Waterbirth: a national retrospective cohort study of factors associated with its use among women in England

Table 1 Rate of waterbirth according to maternal and obstetric risk factors

Characteristic	Number of women in group	Number of women who give birth in water	Rate of birth in water (%)	Crude OR (95% CI)	Adjusted OR (95% CI)	p (Wald test)
All women	46,088	6264	13.6
Age
18–24	9569	993	10.4	0.78 (0.72,0.85)	0.76 (0.70,0.82)	< 0.001
25–29	13,810	1783	12.9	Ref	Ref
30–34	14,359	2281	15.9	1.27 (1.19,1.36)	1.17 (1.09,1.25)
35–39	7142	1103	15.4	1.23 (1.14,1.34)	1.12 (1.03,1.22)
40–44	1208	104	8.6	0.64 (0.52,0.78)	0.60 (0.48,0.74)
Maternal BMI
18.5–24.9	27,011	3890	14.4	Ref	Ref	< 0.001
25.0–29.9	13,698	1818	13.3	0.91 (0.86,0.97)	0.98 (0.92,1.04)
30–34.9	5379	556	10.3	0.69 (0.62,0.75)	0.77 (0.70,0.85)
Parity
0	17,206	2393	13.9	Ref	Ref
1	18,914	2835	15.0	1.09 (1.03,1.16)	1.01 (0.95,1.08)
2	6691	798	11.9	0.84 (0.77,0.91)	0.86 (0.79,0.94)
3+	3277	238	7.3	0.48 (0.42,0.56)	0.56 (0.47,0.66)
Ethnicity
White	37,581	5793	15.4	Ref	Ref	< 0.001
Black	2339	139	5.9	0.35 (0.29,0.41)	0.42 (0.35, 0.50)
Asian	4506	189	4.2	0.24 (0.21,0.28)	0.26 (0.23,0.30)
Other	143	143	8.6	0.52 (0.43,0.61)	0.56 (0.47,0.66)
Socioeconomic status
Least deprived = 1	9450	1787	18.9	Ref	Ref	< 0.001
2	7278	1180	16.2	0.83 (0.77,0.90)	0.89 (0.82, 0.96)
3	10,120	1448	14.3	0.72 (0.66, 0.77)	0.81 (0.75, 0.87)
4	10,049	1140	11.3	0.55 (0.51,0.59)	0.68 (0.62, 0.74)
Most deprived = 5	9191	709	7.7	0.36 (0.33,0.39)	0.47 (0.43, 0.52)
Birthweight
< 2500 g	594	15	2.5	0.17 (0.10,0.28)	0.19 (0.11, 0.32)	< 0.001
2500-4000 g	40,204	5385	13.4	Ref	Ref
> 4000 g	5290	864	16.3	1.26 (1.17,1.37)	1.12 (1.03,1.21)

This table shows the rate of waterbirth in 46,088 women who had an unassisted vaginal birth in England in 2015/16 according to maternal and obstetric risk factors

ISSN: 1471-2393