Brain Biology, Hormones, and Mood Before Pregnancy
- Kathy Morelli
- Mar 31, 2014
- 5 min read
Updated: Feb 19
Women’s mental health is shaped by an intricate interaction between genetics, reproductive hormones, stress physiology, and lived experience. Understanding how brain biology and hormonal systems interact before pregnancy helps explain why some women are more vulnerable to mood changes during the perinatal period.
Somatic psychology bridges the study of emotion, physiology, and lived experience. It recognizes that the mind and body are not separate systems, but parts of a continuous feedback process. Emotional responses are shaped not only by thought patterns, but also by the health and regulation of the nervous system.
This integrative perspective is especially relevant in reproductive mental health, where hormonal, psychological, and relational systems converge.
Genetic vulnerability and stress sensitivity may increase risk for mood disorders during reproductive transitions.
Perinatal mental health is deeply influenced by how the nervous system and endocrine system respond to reproductive transitions. These systems are not separate from emotional experience — they are foundational to it.
Genetics: Innate temperament and family history
Innate temperament is a concept developed and researched by Alexander Thomas and Stella Chess. In the 1950’s, by studying infants and children across many years. They identified nine dimensions of temperament: activity (constant motion or less so), rhythmicity (internal biological schedule), initial reaction of approach or withdrawal in new situations, adaptability to change, intensity of emotion, general upbeat or downbeat mood, distractibility (tendency to be sidetracked), persistence and sensitivity to external stimuli.
Chess and Thomas also found that 65% of infants and babies are innately “easy” “difficult” or “slow to warm up.” Easy babies tend to have regular sleep and eating schedules, adapt to change easily and don’t fuss a lot. Difficult babies tend to have irregular sleeping and eating schedules, and fuss a lot. Slow to warm up babies withdraw from new experiences. Chess and Thomas found that these traits are stable throughout childhood.
These traits often persist into adulthood, yet are modifiable through awareness, life experiences and training. But innate temperament influences how one regulates stress and emotion.
A family history of mental illness, such as schizophrenia, bipolar disorder, major depressive disorder, generalized anxiety disorder is an indication that an individual might have a genetic predisposition to mental health issues.
Reproductive Hormones and Mood: The Estrogen–Serotonin Relationship
Fluctuating estrogen levels influence neurotransmitter systems, including serotonin.
Serotonin plays a significant role in mood regulation, sleep, appetite, and anxiety.
Estrogen does not directly “produce” serotonin, but it modulates serotonin activity in the brain. When estrogen levels shift — as they do across the menstrual cycle — serotonin activity may shift as well.
This helps explain why some women experience mood changes premenstrually or during other hormonal transitions.
The Stress Response System: The HPA Axis
The Hypothalamic–Pituitary–Adrenal (HPA) axis is the body’s central stress response system.
When the brain perceives a stressor:
The hypothalamus releases corticotropin-releasing hormone (CRH).
The pituitary gland releases adrenocorticotropic hormone (ACTH).
The adrenal glands release cortisol.
Cortisol mobilizes energy and prepares the body to respond to challenge.
This process unfolds rapidly and is designed for short-term adaptation. However, chronic activation of the HPA axis — especially in individuals with prior trauma or ongoing stress — can dysregulate mood, sleep, and immune function.
The limbic system, including the amygdala and hippocampus, continuously evaluates perceived safety and threat. These brain regions interact with the HPA axis in a dynamic feedback loop.
The stress system and the reproductive hormone system are not separate. They influence one another.
The Ovarian–Hypothalamic–Pituitary Feedback Loop
The menstrual cycle reflects ongoing communication between the ovaries and the brain.
Across an average 28-day cycle:
Estrogen rises during the follicular phase.
It peaks prior to ovulation.
Progesterone rises during the luteal phase.
Both hormones decline before menstruation.
These fluctuations influence neurotransmitter systems and stress reactivity.
For some women, sensitivity to hormonal change contributes to premenstrual mood symptoms. This sensitivity may also signal increased vulnerability during larger hormonal transitions — including pregnancy and postpartum.
The Limbic System and Lived Experience
In addition, keep in mind the limbic system is an open feedback loop. We continuously gather information from our perception of the external world, feed into our internal emotional system and then react based on our interpretation of those perceptions.
The limbic system — including the amygdala, hippocampus, and hypothalamus — continuously evaluates internal and external cues for safety and threat. It is not a closed mechanical system. It responds dynamically to lived experience.
Past trauma, current stress, relational safety, and perceived meaning all influence how the stress-response system activates. This ongoing interaction between perception, memory, and hormonal regulation creates a fluid feedback process rather than a fixed biological state.
In this sense, emotional experience and physiology are in constant dialogue. Life situations influence neurobiology, and neurobiology influences emotional experience.
This dynamic responsiveness of the limbic system helps explain why two women with similar hormone levels may have very different emotional experiences.
The Estrogen–Serotonin Relationship
Estrogen plays a regulatory role in serotonin function. Serotonin is a neurotransmitter involved in mood stability, sleep regulation, appetite, and anxiety modulation.
Rather than being a simple “precursor,” estrogen influences serotonin in several ways:
It affects serotonin synthesis and receptor sensitivity.
It influences serotonin transport and breakdown.
It modulates brain regions involved in mood regulation.
As estrogen fluctuates across the menstrual cycle, serotonin activity may shift as well. For women who are particularly sensitive to hormonal changes, this interaction may contribute to premenstrual mood symptoms.
This sensitivity to hormonal fluctuation can become clinically relevant during larger endocrine transitions, such as pregnancy and postpartum.
Serotonin interacts closely with limbic structures such as the amygdala and hippocampus.
Because these brain regions are involved in emotional processing and memory, shifts in serotonin activity may influence how stress and relational experiences are perceived and integrated.
Why This Matters Before Pregnancy
Before pregnancy even begins, three major biological systems are already interacting:
Genetic vulnerability
Hormonal regulation
Stress physiology
These systems shape how a woman’s nervous system adapts to reproductive change.
Serotonin, the Limbic System, and Lived Experience
Serotonin is deeply involved in mood regulation, emotional flexibility, sleep, and stress tolerance. It interacts closely with limbic structures such as the amygdala and hippocampus — brain regions responsible for emotional memory, threat detection, and attachment.
When serotonin signaling is well regulated, the limbic system tends to process emotional stimuli with greater balance. When serotonin activity is disrupted — whether through hormonal fluctuation, chronic stress, or genetic vulnerability — emotional responses may become more intense, rigid, or difficult to regulate.
Importantly, this relationship is bidirectional.
Life experience influences serotonin function. Chronic stress, trauma exposure, relational safety, and perceived meaning can alter stress hormone output and neurotransmitter activity. In turn, serotonin levels influence how the limbic system interprets and responds to life events.
In this way, biology and lived experience are in constant dialogue.
Takeaway
Before pregnancy begins, the nervous system already reflects a lifetime of biological sensitivity and lived experience — both of which influence how a woman adapts to reproductive change.
Continue exploring the neurobiology of perinatal mental health:
• Postpartum Hormones and Mood
Serotonin is involved with mood. Decreased serotonin levels are associated with depression, anxiety, aggression, sleep disruption, and irritability.
The precursor to serotonin is, guess what, estrogen!
So estrogen is powerhousing the availability of serotonin, the mood hormone, which, in turn, greases our brain-bio loop, the HPA axis, and affects how we feel!
Next, let’s look at how much the availability of estrogen fluctuates during a woman’s reproductive cycle.
Serotonin, one of the kick-off hormones of the HPA axis, is produced in the hypothalamus, which is a part of the emotional brain center, and affects mood: anger, depression and anxiety.
The precursor to serotonin, produced in the hypothalamus, is estrogen, which is produced in the ovaries.
And estrogen fluctuates with our menstrual cycle! So, women’s hormonal cycles are directly related to the chemistry of the emotional brain and the stress feedback loop.
Now let’s look at the enormous hormonal changes pregnancy, birth and postpartum bring to emotional brain chemistry!
In Part Two, we’ll look at the enormous hormonal changes pregnancy, birth and postpartum bring to emotional brain chemistry!
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