Risks of repeated miscarriage.

There is a lack of well-designed epidemiological studies of possible risk factors for repeated miscarriage. In this Swedish population-based case-control study, we investigated the association between sociodemographic and anthropometric factors, obstetric history and life-style factors, with respect to the risks of first-trimester repeated miscarriage. Information on maternal characteristics was collected through in-person interviews. Plasma blood samples were analysed for cotinine and folate concentrations. Adjusted odds ratios (OR) with 95% confidence interval [CI] were used to estimate the relative risk of repeated miscarriage. The risks of repeated miscarriage were increased for women aged > or = 35 years (adjusted OR 2.9 [95% CI 1.4, 5.8]), as well as for women aged < or = 24 years (OR 2.8 [95% CI 1.1, 6.8]). Women with a history of at least one preceding miscarriage prior to the two index pregnancies, women reporting prolonged time to conceive, and women with a history of myoma, faced a more than fourfold increased risk of repeated miscarriage. Smokers were at an increased risk of repeated miscarriage (OR 2.1 [95% CI 1.1, 4.1]). Among non-smoking women with high caffeine intake, there was an increased risk of repeated miscarriage, whereas there was no such association among smokers. Low plasma folate levels were not associated with increased risks.

Plasma folate levels and risk of spontaneous abortion.

CONTEXT: Both folate deficiency and folic acid supplements have been reported to increase the risk of spontaneous abortion. The results are inconclusive, however, and measurements of folate have not been available in all studies. OBJECTIVE: To study the association between plasma folate levels and the risk of spontaneous abortion. DESIGN, SETTING, AND POPULATION: Population-based, matched, case-control study of case women with spontaneous abortion and control women from January 1996 through December 1998 in Uppsala County, Sweden. Plasma folate measurements were available for 468 cases and 921 controls at 6 to 12 gestational weeks. MAIN OUTCOME MEASURE: Risk of spontaneous abortion vs maternal plasma folate level. RESULTS: Compared with women with plasma folate levels between 2.20 and 3.95 ng/mL (5.0 and 8.9 nmol/L), women with low (< or =2.19 ng/mL [< or =4.9 nmol/L]) folate levels were at increased risk of spontaneous abortion (adjusted odds ratio [OR], 1.47; 95% confidence interval [CI], 1.01-2.14), whereas women with higher folate levels (3.96-6.16 ng/mL [9.0-13.9 nmol/L] and > or =6.17 ng/mL [> or =14.0 nmol/L]) showed no increased risk of spontaneous abortion (OR, 0.84; 95% CI, 0.59-1.20; and OR, 0.74; 95% CI, 0.47-1.16, respectively). Low folate levels were associated with a significantly increased risk when the fetal karyotype was abnormal (OR, 1.95; 95% CI, 1.09-3.48) but not when the fetal karyotype was normal (OR, 1.11; 95% CI, 0.55-2.24) or unknown (OR, 1.45; 95% CI, 0.90-2.33). CONCLUSION: Low plasma folate levels were associated with an increased risk of early spontaneous abortion.