. Author manuscript; available in PMC: 2023 Dec 1.

Published in final edited form as: J Matern Fetal Neonatal Med. 2021 Sep 27;35(25):8364–8371. doi: 10.1080/14767058.2021.1974388

Table 1:

Reference values for serial measurements of the umbilical artery systolic/diastolic ratio in normally grown trisomy 21 fetuses. Created from 341 observations.

	Percentile
Gestation (wk)	2.5^th	5^th	10^th	25^th	50^th	75^th	90^th	95^th	97.5^th
19	3.11	3.27	3.47	3.83	4.30	4.85	5.45	5.86	6.27
20	2.98	3.15	3.36	3.75	4.27	4.89	5.57	6.05	6.53
21	2.86	3.04	3.26	3.69	4.24	4.93	5.70	6.26	6.82
22	2.78	2.96	3.20	3.64	4.24	4.98	5.84	6.46	7.09
23	2.73	2.92	3.16	3.62	4.24	5.02	5.93	6.60	7.28
24	2.72	2.91	3.15	3.61	4.24	5.03	5.96	6.64	7.34
25	2.70	2.89	3.13	3.59	4.22	5.01	5.93	6.61	7.30
26	2.68	2.86	3.10	3.55	4.17	4.95	5.85	6.52	7.21
27	2.63	2.81	3.04	3.49	4.09	4.85	5.73	6.38	7.05
28	2.58	2.76	2.98	3.41	4.00	4.73	5.58	6.21	6.85
29	2.52	2.69	2.91	3.33	3.90	4.62	5.45	6.06	6.68
30	2.45	2.62	2.84	3.25	3.80	4.51	5.32	5.92	6.54
31	2.40	2.57	2.78	3.18	3.72	4.41	5.21	5.79	6.39
32	2.37	2.53	2.74	3.13	3.66	4.33	5.10	5.67	6.25
33	2.35	2.51	2.71	3.09	3.61	4.25	4.99	5.53	6.09
34	2.32	2.48	2.67	3.04	3.54	4.17	4.88	5.40	5.93
35	2.26	2.41	2.60	2.97	3.47	4.09	4.81	5.33	5.86
36	2.16	2.31	2.50	2.88	3.38	4.03	4.78	5.34	5.91
37	2.04	2.19	2.39	2.77	3.30	3.98	4.79	5.41	6.05
38	1.92	2.08	2.28	2.67	3.22	3.95	4.83	5.51	6.23
39	1.82	1.97	2.17	2.57	3.14	3.91	4.87	5.63	6.44
40	1.71	1.87	2.07	2.48	3.07	3.88	4.92	5.76	6.68