STUDY QUESTION: What are the comparative pregnancy outcomes in women who receive up to six consecutive cycles of ovulation induction with letrozole versus clomiphene citrate? SUMMARY ANSWER: The risks of pregnancy, livebirth, multiple gestation, preterm birth, neonatal intensive care unit (NICU) admission and congenital malformations were higher for letrozole compared with clomiphene in participants with polycystic ovarian syndrome (PCOS), though no treatment differences were observed in those with unexplained infertility. WHAT IS KNOWN ALREADY: Randomized trials have reported higher pregnancy and livebirth rates for letrozole versus clomiphene among individuals with PCOS, but no differences among those with unexplained infertility. None of these trials were designed to study maternal or neonatal complications. STUDY DESIGN, SIZE, DURATION: We emulated a hypothetical trial of the comparative effectiveness of letrozole versus clomiphene citrate for ovulation induction among all women, then stratified by PCOS and unexplained infertility status. We used real-world data from a large healthcare claims database in the USA (2011-2015). PARTICIPANTS/MATERIALS, SETTING, METHODS: We analyzed data from 18 120 women who initiated letrozole and 49 647 women who initiated clomiphene during 2011-2014, and who were aged 18-45 years with no history of diabetes, thyroid disease, liver disease or breast cancer and had no fertility treatments for 3 months before trial initiation. The treatment strategies were clomiphene citrate or letrozole for six consecutive cycles. The outcomes were pregnancy, livebirth, multiple gestation, preterm birth, small for gestational age (SGA), NICU admission and major congenital malformations. We estimated the probability of each outcome under each strategy via pooled logistic regression and used standardization to adjust for confounding and selection bias due to loss to follow-up. MAIN RESULTS AND THE ROLE OF CHANCE: The estimated probabilities of pregnancy, livebirth and neonatal outcomes were similar under each strategy, both overall and among individuals with unexplained infertility. Among women with PCOS, the probability of pregnancy was 43% for letrozole vs 37% for clomiphene (risk difference [RD] = 6.0%; 95% CI: 4.4, 7.7) in the intention-to-treat analyses. The corresponding probability of livebirth was 32% vs 29% (RD = 3.1%; 95% CI: 1.5, 4.8). In per protocol analyses, the risk of multiple gestation was 19% vs 9%, the risk of preterm birth was 20% vs 15%, the risk of SGA was 5% vs 3%, the risk of NICU admission was 22% vs 16% and the risk of congenital malformation was 8% vs 2% among those with a livebirth. LIMITATIONS, REASONS FOR CAUTION: We cannot completely rule out the possibility of residual confounding by body mass index or duration of infertility. However, we adjusted for proxies identified in administrative data and results did not change. WIDER IMPLICATIONS OF THE FINDINGS: Our findings suggest that for women with unexplained infertility, the two treatments result in comparable probabilities of a livebirth. For women with PCOS, letrozole appears slightly more effective for attaining a livebirth. Neonatal outcomes were similar for the two treatments among women with unexplained infertility; we did not confirm the hypothesized higher risk of adverse neonatal outcomes for clomiphene versus letrozole. The risks of adverse neonatal outcomes were slightly greater among women with PCOS who were treated with letrozole versus clomiphene. It is likely that these effects are partially mediated through an increased risk of multiple gestation among women who received letrozole. STUDY FUNDING/COMPETING INTEREST(S): This work was supported by the National Institute of Child Health and Human Development (R01HD088393). Y.-H.C. reports grants from the American Heart Association (834106) and NIH (R01HD097778). P.R. reports grants from the National Institutes of Health. J.H. reports grants from the National Institutes of Health, the Agency for Healthcare Research and Quality, and the California Health Care Foundation during the conduct of the study; and consulting for several health care delivery organizations including Cambridge Health Alliance, Columbia University, University of Southern California, Community Servings, and the Delta Health Alliance. S.H.-D. reports grants from the National Institutes of Health and the US Food and Drug Administration during the conduct of the study; grants to her institution from Takeda outside the submitted work; consulting for UCB (biopharmaceutical company) and Roche; and being an adviser for the Antipsychotics Pregnancy Registry and epidemiologist for the North American Antiepileptics Pregnancy Registry, both at Massachusetts General Hospital. M.A.H. reports grants from the National Institutes of Health and the U.S. Veterans Administration during the conduct of the study; being a consultant for Cytel; and being an adviser for ProPublica. TRIAL REGISTRATION NUMBER: N/A.

BACKGROUND: Intake of conventionally grown fruits and vegetables (FVs) is an important route of exposure to pesticide residues in the general population. However, whether health risk stemming from exposure to pesticides through diet could offset benefits of consuming FVs is unclear. OBJECTIVE: We assessed the association of FV intake, classified according to their pesticide residue status, with total and cause-specific mortality. METHODS: We followed 137,378 women (NHS, 1998-2019, and NHSII, 1999-2019) and 23,502 men (HPFS, 1998-2020) without cardiovascular disease, cancer, or diabetes at baseline. FV intake was assessed using validated food frequency questionnaires and categorized as having high- or low-pesticide-residues using data from the USDA Pesticide Data Program. Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CI) for total and cause-specific mortality associated with high- and low-pesticide-residue FV intake. RESULTS: A total of 27,026 deaths, including 4,318 from CVD and 6,426 from cancer, were documented during 3,081,360 person-years of follow-up. In multivariable-adjusted analyses, participants who consumed ≥4 servings/day of low-pesticide-residue FVs had 36% (95% CI: 32%-41%) lower mortality risk compared to participants who consumed <1 serving/day. The corresponding estimate for high-pesticide residue FV intake was 0.93 (95% CI: 0.81-1.07). This pattern was similar across the three most frequent causes of death (cardiovascular disease, cancer and respiratory diseases). CONCLUSIONS: High-pesticide-residue FV intake was unrelated whereas low-pesticide residue FV intake was inversely related to all-cause mortality, suggesting that exposure to pesticide residues through diet may offset the beneficial effect of FV intake on mortality.

Several studies have identified positive associations between pesticides and glioma. We aimed to determine whether intake of pesticide residues from fruits and vegetables (FV) was associated with glioma. Within three prospective cohorts from 1998-2016-the Nurses' Health Study (NHS), Nurses' Health Study II (NHSII), and Health Professionals Follow-Up Study (HPFS)-we computed multivariable-adjusted (MV) hazard ratios (HR) and 95% confidence intervals (CI) for glioma by quintiles of intake of low and high pesticide residue FVs using Cox proportional hazards regression. FVs were categorized as high or low residue using a validated method based on pesticide surveillance data. We confirmed 275 glioma cases across 2,745,862 person-years. A significant association was observed between intake of high-residue FVs and glioma in NHS (MVHR=2.99, 95%CI:1.38-6.44 comparing highest to lowest quintile, p-trend=0.02). This was not identified in NHSII (MVHR=0.52, 95%CI:0.19-1.45, p-trend=0.20) or HPFS (MVHR=1.01, 95%CI:0.42-2.45, p-trend=0.39). No significant associations were observed by intake of low-residue FVs. Overall FV intake was not significantly associated with glioma in any cohort. We found no evidence for an inverse relation of FV intake with glioma. Although limited in power, this study suggests a possible association between FV pesticide residue intake and risk of glioma that merits further study.

BACKGROUND: Pesticide exposure is linked to a myriad of negative health effects; however, the mechanisms underlying these associations are less clear. We utilized metabolomics to describe the alterations in the serum metabolome associated with high and low pesticide residue intake from fruits and vegetables (FVs), the most common route of exposure in humans. METHODS: This analysis included 171 women undergoing in vitro fertilization who completed a validated food frequency questionnaire and provided a serum sample during controlled ovarian stimulation (2007-2015). FVs were categorized as high or low-to-moderate pesticide residue using a validated method based on pesticide surveillance data from the USDA. We conducted untargeted metabolic profiling using liquid chromatography with high-resolution mass spectrometry and two chromatography columns. We used multivariable generalized linear models to identified metabolic features (p < 0.005) associated with high and low-to-moderate pesticide residue FV intake, followed by enriched pathway analysis. RESULTS: We identified 50 and 109 significant features associated with high pesticide residue FV intake in the C18 negative and HILIC positive columns, respectively. Additionally, we identified 90 and 62 significant features associated with low-to-moderate pesticide residue FV intake in the two columns, respectively. Four metabolomic pathways were associated with intake of high pesticide residue FVs including those involved in energy, vitamin, and enzyme metabolism. 12 pathways were associated with intake of low-to-moderate pesticide residue FVs including cellular receptor, energy, intercellular signaling, lipid, vitamin, and xenobiotic metabolism. One energy pathway was associated with both high and low-to-moderate pesticide residue FVs. CONCLUSIONS: We identified limited overlap in the pathways associated with intake of high and low-to-moderate pesticide residue FVs, which supports findings of disparate health effects associated with these two exposures. The identified pathways suggest there is a balance between the dietary antioxidant intake associated with FVs intake and heightened oxidative stress as a result of dietary pesticide exposure.

The noniterative conditional expectation (NICE) parametric g-formula can be used to estimate the causal effect of sustained treatment strategies. In addition to identifiability conditions, the validity of the NICE parametric g-formula generally requires the correct specification of models for time-varying outcomes, treatments, and confounders at each follow-up time. An informal approach for evaluating model specification is to compare the observed distributions of the outcome, treatments, and confounders with their parametric g-formula estimates under the “natural course.” In the presence of losses to follow-up, however, the observed and natural course risks can differ even if the identifiability conditions of the parametric g-formula hold and there is no model misspecification. Here, we describe two approaches to evaluate model specification when using the parametric g-formula in the presence of censoring: (1) comparing factual risks estimated by the g-formula with nonparametric Kaplan-Meier estimates, and (2) comparing natural course risks estimated by inverse probability weighting with those estimated by the g-formula. We also describe how to correctly compute natural course estimates of time-varying covariate means when using a computationally efficient g-formula algorithm. We evaluate the proposed methods via simulation and implement them to estimate the effects of dietary interventions in two cohort studies.

Investigators are increasingly using novel methods for extending (generalizing or transporting) causal inferences from a trial to a target population. In many generalizability and transportability analyses, the trial and the observational data from the target population are separately sampled, following a non-nested trial design. In practical implementations of this design, non-randomized individuals from the target population are often identified by conditioning on the use of a particular treatment, while individuals who used other candidate treatments for the same indication or individuals who did not use any treatment are excluded. In this paper, we argue that conditioning on treatment in the target population changes the estimand of generalizability and transportability analyses and potentially introduces serious bias in the estimation of causal estimands in the target population or the subset of the target population using a specific treatment. Furthermore, we argue that the naive application of marginalization-based or weighting-based standardization methods does not produce estimates of any reasonable causal estimand. We use causal graphs and counterfactual arguments to characterize the identification problems induced by conditioning on treatment in the target population and illustrate the problems using simulated data. We conclude by considering the implications of our findings for applied work.

Maternal fat intake during pregnancy affects fetal growth, but mechanisms underlying this relationship are unclear. We performed an exploratory study of the associations of fat consumption during pregnancy with cord blood DNA methylation of the insulin-like growth factor 2 (IGF2) and H19 genes. We used data from 96 uncomplicated full-term pregnancies of mothers of whom majority had normal body mass index (BMI) (66%) in Project Viva, a prospective pre-birth cohort. We assessed maternal diet with validated food frequency questionnaires during the first and second trimesters and measured DNA methylation in segments of the IGF2- and H19-differentially methylated regions (DMRs) by pyrosequencing DNA extracted from umbilical cord blood samples. Mean (SD) age was 32.8 (4.1) years and prepregnancy BMI was 24.0 (4.4) kg/m2 . Mean DNA methylation was 56.3% (3.9%) for IGF2-DMR and 44.6% (1.9%) for H19-DMR. Greater first trimester intake of omega-6 polyunsaturated fat (effect per 1% of calories at the expense of carbohydrates) was associated with lower DNA methylation of IGF2-DMR (-1.2%; 95% confidence interval [CI]: -2.2%, -0.2%) and higher DNA methylation at H19-DMR (0.8%; 95% CI: 0.3%, 1.3%). On the other hand, greater first trimester intake of omega-3 polyunsaturated fat was associated with lower DNA methylation of the H19-DMR (-4.3%; 95% CI: -7.9%, -0.8%). We did not find significant associations of IGF2 and H19 methylation with IGF2 cord blood levels. Our findings suggest that early prenatal fat intake (omega-3, omega-6, and saturated fatty acids) may influence DNA methylation at the IGF2 and H19 locus, which could impact fetal development and long-term health.

BACKGROUND: Because randomized trials of sustained dietary changes are sometimes impractical for long-term outcomes, the explicit emulation of a (hypothetical) target trial using observational data may be an important tool for nutritional epidemiology. OBJECTIVES: We describe a methodological approach that aims to emulate a target trial of dietary interventions sustained over many years using data from observational cohort studies. METHODS: We estimated the 20-y risk of all-cause mortality under the sustained implementation of the food-based goals of the American Heart Association (AHA) 2020 using data from 3 prospective observational studies of US men [Health Professionals Follow-up Study (HPFS)] and women [Nurses' Health Study (NHS) and Nurses' Health Study II (NHS II)]. We applied the parametric g-formula to estimate the 20-y mortality risk under a dietary intervention and under no dietary intervention. RESULTS: There were 165,411 participants who met the eligibility criteria. The mean age at baseline was 57.4 y (range, 43-82 y) in the HPFS, 52.4 y (range, 39-66 y) in the NHS, and 40.2 y (range, 30-50 y) in the NHS II. During 20 y of follow-up, 13,241 participants died. The estimated 20-y mortality risks under a dietary intervention versus no intervention were 21.9% compared with 25.8%, respectively, in the HPFS (risk difference, -3.9%; 95% CI: -4.9% to -3.2%); 10.0% compared with 12.6%, respectively, in the NHS (risk difference, -2.6%; 95% CI: -3.1% to -1.8%); and 2.1% compared with 2.5%, respectively, in the NHS II (risk difference, -0.35%; 95% CI: -0.56% to -0.09%). The corresponding risk ratios were 0.85 (95% CI: 0.81-0.88) in the HPFS, 0.79 (95% CI: 0.75-0.85) in the NHS, and 0.86 (95% CI: 0.78-0.96) in the NHS II. CONCLUSIONS: We estimated that adherence to the food-based AHA 2020 Dietary Goals starting in midlife may reduce the 20-y risk of mortality.

BACKGROUND: Conventionally grown fruits and vegetables (FVs) are the main source of general population exposure to pesticide residues. OBJECTIVE: To evaluate the relation of intake of high- and low-pesticide-residue FVs with cancer risk. METHODS: We followed 150,830 women (Nurses' Health Study, 1998-2016, and Nurses' Health Study II, 1999-2017) and 29,486 men (Health Professionals Follow-up Study, 1998-2016) without a history of cancer. We ascertained FV intake via validated food frequency questionnaires and categorized FVs as having high or low pesticide residue levels based on USDA surveillance data. We used Cox proportional hazards models to estimate hazard ratios (HR) and 95% confidence intervals (CI) of total and site-specific cancer related to quintiles of high- and low-pesticide-residue FV intake. RESULTS: We documented 23,678 incident cancer cases during 2,862,118 person-years of follow-up. In the pooled multivariable analysis, neither high- nor low-pesticide-residue FV intake was associated with cancer. The HRs (95% CI) per 1 serving/day increase in intake were 0.99 (0.97-1.01) for high- and 1.01 (0.99-1.02) for low-pesticide-residue FVs. Additionally, we found no association between high-pesticide-residue FV intake and risk of specific sites, including malignancies previously linked to occupational pesticide exposure ([HR, 95% CI comparing extreme quintiles of intake] lung [1.17 (0.95-1.43)], non-Hodgkin lymphoma [0.89 (0.72-1.09)], prostate [1.31 (0.88-1.93)]) or inversely related to intake of organic foods (breasts [1.03 (0.94-1.31)]). CONCLUSIONS: These findings suggest that overall exposure to pesticides through FV intake is not related to cancer risk, although they do not rule out associations with specific chemicals or sub-types of specific cancers.

When studying the effect of a prenatal treatment on events in the offspring, failure to produce a live birth is a competing event for events in the offspring. A common approach to handle this competing event is reporting both the treatment-specific probabilities of live births and of the event of interest among live births. However, when the treatment affects the competing event, the latter probability cannot be interpreted as the causal effect among live births. Here we provide guidance for researchers interested in the effects of prenatal treatments on events in the offspring in the presence of the competing event "no live birth." We review the total effect of treatment on a composite event and the total effect of treatment on the event of interest. These causal effects are helpful for decision making but are agnostic about the pathways through which treatment affects the event of interest. Therefore, based on recent work, we also review three causal effects that explicitly consider the pathways through which treatment may affect the event of interest in the presence of competing events: the direct effect of treatment on the event of interest under an intervention to eliminate the competing event, the separable direct and indirect effects of treatment on the event of interest, and the effect of treatment in the principal stratum of those who would have had a live birth irrespective of treatment choice. As an illustrative example, we use a randomized trial of fertility treatments and risk of neonatal complications.

BACKGROUND: There is great interest in understanding whether interventions on sugar-sweetened beverage (SSB) consumption through pregnancy and early childhood affect adolescent body mass index (BMI). Without data from randomised trials, unbiased estimation of such effects might be achieved with observational data given sufficient and appropriate adjustment for both baseline and time-varying confounders. OBJECTIVES: To illustrate the use of inverse probability (IP) weighting of marginal structural models (MSM) for estimating the effects of SSB consumption through pregnancy and early childhood on the mean early adolescent BMI z-score. METHODS: Our baseline sample consisted of 1584 pregnant women from a pre-birth cohort. We defined 6 intervention intervals: early pregnancy, late pregnancy, 3, 4, 5, and 6 years. We fitted a MSM via a weighted linear regression with IP exposure and censoring weights to estimate the mean difference in BMI z-score under interventions: "maintain SSB consumption below (vs above) 0.5 servings/day in all intervals." RESULTS: The estimated difference in mean BMI z-score under interventions maintaining SSB consumption at or below (vs above) 0.5 servings/day from pregnancy to 6 years was -0.94 (95% confidence interval [CI] -1.52, -0.08). The effect estimate in pregnancy, while fixing the exposure range in childhood, was -0.05 (95% CI -0.34, 0.23), and in early childhood, while fixing the range in pregnancy was -0.89 (95% CI -1.46, -0.11). The effect estimates were largely unchanged under sensitivity analyses to different implementation choices except for the choice of time interval length. CONCLUSIONS: Under assumptions that include no unmeasured confounding and selection bias, and no model misspecification, results of this IP weighting application are in line with a lower mean BMI z-score in early adolescence under interventions ensuring lower, vs greater, SSB consumption in early life. This application provides a resource for researchers working with longitudinal birth cohort studies and interested in similar causal questions.

BACKGROUND: Trans fatty acid (TFA) intake persists in much of the world, posing ongoing threats to public health that warrant further elucidation. Published evidence suggests a positive association of self-reported TFA intake with non-Hodgkin lymphoma (NHL) risk. OBJECTIVES: To confirm those reports, we conducted a prospective study of prediagnosis RBC membrane TFA levels and risk of NHL and common NHL histologic subtypes. METHODS: We conducted a nested case-control study in Nurses' Health Study and Health Professionals Follow-Up Study participants with archived RBC specimens and no history of cancer at blood draw (1989-1090 and 1994-1995, respectively). We confirmed 583 incident NHL cases (332 women and 251 men) and individually matched 583 controls on cohort (sex), age, race, and blood draw date/time. We analyzed RBC membrane TFA using GLC (in 2013-2014) and expressed individual TFA levels as a percentage of total fatty acids. We used unconditional logistic regression adjusted for the matching factors to estimate ORs and 95% CIs for overall NHL risk per 1 SD increase in TFA level and assessed histologic subtype-specific associations with multivariable polytomous logistic regression. RESULTS: Total and individual TFA levels were not associated with risk of all NHL or most subtypes. We observed a positive association of total TFA levels with diffuse large B cell lymphoma (DLBCL) risk [n = 98 cases; OR (95% CI) per 1 SD increase: 1.30 (1.05, 1.61); P = 0.015], driven by trans 18:1n-9(ω-9)/elaidic acid [OR (95% CI): 1.34 (1.08, 1.66); P = 0.007], trans 18:1n-7/vaccenic acid [OR (95% CI): 1.28 (1.04, 1.58); P = 0.023], and trans 18:2n-6t,t [OR (95% CI): 1.26 (1.01, 1.57); P = 0.037]. CONCLUSIONS: Our findings extended evidence for TFA intake and DLBCL risk but not for other NHL subtypes. Reduced TFA consumption through dietary choices or health policy measures may support prevention of DLBCL, an aggressive NHL subtype.

BACKGROUND: Fruit and vegetable (FV) intake is recommended for the prevention of coronary heart disease (CHD). FVs are also an important source of exposure to pesticide residues. Whether the relations of FV intake with CHD differ according to pesticide residue status is unknown. OBJECTIVE: To examine the associations of high- and low-pesticide-residue FVs with the risk of CHD. METHODS: We followed 145,789 women and 24,353 men free of cardiovascular disease and cancer (excluding non-melanoma skin cancer) at baseline and participating in three ongoing prospective cohorts: the Nurses' Health Study (NHS: 1998-2012), the NHS-II (1999-2013), and the Health Professionals Follow-up Study (HPFS: 1998-2012). FV intake was assessed via food frequency questionnaires. We categorized FVs as having high- or low-pesticide-residues using a validated method based on pesticide surveillance data from the US Department of Agriculture. Multivariable Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% confidence intervals (95%CI) of CHD in relation to high- and low-pesticide-residue FV intake. RESULTS: A total of 3707 incident CHD events were identified during 2,241,977 person-years of follow-up. In multivariable-adjusted models, a greater intake of low-pesticide-residue FVs was associated with a lower risk of CHD whereas high-pesticide-residue FV intake was unrelated to CHD risk. Specifically, compared with individuals consuming <1 serving/day of low-pesticide-residue FVs, those consuming ≥4 servings/day had 20% (95CI: 4%, 33%) lower risk of CHD. The corresponding HR (comparing ≥4 servings/day to <1 serving/day) for high-pesticide-residue FV intake and CHD was 0.97 (95%CI: 0.72, 1.30). CONCLUSIONS: Our data suggested exposure to pesticide residues through FV intake may modify some cardiovascular benefits of FV consumption. Further confirmation of these findings, especially using biomarkers for assessment of pesticide exposure, is needed.

BACKGROUND: There is growing acceptance that nutrition may be related to fertility and specifically to assisted reproductive technologies success in women; however, there is still no specific dietary guidance. OBJECTIVE: The objective of the study was to evaluate the relationship between pretreatment adherence to various dietary patterns and outcomes of assisted reproductive technologies. STUDY DESIGN: We followed up 357 women enrolled in the prospective Environment and Reproductive Health (EARTH) study, who underwent 608 assisted reproductive technologies cycles (2007-2017). Using a validated food frequency questionnaire completed prior to treatment, we assessed adherence to the Mediterranean diet, the alternate Healthy Eating Index 2010, the Fertility Diet (developed based on risk factors for anovulatory infertility), and a profertility diet we developed based on factors previously related to assisted reproductive technologies outcomes (higher intake of supplemental folic acid, vitamin B12, vitamin D, low- rather than high-pesticide residue produce, whole grains, dairy, soy foods, and seafood rather than other meats). RESULTS: Higher adherence to the alternate Healthy Eating Index 2010 and Fertility Diet was not related to live birth following assisted reproductive technologies. Women in the second through the fourth quartiles of Mediterranean diet adherence had significantly higher probability of live birth (0.44, 95% confidence interval, 0.39-0.49) compared with women in the first quartile (0.31, 95% confidence interval, 0.25-0.39); however, there was no additional benefit of adherence to the Mediterranean diet above the second quartile. Increased adherence to the profertility diet was linearly associated with assisted reproductive technologies outcomes. The adjusted odds (95% confidence interval) of implantation, clinical pregnancy, and live birth were higher by 47% (21%, 77%), 43% (19%, 72%), and 53% (26%, 85%), respectively, per SD increase. The adjusted difference in the proportion of cycles resulting in live birth for women in the fourth vs first quartile of adherence to the profertility diet was 0.28 (95% confidence interval, 0.16-0.38). While the profertility diet was not related to estradiol levels, oocyte counts, or endometrial thickness, it was inversely associated with clinical pregnancy loss (odds ratio, 0.69, 95% confidence interval, 0.53-0.90 per SD increase). CONCLUSION: Higher pretreatment adherence to the profertility diet was associated with an increased probability of live birth among women undergoing assisted reproductive technologies. Commonly recommended dietary advice such as adhering to the Mediterranean diet may not provide the most appropriate guidance for women undergoing infertility treatment in the United States.

BACKGROUND: Randomized trials of supplementation with antioxidant mixtures during infertility treatment show no benefit on pregnancy or live birth rate. However, the roles of individual antioxidants are poorly understood. We examined the association of baseline intake of vitamins A, C, E, and carotenoids with outcomes of assisted reproductive technologies (ART). METHODS: We followed 349 women undergoing a total of 588 ART cycles for infertility treatment at the Massachusetts General Hospital. We assessed antioxidant intakes from food and supplements before treatment using a validated food frequency questionnaire. We used generalized linear mixed models to account for multiple ART cycles per woman while adjusting for confounding. RESULTS: Mean (SD) age and body mass index were 35.1 (4.0) years and 24.1 (4.3) kg/m. Total intake of vitamins A, C, and E were not associated with the probability of live birth. Women in the highest intake category of β-carotene from foods had a lower probability of live birth than women in the lowest intake quartile (50% vs 22%; p-trend=0.03); for lutein and zeaxanthin, the probability for the highest intake group was 44% vs 28% for the lowest). Intake of β-carotene from supplements and intakes of retinol and all other carotenoids was unrelated to live birth rates. CONCLUSIONS: We found unexpected inverse associations of β-carotene intake from foods and of lutein and zeaxanthin intake with live birth rates. Within the observed intake ranges, total consumption of vitamins A, C, and E prior to starting infertility treatment with ART were not associated with live birth rates.

BACKGROUND: Randomized clinical trials show that men's use of antioxidant supplements during infertility treatment may improve clinical outcomes. However, important limitations in the design of most trials make it difficult to draw firm conclusions on their findings. OBJECTIVE: We examined whether men's intake of antioxidants and biologically related compounds without direct antioxidant capacity is associated with outcomes of assisted reproductive technologies (ARTs). METHODS: We conducted a prospective cohort study of men in couples who underwent infertility treatment with ART using their own gametes between 2007 and 2017. We followed 171 couples who presented at Massachusetts General Hospital Fertility Center and underwent 294 autologous ART cycles for infertility treatment. Diet was assessed in both partners using an FFQ. The primary study outcome was the probability of achieving a live birth as a result of infertility treatment. Secondary outcomes were fertilization, implantation, and clinical pregnancy rates. Generalized linear mixed models with random intercepts were fitted to account for multiple ART cycles per woman while adjusting for confounding. RESULTS: Men's vitamin C intake was positively associated with fertilization rate. The adjusted fertilization rate (95% CI) for couples in the lowest and highest quartiles of men's vitamin C intake were 69% (61-76%) and 81% (74-86%) (P-trend = 0.02). Men's β-carotene intake was positively associated with fertilization rate in intracytoplasmic sperm injection cycles but not in conventional in vitro fertilization cycles (P-interaction = 0.01). Men's α-carotene intake was inversely related to the probability of live birth. The adjusted probabilities of live birth for men in the lowest and highest quartiles of α-carotene intake were 43% (28-60%) and 22% (12-36%), respectively. CONCLUSIONS: Men's intake of vitamin C and β-carotene is positively related to fertilization rate but this does not translate into higher pregnancy or live birth rates in couples undergoing infertility treatment.

Animal models suggest a protective role of antioxidants against the adverse effect of di-2-ethylhexyl phthalate (DEHP) on insulin resistance. However, no epidemiologic study has examined the effects observed in the animal model. We conduct a study to examine associations of urinary concentrations of phthalate metabolites (individually and as a mixture) with insulin resistance, along with potential effect modification by serum antioxidant concentrations. This cross-sectional study included 1605 participants (51% males) aged 12-85 from the National Health and Nutrition Examination Surveys (2003-2006). Urinary concentrations of 9 phthalate metabolites were measured from spot urine samples. Antioxidant (vitamin A, C, E, and carotenoids) concentrations were measured from a fasting serum sample. We used Bayesian Kernel Machine Regression (BKMR) to evaluate associations between phthalate metabolite mixtures and insulin resistance, and examined whether serum antioxidant levels modified these associations, while accounting for the correlations of multiple concurrent exposures. A change in urinary ΣDEHP concentrations from the 25th to the 75th percentile was associated with a higher log HOMA-IR of 0.07 (95% CI = 0.01, 0.14) (4.85% increase in HOMA-IR). In contrast, the same change in urinary monoethyl phthalate (MEP) was associated with a lower HOMA-IR of -0.07 (95% CI = -0.14, -0.02) (6.68% decrease in HOMA-IR). The positive association between ΣDEHP and HOMA-IR became weaker at higher concentrations of serum β-carotene. The relationship between MEP and HOMA-IR, however, was not modified by the serum antioxidants examined. The remaining phthalate metabolites were unrelated to HOMA-IR. In this cross-sectional study, the positive association between DEHP exposure and insulin resistance weakened among participants with higher concentrations of serum β-carotene. As this is the first human report on the protective role of serum β-carotene on DEHP induced insulin resistance, future studies are needed.

Benzophenone-3 is used in a variety of cosmetic products as a sunscreen, and has shown weak estrogenic and antiandrogenic activity in animal and in vitro studies. Few studies have evaluated whether benzophenone-3 is associated with reproductive outcomes among women. We studied 304 women undergoing infertility treatment (2007-2017) in the prospective Environment and Reproductive Health cohort study and who underwent 449 treatment cycles (n = 788 urines). Generalized linear mixed models were used with random intercepts to account for multiple cycles, and adjusting for confounders including physical activity. Analyses were also stratified by self-reported moderate/heavy outdoor work. The cycle-specific median (IQR) urinary benzophenone-3 concentration was 147 (58, 462) μg/L, and 98% samples had detectable concentrations. Self-reported sunscreen use, physical activity, and time spent on moderate/heavy outdoor work were positively associated with urinary benzophenone-3. Adjusted probabilities of implantation, clinical pregnancy and live birth were higher in increasing quartiles of benzophenone-3, but these associations were restricted to women who reported spending time outdoors performing moderate/heavy work. Specifically, among these women, those in the highest quartile of benzophenone-3 concentrations had 51% higher implantation (p,trend = 0.02), 68% higher clinical pregnancy (p,trend = 0.01) and 75% higher live birth (p,trend = 0.02) adjusted probabilities than women in the lowest quartile. Benzophenone-3 was unrelated to these outcomes among women who did not report doing moderate/heavy work outdoors. These results confirm that sunscreen use is a source of benzophenone-3 exposure, and show positive associations between benzophenone-3 and pregnancy outcomes, especially among women who reported engaging in outdoor work. Since these associations may be subject to important residual confounding by lifestyle factors, further research is needed to confirm these novel results in other populations, and to investigate whether other factors may be affecting the relation of benzophenone-3 with fertility and other health outcomes.