How do we know that eating garlic makes your amniotic fluid smell? And of what?

The “of what” is probably obvious, it smells garlicky.

We know this because of a small experiment, designed to be part of a larger investigation, studying the food preferences of adults. The suspicion was that food preferences may be formed whilst in utero and be heavily influenced by the tastes they are exposed to whilst in the mothers womb. The experiment was designed to demonstrate that the smell of amniotic fluid can be altered by strongly flavoured foods, and therefore they will be experienced by the baby.

The study consisted of 10 women who were already undergoing amniocentesis (AKA amniotic fluid test or AFT, where amniotic fluid is taken to determine certain genetic disorders or chromosomal abnormalities). Half were given a placebo pill and the other half a garlic pill approximately 45 minutes before the procedure. These samples were then randomly paired, one from the placebo group and one from the garlic, and offered up to a panel of adults. The panel were asked to smell each sample, at room temperature, and state which of the two substances (they were not aware they were smelling amniotic fluid at the time) smelled more strongly of garlic. The results showed that of the 5 garlic capsule group samples, 4 were judged to be stronger or more like garlicky than the samples taken from the placebo group.

http://chemse.oxfordjournals.org/content/20/2/207.abstract