Question: In my world human(oid)s are not born anymore, they are grown in pods which mirror the conditions of a natural womb.

Children are educated before birth and are "born" as fully mature adults with a standard education ready to join society.

How long would this process take? I assume that artificial growth could be much quicker than a natural 18-20 year period. Could a human be grown in a year? A decade?

Answer: 
**18 weeks to 6 or 8 years, but it does not matter**

9 months to produce an infant is a long time compared to the initial growth rate of the embryo. At 4 weeks, the embryo is the size of a poppy seed (2 mm long), at 8 weeks, the size of a kidney bean (16 mm head to bottom). During that period, the human increased by at least a factor of 8. This is a growth rate of about 68% per week. At this rate, you are large newborn at 15 week and a full sized adult in under 18 weeks.

So, we have a reasonable lower bound of about 18 weeks and an upper bound of about 18 years. But can we find a better upper bound? Yes we can, [Robert Wadlow](https://en.wikipedia.org/wiki/Robert_Wadlow) was the tallest modern man that can be reliably documented. At age 6, he 5'7" and was already taller than his father at age 8. So 6-8 years seems like a better upper bound since people can grow that fast with too much human growth hormone.

Robert Wadlow had health problems and in fact died of medical complications of an autoimmune disease (possibly related to his HGH levels) at age 22. He was reportedly in good health until the final year of his life. His brain was certainly not mature at age 6 or 8, but lets assume that it could be close enough to be considered adult if he had a magical efficient training systems and nanotech to re-arrange brain structures as needed.

So 18 weeks to 6 years. Hypothetically speaking, after all of the needed advances in technology, including nano-tech what could we do?

The answer is simply unknown since we don't have the medical knowledge of the complications of accelerated growth in an artificial womb. Perhaps with nano-technology we could control physical growth, perform the necessary muscle and bone training, deal with the psychological and sociological training. Training the interactions between the brain and eyes, ears, hands, etc. Perhaps it is also possible to teach language, reading, writing, arithmetic, etc. in the womb.

There is a huge gulf between our current state of knowledge and that needed to perform all development in the womb. And there is very little incentive to acquire it. 

Parents want to watch their children grow up, play, learn from their environment, etc. I can't image any parent I know desiring to replace this process with an artificial one.
Human growth is subject to many limiting factors, including the ability of the mother to supply the required nutrients to the foetus, and after birth, the ability of the child to acquire the full range of expected social skills.

A young human is physically small in order to convey the impression of youth to other humans. Since learning to be an adult human takes around eighteen to twenty-five years, that is how long it takes for the human body to mature fully. Size and other physical traits conveys an impression of age to others.

Now, if humans could grow to maturity and be born with all necessary knowledge to be fully functioning adults, as well as be free of the limitations of maternal nutrition, growing such a human in-vitro could occur in a relative short period of time.

In larger mammalian - and dinosaur - species where achieving an adult body-size (of several hundred kilograms to many tons) as quickly as possible is of paramount importance, very high growth rates can be achieved, with newborns achieving maturity within a handful of years, certainly within 5 years or less.

We could therefore expect that with genetic engineering - or some clever artificial stimulation - to remove the limits on pre-maturity growth-rate, a fully mature human could be produced within three years.

I should point out that if humans were genetically engineered to grow that quickly, it would effectively sterilize the population and make them dependent on artificial reproduction. Should a modified human mother become pregnant, her body would not be able to supply the huge metabolic needs that such a foetus impose on her, and a significant or even fatal loss of body mass would likely occur. Should the foetus survive, it would be no better educated than any normal human newborn.

On the other hand, if humans were grown rapidly and educated in-vitro through medical trickery rather than genetic engineering, a natural pregnancy would most likely be possible, with a normal-sized infant being born after the usual period of gestation. It is up to you if the mother would have been educated sufficiently to have the knowledge to handle a naturally-born child.