Unlike screening methods, invasive diagnostic procedures give a definite diagnosis. The weakness of
these methods (amniocentesis, cordocentesis, chorionic willi biopsy, etc) is the fact that they are
performed later in pregnancy comparing to screening methods, and thus may have complications that
present danger to the mother and the fetus, i.e. pregnancy (infections, bleedings, hematoma,
miscarriage). Well-prepared maternal organism and competent perinatologist significantly decrease the
incidence of complications.