First trimester amnifiltration: technical, cytogenetic and pregnancy outcome of 104 consecutive procedures

To investigate the technical, cytogenetic and pregnancy complications of first trimester amnifiltration for the diagnosis of fetal karyotype.

Observational study.

The fetal medicine unit, UMDS St Thomas' Campus, London.

One hundred and four women seeking prenatal diagnosis of fetal karyotype.

Sampling success, culture rate, harvest time and karyotype, pregnancy outcome and complications.

Sampling was successful in all 104 cases, but equipment failure forced the procedure to be changed to early amniocentesis in eight (7%) cases. The karyotype was normal in 101 (97%) cases, abnormal in three. The mean harvest time was 14 days (range 9-26 days; SD = 3.4), and three cultures failed (2.8%). Pregnancies resulted in 99 (95%) live births, with a mean gestation of 277 days (range 182-300 days; SD = 16). There was one termination for trisomy 21 and four spontaneous miscarriages (3.8%). Amniotic fluid leakage occurred in six cases (5%), all resulted in live births, five at term and one at 35 weeks.

This study demonstrates that amnifiltration is technically possible in the first trimester of pregnancy, and that samples can be successfully karyotyped. The harvest time for culture is similar to early amniocentesis and chorion villus sampling. The rate of fetal loss, adjusted by the estimated natural loss, is 1.7%, which compares favourably with both chorionic villus sampling and early amniocentesis.