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Dr. Andrew Rynne
MD
Dr. Andrew Rynne

Family Physician

Exp 50 years

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Is urine test or blood test advisable to test for pregnancy?

My girlfriend is late with her period, over 40 days. We went to get tested at the doctor s office for urine test and it came back negative. What are the chances of her being positive? How accurate is the urine test at the doctor s office? Should we go get a blood test done?
Mon, 15 Feb 2016
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Anesthesiologist 's  Response
Thanks for posting your question to Health Care Magic,

Human Chorionic Gonadotropin (HCG) start rising just after egg fertilization and attachment to uterine, since then the placenta forms and begins to produce HCG. Then HCG arrives in blood and urine. HCG doubles about every 2-3 days in early pregnancy.

Measurement of urine HCG is called qualitative method while blood test is named quantitative. Urine test is usually about 95-97% accurate after first day of missed period. Some days later the accuracy is about 99%. Please notice that in ectopic pregnancy HCG increases at a slower rate than standard level. After 1.5 - 2 months of pregnancy it decreases.

There are many issues may mimic a negative pregnancy test while you are pregnant including:

1.     Complicated pregnancy can disturb the amount of HCG.
2.     Very diluted urine because of medications such as diuretics or drinking too much water before test.

According to your chief complaint and my experience, to rule out unforeseen events such as ectopic pregnancy and so on, my recommendations are:

1.     Take a quantitative test (Blood test).
2.     Perform an obstetric ultrasonography to distinguish normal pregnancy.

You may demand more health care and follow up after visiting your doctor specialist and viewing tests results.

Hope you get fine soon,
Regards
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