OBJECTIVE: Menstruation serves as an indicator of women\'s reproductive well-being and plays a pivotal role in their fertility; nevertheless, there remains an ongoing debate regarding the epidemiological evidence linking menstrual characteristics as well as fertility.
OBJECTIVE: To explore the correlation between menstrual characteristics and fertility in women of reproductive age.
METHODS: A comprehensive literature search was conducted using PubMed, Embase, Web of Science, and Cochrane libraries to identify research articles published up until February 9, 2024.
UNASSIGNED: We included all studies in which the relationship between menstrual characteristics and pregnancy rates among women of reproductive age was investigated. We excluded studies involving the administration of oral contraceptives, the application of assisted reproductive technologies, and individuals with a documented history of infertility or partners with a known history of infertility.
METHODS: Clinical pregnancy and miscarriage.
RESULTS: This meta-analysis was composed of nine studies involving a total of 399,966 women, and the evidential quality derived from these studies was deemed to be high with a low risk of bias. Compared with a normal menstrual cycle length (25-32 days), the impact of a short (<25 days) or long (>32 days) menstrual cycle on a woman\'s pregnancy was relatively insignificant ([odds ratio {OR}, 0.81; 95% confidence interval {CI}, 0.65-1.01; I2, 68%]; [OR, 0.89; 95% CI, 0.75-1.06; I2, 60%], respectively); however, a change in cycle length may increase the risk of miscarriage ([relative risk, 1.87; 95% CI, 1.11-3.15; I2, 0]; [relative risk, 1.66; 95% CI, 1.07, 2.57; I2, 43%], respectively). In comparison to women experiencing menarche at a typical age (12-14 years), those with a late age at menarche (>14 years) exhibited a decreased likelihood of pregnancy (OR, 0.92; 95% CI, 0.91-0.93; I2, 0%); and compared with women experiencing a normal duration of menstrual bleeding (4-7 days), those with a short duration of menstrual bleeding (<4 days) exhibited reduced fertility potential (OR, 0.86; 95% CI, 0.84-0.88; I2, 29%).
CONCLUSIONS: Short and long menstrual cycle lengths may elevate women\'s susceptibility to spontaneous abortion, whereas late age at menarche as well as short duration of menstrual bleeding appear to be linked to diminished fertility among women of reproductive age.
BACKGROUND: PROSPERO CRD42023487458 (9 December 2023).

The endocrine-disrupting effects of human exposure to polybrominated diphenyl ethers (PBDEs) have been studied, but their associations with menstrual status were not clearly clarified. This study was to evaluate the associations between PBDE levels in adipose tissues and the menstrual cycle and menstrual bleeding duration alteration. A total of 298 female cases undergoing surgery were recruited from two hospitals in Shantou, China. Demographic, clinical, and pathological information were collected, and adipose tissues were obtained during mammary or abdominal surgery. Gas chromatography with mass spectrometry was used to analyze 14 PBDE congeners in the adipose samples. The associations between PBDE levels and menstrual cycle (MC) and menstrual duration (MD) were analyzed by logistic regression models, estimating odds ratios (ORs) and 95% confidence intervals (CIs). BDE-153 had the highest level in the adipose samples, followed by BDE-209, BDE-183 and BDE-47. Compared with referents, median levels of BDE-47, -71, -153, -183 were higher in women with MC > 30 days (all P < 0.05); BDE-47, -153, -183, -209 were also higher in women with MD > 5.5 days (all P < 0.05). After adjusted for age and parity, BDE-47, -71, -153, -183 were associated with prolonged MC (OR = 1.20, 1.15, 1.12, 1.11, respectively, all P < 0.05) in the logistic regression models; and BDE-47, -153, -183, -209 were associated with the prolonged MD (OR = 1.13, 1.09, 1.10, 1.11, respectively, all P < 0.05). Several individual PBDE congeners in female adipose were found associated with prolonged menstrual cycle and menstrual duration. PBDEs may influence reproductive health of women by altering menstrual status.

OBJECTIVE: To investigate the relations among age at menarche (AAM), menstrual cycle length, menstrual bleeding duration and time to pregnancy in a large cohort of rural Chinese women.
METHODS: A prospective cohort study.
METHODS: Local family-planning service agencies and maternal/child care service centres.
METHODS: A total of 391 320 rural women of reproductive age who participated in the National Free Pre-pregnancy Checkups and were planning to conceive were enrolled.
METHODS: Menstrual characteristics were collected via face-to-face interviews. The Cox proportional hazards model were used to estimate the fecundability ratios (FRs) and 95% confidence intervals for each measure relative to its reference category.
METHODS: Time to pregnancy.
RESULTS: Women with an AAM later than 14 years of age were less likely become pregnant compared with women with AAM at 13-14 years of age (FR 0.93, 95% CI 0.92-0.94). Those with menstrual cycle lengths >29 days were less likely to come pregnant (FR 0.91, 95% CI 0.90-0.92) compared with the reference cycle length of 27-29 days. Women with bleeding durations of <4 (FR 0.88; 95% CI 0.86-0.91) or >5 days (FR 0.91; 95% CI 0.90-0.91) showed lower FRs compared with those reporting 4-5 days of bleeding. The associations were independent of maternal age, ethnicity, education level, occupation, tobacco use, alcohol use and body mass index.
CONCLUSIONS: A later onset of menarche, longer menstrual cycle length, both shorter (<4 days) and longer (>5 days) bleeding duration were associated with a lower FR and longer time to pregnancy in rural Chinese women.
UNASSIGNED: A later menarche, longer cycle, shorter or longer bleeding duration were associated with lower fecundity.