Two factors affecting the success rate of the second non-invasive prenatal screening after initial no-call result: experience from a single tertiary center in China.

BACKGROUND: One inevitable shortcoming of non-invasive prenatal screening (NIPS)/cell-free DNA (cfDNA) sequencing is the uninterpretable ("no-call") result, which is mainly caused by an insufficient fetal fraction. This study was performed to investigate the factors associated with a successful second NIPS in these cases and determine the optimal management for women with initial no-call results. METHODS: We retrospectively analyzed the data of women who underwent NIPS with initial no-call results due to an insufficient fetal fraction from 2017 to 2019 in our center. We compared these women's maternal and pregnancy information with the data of women who had attained a successful second NIPS result and women who had received no-call results for a second time. RESULTS: Among the 33,684 women who underwent NIPS, 137 with a no-call result underwent a retest. Comparison between the 87 (63.50%) women with a successful retest and the other 50 (36.50%) women showed a significant difference in both the initial fetal fraction and maternal body mass index (BMI), whereas the other factors showed no significant differences. In addition, with an initial fetal fraction of < 2.00%, the retest success rate was very limited. CONCLUSIONS: We identified two major factors associated with a successful NIPS retest: the initial fetal fraction and the maternal BMI. These findings suggest the need for specialized management for this subset of women and would be instructional for the counseling for these women.

[Prenatal diagnosis of 22q11.2 microdeletion by multiplex ligation-dependent probe amplification].

OBJECTIVE: To explore the clinical value of multiplex ligation-dependent probe amplification (MLPA) technique performed in prenatal diagnosis of chromosome 22q11.2 microdeletion. METHODS: MLPA was performed to detect chromosome 22q11.2 mircodeletion in 62 fetuses with congenital heart defects by fetal echocardiography and a normal karyotype by standard G-banding analysis.For a 22q11.2 mircodeletion fetus, his parents were detected to know if it is inherited or de novo. The microdeletion was confirmed by array-based comparative genomic hybridization (arrayCGH). RESULTS: MLPA revealed five 22q11.2 mircodeletions in the 62 fetuses, and the positive detection rate was 8% (5/62). Among these, 4 cases carried the 3M typically deletion which all are de novo, and 1 case carried the 1.5M non-typically deletion which was inherited from his father.arrayCGH confirmed the 22q11.2 microdeletions and delineated the precise location and size of microdeletions. CONCLUSION: MLPA has clinical value in prenatal diagnosis of 22q11.2 mircodeletion, which could provide important genetic information for genetic consulting, pregnancy management and intervention after birth.