New dads are almost as likely as new mothers to suffer obsessional and distressing worries about the health of the baby, researchers have found.
New dads suffer irrational thoughts too, say researchers
Experts from the Mayo Clinic in Maryland, US, surveyed 300 mothers and their partners.
They found that as many men as women had fears about cot death or drowning the baby during bathing.
Previously it had been suggested that women might be more prone due to hormone fluctuations after childbirth.
Irrational or obsessive thoughts following childbirth are regular and upsetting feature for many new mothers.
Of those who responded to the survey, 69% admitted having distressing thoughts.
These included not only fears for the safety of the baby, but even those about intentional harm and unacceptable sexual thoughts in some parents.
More than half
Among the fathers, 58% admitted to having some form of irrational thought about the baby.
The experts running the survey said that the findings showed that it was perfectly normal to have some unwelcome and intrusive thoughts about the baby - and that the best thing to do was to dismiss them rather than feel abnormal.
However, they say that help should be sought when the thoughts keep recurring and the parent feels they cannot control this.
Drugs are available which can help manage the most extreme feelings that parents suffer after the birth of a child.
Dr Jon Abramovitz, a psychologist who helped carried out the study, said: "Everyone occasionally has thoughts that are contradictory to their moral or ethical beliefs.
"The difference is that people who develop problems with obsessional thoughts manage those thoughts differently.
"Usually we dismiss disgusting thoughts - such as pushing our baby out of the window - as something we would never do.
"However, people who develop problems tend to believe that thinking the thought means they are bad people who might actually act on it."
He said that it was only when the parent viewed the irrational thought as something rational or realistic that the risk of some form of psychotic behaviour increased.
The cause of the thoughts is still unknown, but the evidence that men feel them too suggests that hormone changes following childbirth may not necessarily be to blame in all cases in women.
The study was published the Journal of Clinical Psychology in Medical Settings.