Risks and Drawbacks
Amniocentesis is performed between the 15th and 20th week of pregnancy; performing this test earlier may result in fetal injury. The term "early amniocentesis" is sometimes used to describe use of the process between weeks 11 and 13.
Complications of amniocentesis include preterm labor and delivery, respiratory distress, postural deformities, fetal trauma and alloimmunisation of the mother (rhesus disease). Studies from the 1970s originally estimated the risk of amniocentesis-related miscarriage at around 1 in 200 (0.5%). Three more recent studies from 2000-2006 estimated the procedure-related pregnancy loss at 0.6-0.86%. A more recent study (2006) has indicated this may actually be much lower, perhaps as low as 1 in 1,600 (0.06%). Unlike the previous studies, the number in this study only reflects the loss that resulted from amniocentesis complications and excluded the cases when parents decided for an abortion following the test results. In contrast to amniocentesis, the risk of miscarriage from chorionic villus sampling (CVS) is believed to be approximately 1 in 100, although CVS may be done up to four weeks earlier, and may be preferable if the possibility of genetic defects is thought to be higher.
Amniotic fluid embolism has been described as a possible risk.
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