Need help...

Just want some advice on lifting heavy objects (things at work) to lifting up your doggies for a cuddle to lifting children up and walking around with them.

I know you have to be careful but for example, holding your kids... in this instance, its my niece. I always lift her up and cuddle her and carry her (she is about 13kg) and the other day my sister said as my niece put her hands up to me for me to pick her up, (think trying to get out of me if I am pregnant or not as I haven't said anything to family and friends this time round until I reach 12 weeks in case something happens a fourth time) 'your not pregnant are you????'

And I thought, well what if I am... does that really matter???? what do mothers do with their kids when they are pregnant? not pick them up???

So any help will be good. I need to know if I should be avoiding picking her up or anything else heavy...