Nearly half of all mothers suffering from post-natal depression lie to their health visitors about it, BBC One's Real Story has found.
The survey was designed to find out how mothers feel about PND
A survey for the programme found 44% of new mothers do not tell the truth about their symptoms because they are afraid of the consequences.
Post-natal depression (PND) is currently thought to affect around 10% of new mothers.
Symptoms can range from self-harm, depression or in extreme cases suicide.
Most new mothers are asked by their health visitors to fill in a form called the Edinburgh Scale which is designed to assess them for PND.
According to the 597 depressed mothers who responded to the survey, carried out with the online support group Netmums, 236 or 44% of them lied on the form about their feelings.
One explanation many gave was that they were afraid that health visitors would call in the social services, leading to the possibility they would lose their children.
Others felt that they would be seen as bad mothers.
Jean Robinson, of the Association for the Improvement in Maternity Services, said recent high-profile child abuse cases may have led to a focus by health visitors on spotting abuse.
"Since the Climbie Inquiry the government has asked all healthcare personnel and health visitors to look out for risk for children so that their primary priority is not to help the mother and support the family, but to say 'Are these children at risk, we must report it to social services, I cover my back by doing this'."
Real Story with Fiona Bruce will be broadcast on Monday 28th November at 7.30pm on BBC One.