Some of the new mothers go on a mental overdrive with concern over germs or of over injuring their baby.
OCD is known to affect nearly 3% of adults. The concern about motherhood and its host of responsibilities is increasing the risk of women coming own with this condition.
Many new mothers experience irrational fears of accidental injuries to the baby and this causes them to check for mistakes obsessively. They also tend to worry abnormally about germs and hygiene.
This condition is more common than post-natal depression, which affects around one in ten. Scientists also feel that the two conditions may actually be interlinked, although the connection needs to be studied further.
OCD is thought to be triggered by stress. Some of the women who showed symptoms said that they kept experiencing intrusive thoughts about dirt and germs and they felt a compulsion to check if they had made a mistake. Other symptoms included checking baby monitors to ascertainif a baby is breathing or not and, washing and re-washing bottles.
'There is some debate as to whether post-partum (post-natal) depression is simply a major depressive episode that happens after birth, or its own disease with its own features,' said co-author Dr Emily Miller, also from Northwestern University.
'Our study supports the idea that it may be its own disease with more of the anxiety and obsessive-compulsive symptoms than would be typical for a major depressive episode.'