Table 2.

Weighted Distributions of Thyroid Hormone and Raw Ultrasound Measurements by Study Visit of Sample Collection

	n	Selected Percentiles
		25th	50th	75th	90th	95th	Max
Visit 1 (median 10 wk)
Thyroid hormonesa
TSH, µIU/mL	317	0.54	0.91	1.50	1.97	2.36	7.23
FT4, ng/dL	374	1.16	1.39	1.64	2.07	2.57	12.5
T4, µg/dL	364	8.70	10.0	11.3	12.6	13.7	18.0
T3, ng/mL	304	1.11	1.31	1.61	1.86	2.11	2.91
Visit 2 (median 18 wk)
Ultrasound measurements
HC, mm	389	141	148	159	166	173	202
AC, mm	389	119	127	137	148	154	177
FL, mm	390	25	27	29	31	32	40
EFW, g	324	221	253	290	334	361	528
Thyroid hormonesa
TSH, µIU/mL	317	0.98	1.36	1.91	2.52	3.15	6.08
FT4, ng/dL	368	0.92	1.13	1.30	1.54	1.77	8.96
T4, µg/dL	357	9.50	10.6	11.8	12.7	13.6	16.4
T3, ng/mL	301	1.36	1.60	1.90	2.16	2.28	2.86
Visit 3 (median 26 wk)
Ultrasound measurements
HC, mm	201	231	248	263	280	288	307
AC, mm	201	207	221	239	255	263	280
FL, mm	201	46	50	54	57	60	68
EFW, g	201	810	978	1200	1442	1619	2032
Thyroid hormonesa
TSH, µIU/mL	306	0.90	1.29	1.70	2.31	2.86	8.73
FT4, ng/dL	349	0.81	1.00	1.18	1.44	1.97	12.5
T4, µg/dL	333	9.20	10.3	11.4	12.7	13.5	21.7
T3, ng/mL	286	1.36	1.62	1.90	2.15	2.37	2.79
Visit 4 (median 35 wk)
Ultrasound measurements
HC, mm	221	308	317	326	333	340	366
AC, mm	223	302	317	333	349	361	393
FL, mm	223	65	68	71	74	75	77
EFW, g	223	2323	2671	3034	3478	3643	4384
Thyroid hormonesa
TSH, µIU/mL	270	0.97	1.35	1.92	2.44	2.71	6.22
FT4, ng/dL	344	0.77	0.96	1.17	1.43	1.58	6.19
T4, µg/dL	337	8.90	10.0	11.4	12.7	13.6	20.2
T3, ng/mL	239	1.40	1.66	2.00	2.21	2.4	3.22
Birth (median 38 wk)
Birth weight, g	439	2946	3345	3660	3909	4139	4720

Analyses weighted by preterm birth case-control sampling probabilities.

^aNumber of samples per hormone varied due to limitations in sample volume.