No doubt your day job takes your diary to beyond bursting point and if you've opted for reduced hours that may well compound the issue. However, there's bound to be at least four business development events a year that would be useful to your long-term career prospects and probably for your performance in your current role. Can you identify some off the top of your head? And where else might you find out about them? Get them in the diary and to ensure they happen, highlighting in a one-to-one with your line manager how your attending them would be good for the team/wider organisation. Could you include them in your personal or performance development plan?
"Network when you are out with the baby. Other women/men who could be your clients have babies and small children. Get involved with others with babies/small children. Demonstrate you are human. Speak to HR about child-friendly fun days to ensure client development. Pass out your business card."
"Just try to do what you've always done. Everything's changed for you, but your employer wants to know that nothing has changed. If you are doing the job well, just as you did before, that should be reassurance enough. Be prepared to do the occasional out-of-hours business development task too, to make sure your employer knows that you are up for putting work ahead of family if you need to."
"Write articles, attend/provide training for clients/colleagues, attend firm and external marketing events, go and speak to colleagues you dealt with before leave and see what they have on and remind them you're back. Arrange to meet clients for coffee/lunch to see where their business is going and what's keeping them busy. Get involved in marketing events with the firm."