Early risk assessment and aspirin prophylaxis did not reduce preterm preeclampsia in Sweden: a population-based study.

BACKGROUND

Preeclampsia is a substantial cause of maternal and perinatal morbimortality, with complications becoming more severe the earlier it manifests during pregnancy. The Fetal Medicine Foundation has developed a method that combines anamnestic risk factors and biochemical and biophysical tests to assess the individual risk of developing preterm preeclampsia. Previous studies have demonstrated that the combination of the Fetal Medicine Foundation method with the use of aspirin significantly reduces the prevalence of preterm preeclampsia. To our knowledge, no published studies have applied this method to an entire population before.

OBJECTIVE

To evaluate the prevalence of preterm preeclampsia, defined as preterm birth with a preeclampsia diagnosis, before and after the Fetal Medicine Foundation method was introduced in an unselected Swedish population.

STUDY

DESIGN

This population-based, retrospective cohort study included 61,840 deliveries from 5 obstetric units in Sweden from 2012 to 2022. Two cohorts were defined: one before and one after the implementation of the Fetal Medicine Foundation method. The primary outcome was the prevalence of preterm preeclampsia. The analysis followed an intention-to-treat approach. The intervention cohort comprised 30,777 women. Individuals with a risk score of ≥1:100 were considered high risk and were subsequently recommended a daily dose of 150 mg of aspirin until 36 weeks of gestation or until the onset of preeclampsia.

RESULTS

No significant reduction in the prevalence of preterm preeclampsia was observed (adjusted odds ratio, 1.13; 95% confidence interval, 0.9-1.5) but a tendency toward an increase in term preeclampsia rates was noted (adjusted odds ratio, 1.14; 95% confidence interval, 1.00-1.30). No other differences in obstetrical or neonatal outcomes were found between the cohorts (P=not significant, not significant). The Fetal Medicine Foundation method was successfully conducted in more than 85% of the pregnant population.

CONCLUSION

The implementation of the Fetal Medicine Foundation method showed no reduction in preterm birth combined with preeclampsia in this intention-to-treat analysis. The Fetal Medicine Foundation method was both feasible and well accepted in this unselected population, demonstrating its applicability in routine clinical practice. Further population-based studies using a per-protocol approach are needed to evaluate the efficacy of aspirin prophylaxis among individuals identified as high risk according to the Fetal Medicine Foundation method.