Predictive value of the trans-perineal three-dimensional ultrasound measurement of the pubic arch angle for vaginal delivery

Table 1 General information (mean ± SD) on the sample population and differences among delivery groups

Characteristic	Sample		Mode of delivery				P value
	M	Range	Pre-labor CS (n = 82)	Normal vaginal delivery (n = 155)	Forceps delivery (n = 15)	CS in labor (n = 49)
SPAA (°)	99.37	81-122.2	101.77 ± 6.12	99.29 ± 6.48	99.18 ± 5.28	95.62 ± 5.42	0.000
1st stage of labor (h)	-	-	-	5.93 ± 3.53	6.23 ± 3.37	-	-
2nd stage of labor (h)	-	-	-	0.48 ± 0.31	0.52 ± 0.40	-	-
Age (yr)	30.22	21-41	30.67 ± 3.06	29.76 ± 2.97	30.33 ± 2.87	30.88 ± 3.38	0.059
Height (meters)	1.63	1.50-1.78	1.63 ± 0.04	1.64 ± 0.05	1.62 ± 0.04	1.62 ± 0.05	0.091
Gestational age at delivery (wk)	39.40	36-41	39.35 ± 1.10	39.31 ± 0.97	39.73 ± 1.16	39.67 ± 0.97	0.173
BMI (kg/m2)	27.14	19-38	27.91 ± 3.45	26.51 ± 2.76	26.61 ± 2.57	27.99 ± 2.56	0.001
Weight gain (kg)	14.05 ± 6.21	9-52	14.37 ± 5.21	13.10 ± 4.12	12.60 ± 3.07	14.43 ± 4.59	0.084
Birth weight (g)	3426.13	2500-4500	3496.95 ± 394.84	3336.86 ± 344.73	3522.67 ± 336.99	3560.41 ± 410.54	0.000

BMI: Body mass index; CS: Cesarean section; SPAA: Subpubic arch angle.

Table 2 Effects of the subpubic arch angle and other factors on the ability to deliver vaginally

Predictors	Odds ratio (95%CI)	P value
Age (yr)	1.13 (1.00–1.27)	0.042
Height (meters)	0.00 (0.00–0.41)	0.026
Gestational age at delivery (wk)	1.27 (0.87–1.84)	0.214
BMI (kg/m2)	1.11 (0.97–1.26)	0.130
Weight gain (kg)	1.05 (0.97–1.14)	0.256
Birth weight (g)	1.00 (1.001–1.003)	0.000
SPAA (°)	0.90 (0.84–0.95)	0.000

BMI: Body mass index; SPAA: Subpubic arch angle.

Table 3 Predictive effect of the subpubic arch angle with respect to the duration of the first stage of vaginal delivery and other factors

Predictors	B (95%CI)	P value
Age (yr)	-0.02 (-0.21 to 0.16)	0.789
Height (meters)	-0.09 (-17.39 to 4.62)	0.254
Gestational age at delivery (wk)	0.02 (-0.50 to 0.66)	0.785
BMI (kg/m2)	-0.03 (-0.25 to 0.18)	0.758
Weight gain (kg)	-0.19 (-0.31 to 0.02)	0.025
Birth weight (g)	0.13 (0.000 to 0.003)	0.135
SPAA (°)	0.06 (-0.05 to 0.12)	0.459

BMI: Body mass index; SPAA: Subpubic arch angle.

Table 4 Predictive effect of the subpubic arch angle with respect to the second stage of labor in the normal vaginal delivery group

Predictors	B (95%CI)	P value
Age (yr)	0.17 (0.002 to 0.071)	0.039
Height (meters)	-0.18 (-4.63 to -0.55)	0.013
Gestational age at delivery (wk)	0.02 (-0.10 to 0.13)	0.853
BMI (kg/m2)	-0.11 (-0.074 to 0.005)	0.087
Weight gain (kg)	0.02 (-0.02 to 0.03)	0.765
Birth weight (g)	0.09 (0.000 to 0.001)	0.316
SPAA (°)	0.13 (-0.001 to 0.03)	0.045

BMI: Body mass index; SPAA: Subpubic arch angle.