Reliability of trans-cervical recovery of placental cells from the lower uterine pole using a minimally invasive procedure. Evidence based on fetal sexing and analysis of recovered cell populations.

OBJECTIVE

Efficient recovery of placental cells (and their subsequent characterisation) from the lower uterine pole (L.U.P) by trans-cervical flushing or aspiration.

SUBJECTS

Women attending for termination of pregnancy (7-17 weeks' gestation) for social reasons. All patients gave their consent to the procedures outlined below.

METHODS

Trans-cervical intrauterine flushing (using 0.15 M NaCl) or mucus aspiration. Embryo transfer catheters were used in both procedures. Fetal sexing was achieved by gene amplification of Y-specific DNA sequences (Y-PCR), and by in situ hybridisation (bright-field and fluorescence) to the Y-chromosome. Data were compared with results obtained from fetal tissues recovered following termination of pregnancy. Gender-independent tests for fetal cells utilised immunocytochemistry with trophoblast-specific antibodies and dual immunocytochemistry/ISH, where appropriate.

RESULTS

(1) Fetal sexing by Y-PCR: 71/122 (58%) aspirates contained Y-specific DNA. In addition, the sexing of 72/86 (84%) aspirates and their corresponding samples of placental tissue, agreed exactly. (2) Microscopic detection of fetal cells. Placentally-derived syncytiotrophoblast was detected in 17/45 (38%) flushings and 39/173 (23%) aspirates. In most other Y-PCR+ samples which were negative for syncytiotrophoblast, Y-chromosome-bearing nuclei of unknown origin, were observed by ISH and immunocytochemical evidence for cytotrophoblastic cells was also uncovered.

CONCLUSIONS

Since Y-derived DNA can be detected in > 50% of flushings and aspirations, and gender-independent evidence for placental cells was obtained, regardless of fetal sex, we believe that most or all of these samples contained placental cells, including trophoblasts and naked nuclei. Trans-cervical placental cell recovery is a potentially valuable alternative to more invasive methods of aneuploid detection which require amniocentesis and CVS, provided its level of accuracy and above all, safety, can be evaluated.