Iron Consumption Is Not Consistently Associated with Fecundability among North American and Danish Pregnancy Planners

Iron intake in relation to ovarian reserve among women seeking infertility treatment

STUDY QUESTION

Is there an association between iron intake and ovarian reserve among women seeking fertility care?

SUMMARY ANSWER

Supplemental iron intake above 45 mg/day is associated with lower ovarian reserve among women seeking fertility care.

WHAT IS KNOWN ALREADY

Although the literature regarding iron intake in relation to ovarian reserve is scant and inconsistent, some evidence suggests that iron may have gonadotoxic effects.

STUDY DESIGN, SIZE, DURATION

This observational study included 582 female participants attending the Massachusetts General Hospital Fertility Center (2007-2019) enrolled in the Environment and Reproductive Health (EARTH) Study.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Iron intake was estimated using a validated food frequency questionnaire. Markers of ovarian reserve included antral follicle count (AFC) (assessed via transvaginal ultrasound) and Day 3 FSH, both obtained during the course of an infertility evaluation.

MAIN RESULTS AND THE ROLE OF CHANCE

Participants had a median age of 35 years and median total iron intake of 29 mg/day. Total iron intake was inversely related to AFC and this association was driven by intake of supplemental iron. Compared to women with a supplemental iron intake of ≤20 mg/day, women consuming 45-64 mg/day of supplemental iron had a 17% (-35%, 0.3%) lower AFC and women consuming ≥65 mg/day of supplemental iron had a 32% (-54%, -11%) lower AFC after adjusting for potential confounders (P, linear trend = 0.003). Similarly, in a multivariable-adjusted analysis, Day 3 FSH levels were 0.9 (0.5, 1.3) IU/ml higher among women with a supplemental iron intake of ≥65 mg/day when compared to women with a supplemental iron intake of ≤20 mg/day (P, linear trend = 0.02).

LIMITATIONS, REASONS FOR CAUTION

Iron intake was estimated using a method that relies on self-report and we had no biomarkers of iron status in our participants; only 36 women consumed ≥45 mg/day of supplemental iron.

WIDER IMPLICATIONS OF THE FINDINGS

Since all study participants were seeking fertility treatment, our findings may not apply to women in the general population. Although our findings are consistent with studies of women with iron overload, given the paucity of literature on this topic, it is essential that this question is revisited in studies designed to better understand the dose-response relation of this association across the entire distribution of ovarian reserve and the risk-benefit balance of pre-conceptional iron supplementation given its many positive effects on pregnancy outcomes.

STUDY FUNDING/COMPETING INTEREST(S)

The project was funded by Grants R01ES022955, R01ES033651, R01ES009718, P30ES000002, and P30DK046200 from the National Institutes of Health. N.J.-C. was supported by a Fulbright Scholarship. N.J.-C., M.M., L.M.-A., E.O.-P., S.W., I.S., and J.E.C. declare no conflict of interest related to the work in the manuscript. R.H. has received grants from the National Institute of Environmental Health Sciences.

TRIAL REGISTRATION NUMBER

N/A.

Iron status in women with infertility and controls: a case-control study

Background

Iron deficiency is a common problem in subfertile women. The influence of iron status on unexplained infertility is unknown.

Methods

In a case-control study, 36 women with unexplained infertility and 36 healthy non-infertile controls were included. Parameters of iron status including serum ferritin and a serum ferritin <30 µg/dL served as main outcome parameters.

Results

Women with unexplained infertility demonstrated a lower transferrin saturation (median 17.3%, IQR 12.7-25.2 versus 23.9%, IQR 15.4-31.6; p= 0.034) and a lower mean corpuscular hemoglobin concentration (median 33.6 g/dL, IQR 33.0-34.1 versus 34.1 g/dL, IQR 33.2-34.7; p= 0.012). Despite the fact that there was no statistically significant difference in median ferritin levels (p= 0.570), women with unexplained infertility had ferritin levels <30µg/L more often (33.3%) than controls (11.1%; p= 0.023). In a multivariate model, unexplained infertility and abnormal thyroid antibodies were associated with ferritin <30µg/L (OR 4.906, 95%CI: 1.181-20.388; p= 0.029 and OR 13.099; 2.382-72.044; p= 0.029, respectively).

Conclusion

Ferritin levels <30µg/L were associated with unexplained infertility and might be screened in the future. Further studies with a focus on iron deficiency and iron treatment on women with unexplained infertility are warranted.

The Role of Dietary Nutrients in Male Infertility: A Review

Male infertility is the main health issue with economic, psychological, and medical attributions. Moreover, it is characterized by an inability to produce a sufficient amount of sperm for the fertilization of an oocyte. Dietary nutrients (DN) have a great effect on male reproductive potential. Observations have indicated that adding DN may protect or treat male infertility. The scope of this criticism is to scrutinize the DN, such as omega-3 fatty acids, vitamins, minerals and other phytochemicals, in enhancing the semen attributes, sperm bioenergetics and sperm functionality in male infertility. It seems that diets rich in omega-3 fatty acids affect sperm quality and maintain the sperm membrane and mitochondria stability. An administration of phytochemicals caused an escalation in sperm mitochondrial function and a decrease in oxidative damage. Furthermore, sundry dietary natural phytochemicals differentially affect (negatively or positively) sperm motility, semen quality, and mitochondrial function, dependent on their levels. Vitamins and trace elements are also nutritional modulators in reducing oxidative stress, thereby enhancing sperm quality, which is accurately connected with sperm mitochondrial function. Also, we described the different types of DN as mitochondrial enhancer for sperm functionality and health. We believe that understanding the DN supports sperm mitochondria and epigenetic modulators that may be responsible for sperm quality and health, and will lead to more embattled and efficient therapeutics for male infertility.

Dietary Supplement Intake and Fecundability in a Singapore Preconception Cohort Study

Subfertility is a global problem affecting millions worldwide, with declining total fertility rates. Preconception dietary supplementation may improve fecundability, but the magnitude of impact remains unclear. This prospective cohort study aimed to examine the association of preconception micronutrient supplements with fecundability, measured by time to pregnancy (TTP). The study was conducted at KK Women's and Children's Hospital, Singapore, between February 2015 and October 2017, on 908 women aged 18-45 years old, who were trying to conceive and were enrolled in the Singapore PREconception Study of long-Term maternal and child Outcomes (S-PRESTO). Baseline sociodemographic characteristics and supplement intake were collected through face-to-face interviews. The fecundability ratio (FR) was estimated using discrete-time proportional hazard modelling. Adjusting for potentially confounding variables, folic acid (FA) (FR 1.26, 95% confidence interval 1.03-1.56) and iodine (1.28, 1.00-1.65) supplement users had higher fecundability compared to non-users. Conversely, evening primrose oil supplement users had lower fecundability (0.56, 0.31-0.99) than non-users. In this study, preconception FA and iodine supplementation were associated with shortened TTP, while evening primrose oil use was associated with longer TTP. Nonetheless, the association between supplement use and the magnitude of fecundability changes will need to be further confirmed with well-designed randomised controlled trials.

Prepregnancy adherence to plant-based diet indices and exploratory dietary patterns in relation to fecundability

BACKGROUND

Modest associations have been reported between specific food groups or nutrients and fecundability [measured by time to pregnancy (TTP)]. Examining overall diets provides a more holistic approach towards understanding their associations with fecundability. It is not known whether plant-based diets indices or exploratory dietary patterns are associated with fecundability.

OBJECTIVES

We examine the associations between adherence to 1) plant-based diet indices; and 2) exploratory dietary patterns and fecundability among women planning pregnancy.

METHODS

Data were analyzed from the Singapore Preconception Study of Long-Term Maternal and Child Outcomes (S-PRESTO) study. Prepregnancy diet was assessed using a semi-quantitative FFQ from which the overall, healthful, and unhealthful plant-based diet indices (oPDI, hPDI, and uPDI, respectively) were calculated. Exploratory dietary patterns were derived using factor analysis based on 44 predefined food groups. Participants were categorized into quintiles based on their dietary pattern scores. TTP (expressed in menstrual cycles) was ascertained within a year from the prepregnancy dietary assessment. Discrete-time proportional hazard models, adjusted for confounders, were used to estimate fecundability ratios (FRs) and 95% CIs, with FR > 1 indicating a shorter TTP.

RESULTS

Among 805 women, 383 pregnancies were confirmed by ultrasound scans. Compared with women in the lowest quintile, those in the highest quintile of the uPDI had reduced fecundability (FR of Q5 compared with Q1, 0.65; 95% CI, 0.46-0.91; P trend, 0.009). Conversely, greater adherence to the hPDI was associated with increased fecundability (1.46; 95% CI, 1.02-2.07; P trend, 0.036). The oPDI was not associated with fecundability. Among the 3 exploratory dietary patterns, only greater adherence to the Fast Food and Sweetened Beverages (FFSB) pattern was associated with reduced fecundability (0.61; 95% CI, 0.40-0.91; P trend, 0.018).

CONCLUSIONS

Greater adherence to the uPDI or the FFSB dietary pattern was associated with reduced fecundability among Asian women. Greater adherence to the hPDI may be beneficial for fecundability, though this requires confirmation by future studies.

Female Fertility and the Nutritional Approach: The Most Essential Aspects

Infertility is an increasing problem that affects couples attempting pregnancy. A growing body of evidence points to a link between diet and female fertility. In fact, data show that a diet high in trans fats, refined carbohydrates, and added sugars can negatively affect fertility. Conversely, a diet based on the Mediterranean dietary patterns, i.e., rich in dietary fiber, omega-3 (ɷ-3) fatty acids, plant-based protein, and vitamins and minerals, has a positive impact on female fertility. An unhealthy diet can disrupt microbiota composition, and it is worth investigating whether the composition of the gut microbiota correlates with the frequency of infertility. There is a lack of evidence to exclude gluten from the diet of every woman trying to become pregnant in the absence of celiac disease. Furthermore, there are no data concerning adverse effects of alcohol on female fertility, and caffeine consumption in the recommended amounts also does not seem to affect fertility. On the other hand, phytoestrogens presumably have a positive influence on female fertility. Nevertheless, there are many unanswered questions with regard to supplementation in order to enhance fertility. It has been established that women of childbearing age should supplement folic acid. Moreover, most people experience vitamin D and iodine deficiency; thus, it is vital to control their blood concentrations and consider supplementation if necessary. Therefore, since diet and lifestyle seem to be significant factors influencing fertility, it is valid to expand knowledge in this area.

Can Nutrition Help in the Treatment of Infertility?

Infertility is defined as the inability to conceive after 12 months of unprotected intercourse or six months for women aged 35 years or older. The physical, emotional, psychological, and financial statuses of infertile couples are tremendously affected especially after undergoing diagnostic and/or curative treatments. Human fertility is influenced by multiple factors including female or male, and modifiable or non-modifiable factors. There is growing evidence that nutri-tion may play an important role in adjusting fertility-related outcomes in both men and women. The objective of our study was to summarize the latest data on nutritional factors (specific food groups, nutrients, and nutritional supplements) that have an impact on female or male sexual and reproductive function. PubMed and Google Scholar platforms were used to collect appropriate articles for the review using several combinations of keywords (infertility, diet, dietary supplements, antioxidants, and beverages). Adherence to a healthy dietary pattern favoring fish, poultry, whole grains, fruits, vegetables, and healthy fats, was related to better fertility in both genders. Despite the multifactorial etiology of sexual infertility, nutrition may affect the sexual/reproductive function in both women and men.

Serum ferritin level is inversely related to number of previous pregnancy losses in women with recurrent pregnancy loss

OBJECTIVE

To study whether low serum ferritin (s-ferritin) levels are associated with recurrent pregnancy loss (RPL), and whether low s-ferritin predicts the risk of another pregnancy loss or the ability to conceive.

DESIGN

Cohort study.

SETTING

Fertility clinic at a university hospital.

PATIENT(S)

Eighty-four women referred to the RPL Unit and 153 women of reproductive age with no known fertility problem. s-Ferritin levels were measured in serum samples taken before pregnancy attempt.

INTERVENTION

None.

MAIN OUTCOME MEASURE(S)

s-Ferritin levels were correlated to pregnancy history, ability to conceive, and time to conception during the first 2 years after sampling. Furthermore, s-ferritin levels were correlated to outcome of the first pregnancy after referral for RPL.

RESULT(S)

Women with RPL had lower s-ferritin than the comparison group, 39.9 μg/L versus 62.2 μg/L, and had a higher prevalence of low iron stores (s-ferritin <30 μg/L), 35.7% versus 13.7%. We found an inverse relationship between s-ferritin level and number of pregnancy losses before referral. We did not find s-ferritin level to be associated with ability to conceive or time to pregnancy in either group. Nor did s-ferritin level predict the risk of losing the first pregnancy after referral for RPL.

CONCLUSION(S)

The inverse relationship between s-ferritin levels and previous pregnancy losses suggests that low s-ferritin is associated with a more severe reproductive disturbance in women with RPL. Whether low s-ferritin is causally related to RPL and if such women could benefit from iron supplementation to achieve a live birth warrants further investigation.

Preconception diet, fertility, and later health in pregnancy

PURPOSE OF REVIEW

Women should enter pregnancy in the best possible health. There is increasing recognition of the importance of nutrition for reproductive health; however, key dietary factors in relation to optimizing fertility are nonexistent. The purpose of this review is to investigate dietary factors, preconception, and the association with fertility and later health in pregnancy.

RECENT FINDINGS

This article summarizes recent literature assessing preconception dietary intake and the association with fertility, time to pregnancy, and also the relationship with polycystic ovary syndrome and gestational diabetes; these conditions associate with each other, and also with infertility. The impact of paternal diet is also reported.

SUMMARY

There is recent interest investigating diet and time to pregnancy, suggesting higher intakes of fruit, minimal intake of fast food and sugar sweetened beverages, and a diet lower in glycemic load, may improve time to pregnancy. There is minimal recent literature on paternal diet and impact on fertility. Present advice to women with polycystic ovary syndrome is in line with international recommendations for lifestyle management to improve reproductive outcomes; and for gestational diabetes, prepregnancy may be an optimal time to improve dietary intakes, particularly through consumption of an overall healthy dietary pattern or a Mediterranean-style dietary pattern.