I would agree that you shouldn't necessarily hide your child on your PS but whether you should really emphasise the fact depends on your course IMHO.
I have 2 kids and was applying for Veterinary Medicine when my youngest was only 6 months old! The fact that the course was so very competitive and that I didn't have exactly the right qualifications (was a graduate but didn't have an A in Chemistry A level) meant that I was worried about giving them an "excuse" IYSWIM not to accept me. Of course that it very cynical of me but on a course like VetMed where it is really really hard to get a place and then the degree itself is extremely demanding, I thought that some kind of bias against me was possible.
Admittedly I am not in the UK and the situation is different here. I had to apply with a CV rather than a personal statement and my maternity leave was mentioned on that, so I didn't hide my kids really! I just didn't mention them at the interview (which was very vet-based anyway).
If you do mention your child, then be prepared to explain how you will cope with studying, childcare etc. Most importantly if you have a Plan B for when the child is ill and can't go to nursery/school (mine always get sick the week I have exams! Broken arm, ear infection, chicken pox! We've had them all!). Of course I totally agree with the others about the organisational skills, multitasking, motivation etc that comes from motherhood but you have to be realistic too!
Hope that helps a bit