Start with the basic requirements. Is your trainer an expert in how to recover safely from pregnancy and birth? Your trainer must know how to rebuild your core muscles, and what the most important areas are for mums to work on for maximum benefit. Familiarity with the common health risks for new mums doing exercise is also vital, to ensure you don't damage yourself (some helpful info is here). Also, does your trainer appreciate the extra exercise challenges mums may have? Sore boobs? Exhaustion? Lack of childcare? Can they advise you on diet?
The best Personal Trainers for mums have all the basics - AND they are clear about EXACTLY what they offer in terms of style.
Let me share a couple of case studies.
Here are two trainers who DO know what they're about. Both provide amazing services for clients, but they couldn't really be more different: