, in fact,
pregnant. We asked Dr Preethi Daniel, Medical Director at London Doctors Clinic to talk us through all the ways either of these eventualities could happen:
1. Expired pregnancy test
"Pregnancy
tests expire, which can result in a false-negative test. Heat or
moisture can cause damage to the test window on a pregnancy test and
this can also result in inaccurate results. If you want to buy a
pregnancy test, go to the pharmacy so you can guarantee it's within
date."
2. Fertility medication
"HCG (or if you want to get technical, human chorionic gonadotrophin)
is a hormone released by the placenta after the embryo has been
implanted into the womb. This hormone can be detected in the woman’s
urine or blood even before a missed period. But if you've been going
through fertility treatment, like IVF for example, and you are given
fertility medication, this can cause a false positive reading on a
pregnancy test. Fertility treatments are hormones which may mimic or
even contain HCG, which is why this may happen."
3. Miscarriage
"If you have
had a recent miscarriage, the HCG level can stay in your bloodstream
for a number of days. This can result in a false positive test result.
4. Medication
"Some
medications can alter the level of HCG in the blood. These include
benzodiazepines taken for anxiety (diazepam, alprazolam), diuretics
taken for excess water retention (furosemide) and even antihistamines
such as promethazine.
"These medications could
theoretically lead to a false positive result if a woman has experienced
either a chemical pregnancy (more on that below) or a miscarriage, both
of which would leave a small, undetectable level of HCG in the woman's
bloodstream. The medication could increase this level slightly, bringing
it into a detectable range, hence the possibility of a false positive
result emerging from the test."
5. Chemical pregnancy
"This
is where a sperm and an egg meet but the fertilised egg - known as an
embryo - is unable to implant in the womb. This can still cause a rise
in HCG levels despite there being no viable pregnancy. For some woman,
this false positive result can be emotionally draining. It's for this
reason it is always recommended you wait a week or so after you miss
your period to take a pregnancy test."
[post_ads_2]6. Ectopic pregnancy
"An
ectopic pregnancy can result in a positive reading on a pregnancy test,
and this does indeed mean you are pregnant. Sadly, though, this
pregnancy is not in the right place. The foetus is most likely in one of
your fallopian tubes (the tubes that carry the egg to the womb) and
this is a medical emergency. If you have a positive test result at home
and start experiencing abdominal pain, bleeding or are feeling unwell,
it's vital you see a doctor as soon as possible."
7. You've left the test sitting too long before looking
"You've
urinated on the stick, and are now eagerly awaiting. You might want to
take your mind off the nervous wait, but don't wander off and forget;
leaving the test 'cooking' for too long can give a false positive
result. The reason for this is due to the urine evaporating if left for
too long; it can leave a faint line which can be mistaken as a positive
test. Its recommended to not read a pregnancy test after the recommended
time frame (10 minutes) as most brands have a possibility of
evaporation lines."
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8. Medical conditions
"There
are certain medical conditions that can impact the outcome of a
pregnancy test. If you're suffering from a urinary tract infection,
kidney disease or have ovarian cysts, this may alter the result of your
test:
Urinary tract infection or kidney
disease may result in a contaminated sample (with red or white blood
cells in your urine) which may result in a false positive result. It
does depend on the method used by individual brands but in general any
impurity or even blood can cause a false reading.
Ovarian cysts/cancer or disorders of the pituitary gland (in the brain) can either produce HCG leading to a false result or produce hormones mimicking HCG, once again leading to a false positive. These cancers often produce small amounts of the hormone, but home pregnancy tests can be sensitive enough to pick this up."
