Table 3.

Statistical significance (p-values) for dichorionic twin comparisons to the singleton standard of fetal anthropometric measurements by gestational age.

	Biparietal Diameter	Head Circumference	Abdominal Circumference	Femur Length	Humerus Length	Estimated Fetal Weight	Head Circumference / Abdominal Circumference	Femoral Length / Abdominal Circumference
Gestational age, weeks	P-value	P-value	P-value	P-value	P-value	P-value	P-value	P-value
11	0.008	0.085	0.017	0.883	0.016	-	0.683	0.052
12	0.284	0.609	0.101	0.162	0.726	-	0.342	0.001
13	0.630	0.635	0.486	0.050	0.036	-	0.289	0.002
14	0.172	0.367	0.844	0.136	0.029	-	0.354	0.058
15	0.064	0.313	0.964	0.555	0.178	0.469	0.427	0.460
16	0.028	0.312	0.944	0.668	0.876	0.340	0.499	0.736
17	0.010	0.260	0.908	0.300	0.537	0.317	0.537	0.343
18	<0.001	0.134	0.951	0.446	0.709	0.413	0.499	0.456
19	<0.001	0.070	0.996	0.861	0.813	0.582	0.461	0.799
20	<0.001	0.069	0.987	0.943	0.624	0.738	0.488	0.981
21	<0.001	0.118	0.939	0.966	0.717	0.857	0.580	0.948
22	<0.001	0.248	0.876	0.693	0.984	0.936	0.725	0.776
23	0.004	0.474	0.819	0.409	0.620	0.979	0.895	0.574
24	0.015	0.710	0.788	0.244	0.371	0.994	0.947	0.427
25	0.039	0.866	0.784	0.181	0.254	1.000	0.825	0.353
26	0.080	0.944	0.778	0.170	0.207	0.972	0.763	0.339
27	0.152	0.971	0.736	0.187	0.198	0.891	0.784	0.384
28	0.279	0.982	0.630	0.209	0.205	0.731	0.912	0.494
29	0.504	0.992	0.450	0.204	0.205	0.493	0.836	0.671
30	0.862	0.931	0.252	0.166	0.190	0.252	0.519	0.911
31	0.681	0.829	0.110	0.121	0.169	0.096	0.257	0.794
32	0.302	0.711	0.041	0.090	0.154	0.030	0.106	0.507
33	0.113	0.625	0.015	0.076	0.143	0.009	0.040	0.305
34	0.048	0.603	0.007	0.068	0.124	0.004	0.014	0.187
35	0.031	0.675	0.003	0.059	0.092	0.002	0.004	0.119
36	0.043	0.872	0.003	0.067	0.075	0.002	<0.001	0.100
37	0.133	0.840	0.008	0.165	0.132	0.004	0.003	0.184
38	0.459	0.621	0.054	0.421	0.343	0.022	0.028	0.400

P-values obtained by the Wald test from the linear mixed model with adjustment for maternal age, height, weight, parity, race, job, marital status, insurance, income, education and infant sex. Note: Estimated fetal weight not calculated less than 15 weeks of gestation.