*In utero*, the growing little human is getting ready to be an independently functioning individual. While it is everything but that, it must be able to obtain fluids and nutrients through its mother's milk, and that from pretty much the first hour of its life.

To develop proper kidney function, the growing fetus needs to ingest fluids just as it will do *post partum*. Because a mini bar isn't available, it has to drink whatever is available, i.e., amniotic fluid and indeed, its own urine. Shortly after the kidneys start to produce urine, the fetal swallowing commences [(Underwood *et al*., 2005)][2]. 

If the fetus would have to prevent the production of urine *in utero*, the kidneys would have to remain nonfunctional during development, which would be disastrous once it is born. Renal failure is in fact pretty common in newborns, but can be fatal without proper treatment [(Andreoli, 2004)][1].

The water in amniotic fluid originally comes from maternal plasma and passes through the fetal membranes. As the placenta develops, water and solutes from maternal plasma pass across the placenta to the fetus and then to the amniotic fluid [(Underwood *et al*., 2005)][2]. 

<sub>**Reference**  
**-** [Andreoli, *Semin Perinatol* (2004); **28**(2): 112-23)][1]  
**-** [Underwood *et al*., J Perinatol (2005); **25**: 341–48][2]</sub>

  [1]: http://www.ncbi.nlm.nih.gov/pubmed/15200250     
  [2]: http://www.nature.com/jp/journal/v25/n5/full/7211290a.html