Boob sagging

Can anybody here give any tips for battling with boob sagging post pregnancy? I am pregnant with my 2nd baby. I had noticed difference in my breasts after my 1 child was born; I had breast fed her for about 6 months then weaned off. I am scared now after 2nd baby will it be worse... I know one can't totally prevent it, but any tips are welcome. Thanks a bunch!