Fetal habituation to vibroacoustic stimulation in uncomplicated postterm pregnancies.

OBJECTIVES: Testing of fetal habituation to repeated vibroacoustic stimulation might give additional information concerning the fetal condition and central nervous system (CNS) functioning in postterm pregnancies. This study is designed to investigate whether healthy postterm fetuses are able to habituate and if so, if the habituation pattern of postterm fetuses differs from that of term fetuses. STUDY DESIGN: Twenty women with an uncomplicated pregnancy beyond 41 weeks gestational age (GA) participated, and 37 women with a GA between 37 and 40 weeks served as controls. The vibroacoustic stimulus was repeatedly applied to the maternal abdomen above the fetal legs for a period of 1s every 30s. A fetal trunk movement within 1s of stimulus application was considered a positive response. Lack of response to four consecutive stimuli indicated habituation. The habituation rate is defined as the number of stimuli applied before the fetus stopped responding. Data were compared using Mann-Whitney U test. RESULTS: Of the 18 postterm fetuses in which the presence or absence of habituation could be established, 14 habituated and four persisted in responding. Twenty-six of the 32 term fetuses, in which the presence or absence of habituation could be established, habituated and six persisted in responding. The habituation rate varied widely in postterm (median of eight stimuli, quartile ranges of 6 and 18) as well as in term fetuses (median of 9.5 stimuli, quartile ranges of 6 and 15). There was no difference in median habituation rate between postterm and term fetuses. CONCLUSION: The ongoing maturation of the CNS in the last weeks of pregnancy appears not to be reflected in the fetal habituation pattern. Furthermore, the interfetal variability in habituation of healthy postterm fetuses is such that testing of habituation appears not to be suitable for the identification of the fetus at risk for an adverse neonatal outcome.

[From gene to disease; congenital thrombotic thrombocytopenic purpura due to mutations in the ADAMTS13 gene]. / Van gen naar ziekte; congenitale trombotische trombocytopenische purpura door mutaties in het ADAMTS13-gen.

Thrombotic thrombocytopenic purpura (TTP) is characterised by haemolytic anaemia with fragmented erythrocytes and thrombocytopenia, accompanied by other symptoms such as renal dysfunction, neurological signs and fever. Proteolysis of the Von Willebrand blood-clotting factor (VWF) by a VWF cleaving protease or ADAMTS13 is decreased in patients with TTP, leading to ultra-large Von Willebrand multimers in the circulation. A lack of ADAMTS13 activity can be caused by autoimmune inhibitors or may be due to a constitutional deficiency of this protein. Recently, the ADAMTS13 gene that encodes for the ADAMTS13 protein was found. It was mapped to chromosome 9q34 and consists of 29 exons. Several mutations have been identified in the ADAMTS13 gene in patients with the congenital form of TTP. Symptomatic episodes in congenital TTP can be prevented by prophylactic plasma infusions every 2-3 weeks, hereby preventing further organ damage due to thrombotic microangiopathy.