Study looks into the risk factors of miscarriage and estimates a quarter of them could be prevented

Published on 02/19/14

Over a quarter of miscarriages may be preventable, estimate researchers in a new study published in BJOG.

This large nationwide study used data from 91,427 pregnancies included in the Danish National Birth Cohort, between 1996 and 2002, in order to identify the modifiable risk factors for miscarriage and to estimate the preventable proportion of miscarriages which could be attributed to these factors.

Miscarriage in Denmark is defined as a fetal death and/or expulsion before 22 completed weeks of gestation. Of the 91,427 pregnancies examined in this study, 3,177 resulted in miscarriage. Information on lifestyle was collected by computer-assisted telephone interviews.

The study examines nine potentially modifiable risk factors for miscarriage using the Cox regression model to provide the estimations. The risk factors include; amount of exercise, alcohol consumption, smoking, coffee consumption, work schedule (i.e. night shifts, rotating shifts), lifting of more than 20 kilograms daily, maternal age at conception, pre-pregnancy weight status and previously diagnosed genital diseases.

The results show that the potentially modifiable risk factors associated with increased miscarriage risk include; age of 30 years or more at conception, underweight or obese pre-pregnancy, alcohol consumption during pregnancy, lifting of more than 20 kilograms daily and night work during the antenatal period.

The study estimates that 25.2% of the miscarriages might be prevented by reduction of all the associated risk factors to low levels, and modification of risk factors acting before and during pregnancy could lead to prevention of 14.7% and 12.5% of the miscarriages respectively.

Furthermore, the paper concludes that maternal age at conception and alcohol consumption during pregnancy were the most important risk factors. The researchers estimate that 11.4% of miscarriages may be prevented if maternal age at conception is between 25 and 29 years, and 9% of miscarriages could be prevented if no alcohol was consumed during pregnancy.

Sandra Feodor Nilsson, PhD student from the Department of Public Health at the University of Copenhagen and co-author of the study said:

“Miscarriage is the most common adverse pregnancy outcome affecting at least one in seven pregnancies and is considered irreversible. Therefore, prevention may be the only way of reducing the number of miscarriages that occur.

“Our results indicate that the risk of miscarriage is increased by multiple potentially modifiable risk factors and a considerable proportion of miscarriages may be preventable. We know that the modifiable aspects of the risk factors may be questioned as they often depend on other factors that are not necessarily easy to change.

“However, we think that information about increased chances of having a successful pregnancy at a relatively young age is an important perspective. If our findings are supported by future prospective cohort studies they may support a prevention strategy towards miscarriage.”

John Thorp, BJOG Editor-in-chief, added:

“This is an interesting study as it uses a large data pool and adds an important perspective by suggesting that some miscarriages are preventable.

“However, the study may underestimate the miscarriage rate as interviews were conducted with participants at 16 weeks. Given that miscarriages can occur up until 22 weeks by Danish definition, the rate of 3.5% suggested by this study may actually be higher.”

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