The effect of maternal body mass index and gestational age on circulating trophoblast yield in cell-based noninvasive prenatal testing.

OBJECTIVE To examine the effect of maternal body mass index (BMI) and gestational age (GA) on the number of single circulating trophoblasts (SCT). METHODS Maternal blood was collected in 20-40 mL. All singleton pregnant women at any gestation were recruited. Trophoblasts were recovered by immunomagnetic enrichment and stained for cytokeratin and CD45. Candidate trophoblasts were identified by fluorescence microscopy. RESULTS Blood samples were collected from 425 singleton pregnancies; April 2018 to December 2019. At least one candidate cell was identified in 88% (373/425). There was an inverse correlation between trophoblasts yield and increasing BMI (r = -0.19, P < 0.001). The mean ± SD number of trophoblasts/mL was 0.12 ± 0.22 in the underweight group (n = 5), 0.23 ± 0.25 in the normal weight (n = 169), 0.18 ± 0.19 in the overweight (n = 114) and 0.13 ± 0.15 in the obese (n = 109). Significantly more cells were identified in the normal weight compared to those in the obese (P = 0.001). In addition, the mean ± SD number of cells/mL was 0.21 ± 0.21 at GA 10-14 weeks (n = 260), 0.14 ± 0.23 at GA ≥15 (n = 102) and 0.12 ± 0.12 at GA <10 (n = 63); P < 0.001. CONCLUSION The lower number of SCT were identified from samples of women with a high BMI. Cell recovery for SCT testing seems optimal at GA 10-14 weeks, but earlier and later testing are still possible. This article is protected by copyright. All rights reserved.