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

Objective To examine the effects 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 to 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 from 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 < .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 than those in the obese (P= .001). In addition, the mean +/- SD number of cells/mL was 0.21 +/- 0.21 at GA of 10 to 14 weeks (n = 260), 0.14 +/- 0.23 at GA >= 15 (n = 102) and 0.12 +/- 0.12 at GA <10 (n = 63);P < .001. Conclusion The lower number of SCT was identified from the samples of women with a high BMI. Cell recovery for SCT testing seems optimal at GA of 10 to 14 weeks, but earlier and later testing is still possible.