From Molecules to Monitors: Advancing Fertility Biomarker Science for Precision Reproductive Health

The female reproductive cycle is governed by a tightly choreographed sequence of hypothalamic, pituitary, and ovarian signals. For decades, clinical assessment has relied on a limited set of established markers - serum estradiol, luteinizing hormone, and progesterone - supplemented by basal body temperature and cervical-fluid observation. Newer analytes, including urinary pregnanediol-3-glucuronide, inhibin A and B, anti-Müllerian hormone, CA125, and cervicovaginal mucins, are expanding the toolbox, while quantitative home monitors now bring laboratory-grade hormone measurements to the bedside. Critically, biomarker science now extends well beyond the fertile window of the ovulatory cycle: the same endocrine transitions that govern ovulation also shape the postpartum return of fertility and the hormonal cascade of perimenopause - a lifespan perspective that clinical practice is only beginning to capture. Despite this progress, the field still lacks an integrated, time-resolved picture of which biomarkers best identify the fertile window, predict ovulation, and flag pathologies such as polyendocrine metabolic ovarian syndrome (PMOS), luteal-phase deficiency, and premature ovarian insufficiency.

This Research Topic aims to consolidate current knowledge on fertility biomarkers and chart the next generation of measurable signals, analytical methods, and clinical applications that will improve the diagnosis, management, and lived experience of reproductive health across the lifespan. We invite contributions that (i) describe the molecular, cellular, and anatomical events of the ovulatory cycle in quantitative, time-resolved terms; (ii) benchmark established and novel biomarkers against gold-standard endpoints such as ultrasound-confirmed ovulation and conception; (iii) translate biomarker science into clinical assays and at-home monitoring devices that are accurate, affordable, and user-friendly; and (iv) apply computational approaches - including functional data analysis, mixed-effects modeling, and machine learning - to combine multiple biomarkers into robust predictors of fertility and reproductive transitions.

To gather further insights into the molecular-to-clinical continuum of fertility assessment, we welcome contributions that investigate, compare, or apply biomarkers across the full spectrum of ovulatory physiology and its adjacent reproductive transitions.

We welcome articles addressing, but not limited to, the following themes:

• Time-resolved measurement of hormonal biomarkers - estradiol, LH, progesterone, PDG, FSH, inhibin A/B, and AMH - across the ovulatory cycle, the postpartum period, and the perimenopause transition.
• Biochemical, cellular, and anatomical characterization of folliculogenesis, ovulation, and the luteal-follicular transition.
• Cervical and cervicovaginal mucin biomarkers and other non-hormonal indicators of the fertile window.
• Application of these tools to the diagnosis and management of reproductive disorders, including PMOS, luteal-phase deficiency, unexplained infertility, premature ovarian insufficiency, and perimenopause.

Topic Editor Stephen J. Usala is a co-inventor on an international patent application (PCT/US2025/026119, filed by Texas Tech University Health Sciences Center) related to the use of inhibins as biomarkers. Topic Editor Thomas P. Bouchard receives financial support from Quanovate Tech Inc. through a Mitacs-cosponsored grant. Topic Editor Indrajit Chowdhury declares no competing interests with regard to the Research Topic subject.