OnMedica – News – Risk of miscarriage increases with age and previous pregnancy problems

Higher risk after miscarriage and other complications of pregnancy and could have the same underlying causes

A Norwegian research has shown that the risk of miscarriage is closely related to its age, considerably higher after a previous miscarriage and also increases after some complications of pregnancy. The authors of study*, published today in the BMJ, said that more targeted studies of these badociations could lead to a better understanding of the common underlying causes of pregnancy complications and miscarriages.

The team, led by the Norwegian Institute of Public Health, badyzed data from the Norwegian Medical Birth Registry, the Norwegian Patient Register and the Induced Abortion Registry to estimate the burden of miscarriage in the Norwegian population and evaluate badociations with maternal age. and a history of pregnancy. These covered all pregnant Norwegian women between 2009 and 2013, making a total of 421,201 pregnancies during the study period. They identified a miscarriage such as a pregnancy loss between six and 20 weeks, or a fetal death before 20 weeks with a birth weight of less than 500 g; fetal death at 20 weeks of gestation or later, or with a birth weight of 500 g or more, which was considered a stillbirth.

They found that the risk of miscarriage was lowest among women aged 25 to 29, with the lowest absolute risk at age 27 (9.5%) and increasing rapidly after age 30, reaching 53% at women aged at least 45 years old; mothers under the age of 20 had a 15.8% risk.

The risk of miscarriage was high, with an age-adjusted odds ratio (OR) of 1.54 after miscarriage, 2.21 after two, and 3.97 after three consecutive miscarriages. The risk of miscarriage was moderately but significantly increased if the previous pregnancy had resulted in premature (live) delivery (OR 1.22), stillbirth (1.30), caesarean section (1.16), or woman had gestational diabetes during the previous pregnancy (1.19). The risk of miscarriage was also significantly, although slightly higher, among women who were themselves small for gestational age (1.08).

The authors of the study stated that badociations of risk of miscarriage and complications in previous pregnancies suggest the presence of causal factors that increase the risk of both. They commented, "We have found evidence that some other pregnancy outcomes combine the risk of miscarriage, suggesting that these findings may have common causes. Specifically, the risk of miscarriage was moderately increased among women who had had a stillbirth, preterm birth, or gestational diabetes during their previous pregnancy. "

They pointed out that their study did not allow to establish the causal link as it was about observations. Other limitations include the lack of some early miscarriages during which women have not contacted specialized health care services. information from the birth certificate of the woman.

They concluded: "The risk of miscarriage varies considerably with the age of the mother, shows a strong tendency to recurrence and also increases after some adverse consequences of pregnancy. Miscarriage and other complications of pregnancy may have common causes, which may be unmeasured biological conditions or common risk factors. "

*Magnus MC, Wilcox AJ, Morken N-H et al. Role of the mother's age and pregnancy history in the risk of miscarriage: prospective study based on a register. BMJ 2019; 364: l869 http://dx.doi.org/10.1136/bmj.l86