Magnus, M. C., Wilcox, A. J., Morken, N. H., Weinberg, C. R., & Haberg, S. E. (2019). Role of maternal age and pregnancy history in risk of miscarriage: prospective register based study. BMJ. https://doi.org/10.1136/bmj.l869
Magnus MC, Wilcox AJ, Morken NH, Weinberg CR, Haberg SE. Role of maternal age and pregnancy history in risk of miscarriage: prospective register based study. BMJ. 2019. doi:10.1136/bmj.l869
Magnus, Maria C., et al. "Role of maternal age and pregnancy history in risk of miscarriage: prospective register based study." BMJ, 2019.
Epidemiology Branch, National Institute of Environmental Health Sciences, PO Box 12233, Research Triangle Park, NC 27709, USA00j4k1h63
Linked to ROR, the Research Organization Registry
RRM Academy Synopsis
Miscarriage risk in Norway rose with age and earlier miscarriages
A Norwegian register study of 421 201 pregnancies found that miscarriage risk was lowest at ages 25 to 29 and highest at 45 and over. The rates were about 1 out of 10 and more than 5 out of 10, respectively. The risk of another miscarriage rose with each consecutive earlier miscarriage. Some earlier complications were linked to higher risk.
Key Findings
Of 421 201 registered pregnancies, 43 803 ended in miscarriage. Adjusting for induced abortions, the study put the overall risk at 12.8%.
Risk was 15.8% under age 20, 9.8% at 25 to 29, 16.7% at 35 to 39, 32.2% at 40 to 44, and 53.6% at 45 and over.
Versus first pregnancies, age-adjusted odds ratios were 1.54 (95% CI 1.48 to 1.60), 2.21 (2.03 to 2.41), and 3.97 (3.29 to 4.78) after one, two, and three or more consecutive miscarriages.
Adjusted odds ratios for miscarriage were 1.22 (95% CI 1.12 to 1.29) after a preterm birth, 1.19 (1.05 to 1.36) after gestational diabetes, and 1.16 (1.12 to 1.21) after cesarean section.
After a previous stillbirth, the adjusted odds ratio for miscarriage was 1.30 (95% CI 1.11 to 1.53), compared with women with no previous pregnancy.
Interpretation
The study used national registers of registered pregnancies in Norway from 2009 to 2013, excluding ectopic pregnancies. An odds ratio above 1 means higher odds than the comparison group. The results are associations. The authors call the links with earlier complications exploratory. They suggest a common cause might sit behind these outcomes, either a biological condition or a risk factor the registers did not measure. They note likely under-ascertainment of early miscarriages and missing data on paternal age, ethnicity, education, and body mass index.
RRM Context
The authors report that risk varies considerably between couples. They also note that miscarriage and other pregnancy problems might share underlying causes. Restorative reproductive medicine asks why a loss happened and evaluates before it treats.
Our editorial summary of this paper, not the article's abstract.
Abstract
Objectives
To estimate the burden of miscarriage in the Norwegian population and to evaluate the associations with maternal age and pregnancy history.
Design
Prospective register based study.
Setting
Medical Birth Register of Norway, the Norwegian Patient Register, and the induced abortion register.
Participants
All Norwegian women that were pregnant between 2009-13.
Main Outcome Measures
Risk of miscarriage according to the woman's age and pregnancy history estimated by logistic regression.
Results
There were 421 201 pregnancies during the study period. The risk of miscarriage was lowest in women aged 25-29 (10%), and rose rapidly after age 30, reaching 53% in women aged 45 and over. There was a strong recurrence risk of miscarriage, with age adjusted odds ratios of 1.54 (95% confidence interval 1.48 to 1.60) after one miscarriage, 2.21 (2.03 to 2.41) after two, and 3.97 (3.29 to 4.78) after three consecutive miscarriages. The risk of miscarriage was modestly increased if the previous birth ended in a preterm delivery (adjusted odds ratio 1.22, 95% confidence interval 1.12 to 1.29), stillbirth (1.30, 1.11 to 1.53), caesarean section (1.16, 1.12 to 1.21), or if the woman had gestational diabetes in the previous pregnancy (1.19, 1.05 to 1.36). The risk of miscarriage was slightly higher in women who themselves had been small for gestational age (1.08, 1.04 to 1.13).
Conclusions
The risk of miscarriage varies greatly with maternal age, shows a strong pattern of recurrence, and is also increased after some adverse pregnancy outcomes. Miscarriage and other pregnancy complications might share underlying causes, which could be biological conditions or unmeasured common risk factors.
00j4k1h63 