A first-time mum-to-be is thanking her intuition after a negative pregnancy test at her local medical centre - despite being at least three weeks pregnant.

Sarah Pethybridge, now 26 weeks pregnant and expecting a baby boy in September with partner Lewis Stevens, used a home pregnancy test the morning of New Year's Eve last year and returned a positive result.

The 28-year-old repeated the test two more times to be sure and each test was positive.

With the results in her bag, she went to the Ranui Medical Centre near her West Auckland home to confirm her exciting news.


"They did several tests there and I was told I was not pregnant, even though I had taken in several positive tests from earlier that morning to show the nurse," Ms Pethybridge said. "I was told I was not pregnant and to go out and celebrate New Year's Eve that evening."

Ms Pethybridge queried the earlier positive results but the nurse said she didn't know.

"They did not even offer me a blood test, which can check the levels and confirm pregnancy if suspected but not detected on a urine test."

Dr Richard Hulme from East Tamaki Healthcare, which owns the Ranui Medical Centre, confirmed all 25 of its clinics use the EasyCheck cassette tests.

The EasyCheck brand sparked warnings this week from the Health Ministry's Medsafe division, which had received several reports from health workers, district health boards and clinics about the EasyCheck Pregnancy Test Cassette. The problems relate to "false negative test results and technical faults".

Dr Hulme said he could not discuss individual patients' care but invited concerned patients to contact their GP.

Brad Rodger from EasyCheck supplier, Phoenix MedCare, said the false negative results were likely due to incorrect procedural or storage techniques or individual patient circumstance.

The company had 150 cassettes randomly tested by Labtec Scientific & Technical Services and the cassettes returned the correct result when instructions were followed.

"We have only been able to replicate this issue by purposely following an incorrect testing method such as shaking the product after the test has been taken," Mr Rodger said.

He said in Ms Pethybridge's case the nurse should have done the test first thing in the morning when the pregnancy hormone Human Chorionic Gonadotropin (hCG) levels are highest.

"All urine pregnancy tests are screening tests only and if there is any doubt that there might be pregnancy the clinician should follow up with a first morning urine test 48-72 hours later or order a blood test," he said.

Ms Pethybridge understood that some tests in early pregnancy returned a false negative result and said the three positive results and the fact she had missed her period should have prompted the nurse to send her for further tests.

"Instead she told me to go out and celebrate New Year's Eve. My gut instinct told me that I was pregnant," so she decided to err on the side of caution and didn't drink.