Websites selling home fertility tests are making misleading claims about their usefulness and could influence plans to conceive, researchers warn.

The 'egg timer' tests measure the level of anti-Mullerian hormone in the blood, a hormone produced by follicles in the ovaries.

Of the 27 websites selling the tests directly to consumers online, 20 stated it could provide information about fertility or the likelihood of conceiving, University of Sydney researchers found.

The majority contained poor quality information or made unsupported claims, including marketing the test as a reliable predictor of fertility, according to a study published in JAMA Network Open on Tuesday.

Researchers cautioned women may rely on website information to decide whether to have the test.

They may also make decisions or plans to conceive or delay doing so, or seek potentially unnecessary fertility treatments such as IVF or egg freezing on the basis of test results.

Evidence shows the AMH test cannot reliably predict current or future fertility in the general population.

Researchers called for more regulation and oversight on the marketing of home fertility tests.

Currently direct to consumer AMH test marketing has minimal regulation.

Co-author Rachel Thompson from the Sydney School of Health Sciences Faculty of Medicine and Health said false and misleading claims about the usefulness of the AMH test undermine women's ability to make an informed decision.

"People may also be worried or reassured by the test results without basis and may change their reproductive plans and behaviour as a result."

The researchers said increasing public knowledge about fertility, greater attention to reproductive health and addressing structural barriers to earlier childbearing are likely to be more effective in helping people to achieve their reproductive aspirations.