The association between dietary patterns and risk of miscarriage: a systematic review and meta-analysis

Effectiveness and Safety of IVF Add-Ons: A Meta-Review of 10 Common IVF Add-Ons

Lensen SF et al., 2025 · SSRN

Vaginal micronised progesterone for the prevention of hypertensive disorders of pregnancy: A systematic review and meta-analysis

Melo P et al., 2023 · BJOG · Free to read

Treatment with vaginal progesterone reduces the risk of miscarriage and preterm birth in selected high-risk women. The hypothesis that vaginal progesterone can reduce the risk of hypertensive disorders of pregnancy (HDP) is unexplored. To summarise the evidence on the effectiveness of vaginal progesterone to reduce the risk of HDP. Search Strategy: We searched Embase (OVID), MEDLINE (OVID), PubMed, CENTRAL and clinicaltrials.gov from inception until 20 June 2023. Selection Criteria: We included placebo-controlled randomised trials (RCTs) of vaginal progesterone for the prevention or treatment of any pregnancy complications. Data Collection and Analysis: We extracted absolute event numbers for HDP and pre-eclampsia in women receiving vaginal progesterone or placebo, and meta-analysed the data with a random effects model. We appraised the certainty of the evidence using GRADE methodology. MAIN The quantitative synthesis included 11 RCTs, of which three initiated vaginal progesterone in the first trimester, and eight in the second or third trimesters. Vaginal progesterone started in the first trimester of pregnancy lowered the risk of any HDP (risk ratio [RR] 0.71, 95% confidence interval [CI] 0.53-0.93, 2 RCTs, n = 4431 women, I(2) = 0%; moderate-certainty evidence) and pre-eclampsia (RR 0.61, 95% CI 0.41-0.92, 3 RCTs, n = 5267 women, I(2) = 0%; moderate-certainty evidence) when compared with placebo. Vaginal progesterone started in the second or third trimesters was not associated with a reduction in HDP (RR 1.19, 95% CI 0.67-2.12, 3 RCTs, n = 1602 women, I(2) = 9%; low-certainty evidence) or pre-eclampsia (RR 0.97, 95% CI 0.71-1.31, 5 RCTs, n = 4274 women, I(2) = 0%; low-certainty evidence). Our systematic review found first-trimester initiated vaginal micronised progesterone may reduce the risk of HDP and pre-eclampsia.

Vitamin D and miscarriage: a systematic review and meta-analysis

Tamblyn JA et al., 2022 · Fertility and sterility · Free to read

To investigate whether a significant association between vitamin D status and the risk of miscarriage or recurrent miscarriage (RM) exists. Systematic review and meta-analysis. Not applicable. PATIENT(S): Women with miscarriage and RM. INTERVENTION(S): We searched the Ovid MEDLINE, Embase, the Cumulative Index to Nursing and Allied Health Literature, and Cochrane Central Register of Controlled Trials from database inception to May 2021. Randomized and observational studies investigating the association between maternal vitamin D status and miscarriage and/or vitamin D treatment and miscarriage were included. MAIN OUTCOME MEASURE(S): The primary outcome was miscarriage or RM, with vitamin D status used as the predictor of risk. Whether vitamin D treatment reduces the risk of miscarriage and RM was also assessed. RESULT(S): Of 902 studies identified, 10 (n = 7,663 women) were included: 4 randomized controlled trials (n = 666 women) and 6 observational studies (n = 6,997 women). Women diagnosed with vitamin D deficiency (<50 nmol/L) had an increased risk of miscarriage compared with women who were vitamin D replete (>75 nmol/L) (odds ratio, 1.94; 95% confidence interval, 1.25-3.02; 4 studies; n = 3,674; I2 = 18%). Combined analysis, including women who were vitamin D insufficient (50-75 nmol/L) and deficient (<50 nmol/L) compared with women who were replete (>75 nmol/L), found an association with miscarriage (odds ratio, 1.60; 95% confidence interval, 1.11-2.30; 6 studies; n = 6,338; I2 = 35%). Although 4 randomized controlled trials assessed the effect of vitamin D treatment on miscarriage, study heterogeneity, data quality, and reporting bias precluded direct comparison and meta-analysis. The overall study quality was "low" or "very low" using the Grading of Recommendations, Assessment, Development and Evaluations approach. CONCLUSION(S): Vitamin D deficiency and insufficiency are associated with miscarriage. Whether preconception treatment of vitamin D deficiency protects against pregnancy loss in women at risk of miscarriage remains unknown. CRD42021259899.

Micronized vaginal progesterone to prevent miscarriage: a critical evaluation of randomized evidence

Coomarasamy A et al., 2020 · Am J Obstet Gynecol · Free full text on PubMed Central

Progesterone is essential for the maintenance of pregnancy. Several small trials have suggested that progesterone supplementation may reduce the risk of miscarriage in women with recurrent or threatened miscarriage. Cochrane Reviews summarized the evidence and found that the trials were small with substantial methodologic weaknesses. Since then, the effects of first-trimester use of vaginal micronized progesterone have been evaluated in 2 large, high-quality, multicenter placebo-controlled trials, one targeting women with unexplained recurrent miscarriages (the PROMISE [PROgesterone in recurrent MIScarriagE] trial) and the other targeting women with early pregnancy bleeding (the PRISM [PRogesterone In Spontaneous Miscarriage] trial). The PROMISE trial studied 836 women from 45 hospitals in the United Kingdom and the Netherlands and found a 3% greater live birth rate with progesterone but with substantial statistical uncertainty. The PRISM trial studied 4153 women from 48 hospitals in the United Kingdom and found a 3% greater live birth rate with progesterone, but with a P value of .08. A key finding, first observed in the PROMISE trial, and then replicated in the PRISM trial, was that treatment with vaginal micronized progesterone 400 mg twice daily was associated with increasing live birth rates according to the number of previous miscarriages. Prespecified PRISM trial subgroup analysis in women with the dual risk factors of previous miscarriage(s) and current pregnancy bleeding fulfilled all 11 conditions for credible subgroup analysis. For the subgroup of women with a history of 1 or more miscarriage(s) and current pregnancy bleeding, the live birth rate was 75% (689/914) with progesterone vs 70% (619/886) with placebo (rate difference 5%; risk ratio, 1.09, 95% confidence interval, 1.03-1.15; P=.003). The benefit was greater for the subgroup of women with 3 or more previous miscarriages and current pregnancy bleeding; live birth rate was 72% (98/137) with progesterone vs 57% (85/148) with placebo (rate difference 15%; risk ratio, 1.28, 95% confidence interval, 1.08-1.51; P=.004). No short-term safety concerns were identified from the PROMISE and PRISM trials. Therefore, women with a history of miscarriage who present with bleeding in early pregnancy may benefit from the use of vaginal micronized progesterone 400 mg twice daily. Women and their care providers should use the findings for shared decision-making.

The Association Between History of Infertility and Dietary Practices: A Cross-Sectional Study Among Preconception Females

Velmahos AH et al., 2026 · Journal of Restorative Reproductive Medicine · Free to read

To evaluate the extent to which a history of infertility is associated with adherence to specific diets among reproductive-aged females. Cross-sectional analysis Between 2017–2023, 7,227 North American female pregnancy planners aged 21-45 years enrolled in PRESTO (Pregnancy Study Online), a preconception cohort study. Participants completed self-administered baseline questionnaires during preconception. Exposure: Infertility history, defined as: 1) self-reported 12-month clinical infertility, 2) history of visiting a clinician for an infertility work-up, and/or 3) clinician-identified cause of infertility (e.g., ovulatory or tubal). Adherence to specific diets, including vegetarian, vegan, Mediterranean, Paleo, Weight Watchers®, ketogenic, dairy free, gluten free, Atkins®, South Beach®, Zone®, raw foods, or other at baseline. Multivariable log-binomial regression models estimated the prevalence ratios (PRs) and 95% confidence intervals (CIs), adjusted for age, income, and body mass index (BMI). The percentage of participants with a history of infertility was 26% based on the 12-month clinical infertility definition, 30% based on visiting a physician for infertility evaluation, and 26% based on an infertility diagnosis following a physician visit. Overall adherence to any particular diet was low (4.6% vegetarian, 2.8% ketogenic, 1.7% Weight Watchers®, 1.4% Mediterranean, 1.3% vegan, 0.8% Paleo, and all other diets: <0.8%); 86.6% reported not adhering to any particular diet. A history of 12-month clinical infertility was associated with lower adherence to vegetarian (PR=0.78; 95% CI: 0.60-1.03), Paleo (PR=0.43; 95% CI: 0.19-0.98), and Weight Watchers® (PR=0.55; 95% CI: 0.34-0.91) diets. An infertility history involving a medical work-up was associated with a higher prevalence of adherence to a ketogenic diet (PR=1.56; 95% CI: 1.17-2.09). Participants whose infertility was attributed to ovulatory or tubal causes were nearly two times more likely to adhere to a ketogenic diet (PR=2.01; 95% CI: 1.38-2.94; PR=2.22; 95% CI: 1.09-4.49, respectively). The cross-sectional design cannot establish temporality or causality. Data on dietary patterns and infertility history were self-reported, which can introduce misclassification. Generalizability may be limited because participants were pregnancy planners not using fertility treatments; participants were also more likely to be non-Hispanic White and of higher socioeconomic status than the general population. The ketogenic diet was more prevalent among females with an infertility history, while vegetarian, Paleo, and Weight Watchers® diets were less prevalent. These associations mirror the results of studies evaluating the reverse relationship, suggesting that some patients with infertility seek information for behavioral modifications via evidence-based medicine.

Diet and lifestyle in the prevention of ovulatory disorder infertility

Chavarro JE et al., 2007 · Obstetrics and gynecology

To evaluate the relation of a dietary pattern and other lifestyle practices to risk of ovulatory disorder infertility. We followed a cohort of 17,544 women without a history of infertility for 8 years as they tried to become pregnant or became pregnant. A dietary score based on factors previously related to lower ovulatory disorder infertility (higher consumption of monounsaturated rather than trans fats, vegetable rather than animal protein sources, low glycemic carbohydrates, high fat dairy, multivitamins, and iron from plants and supplements) and other lifestyle information was prospectively related to the incidence of infertility. Increasing adherence to a "fertility diet" pattern was associated with a lower risk of ovulatory disorder infertility. The multivariable-adjusted relative risk of ovulatory disorder infertility comparing women in the highest with women in the lowest quintile of the "fertility diet" pattern score was 0.34 (95% confidence interval 0.23-0.48; P for trend<.001). This inverse relation was similar in subgroups defined by women's age, parity, and body weight. A combination of five or more low-risk lifestyle factors, including diet, weight control, and physical activity was associated with a 69% lower risk of ovulatory disorder infertility and an estimated population attributable risk of 66% (95% confidence interval 29-86%). Following a "fertility diet" pattern may favorably influence fertility in otherwise healthy women. Further, the majority of infertility cases due to ovulation disorders may be preventable through modifications of diet and lifestyle. II.

Association of a Mediterranean Diet Pattern With Adverse Pregnancy Outcomes Among US Women

Makarem N et al., 2022 · JAMA network open · Free full text on PubMed Central

The Mediterranean diet pattern is inversely associated with the leading causes of morbidity and mortality, including metabolic diseases and cardiovascular disease, but there are limited data on its association with adverse pregnancy outcomes (APOs) among US women. To evaluate whether concordance to a Mediterranean diet pattern around the time of conception is associated with lower risk of developing any APO and individual APOs. DESIGN, SETTING, This prospective, multicenter, cohort study, the Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-to-Be, enrolled 10 038 women between October 1, 2010, and September 30, 2013, with a final analytic sample of 7798 racially, ethnically, and geographically diverse women with singleton pregnancies who had complete diet data. Data analyses were completed between June 3, 2021, and April 7, 2022. An Alternate Mediterranean Diet (aMed) score (range, 0-9; low, 0-3; moderate, 4-5; and high, 6-9) was computed from data on habitual diet in the 3 months around conception, assessed using a semiquantitative food frequency questionnaire. Adverse pregnancy outcomes were prospectively ascertained and defined as developing 1 or more of the following: preeclampsia or eclampsia, gestational hypertension, gestational diabetes, preterm birth, delivery of a small-for-gestational-age infant, or stillbirth. Of 7798 participants (mean [SD] age, 27.4 [5.5] years), 754 (9.7%) were aged 35 years or older, 816 (10.5%) were non-Hispanic Black, 1294 (16.6%) were Hispanic, and 1522 (19.5%) had obesity at baseline. The mean (SD) aMed score was 4.3 (2.1), and the prevalence of high, moderate, and low concordance to a Mediterranean diet pattern around the time of conception was 30.6% (n=2388), 31.2% (n=2430), and 38.2% (n=2980), respectively. In multivariable models, a high vs low aMed score was associated with 21% lower odds of any APO (adjusted odds ratio [aOR], 0.79 [95% CI, 0.68-0.92]), 28% lower odds of preeclampsia or eclampsia (aOR, 0.72 [95% CI, 0.55-0.93]), and 37% lower odds of gestational diabetes (aOR, 0.63 [95% CI, 0.44-0.90]). There were no differences by race, ethnicity, and prepregnancy body mass index, but associations were stronger among women aged 35 years or older (aOR, 0.54 [95% CI, 0.34-0.84]; P = .02 for interaction). When aMed score quintiles were evaluated, similar associations were observed, with higher scores being inversely associated with the incidence of any APO. This cohort study suggests that greater adherence to a Mediterranean diet pattern is associated with lower risk of APOs, with evidence of a dose-response association. Intervention studies are needed to assess whether dietary modification around the time of conception can reduce risk of APOs and their downstream associations with future development of cardiovascular disease risk factors and overt disease.

Shorter Time to Pregnancy With Increasing Preconception Carotene Concentrations Among Women With 1-2 Previous Pregnancy Losses

Kim K et al., 2018 · Am J Epidemiol · Free full text on PubMed Central

Although maternal nutrition may affect fecundity, associations between preconception micronutrient levels and time to pregnancy (TTP) have not been examined. We assessed the relationship between preconception fat-soluble micronutrient concentrations and TTP among women with 1-2 prior pregnancy losses. This was a prospective cohort study of 1,228 women set within the Effects of Aspirin in Gestation and Reproduction (EAGeR) Trial (United States, 2007-2011), which assessed the association of preconception-initiated daily low-dose aspirin with reproductive outcomes. We measured preconception levels of zeaxanthin, cryptoxanthin, lycopene, αand β-carotene, and αand γ-tocopherol in serum. We used discrete Cox regression models, accounting for left-truncation and right-censoring, to calculate fecundability odds ratios and 95% confidence intervals. The models adjusted for age, body mass index, race, smoking, alcohol, physical activity, income, vitamin use, cholesterol, treatment arm, and study site. Serum α-carotene levels (per log unit (μg/dL) increase, fecundability odds ratio (FOR) = 1.17, 95% confidence interval (CI): 1.00, 1.36) and serum α-carotene concentrations at or above the US average (2.92 μg/dL) versus below the average (FOR = 1.21, 95% CI: 1.02, 1.44) were associated with shorter TTP. Compared with levels below the US average (187 μg/dL), γ-tocopherol concentrations at or above the average were associated with longer TTP (FOR = 0.83, 95% CI: 0.69, 1.00). The potential for these nutrients to influence fecundability deserves further exploration.