Menstrual bleeding patterns among regularly menstruating women

Endometriosis phenotypes and staging in relation to lipid biomarkers: Findings from the ENDO Cohort Study

Schliep KC et al., 2026 · J Gynecol Obstet Hum Reprod · Free full text on PubMed Central

Endometriosis has been linked to cardiometabolic alterations, but whether these associations vary by disease severity or phenotype is unclear. We examined lipid profiles across endometriosis diagnosis, stage, and typology. Data came from 476 women in the NICHD ENDO cohort. Endometriosis was confirmed laparoscopically and staged using the rASRM criteria (I-IV). Typology was categorized as superficial endometriosis (SE), ovarian endometrioma (OE), deep infiltrating endometriosis (DE), and OE+DE. We compared endometriosis status, stage (I/II vs III/IV), and typology to no endometriosis using adverse lipid thresholds (total cholesterol ≥200 mg/dL, HDL <50 mg/dL, LDL ≥100 mg/dL, triglycerides ≥175 mg/dL, non-HDL ≥130 mg/dL, VLDL ≥30 mg/dL, ApoA1 <125 mg/dL, and ApoB ≥120 mg/dL). Adjusted prevalence ratios (aPR) and 95 % CIs were estimated via generalized linear models, controlling for age, race/ethnicity, BMI, income, marital status, and serum cotinine. Endometriosis diagnosis alone was not associated with adverse lipid profiles. In contrast, moderate/severe disease showed higher prevalence of elevated triglycerides (aPR= 2.27; 95 % CI: 1.18,4.35) and VLDL (aPR= 2.41; 95 % CI: 1.50, 3.85). Typology revealed stronger patterns: OE and OE+DE were associated with adverse profiles across multiple markers (aPRs 1.59-4.09), particularly ApoB and triglycerides. Minimal/mild disease and SE were not associated. The metabolic signal was phenotype-driven rather than diagnosis-driven, with severe stage and OE/OE+DE showing clear associations with adverse lipid profiles. These findings suggest lipid profiles may serve as markers of phenotype severity or shared biological milieu. Replication in larger cohorts is needed.

Incident endometriosis diagnosis and anti-müllerian hormone (AMH): how surgical staging and typology relate to serum AMH levels

Valenti M et al., 2026 · Am J Obstet Gynecol · Free full text on PubMed Central

Endometriosis is a chronic, gynecologic condition in which tissue similar to the lining of the uterus implants throughout the body. Women with endometriosis have a higher prevalence of infertility and a greater risk of early natural menopause compared to those without endometriosis. This study aimed to evaluate preoperative serum AMH levels among women with and without incident endometriosis and to assess whether levels differ by surgical staging and typology. The ENDO (Endometriosis: Natural History, Diagnosis, and Outcomes) study was conducted between 2007 and 2009. The ENDO study consisted of an operative and population cohort (n=600). Only those in the ENDO operative cohort from the Utah site were used for this analysis, and included women aged 18 to 44 years who were scheduled for gynecologic surgery, irrespective of clinical indication (n=476). AMH levels were measured from stored serum collected before surgery using a quantitative enzyme-linked immunosorbent assay. After excluding participants with missing outcome data (n=51), unilateral oophorectomy (n=8), or those within the population cohort (n=69), 348 participants remained for the analysis. Surgically confirmed endometriosis diagnosis, staging (American Society for Reproductive Medicine I-IV), and typology (superficial, deep, ovarian) were ascertained by the operative report. Outliers for AMH (>14.0 ng/mL) were excluded from the analyses and AMH values were log-transformed. Multivariable linear regression models adjusted for age (squared and continuous), body mass index, serum cotinine levels, and exogenous hormonal contraceptive use were conducted. Percentage differences in AMH were calculated as (exp[β]-1)×100, and 95% confidence intervals were reported. Compared with no endometriosis, incident endometriosis diagnosis was associated with lower AMH levels (-19.8%; 95% confidence interval, -37.0 to 1.0); however, this association was not statistically significant. Stage III to IV disease was associated with 40.1% lower AMH levels (95% confidence interval, -58.9 to -12.7). Ovarian endometriomas were most strongly associated with lower AMH levels (-54.3%; 95% confidence interval, -69.4 to -31.8), with a more pronounced association among those with infertility (-72.6%; 95% confidence interval, -85.4 to -48.5). Deep (-24.1%; 95% confidence interval, -48.2 to 11.0) and superficial (-15.5%; 95% confidence interval, -34.6 to 9.3) endometriosis also showed a trend toward lower AMH levels, but these findings were not statistically significant. Compared with a postoperative diagnosis of a normal pelvis, incident endometriosis was associated with 26.8% lower AMH levels (95% confidence interval, -44.6 to -3.4). Stage III to IV disease was associated with 47.8% lower AMH levels (95% confidence interval, -65.8 to -23.2), and all subtypes of endometriosis were statistically significantly associated with lower levels of AMH compared with a postoperative diagnosis of a normal pelvis (ovarian: -60.8%; 95% confidence interval, -74.4 to -39.9; deep: -34.3%; 95% confidence interval, -56.2 to -1.4; superficial: -24.8%; 95% confidence interval, -43.9 to -0.8). Ovarian and moderate to severe (stage III-IV) endometriosis were associated with markedly lower AMH levels compared with no endometriosis. Compared with a postoperative diagnosis of a normal pelvis, incident endometriosis and moderate to severe stages (stage III-IV) were associated with statistically significantly lower AMH levels. Additionally, typology (deep, ovarian, or superficial) was associated with statistically significantly lower AMH levels. However, this association was likely driven by the presence of ovarian endometriomas across all subtypes. These findings are consistent with previous studies and demonstrate that endometriosis lesions themselves, independent of surgical intervention, influence AMH levels.

Ambient air pollution during developmental windows of spermatogenesis and semen quality among an infertility treatment seeking population

Russo LM et al., 2025 · Ecotoxicol Environ Saf · Free full text on PubMed Central

Prior studies have observed impacts of air pollution on semen quality, but timing of exposure during developmental windows of spermatogenesis and impacts of low-to-moderate air pollution is less well understood. We examined the relation between air pollution and semen quality in the Folic Acid and Zinc Supplementation Trial (2013-2018), which enrolled male partners of couples seeking infertility treatment in the Salt Lake City, Utah region (n = 2015). Semen quality parameters were assessed at baseline, 2-, 4-, and 6-months follow-up. Measures of daily air pollutants at each participant's residence were abstracted from Community Multiscale Air Quality models (fine particulate matter: PM2.5, sulfur dioxide, nitrogen dioxide, and ozone: O3), linked to participants' residential addresses, and averaged across the 74-day spermatogenesis window prior to the sample collection date for each study visit, and across four developmental windows of spermatogenesis (mitosis, meiosis I-II, spermiogenesis, and spermiation). Generalized linear mixed models considered four repeated semen sample measures per participant and adjusted for co-pollutants, age, season, and income. In multi-pollutant models, O3 during early-to-mid spermatogenesis (meiosis I+II and spermiogenesis) was related to lower percent normal morphology (% difference -6.73, 95 % CI -9.82, -3.54 and % difference -3.83, 95 % CI -7.51, 0.00, respectively). Additionally, PM2.5 and O3 during late spermatogenesis (spermiation) were associated with lower count and concentration, and PM2.5 with lower progressive motility. These findings suggest that exposure to low-to-moderate levels of air pollution may negatively impact semen quality and indicate that exposure to O3 during meiosis and spermiogenesis may particularly affect normal sperm morphological development.

Child Opportunity Index at birth and asthma with recurrent exacerbations in the US ECHO program

Miller RL et al., 2025 · Journal of Allergy and Clinical Immunology · Free full text on PubMed Central

Menstrual bleeding, cycle length, and follicular and luteal phase lengths in women without known subfertility: A pooled analysis of three cohorts

Najmabadi S et al., 2020 · Paediatr Perinat Epidemiol · Free full text on PubMed Central

There is variability between women for days of menstrual bleeding, cycle lengths, follicular phase lengths, and luteal phase lengths, related to age and parity. To describe total cycle length; anovulatory cycles; follicular and luteal phase lengths; and days and intensity of menstrual and non-menstrual bleeding in women without known subfertility over the course of 1 year. 581 women (3,324 cycles) with no known subfertility (18-40 years of age) were followed for up to 1 year. Women recorded vaginal bleeding and mucus discharge daily. We used the peak day of cervical mucus as the estimated day of ovulation and the last day of the follicular phase. We used generalised linear mixed models stratified by age and parity to describe menstrual cycle parameters. The majority of women were <30 years of age (74.5%), non-Hispanic White (88.6%), and nulliparous (70.4%). The mean menses length was 6.2 (1.5) days, median 6; cycle length 30.3 (6.7) days, median 29; follicular phase length 18.5 (6.5) days, median 17; and luteal phase length 11.7 (2.8) days, median 12. Nulliparous women aged ≥30 years vs nulliparous women aged <30 had shorter cycles (29.2 days, 95% confidence interval (CI) 27.8, 30.7 vs 31.5 days, 95% CI 30.8, 32.2) and shorter follicular phases (17.6 days, 95% CI 16.2, 18.9 vs 19.6 days, 95% CI 18.9, 20.2). Among all women, within-woman differences between the longest and shortest menses length >3 days, total cycle length >7 days, follicular phase >7 days, and luteal phase >3 days were found in 11.6%, 43.0%, 41.7%, and 58.8% of women, respectively. Our findings confirm variability between women of menstrual cycle parameters related to age and parity, and also highlight within-woman variability in the follicular and luteal phases.

Fluid Retention over the Menstrual Cycle: 1-Year Data from the Prospective Ovulation Cohort

White CP et al., 2011 · Obstet Gynecol Int · Free full text on PubMed Central

We report menstrual and mid-cycle patterns of self-reported "fluid retention" in 765 menstrual cycles in 62 healthy women. Self-reported "fluid retention," commonly described as bloating, is one element of the clinical assessment and diagnosis of premenstrual symptoms. These daily diary data were collected as part of an observational prospective one-year study of bone changes in healthy women of differing exercise characteristics. Ovulation was documented by quantitative basal temperature analysis, and serum estradiol and progesterone levels were available from initial and final cycles. Fluid retention scores (on a 0-4 scale) peaked on the first day of menstrual flow (mean ± 0.9 ± 0.1), were lowest during the mid-follicular period, and gradually increased from 0.22 ± 0.05 to 0.50 ± 0.09 over the 11 days surrounding ovulation. Mid-cycle, but not premenstrual, fluid scores tended to be lower in anovulatory cycles (ANOVA P = 0.065), and scores were higher around menstruation than at midcycle (P < 0.0001). Neither estradiol nor progesterone levels were significantly associated with fluid retention scores. The peak day of average fluid retention was the first day of flow. There were no significant differences in women's self-perceived fluid retention between ovulatory and anovulatory cycles.

Menstrual cycle pattern and fertility: a prospective follow-up study of pregnancy and early embryonal loss in 295 couples who were planning their first pregnancy

Kolstad HA et al., 1999 · Fertil Steril

To characterize how the menstrual cycle pattern relates to fertility regardless of potential biases caused by inappropriate coital timing during the menstrual cycle or early embryonal loss. Prospective follow-up study. Healthy couples recruited throughout Denmark. PATIENT(S): Two hundred ninety-five couples who were planning their first pregnancy were followed up from the discontinuation of birth control until a pregnancy was recognized within six menstrual cycles. Early embryonal losses were detected by changes in urinary hCG levels. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): The probability of pregnancy occurring within one menstrual cycle (fecundity). RESULT(S): In women who had a cycle length that differed by >10 days from the usual cycle length, fecundity was approximately 25% that of women who had no variation (odds ratio 0.25, 95% confidence interval 0.09-0.68). When the combined effect of cycle variation and cycle length was assessed, cycle variation was a persistent strong predictor of fecundity. CONCLUSION(S): The mechanisms of the present findings probably are female functional disturbances in ovulation, conception, implantation, or sustained pregnancy, linked with variable menstrual cycle length. Thus, identification of medical and environmental causes of abnormal menstrual cycle patterns may provide clues to the causes of infertility. Moreover, the menstrual cycle pattern also should be taken into consideration in the clinical decision-making process.

Menstrual Cycle Length and Patterns in a Global Cohort of Women Using a Mobile Phone App: Retrospective Cohort Study

Grieger JA et al., 2020 · Journal of medical Internet research · Free full text on PubMed Central

There is increasing information characterizing menstrual cycle length in women, but less information is available on the potential differences across lifestyle variables. This study aimed to describe differences in menstrual cycle length, variability, and menstrual phase across women of different ages and BMI among a global cohort of Flo app users. We have also reported on demographic and lifestyle characteristics across median cycle lengths. The analysis was run based on the aggregated anonymized dataset from a menstrual cycle tracker and ovulation calendar that covers all phases of the reproductive cycle. Self-reported information is documented, including demographics, menstrual flow and cycle length, ovulation information, and reproductive health and diseases. Data from women aged ≥18 years and who had logged at least three cycles (ie, 2 completed cycles and 1 current cycle) in the Flo app were included (1,579,819 women). Of the 1.5 million users, approximately half (638,683/1,579,819, 40.42%) were aged between 18 and 24 years. Just over half of those reporting BMIs were in the normal range (18.5-24.9 kg/m2; 202,420/356,598, 56.76%) and one-third were overweight or obese (>25 kg/m2; 120,983/356,598, 33.93%). A total of 16.32% (257,889/1,579,819) of women had a 28-day median cycle length. There was a higher percentage of women aged ≥40 years who had a 27-day median cycle length than those aged between 18 and 24 years (22,294/120,612, 18.48% vs 60,870/637,601, 9.55%), but a lower percentage with a 29-day median cycle length (10,572/120,612, 8.77% vs 79,626/637,601, 12.49%). There were a higher number of cycles with short luteal phases in younger women, whereas women aged ≥40 years had a higher number of cycles with longer luteal phases. Median menstrual cycle length and the length of the follicular and luteal phases were not remarkably different with increasing BMI, except for the heaviest women at a BMI of ≥50 kg/m2. On a global scale, we have provided extensive evidence on the characteristics of women and their menstrual cycle length and patterns across different age and BMI groups. This information is necessary to support updates of current clinical guidelines around menstrual cycle length and patterns for clinical use in fertility programs.