How accurate are pregnancy tests?

Pregnancy tests are designed to determine the presence of the pregnancy hormone HCG. Until twenty years ago, pregnancy tests were biological, relying on the affects of the hormone on animals. There could be a cross-reaction with other hormones, notably LH. Many women reaching the menopause could have a false alarm as LH levels rise at the menopause and when they missed their periods their pregnancy tests could be falsely positive. Modern pregnancy tests are monoclonal they react only with the specific hormone they are designed to detect. In the early weeks of pregnancy, the HCG level doubles every two days. Whereas the old pregnancy tests would become positive with a concentration of 3,000 IU (about two weeks after the missed period) the monoclonal tests show a positive result at between 25 and 50 IU and these levels are reached before a period is missed.

The accuracy of modern pregnancy tests are not only useful in the early detection of pregnancy but also in assisting in the management of early pregnancy problems such as threatened miscarriage or possible ectopic pregnancy.

A lady presented with vaginal bleeding and left sided pelvic pain. Her pregnancy test was positive and ultrasound did not show any sign of a pregnancy either within or outside the uterus (ectopic pregnancy). Her beta HCG level was 365 units suggesting a very early pregnancy at most. Two days later the level had fallen to 180 units which indicated that the pregnancy was not continuing. We could not say for certain whether this had been an intra-uterine pregnancy that miscarried or a possible ectopic pregnancy that was being resolved by nature but no operative intervention was required.

Please click on the required question.

• 1  What is a miscarriage?
• 2  What are the different types of miscarriage?
• 3  How accurate are pregnancy tests?
• 4 What is a blighted ovum?
• 5 I have had a hydatidiform mole. What is this?
• 6 Why did I have a spontaneous miscarriage?
• 7 How frequently do miscarriages occur?
• 8 I am miscarrying. How should this be treated?
• 8a Can miscarriage result in anxiety and depression?
•  9 What is meant by recurrent miscarriage?
• 10 I have a problem with recurrent miscarriage. What is the chance of my next pregnancy being successful?
• Q 12.11 Recurrent Miscarriage I have miscarried again. Why does this keep happening?
• 12 What congenital problems might be associated with recurrent miscarriage and how could they be treated?
• 13 What traumatic conditions can cause recurrent miscarriage and how can they be treated?
• 14 Can infection cause recurrent miscarriage and would treatment help?
• 15 Could a metabolic disorder cause recurrent miscarriage?
• 16 Could a hormonal problem account for recurrent miscarriage and would hormone treatment help me?
• 17 Could an autoimmune problem cause recurrent miscarriage and how could this be treated?
• 18 Could a tumour cause recurrent miscarriage?
• 19 What degenerative processes may be associated with recurrent miscarriage?
• 20 After every miscarriage I become more depressed. Could this account for the problem?
• 21 Is it always possible to explain recurrent miscarriage?
• 22 I have a problem with recurrent miscarriage. What treatment is available to ensure that this does not happen again?
• 23 What is an ectopic pregnancy?
• 24 How frequently do ectopic pregnancies occur?
• 25 Why do ectopic pregnancies occur?
• 26 How can an ectopic pregnancy be diagnosed?
• 27 How can an ectopic pregnancy be treated?
• 28 Where can I obtain more information?
• 29 Support Groups.
  

Thank you for choosing to visit us.

This is the personal website of David A Viniker MD FRCOG, Consultant Obstetrician and Gynaecologist at Whipps Cross University Hospital, London - Specialist Interests - Reproductive Medicine including Infertility, PCOS, PMS, Menopause and HRT.

I do hope that you find the answers to your women's health questions in the patient information and medical advice provided.

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