How to initialize a shared_ptr that is a member of a class?

I am not sure about a good way to initialize a shared_ptr that is a member of a class. Can you tell me, whether the way that I choose in C::foo() is fine, or is there a better solution?

class A
{
  public:
    A();
};

class B
{
  public:
    B(A* pa);
};

class C
{
    boost::shared_ptr<A> mA;
    boost::shared_ptr<B> mB;
    void foo();
};

void C::foo() 
{
    A* pa = new A;
    mA = boost::shared_ptr<A>(pa);
    B* pB = new B(pa);
    mB = boost::shared_ptr<B>(pb);
}