Assessment of transcervical chorion villus aspiration biopsy in early pregnancy

Chorionic villus sampling for prenatal diagnosis is a relatively new technique and variable success rates have been reported by different authors depending on the methods and instruments used. We describe our experience with chorionic villus sampling in Bombay.

The procedure was attempted on 62 women before termination of their pregnancy via the transcervical route, under constant real-time ultrasound guidance. A metallic cannula was negotiated through the cervix into the uterine cavity to reach the chorionic frondosum and chorionic villi were aspirated by creating a negative pressure in the syringe attached to the cannula. The villus tissue was checked under a dissecting microscope. We calculated the success rate for obtaining a sample depending on the site of the chorionic frondosum, the physique of the mother, the position of the uterus and the size of the cannula.

Villus tissue was aspirated in 47 of the 62 cases. The success rates of sampling at the first and second attempts were 48% and 27% respectively. The factors which were associated with a higher success rate were when the chorionic frondosum was situated posteriorly rather than anteriorly (61% v. 48%; p < 0.01), when the patient was thin rather than fat (58% v. 25%; p < 0.001), when the uterus was anteverted rather than retroverted (53% v. 41%). The commonest complication was bleeding which occurred in 15% of patients.

Transcervical chorionic villus sampling is associated with a high success rate except in fat women with a retroverted uterus and in those with the chorionic frondosum situated in the fundus.