Just wanted to weigh in on this topic, even though this is kind of an old thread. There are a few things to consider in regard to trying to have a baby when one or both partners is HIV positive, but the process doesn't necessarily have to be complicated.
If the female member of the couple is HIV positive then her doctor will keep track of her viral load and immune cell count, and may start her on medication if she isn't already taking it. Her medication will likely increase once she hits the 3rd trimester as well due to an increased blood volume during this time. While many HIV-positive women deliver via c-section, it's entirely possible for an HIV-positive woman to deliver vaginally if her viral load is low enough. She'll be kept on an AZT drip during labor and delivery, with the drip being started an hour or so before delivery if possible.
If the male of a couple is HIV positive and the female isn't then it gets a bit more complicated. In order to safely get pregnant without running the risk of infection then artificial insemination must be performed and the semen must undergo a procedure known as "sperm washing" to separate the sperm from the other fluid (which is what carries the virus.) Since there's no HIV in the sperm itself, a pregnancy achieved in this manner carries no risk to the baby so long as the mother is HIV negative. If the mother is HIV positive then this method is still recommended because of the risk of co-infection (which means that the mother could become infected with the specific strain of HIV that the father has in addition to the strain she was already infected with.)
There is surprisingly little risk to the father if he's HIV negative unless the mother's viral load is out of control; the risk is increased if the father hasn't been circumcised, but in general it's somewhat difficult for a man to catch HIV from a woman provided that he doesn't have any sores, cuts or abrasions on or around his [censored].
As for the baby, it's estimated that he or she has a less than 2% chance of contracting HIV from the mother provided that the mother was adherent to her medication during the pregnancy and proper delivery precautions were taken. The child is tested for HIV at birth, again every few months up until 6 months and then one more time at 1 year. Liquid AZT is administered until the child tests negative twice, at which point an antibiotic is given until another negative test at 6 months. After that point the child doesn't require any additional treatment, and the likelihood of the child being positive on the 1-year test is horribly small.