Does the use of Doppler ultrasound reduce fetal mortality? A population study of all deliveries in Norway 1990-2014

Abstract

Background: The aim of the present study was to examine the effect that the introduction of Doppler ultrasound in obstetric care has had on fetal death in Norway. One mechanism by which Doppler ultrasound may reduce fetal death may be through the increased use of Caesarean delivery. Therefore, we also examined the effect that the use of Doppler ultrasound has had on the use of Caesarean delivery.

Methods: The Medical Birth Registry of Norway provided detailed medical information for ∼1.2 million deliveries from 1990 to 2014. Information about the year of introduction of Doppler ultrasound was collected directly from the maternity units, using a questionnaire. The data were analysed using a hospital fixed-effects regression model with fetal death as the outcome measure. The key independent variable was the introduction of Doppler ultrasound at each maternity ward. Hospital-specific trends and risk factors of the mother for fetal death were included as covariates.

Results: For pre-term deliveries, the introduction of Doppler ultrasound contributed to a reduction in fetal death of ∼30% and to an increase in planned Caesarean section of ∼15%. There were no effects for emergency Caesarean sections or inductions pre-term. The introduction of Doppler ultrasound had no effect on fetal death or Caesarean section for term deliveries.

Conclusions: The introduction of Doppler ultrasound during the 1990s and 2000s made a significant contribution to the decline in the number of pre-term fetal deaths in Norway. Increased use of Caesarean section may have contributed to this reduction.

Keywords: Doppler ultrasound; difference-in-difference estimates; fetal death; obstetric care.

Figure 1

The proportion of fetal deaths according to year and gestational age. Aggregated data at the national level. 1990–2014.

Figure 2

Number and percentage of maternity units, according to year of introduction of Doppler ultrasound. Cumulative figures. 1990–2014.

Figure 3

Trends in the proportion of fetal deaths before Doppler ultrasound was introduced. Single births, hospital-level data.

Figure 4

Lead and lag effects for the use of Doppler ultrasound on fetal deaths for pre-term deliveries. Single births. Regression coefficients with 95% confidence intervals. Covariates included. 1985–2014.