Thousands of people's personal information may have been compromised after Family Planning NSW's online databases were hacked.
In an email to clients, the organisation - which provides advice on contraception, pregnancy and sexual health - said its website was hit by a cyber attack on Anzac Day.
It's believed the databases contained information of clients who had contacted Family Planning NSW to make an appointment, or leave feedback through its website, in the past two-and-a-half years.
"Since the attack we have had no evidence that this information has been used by the cyber attackers," the email, signed off by chair Sue Carrick and chief executive Ann Brassil, said.
"All web database information has been secure since this time and more sensitive medical records held internally were never under threat."
The organisation said the situation has been "contained", but its website will remain offline until a security review and internal testing are completed.
Clients were told Family Planning NSW was one of several agencies targeted by cyber criminals who requested a bitcoin ransom on April 25.
"We are conducting a thorough review of our information security to ensure all clients can continue to trust us for their reproductive and sexual health services."
The not-for-profit has five clinics in NSW, with more than 28,000 people visiting every year.