I'm not sure if this mod exists, but I haven't been able to find it.
With the research station from Sims 3 University, you can make a clone baby of sims and collect DNA from other sims.
With the hospital in Oasis Landing from Sims 3 Into the Future, your sims can go to the future hospital and make a custom baby with two sims' DNA for 5000 simoleons (but the two sims must be present for this to work).
Does anyone know if there is a mod where you can bring DNA samples to the future to make genetically engineered babies with? As in, a sim can request DNA from someone, go to the future, and make a child with them without having to travel with them to the future or being in the same household.