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: 
Certainly not in a year, no. Growth is limited by multiple things, for example:

* bone ossification - bones need to both grow laterally and also get ossified. There's a few values for bone growth in children [in this paper](http://www.boneandjoint.org.uk/content/jbjsbr/44-B/1/42.full.pdf) - basically, a few centimeters a year.
* skin needs to grow. And the larger a person gets, the greater their surface gets. Think about how long wound healing can sometimes take.
* neurons in the brain need to grow - your education alone will need several years, and will often have to wait for the growing brain to catch up

You can estimate a lower limit from two scenarios:

* there's people who never stopped producing human growth hormone, which is one of the factors in determining when children grow. [Robert Wadlow](https://en.wikipedia.org/wiki/Robert_Wadlow)'s body never stopped growing until he died at age 22 and roughly 270 centimeters. If he was born at around 50 centimeters, that's roughly 10 centimeters a year.
* the "peak growth velocity" in teenagers, who grow the fastest, is also [around 9 centimeters a year](http://pediatrics.aappublications.org/content/102/Supplement_3/507)

So basically, 10 centimeters a year would be a believable growth rate, meaning from 50 to 180 centimeters, you'd need about 13 years. Under optimal conditions, with great nutrition etc., a decade sounds believable. 

However, you might want to keep in mind that this is only lateral growth. [The human brain isn't considered fully mature until the mid-20s.](http://hrweb.mit.edu/worklife/youngadult/brain.html)
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.