Smell is the sense responsible for perceiving the concentration of volatile molecules present in the air. Its interaction with the brain allows these stimuli to be decoded and turned into perception. The nerve cells that carry olfactory stimuli reach the hypothalamus and other brain structures of the limbic system* through nerve pathways that are still being studied today. In this way, certain odors can trigger salivation and gastrointestinal motility, or induce nausea and vomiting. Smell is also closely connected to taste; just think of how, when you have a cold that «blocks» your nose, you can't taste your food properly. Considering the link between smell and taste, it becomes clear that this connection serves digestion and the assimilation of useful foods, and helps avoid the ingestion of potentially harmful substances.
In animals, smell plays a fundamental role in mating and reproduction rituals, which are in fact guided by the production of pheromones, molecules that attract the opposite sex through an olfactory stimulus. This involves a different olfactory system known as the «sexual nose» (or vomeronasal organ), which carries sensations to a different area of the brain than the traditional olfactory cortex, specifically to a region thought to be responsible for emotional responses and «innate behaviors». Today, in the human species, it is not clearly known how much of this organ remains functional or through what mechanisms. What is certain, however, is that it is active in the fetus, and that a newborn's recognition of its mother happens through smell, helping the baby find its source of food and form its first forms of interaction with it.
In the womb, olfactory cells begin to develop at 8-9 weeks of pregnancy (a little over a month after the missed period).
The aromatic molecules from foods pass into the amniotic fluid, and since they are perceived by the fetus, they could influence the future child's food choices. Healthy food metabolism (which later affects the onset of obesity and related conditions) is in fact shaped by the first 1000 days of nutrition, which include the entire gestational period.
The child's future food choices are therefore shaped both by the mother's cravings, likes, and dislikes during pregnancy (which should therefore be taken into consideration) and by the smell-food-reward system that forms in the limbic system, which can lead to foods being chosen for reasons other than real nutritional needs.
* The limbic system is the part of the brain that controls emotions, eating and sexual behavior, and memory formation. This is why a particular smell or scent is often connected to emotions and memories, even from far back in time.