Larger hospital units have lower miscarriage rates after invasive pregn...( A study of more than 64000 pregnant ...),Health

A study of more than 64,000 pregnant women has found that miscarriage rates following amniocentesis and chorionic villus sampling (CVS) - two invasive procedures to detect chromosomal abnormalities and birth defects - were 1.4 per cent and 1.9 per cent, respectively.

The research, published in the July issue of Ultrasound in Obstetrics and Gynecology, also found that the number of procedures carried out by a department had a significant effect on miscarriage rates.

For example, the rates in departments carrying out fewer than 500 amniocentesis tests over the 11-year period were 2.2 times higher than those performing 1,500 or more over the same timescale. Similarly, the miscarriage risk for CVS was 1.5 times higher in departments that performed 500 to 1,000 procedures and 1001 to 1,500 procedures, compared to those carrying out more than 1,500 procedures.

The research team from Copenhagen University Hospital analysed the results of all amniocentesis and CVS tests carried out on singleton pregnancies in Denmark between 1996 and 2006. Just over 51 per cent of the 64,207 women underwent an amniocentesis test, with the remainder receiving CVS testing.

"In Denmark all citizens have a unique personal identification number which enables us to link individuals between different health registries" explains lead author Professor Ann Tabor from the Department of Fetal Medicine at the University. "This made it possible for us to compare the chromosome analysis reports lodged with the Danish Central Cytogenic Registry and cross-reference them to the deliveries, miscarriages and terminations in the National Registry of Patients."

The post-procedural miscarriage rate was defined as spontaneous miscarriage or intrauterine death before 24 weeks' gestation.

The study showed that the number of amniocentesis tests fell over the 11-year study period, from 55 per cent to 31 per cent of invasive procedures, while
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