Physically, it is best to give birth as early as possible – the body will have a much easier time during pregnancy, the birth will be easier, and you would get recovered so much better and faster. In addition to that, the fewer illnesses come out for you, the less will be passed over to the next generation. This is why each new generation is sicker and sicker as young people – we are giving birth at a more advanced age now, and by this age people get lots of sicknesses and health issues. On the other hand, psychologically and socially it is best to wait till 30-35 – you will make a much more conscious choice (partner, desire to have a kid), you will be much smarter and will be able to raise the kid better, and will have the financial ability to provide him with more things. This is my opinion.