Anyone choose to have just one child?

We currently have one daughter who is 4 years old. DH and I could never agree on how many kids we wanted, but we always said that we would never have an only child. Well, it now looks like that just might happen. DD's birth mom is pregnant again and considering placing with us, but if she doesn't then we are done. I believe there are pros and cons to both sides, but we're happy with what we have. If K places again, we'll be excited and eagerly welcome this baby into our family. However, if she parents this time, we'll be happy for her and continue to enjoy our family of three.