Table 2. Results of hypothesis tests comparing twin, preterm and term groups.

Variable	Gestation week	Twin median	Preterm median	Term median	Twin vs Term value	Preterm vs Term value
Uterine wall thickness (cm)	20	0.82	0.64	0.64	0.08	0.73
	25	0.75	0.73	0.67	0.07	0.31
	30	0.71	0.78	0.69	0.47	0.05
Intrauterine volume (L)	20	2.232	1.558	1.459		0.40
	25	4.452	2.789	2.637		0.12
	30	7.459	4.406	4.189		0.09
Maximum uterine wall tension (kNm)	20	13.1	12.2	11.9	0.11	0.47
	25	16.5	13.9	16.3	0.33	0.23
	30	22.1	17.5	22.8		0.002