Sexual health is more important to couples than meeting partners' friends and family, a survey revealed today.
Frank discussions about the importance of getting tested for sexually transmitted infections (STIs) are an important indicator of a lasting relationship, the study said.
Researchers questioned 1,000 young adults, and found 70% rank discussing STI tests together as the most important sign that a new relationship will last.
Discussions about infections such as chlamydia have overtaken more traditional milestones such as meeting the parents (66%) or friends (40%).
According to the study, other relationship landmarks include women deciding not to always wear makeup, at 47%, and allowing each other more cupboard space, at 30%.
The Populus poll was conducted on behalf of the "Chlamydia - Worth Talking About" campaign which encourages sexually active under-25s to get tested for chlamydia.
While young people feel they should have honest conversations with new sexual partners, three quarters (73%) have never raised the subject of STIs with a new partner before having sex for the first time.
One third of those asked (30%) said they feel uncomfortable asking a new partner to use a condom.
More than one in four (27%) admitted that they are too embarrassed to talk to their partner about subjects including safe sex, STIs and contraception.
Public Health Minister Gillian Merron said: "STIs can be a difficult subject to talk about, but it's encouraging that young couples are starting to see beyond that. The Government's Chlamydia - Worth Talking About campaign aims to get young people discussing STIs and saying "yes" to chlamydia tests."
Sex and relationship expert Dr Catherine Hood said: "These findings reveal much about the modern relationship game. While many young couples realise the significance of being able to talk openly about accepting tests for STIs, sheer embarrassment is preventing them from doing so, and potentially risking their sexual health as well as the future of their relationship."
The research identified a critical window of opportunity at the start of a relationship to talk about sexual health.
Almost a third of respondents (29%) believe that for a relationship to last, new couples need to have had an open discussion about STIs within the first three months of making it official.
Half of respondents (48%) said a relationship in which a new partner was unwilling to discuss issues of sexual health would not last long.
Dr Hood added: "Chlamydia often doesn't have any symptoms, and so the only way for young people to find out if they have it is to say yes to a free chlamydia test if they are offered one by a healthcare professional.
"If left untreated, chlamydia can lead to infertility and other serious health problems, and so it's vital that new couples take responsibility for their own sexual health by talking openly about safe sex."