The impact of multiple pregnancies and malformations on perinatal mortality

To evaluate the impact of the rate of multiple pregnancies and congenital malformations on perinatal mortality.

The study is based on data from the perinatal audit in Vejle County Denmark. Fetal deaths with gestational age > or = 22 weeks and deaths in livebirths within the first 28 days after birth were included in the calculated perinatal mortality. Total number of births was 30,181 and 252 pregnancies and 268 fetuses/infants were evaluated. The study period was 1995-2000. There was no routine ultrasound screening for congenital malformations in the county, though midtrimester ultrasound was used to assess gestational age.

Perinatal mortality was 8.9 per 1000 births with no significant change over time. Rate of multiple pregnancies was 1.94% ranging from 1.81% during the first 3 years to 2.06% for the last 3 years (not significant). Fetuses and infants from multiple pregnancies contributed 18% of all deaths. Perinatal mortality for single births was 7.6 per 1000 births and for multiple births 42.2/1000 (P<0.0001). The distribution of gestational age for single and multiple births was highly significant (P<0.0001) with 67% of multiple pregnancies with GA < 28 weeks compared to 26% of single pregnancies. Nineteen percent of all deaths were caused by congenital malformations and the majority of these were potentially detectable by ultrasound investigation.

The increasing rate of multiple pregnancies makes it difficult to see improvements in perinatal mortality. Calculated from the perinatal mortality in single and multiple pregnancies in Vejle County assisted conceptions contribute with an an excess of 45 perinatal deaths per year in Denmark. The difference between countries in rate of multiple pregnancies and in prenatal ultrasound screening recommendations for malformations makes it difficult to compare perinatal mortality.