Transabdominal chorion villus sampling: a safe and reliable procedure.
Robinson HP, de Crespigny LC, Ngu AC, Robertson A, Halliday JL.
Aust N Z J Obstet Gynaecol. 1991 Feb;31(1):22-5. doi: 10.1111/j.1479-828x.1991.tb02757.x.
PMID:1872767
[The comparative value of ultrasound examinations and quantitative determinations of chorionic gonadotropin in the differential diagnosis of the disturbed early pregnancy (author's transl)].