You don’t need to declare any pregnancy related condition that occurred during your pregnancy so long as the symptoms don’t persist (or isn’t expected to persist) for more than six months after the completion of your pregnancy. If your condition persists beyond this timeframe, or is permenant, then you’ll need to declare this. For example if you suffer from postnatal depression (also known as postpartum depression) and the condition does not resolve within six months, you will need to declare depression on your policy.
