Table 1. Participant demographics.

MA, maternal age; GA, gestational age; MAD, median absolute deviation; na, not available.

	Cohort 1 (n = 72,932)			Cohort 2 (n = 16,885)			Cohort 1 versus cohort 2
Variable	No flag	Flagged	P	No flag	Flagged	P	P (no flag)	P (flagged)
Samples, n (% total)	72,414 (99.29%)	518 (0.71%)	na	16,776 (99.35%)	109 (0.65%)	na	0.383 (difference in proportions of flagged versus nonflagged, comparing cohort 1 to cohort 2)
MA (years)
Median ± MAD	35.6 ± 4.4	36.1 ± 5.1	0.003	34.4 ± 4.4	35.7 ± 5.5	0.01	<0.0005	0.945
Mean ± SD	34.6 ± 5.4	35.1 ± 5.8		34.4 ± 4.3	35.6 ± 4.9
Min-Max	13.8–66.6	14.0–50.7		18.2–62.2	19.8–46.4
GA (weeks)
Median ± MAD	12.0 ± 3.0	12.0 ± 3.0	0.83	10.0 ± 0	10.0 ± 0	0.847	<0.0005	<0.0005
Mean ± SD	13.8 ± 4.2	13.9 ± 4.4		11.0 ± 1.9	11.2 ± 2.6
Min-Max	10–40	10–35		10–36	10–31
Trimester (% of samples)
First (10–13.9 weeks)	47,498 (65.60%)	331 (63.80%)	0.402	15,560 (92.80%)	97 (89.00%)	0.025	<0.0005	<0.0005
Second (14–27.9 weeks)	23,956 (33.10%)	177 (34.20%)		1,207 (7.20%)	11 (10.10%)
Third (28–40+ weeks)	960 (1.30%)	10 (1.90%)		9 (0.10%)	1 (0.90%)