'Baby blues' tends to describe a common experience that women can have on days 2,3 or 4 following birth. There are physical changes within the body, including big hormone changes, as well as the breast milk 'coming in', regardless of whether she has chosen to breastfeed or not. Of course she is also recovering physically from birth and is likely to be tired from the birthing process; and potentially exhausted if it was not straightforward. Along with these physical changes, there is that inevitable 'coming down' from an incredibly intense and emotional experience. There may also be feeding challenges to deal with. Women can feel low and tearful. This can be especially distressing and unsettling if the woman is normally quite an upbeat person. One mum recently told me that she was convinced it would never happen to her as she never suffered from PMS and has always been a very positive person. Both she and her partner were confused by her sudden tearfulness at seemingly small things like mislaying her phone; however, she recovered within a week or so.
The difference between baby blues and postnatal depression is that baby blues doesn't last long. A few days or occasionally a bit longer. It tends to ease up with a bit of rest and TLC (tender loving care: good food, cuddles, a sympathetic listening ear, supportive friends and family, lots of practical help around the house and good physical care).
Postnatal depression doesn't tend to ease up with these self-help measures alone. If a woman does feel low any time in the first year following birth and it doesn't ease up within a week or so with the self help methods mentioned above... it would be great for her to talk this through with a Heath Visitor or GP. They can administer a simple questionnaire and listen to the woman to ascertain what help would be appropriate. Talking therapies can help, as can a course of (breastfeeding friendly) anti depressants and/or anti anxiety medication. Some areas have support groups too. In many areas it is possible to self refer to NHS Talking Therapies and chat direct with a counsellor over the phone to find out what support you might benefit from. Have a google of: 'self refer NHS talking therapies' for your area to see what's available.
If you have any concerns about your's or someone else's emotional health following birth, don't leave it and hope it will get better. You or your loved one or friend deserve better than that. Seek health. A great and easy starting point is this orgnaisytoon founded by a Mum who experienced and recovered from postnatal depression. Have a look now: www.pandasfoundation.org.uk and you can read more at NCT too: https://www.nct.org.uk/parenting/baby-blues