Safety and risks associated with screening for chromosomal abnormalities during pregnancy

To assess the risk and safety of screening for chromosomal abnormalities during pregnancy through the assessment of exposure to ultrasound and the fetal loss rate after trans-abdominal amniocentesis (AMNIO) or chorionic villus sampling (CVS).

It is a retrospective analysis of the fetal loss rate following AMNIO and CVS as a diagnostic tests for chromosomal abnormalities during pregnancy in 1391 singleton pregnancies who attended our clinic from January 2005 to December 2009 (1038 AMNIO and 353 CVS). Pregnancies were followed up to ascertain the fetal loss rate after the procedure which was defined as intrauterine demise or miscarriage before the 24th week of gestation. Review of literature was the method used for assessing the safety of ultrasound during pregnancy.

In the group of CVS about 86% of the cases were referred because of a positive screening (screening of chromosomal abnormalities on the bases nuchal translucency and biochemical serum markers (pregnancy-associated plasma protein-A and beta-human chorionic gonadotropin)), test with mean maternal age of 31.7 years and a miscarriage rate of 0.6%. In the group of AMNIO, 40% of the cases were referred because of a positive triple test in the second trimester (screening of chromosomal abnormalities on the bases of biochemical serum markers, alpha-fetoprotein, estriol and total human chorionic gonadotropin in the second trimester of pregnancy). Mean maternal age of 33.2 years and a miscarriage rate of 0.8%. The review of the literature indicates that due to limited amount of information available on some factors (gestational age, duration and number of exposure) during the pregnancy the patient should be exposed to the least ultrasound energy necessary to obtain desired information.

The fetal loss rate in our study had confirmed that the risk of both procedures is comparable and is 0.8% for AMNIO and 0.6% for CVS. The lower miscarriage rate after CVS could be explained by the theory that placenta is a spongy organ that will expand easily after the procedure allowing better healing than if the needle had been passed through the amnion which is even more stretched by the amniotic fluid, but we are a wear of that the sample size is too small for such a conclusion. According to the available evidence, exposure to diagnostic ultrasonography during pregnancy appears to be safe.