Preconception vitamin D and miscarriage in a prospective cohort study.

STUDY QUESTION: Is preconception vitamin D level associated with the risk of miscarriage? SUMMARY ANSWER: Preconception vitamin D levels are not associated with the risk of miscarriage in a population of women conceiving naturally. WHAT IS KNOWN ALREADY: In humans, low vitamin D has been associated with prolonged menstrual cycles, delayed ovulation and a lower probability of conception. Animal and in vitro data indicate that vitamin D may affect implantation. STUDY DESIGN, SIZE, DURATION: This prospective time-to-pregnancy study included 362 women who were trying to conceive naturally between 2008 and 2015. PARTICIPANTS/MATERIALS, SETTING, METHODS: This study included participants who had been trying to conceive naturally for 3 months or less at enrollment and aged 30-44 years. A preconception blood sample was collected and 25-hydroxyvitamin D [25(OH)D] was measured. Women who conceived (N = 362) were at risk of a miscarriage from the day of a reported positive pregnancy test until either a participant-reported pregnancy loss or 20 weeks post day of last menstrual period, whichever came first. Gestational age was defined by ovulation. Time to miscarriage (days) or censoring was modeled using a multivariate Cox proportional hazards model. Multiple imputation was performed for missing covariates and missing day of ovulation. MAIN RESULTS AND THE ROLE OF CHANCE: The mean age was 33 years (SD: 3.0 years). Mean 25(OH)D was lower among those who reported their race as African-American and those with a higher BMI. After adjustment for age, race, BMI, education, exercise, alcohol and caffeine intake, compared to the referent group (30-<40 ng/ml), the hazard ratio (HR) and 95% CI for those with a low 25(OH)D level (<30 ng/ml) was 1.10 (CI: 0.62, 1.91). Among participants with a higher 25(OH)D level (≥40 ng/ml), the HR was 1.07 (CI: 0.62, 1.84). LIMITATIONS, REASONS FOR CAUTION: This study was limited by a 25(OH)D measurement at only a single time point. A large percentage of women in this study had sufficient vitamin D levels, which may have limited our power to detect an effect of deficiency. Women in this study were older (30-44 years), and predominantly reported their race as White which may limit generalizability. WIDER IMPLICATIONS OF THE FINDINGS: The findings of this study do not suggest an association between preconception vitamin D and miscarriage. Future research should focus on women at greater risk for miscarriage or in populations at risk for vitamin D deficiency or on supplementation. STUDY FUNDING/COMPETING INTEREST(S): This research was supported in part by the Intramural Research Program of the NIH, National Institute of Environmental Health Sciences (Z01ES103333). This research was also supported by the Eunice Kennedy Shriver National Institute of Child Health and Human Development of the National Institutes of Health (NIH) under award numbers R00HD079659 and R01HD067683. The authors have no conflicts of interest. TRIAL REGISTRATION NUMBER: N/A.

Omega-3 fatty acid supplementation and fecundability.

STUDY QUESTION: Is self-reported use of omega-3 fatty acid supplements associated with fecundability, the probability of natural conception, in a given menstrual cycle? SUMMARY ANSWER: Prospectively recorded omega-3 supplement use was associated with an increased probability of conceiving. WHAT IS KNOWN ALREADY: In infertile women, omega-3 fatty acid intake has been associated with increased probability of pregnancy following IVF. In natural fertility, studies are conflicting, and no study of natural fertility has evaluated omega-3 fatty acid supplementation and fecundity. STUDY DESIGN, SIZE, DURATION: Secondary data analysis of 900 women contributing 2510 cycles in Time to Conceive (TTC), a prospective, time to pregnancy cohort study from 2008 to December 2015. PARTICIPANTS/MATERIALS, SETTING, METHODS: Women aged 30-44 years, trying to conceive <3 months, without history of infertility were followed using standardized pregnancy testing. While attempting to conceive, women daily recorded menstrual cycle events and supplement and medication intake using the Cerner Multum Drug Database. Supplements and vitamins containing omega-3 were identified. Omega-3 use, defined as use in at least 20% of days in a given menstrual cycle, in each pregnancy attempt cycle was determined. A discrete-time Cox proportional hazards model was used to calculate the fecundability ratio. MAIN RESULTS AND THE ROLE OF CHANCE: Women taking omega-3 supplementation were more likely to be younger, thinner, nulligravid, white and to take vitamin D, prenatal and multivitamins compared to women not taking omega-3s. After adjusting for age, obesity, race, previous pregnancy, vitamin D and prenatal and multivitamin use, women taking omega-3 supplements had 1.51 (95% CI 1.12, 2.04) times the probability of conceiving compared to women not taking omega-3s. LIMITATIONS, REASONS FOR CAUTION: Our study was not a randomized controlled trial. The women who used omega-3 supplements may represent a more health-conscious population. We sought to address this by adjusting for multiple factors in our model. Additionally, the omega-3 fatty acid supplements that TTC participants used included multiple types and brands with varying dosages of omega-3 fatty acids. Women reported the type of supplement they were taking but not the concentration of omega-3s in that supplement. It is therefore not possible to compare dosing or a dose-response relationship in our study. WIDER IMPLICATIONS OF THE FINDINGS: Omega-3 supplementation may present a feasible and inexpensive modifiable factor to improve fertility. Randomized controlled trials are needed to further investigate the benefits of omega-3 supplementation for women trying to conceive naturally. STUDY FUNDING/COMPETING INTERESTS: This study was supported by the Division of Reproductive Endocrinology and Infertility at the University of North Carolina at Chapel Hill, the NIH/NICHD (R21 HD060229-01 and R01 HD067683-01), and in part by the Intramural Research Program of the National Institute of Environmental Health Sciences (Z01ES103333). The authors declare that there is no conflict of interest. TRIAL REGISTRATION NUMBER: N/A.

Vitamin D and Reproductive Hormones Across the Menstrual Cycle.

STUDY QUESTION: How do the calciotropic hormones (25-hydroxyvitamin D, 1,25-dihydroxyvitamin D and intact parathyroid hormone (iPTH)) vary across the menstrual cycle and do cyclic patterns of reproductive hormones (estradiol, progesterone, LH, FSH) differ by vitamin D status? SUMMARY ANSWER: Calciotropic hormones vary minimally across the menstrual cycle; however, women with 25-hydroxyvitamin D below 30 ng/ml have lower mean estradiol across the menstrual cycle. WHAT IS KNOWN ALREADY: Prior human studies suggest that vitamin D status is associated with fecundability, but the mechanism is unknown. Exogenous estrogens and prolonged changes in endogenous estradiol (pregnancy or menopause) influence concentrations of 25-hydroxyvitamin D. In vitro, treatment with 1,25-dihydroxyvitamin D increases steroidogenesis in ovarian granulosa cells. There are little data about changes in calciotropic hormones across the menstrual cycle or cyclic patterns of reproductive hormones by categories of vitamin D status. STUDY DESIGN, SIZE, DURATION: A prospective cohort study of 89 self-identified white women aged 18-44, across two menstrual cycles. Participants were a subset of the BioCycle Study, a community-based study conducted at the University of Buffalo, 2005-2007. PARTICIPANTS/MATERIALS, SETTING, METHODS: Eligible participants had self-reported regular menstrual cycles between 21 and 35 days and were not using hormonal contraception or vitamins. Early morning fasting blood samples were drawn at up to eight study visits per cycle. Visits were timed to capture information in all cycle phases. Serum samples for 89 women (N = 163 menstrual cycles) were analyzed for estradiol, progesterone, LH, FSH and 25-hydroxyvitamin D (25(OH)D). Variability in calciotropic hormones within and across menstrual cycles was assessed using intraclass correlation coefficients and non-linear mixed models. Given the relative stability of the calciotropic hormones across the menstrual cycle, non-linear mixed models were used to examine differences in the cyclic patterns of estradiol, progesterone, LH and FSH by categories of each calciotropic hormone (split at the median). These models were conducted for all ovulatory cycles (N = 142 ovulatory menstrual cycles) and were adjusted for age, BMI (measured in clinic) and self-reported physical activity. MAIN RESULTS AND THE ROLE OF CHANCE: Median 25(OH)D concentration was 29.5 ng/ml (SD 8.4), and only 6% of women had vitamin D deficiency (<20 ng/ml). The mean concentration of 25(OH)D did not differ between the luteal and follicular phase; however, both 1,25(OH)2D and iPTH showed small fluctuations across the menstrual cycle with the highest 1,25(OH)2D (and lowest iPTH) in the luteal phase. Compared with women who had mean 25(OH)D ≥30 ng/ml, women with lower 25(OH)D had 13.8% lower mean estradiol (95% confidence interval: -22.0, -4.7) and 10.8% lower free estradiol (95% CI: -0.07, -0.004). Additionally, compared to women with iPTH ≤36 pg/ml, women with higher concentrations of iPTH had 12.7% lower mean estradiol (95% CI: -18.7, -6.3) and 7.3% lower progesterone (95% CI: -13.3, -0.9). No differences in the cyclic pattern of any of the reproductive hormones were observed comparing cycles with higher and lower 1,25(OH)2D. LIMITATIONS, REASONS FOR CAUTION: Women included in this study had self-reported 'regular' menstrual cycles and very few were found to have 25(OH)D deficiency. This limits our ability to examine cycle characteristics, anovulation and the effects of concentrations of the calciotropic hormones found in deficient individuals. Additionally, the results may not be generalizable to women with irregular cycles, other races, or populations with a higher prevalence of vitamin D deficiency. WIDER IMPLICATIONS OF THE FINDINGS: These findings support current clinical practice that does not time testing for vitamin D deficiency to the menstrual cycle phase. We find that women with lower vitamin D status (lower 25(OH)D or higher iPTH) have lower mean concentrations of estradiol across the menstrual cycle. Although this study cannot identify a mechanism of action, further in vitro work or clinical trials may help elucidate the biologic mechanisms linking calciotropic and reproductive hormones. STUDY FUNDING/COMPETING INTEREST(S): This work was supported by the Intramural Research Programs of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health (contract numbers: HHSN275200403394C, HHSN275201100002I and Task 1 HHSN27500001) and the National Institute of Environmental Health Sciences. There are no competing interests.

Pre-conception 25-hydroxyvitamin D (25(OH)D) and fecundability.

STUDY QUESTION: Is pre-conception 25(OH)D associated with the per cycle probability of conception, i.e fecundability, in a prospective cohort study? SUMMARY ANSWER: There are suggestive associations of high 25(OH)D (at least 50 ng/ml) with increased fecundability and low 25(OH)D (<20 ng/ml) with reduced fecundability, but the estimates were imprecise. WHAT IS KNOWN ALREADY: Vitamin D has been associated with reproductive function and fertility in animal studies, but few human studies exist. STUDY DESIGN, SIZE, DURATION: This community-based prospective cohort study included 522 women attempting to become pregnant between 2010 and 2016. The women completed online daily and monthly diaries until a positive home pregnancy test was observed or 12 months had elapsed. PARTICIPANTS/MATERIALS, SETTING, METHODS: The study included women from central North Carolina who were aged 30-44 with no history of infertility, with no more than 3 months of attempt time at recruitment. Women recorded vaginal bleeding so that the ongoing number of attempt cycles could be counted and used to quantify a woman's pregnancy attempt time. Blood collected at the study entry was analysed for 25(OH)D using liquid chromatography tandem mass spectrometry. Associations with fecundability were estimated with a log-binomial discrete time-to-event model. MAIN RESULTS AND THE ROLE OF CHANCE: Among 522 women, 257 conceived during the study. The mean age was 33 years and the mean 25(OH)D was 36 ng/ml. There was an estimated 10% higher fecundability with each 10 ng/ml increase in 25(OH)D (fecundability ratio (FR) 1.10, 95% CI: 0.96, 1.25). The suggestive dose-response association with the continuous measure of 25(OH)D was driven by women in the lowest and the highest categories of 25(OH)D. Compared to women with 25(OH)D of 30-40 ng/ml, women below 20 ng/ml had an estimated 45% reduction in fecundability (FR (CI): 0.55 (0.23, 1.32)), and women with at least 50 ng/ml had an estimated 35% increase in fecundability (FR (CI): 1.35 (0.95, 1.91)). Across these three categories (25(OH)D of <20 ng/ml, 30-40 ng/ml and > 50 ng/ml), the probability of taking longer than 6 months to conceive was, respectively, 51% (17%, 74%), 28% (17%, 39%) and 15% (10%, 37%). LIMITATIONS, REASONS FOR CAUTION: While the distribution of 25(OH)D was wide, the number of observed cycles with high 25(OH)D (N = 107) or low 25(OH)D (N = 56) was small. WIDER IMPLICATIONS OF THE FINDINGS: Our findings are consistent with prior reports of reduced fertility in women with 25(OH)D concentrations below the clinically defined deficiency level (20 ng/ml). Further studies are needed to evaluate the possible reproductive benefits of considerably higher 25(OH)D concentration (>50 ng/ml). STUDY FUNDING/COMPETING INTEREST(S): This research was supported by the Eunice Kennedy Shriver National Institute of Child Health and Human Development of the National Institutes of Health (NIH) under award numbers R00HD079659 and R01HD067683 and supported in part by the Intramural Research Program of the National Institute of Environmental Health Sciences, under projects ES103086, ES049003 and ES044003. ClearBlue ovulation predictor kits were generously donated to AMZJ and AJW by Swiss Precision Diagnostics. Drs Wilcox and Jukic report non-financial support from Swiss Precision Diagnostics during the conduct of the study; Dr Jukic reports non-financial support from Theralogix, LLC, outside the submitted work. Otherwise there are no competing interests. TRIAL REGISTRATION NUMBER: N/A.

The association of maternal factors with delayed implantation and the initial rise of urinary human chorionic gonadotrophin.

BACKGROUND Late implantation and the pattern of early rise in hCG have been associated with early pregnancy loss. We explored factors that might be predictive of these markers of poor embryonic health in spontaneously conceived pregnancies. METHODS Participants in the North Carolina Early Pregnancy Study collected daily first-morning urine specimens while attempting to conceive. Samples were assayed for estrogen and progesterone metabolites (to identify day of ovulation) and hCG (to detect conception). Data were available for 190 pregnancies, 48 of which ended in early loss (within 6 weeks of the last menstrual period). We used logistic regression to identify characteristics associated with late implantation (≥10 days post-ovulation). For pregnancies surviving at least 6 weeks (n= 142), we used linear mixed models to identify factors associated with variations in hCG rise in the first 7 days from detection. RESULTS Later implantation was associated with current maternal smoking [odds ratio (OR): 5.7; 95% confidence interval (CI): 1.1-30] and with oocytes that were likely to have been fertilized late in their post-ovulatory lifespan (OR: 5.1; CI: 1.9-16). Older women had a faster rise in hCG (P= 0.01), as did women who had relatively late menarche (P for trend = 0.02). Women exposed in utero to diethylstilbestrol showed an unusual pattern of slow initial hCG rise followed by a fast increase, a pattern significantly different from that of unexposed women (P= 0.002). CONCLUSIONS Although limited by small numbers and infrequent exposures, our analyses suggest that a woman's exposures both early in life and at the time of pregnancy may influence early development of the conceptus.