Why Pregnancy Can Increase Cravings: New Insights into the Brain

Suddenly craving chocolate, chips, or other particularly tasty foods? Food cravings are a familiar phenomenon for many women during pregnancy. A new study now suggests that habits or metabolic changes may not be the only factors behind this shift in eating behavior. Apparently, pregnancy also alters certain neural circuits in the brain.

Researchers have identified a mechanism in pregnant mice that influences the preference for particularly tasty foods. At the heart of this mechanism are serotonin-producing neurons, a specific potassium channel, and a connection to the brain’s reward system.

The results were published in the journal Nature Neuroscience. It is important to note, however, that the studies were conducted on mice. Whether the same mechanism is responsible for pregnancy cravings in humans remains to be investigated.

A Specific Region in the Brainstem Comes into Focus During Pregnancy

The scientists focused on the so-called dorsal raphe nucleus. This is a region in the brainstem that serves as a particularly important source of serotonin in the brain. From here, nerve fibers extend to numerous other brain regions, where they influence various functions—including mood, motivation, stress responses, and the regulation of food intake.

Serotonin is a neurotransmitter often associated with well-being and mood. However, its roles in the brain are far more diverse. Depending on which nerve cells are activated and in which brain region the signals arrive, serotonin can influence, among other things, how strongly a stimulus is perceived as rewarding, how we react to food, and how easily a certain behavior is triggered or inhibited.

The serotonergic system also plays a role in regulating hunger and satiety. In this context, serotonin does not act as a simple “on” or “off” switch for appetite. Rather, it is part of a complex network that integrates information about the body’s energy needs, food stimuli, and the expected reward from certain foods. The connection between serotonin-producing neurons and the brain regions that control motivation and reward is therefore particularly interesting.

This is precisely where the new study comes in. In the pregnant mice studied, the serotonin-producing neurons in the dorsal raphe nucleus fired less frequently than in non-pregnant animals. At the same time, the animals exhibited a more pronounced craving for particularly palatable food. The researchers suspect that the reduced activity of these neurons could weaken the normal control over reward-driven foraging behavior. As a result, foods with a high reward value—such as particularly sweet or energy-dense foods—might become more prominent during pregnancy.

What is interesting here is that this apparently is not simply a matter of a general increase in hunger. Rather, the findings point to a change in motivation: certain foods could become more appealing due to the altered activity of the serotonergic system. However, the role this mechanism plays in humans remains unclear. The findings to date come from a mouse model and therefore cannot be directly applied to human pregnancies.

The SK3 Channel Acts Like an Electrical Brake

While searching for the cause of the reduced activity, the scientists came across a specific potassium channel: SK3. Such channels influence the electrical activity of nerve cells. Put simply, a more active SK3 channel can make it harder for a nerve cell to generate electrical signals. During pregnancy, the activity of this channel increased in the serotonin-producing nerve cells studied. This dampened their activity.

The researchers were then able to test whether SK3 actually plays a crucial role. They specifically removed the channel from the corresponding nerve cells of female mice. In these animals, the activity of the serotonin neurons remained largely intact during pregnancy. At the same time, the observed, hedonically motivated food-seeking behavior decreased.

The counter-experiment yielded a similar picture: When SK3 was artificially enhanced in non-pregnant mice, the animals developed changes in neuronal activity and food-seeking behavior that resembled those of pregnant mice.

Connection to the Reward System

However, this still did not explain how a change in serotonin activity ultimately influences eating behavior. Therefore, the team investigated the connections between the relevant neurons and other areas of the brain. In the process, the ventral tegmental area (VTA) came into focus.

The VTA is part of a network involved in motivation, reward processing, and reinforcing behavior. The researchers found a connection between serotonin-producing neurons in the dorsal raphe nucleus and this region.

According to the study’s model, this connection normally has an inhibitory effect on reward-related food-seeking behavior. If the activity of serotonin neurons is reduced during pregnancy, this inhibitory effect could weaken. As a result, the reward system might respond more strongly to particularly palatable foods.

A Targeted Intervention Altered Behavior

The researchers went a step further and specifically manipulated the connection between the dorsal raphe nucleus and the VTA. When this signaling pathway was activated in pregnant mice, the observed food-seeking behavior decreased. Conversely, disrupting the signaling pathway in non-pregnant animals led to more intense craving-like behavior.

The research team thus identified a possible link between a molecular mechanism and altered reward and food-seeking behavior during pregnancy. Put simply, the study reveals the following relationship: During pregnancy, the SK3 channel becomes more active in certain serotonin neurons. As a result, these neurons become less active, and their inhibitory signals to the brain’s reward system diminish. This could lead to particularly tasty foods being perceived as more rewarding, thereby creating a more intense craving for them. However, this model describes the results of the mouse study and does not yet prove that the same process occurs in humans.

Why This is Interesting for Pregnancy Research

Food cravings during pregnancy are, first and foremost, a common phenomenon and do not automatically indicate a health problem. However, in cases of very severe or persistent changes in eating behavior, nutrition, weight gain, and metabolism can become relevant factors.

The new research is particularly interesting because it identifies a possible biological basis for changes in food motivation. In the long term, it could help explain why some animals respond more strongly to particularly energy-dense foods during pregnancy. The authors also see this as a potential starting point for further research into pregnancy-related changes in appetite and weight gain.

No Treatment Yet for Pregnant Women

However, research is still a long way from developing a treatment based on these findings. The study provides insights from an animal model. It is therefore unclear whether SK3 and the described serotonin circuit are altered in the same way in humans during pregnancy.

Furthermore, directly manipulating the serotonin system during pregnancy would by no means automatically be safe. The scientists therefore emphasize the need for further research. Among other things, they plan to investigate how pregnancy hormones such as estrogen and progesterone interact with the identified mechanisms.

A New Perspective on Pregnancy Cravings

The study may thus shift our understanding of a well-known pregnancy phenomenon: cravings could be influenced, at least in part, by specific changes in neural networks that alter their activity during pregnancy.

Further research is needed to determine whether the mechanism observed in mice also plays an important role in humans. What is certain so far is that the brain relies on a complex interplay of neurons, neurotransmitters, ion channels, and hormonal signals to regulate hunger and reward behavior.

The new findings provide another piece of the puzzle—and at the same time raise the question of how pregnancy hormones and neural circuits work together to influence which foods suddenly seem particularly tempting.