Kuhr DL, et al. - This article was written with the objective to prospectively evaluate the connection between vitamin D and menstrual cycle length in healthy, fecund women. It was concluded that the vitamin D was not related to total menstrual cycle length or phase lengths among fecund women with a history of pregnancy losses and regular cycles. Further investigation of vitamin D on ovarian function in other populations is required.

Methods

• This was a secondary analysis of the EAGeR trial, which assessed the impact of preconception-initiated low dose aspirin on reproductive outcomes.
• 1228 participants ages 18-40 were attempting to conceive, with 1-2 prior pregnancy losses, no history of infertility, and self-reported regular cycles of 21-42 days.
• Serum vitamin D concentrations were measured at baseline, and women were followed for up to 2 cycles.
• Participants were categorized into vitamin D sufficient (≥30.0 ng/mL) and insufficient groups (<30.0 ng/mL).
• Cycle length was characterized as the number of days between the first days of menstrual bleeding.
• Follicular phase length was the first day of menstrual bleeding through the expected ovulation day based on LH peak on a fertility monitor; luteal phase length was the day after expected ovulation through the day prior to the onset of menses.
• Linear mixed models were utilized to assess the connections between vitamin D and total cycle, follicular phase, and luteal phase lengths, using both vitamin D status and continuous vitamin D concentration, adjusting for age, BMI, race, smoking status, income, physical activity, season, and treatment arm.

Results

• The outcome demonstrates the β-coefficients and 95% confidence intervals for all models with significant results bolded.
• Vitamin D insufficiency was related to shorter follicular phase length in unadjusted models, though the relationship was attenuated after adjustment; results in continuous models were null.
• Total cycle length and luteal phase length were not related to both categorical and continuous models.