A systematic review to calculate background miscarriage rates using life table analysis.

The objectives of the current study were to calculate: (1) the expected rates of miscarriage by gestational week; (2) the cumulative risk of miscarriage; and (3) the remaining risk of miscarriage for gestational weeks five through 20, through a systematic review of the literature. We searched MEDLINE for articles published in English through the end of 2009. References of articles were also searched. Four studies were identified to have the three necessary pieces of information for the proposed calculations: (1) gestational age at study entry, (2) pregnancy outcome; and (3) the gestational age at which the pregnancy outcome occurred. Data were extracted from each study and Life Table Analysis Methods were conducted. Weekly miscarriage rates varied in the early gestational weeks with the highest rate documented at >20 miscarriages per 1000 women-weeks at each week of gestation prior to week 13. By week 14, the rate for all studies became relatively comparable and fell below 10 miscarriages per 1000 woman-weeks at risk and fell even lower through week 20. The cumulative risk of miscarriage for weeks 5 through 20 of gestation ranged from 11 miscarriages per 100 women to 22 miscarriages per 100 women (11-22%). Based on data from comparable study populations, a range of background miscarriage rates by week of gestation for weeks 5 through 20, the cumulative risk of miscarriage, and the remaining risk of miscarriage are presented. Wider variation of miscarriage rates and risks occurred early in gestation (<14 weeks).

Do multivitamin supplements modify the relationship between prenatal alcohol intake and miscarriage?

OBJECTIVE: To determine whether multivitamin supplements modify the relationship between alcohol consumption during pregnancy and the risk of miscarriage. STUDY DESIGN: We used data from a population-based cohort study of pregnant women (n=1061; response rate=39%). Participants were asked about their alcohol consumption and vitamin intake during pregnancy. RESULTS: Among multivitamin nonusers, women who drank alcohol during their pregnancy were more likely to have a miscarriage compared with women who abstained (adjusted hazard ratio, 1.67; 95% confidence interval, 1.04-2.69). However, among multivitamin users, there was no difference in the risk of miscarriage between alcohol consumers and abstainers. Results suggest the volume of alcohol as well as the timing of multivitamin supplementation may also be important. CONCLUSION: Our findings suggest that a woman of childbearing years might decrease her risk of miscarriage associated with alcohol intake by taking multivitamin supplements. However, our findings should be interpreted with caution and future research replicating these findings is necessary.