Hormonal Changes During Breastfeeding
After childbirth, a woman’s body undergoes significant physiological changes as it transitions from pregnancy to the postpartum state. In women who breastfeed, hormonal adaptations associated with lactation affect not only milk production but also reproductive function, the genitourinary tract, and the interpretation of observable fertility signs.
Following delivery of the placenta, progesterone levels decline rapidly while prolactin levels rise, initiating breast milk production. During regular breastfeeding, elevated prolactin suppresses the hypothalamic-pituitary-ovarian axis, resulting in reduced production of estrogen and androgens. As a result, the body enters a temporary hypoestrogenic and hypoandrogenic state.
This is a normal physiological adaptation that helps prevent a new pregnancy while the infant is dependent on breastfeeding. However, this state is not permanent. As breastfeeding becomes less frequent or ovarian function gradually resumes, sex hormone levels begin to rise, and fertility is progressively restored.
How Does This Affect Fertility Awareness Observations?
Women using Fertility Awareness Methods (FAM) can observe these hormonal changes through their daily charting.
During lactation, many women identify a Basic Infertile Pattern (BIP), which may consist of continuous dryness or an unchanging pattern of cervical mucus observed day after day.
The appearance of a new or changing mucus pattern may indicate that ovarian activity is returning and that the first postpartum ovulation is approaching.
However, pronounced vaginal dryness and the absence of cervical mucus may represent not only a specific BIP but also a more marked hypoestrogenic state. These symptoms have led to the introduction of the term Genitourinary Syndrome of Lactation (GSL).
What Is Genitourinary Syndrome of Lactation (GSL)?
Genitourinary Syndrome of Lactation (GSL) is a relatively new term proposed to describe the collection of genitourinary symptoms associated with the physiological decline in estrogen levels during breastfeeding.
Common symptoms include:
- Vaginal dryness
- Reduced cervical mucus production
- Decreased natural vaginal lubrication
- Thinning and increased sensitivity of the vaginal epithelium
- Painful intercourse (dyspareunia)
- Vaginal irritation or burning
- Increased vaginal pH
- Reduced Lactobacillus populations
- Increased susceptibility to urinary tract infections
These changes are considered a consequence of physiological lactational hypoestrogenism and, in most women, gradually improve as ovulatory cycles return.
How Common Are These Symptoms?
Although formal diagnostic criteria for GSL have not yet been established, the symptoms associated with this proposed syndrome are common.
A 2025 systematic review and meta-analysis of 65 studies found that among breastfeeding women:
- 63.9% had signs of vaginal atrophy.
- 53.6% reported vaginal dryness.
- Approximately 60% experienced dyspareunia three months after childbirth.
These findings suggest that hypoestrogenic changes affecting the genitourinary tract are common during lactation and may have a substantial impact on quality of life.
Why Can Fertility Awareness Methods Be Helpful?
Most available studies on GSL are cross-sectional and rely primarily on symptom questionnaires or clinical assessments, capturing women’s condition at a single point in time rather than tracking symptom evolution throughout lactation.
In contrast, women using FAM record cervical mucus observations daily. These charts document changes over weeks and months, including the characteristics of BIP and the gradual return of fertility signs.
Fertility charts cannot diagnose GSL and should not replace medical evaluation. However, they may provide additional information about the pattern and progression of changes, which may be useful for both the woman and her healthcare provider when discussing symptoms. Regular charting may also help women recognize persistent or worsening symptoms and seek medical advice when appropriate.
Are There Any Official Guidelines?
As of August 2026, the term Genitourinary Syndrome of Lactation (GSL) is increasingly used in the scientific literature but has not yet been incorporated into national or international clinical guidelines.
Consequently, there are currently no GSL-specific treatment guidelines. Management is based on existing recommendations for individual symptoms.
First-line treatment generally includes:
- Vaginal moisturizers
- Personal lubricants
- Avoidance of local irritants
- Patient education
- Pelvic floor physical therapy when pain is present
- Treatment of associated conditions such as urinary or vaginal infections
For women with more severe symptoms, some experts consider low-dose vaginal estrogen therapy after an individualized discussion of its potential benefits and risks.
How Might Vaginal Estrogens Affect Fertility Awareness Charting?
Over the past few months, we have received several questions from fertility educators and FAM users about whether vaginal estrogen preparations may affect the fertility biomarkers used for charting. However, evidence specifically addressing their impact on FAM observations remains limited.
To our knowledge, no studies have directly evaluated how vaginal estrogen therapy affects cervical mucus observations within the context of fertility awareness-based methods. Possible effects on charting are therefore inferred from the known physiological actions of estrogens.
Estrogens support the health of the vaginal and cervical epithelium and contribute to cervical mucus production. Therefore, vaginal estrogen therapy may theoretically influence a woman’s usual BIP by changing the amount, consistency, or sensation of vaginal secretions. This may make mucus observations more difficult to interpret, particularly for women who primarily rely on cervical mucus as their fertility biomarker.
If ovulatory cycles have resumed and a clear post-ovulatory temperature shift is established, basal body temperature observations may provide additional information when interpreting fertility patterns.
If ovulation has not yet returned and temperature observations are not informative, women may continue identifying their BIP while recording the days when vaginal estrogen therapy is used. These records may help consider whether changes in vaginal secretions are potentially associated with treatment or reflect the gradual return of fertility-related hormonal activity.
Further research is needed to better understand how vaginal estrogen preparations may influence fertility biomarkers and chart interpretation during lactation and postpartum recovery.
If you have used vaginal estrogen therapy and recorded your fertility chart (including cervical mucus observations, basal body temperature, and relevant notes about treatment timing), we would welcome the opportunity to learn from your experience. Sharing anonymized charts may help improve understanding of how these treatments may interact with fertility awareness observations.
