Table 2 Reference ranges for urinary intact hCG for each day of pregnancy. Duration of pregnancy refers to days since ovulation (with ovulation given as LH surge + 1 day). Data was obtained from 109 UK volunteers who provided daily urine samples, starting prior to conception and continuing through early pregnancy (collection done from 23/01/12 to 12/03/13, with the approval of the local ethics committee). Mean age of the volunteers was 29.50 years (SD 4.27, median 29 years, range 21–40). hCG was measured using the AutoDELFIA immunoassay system (Perkin Elmer).

Duration of pregnancy (days)	n	Median hCG (mIU/ml)	10th and 90th centiles of hCG (mIU/ml)
hCG: human chorionic gonadotropin
7	91	0.00	(0.00, 0.20)
8	102	0.06	(0.00, 2.91)
9	104	4.04	(0.19, 11.32)
10	103	12.23	(3.92, 27.01)
11	104	25.04	(9.47, 57.82)
12	98	48.10	(15.72, 94.09)
13	101	75.25	(29.02, 196.95)
14	103	137.19	(45.06, 301.08)
15	104	208.34	(86.83, 464.51)
16	107	333.73	(139.19, 853.50)
17	100	524.90	(209.98, 1 313.55)
18	105	813.74	(283.89, 1 768.70)
19	99	1 187.00	(426.07, 2 976.40)
20	104	1 644.70	(662.62, 4 169.70)
21	104	2 681.70	(935.46, 6 470.40)
22	104	3 066.80	(1 071.20, 7 300.10)
23	98	4 554.20	(1 316.10, 11 043.00)
24	99	5 056.80	(1 787.40, 13 029.00)
25	100	6 451.55	(2 477.55, 15 310.00)
26	99	7 692.50	(3 157.70, 20 123.00)
27	102	10 170.00	(3 203.30, 25 863.00)
28	103	11 975.00	(4 381.60, 29 184.00)
29	97	12 942.00	(5 301.20, 33 212.00)
30	100	16 109.00	(5 793.00, 41 008.50)
31	96	18 265.50	(8 578.20, 57 419.00)
32	101	26 115.00	(9 176.30, 73 159.00)
33	95	27 485.00	(11 482.00, 70 464.00)
34	93	31 189.00	(12 852.00, 84 109.00)
35	91	35 243.00	(15 541.00, 81 680.00)
36	92	35 177.50	(12 809.00, 87 293.00)
37	93	38 955.00	(17 155.00, 101 990.00)
38	86	40 431.50	(19 484.00, 108 660.00)
39	85	52 411.00	(16 658.00, 106 670.00)
40	88	50 239.50	(17 949.00, 108 820.00)
41	84	57 398.00	(19 243.00, 124 940.00)
42	68	50 480.00	(22 547.00, 106 520.00)