Table 3.

Analysis for interaction between supine going-to-sleep position and prespecified indicators of fetal vulnerability.

Prespecified indicators of fetal vulnerability	Supine	Non–supine	Bi-variable regression
	Univariable odds ratio (95% CI)	Univariable odds ratio (95% CI)	P for interaction
Small-for-gestational-age infant (< 10th infant birthweight customised centile)
Yes	15.66 (6.96–35.25)	3.98 (3.17–4.99)	0.32
No	2.45 (1.6–3.75)	1
Infant birthweight customised centile
< 50th centile	4.85 (3.12–7.53)	1.97 (1.64–2.38)	0.34
≥ 50th centile	3.62 (1.87–7.01)	1
Earliest pregnancy BMI (kg/m2)
BMI < 25.0	3.69 (2.26–6.01)	1	0.30
BMI 25–29.9	4.96 (2.33–10.57)	1.4 (1.13–1.74)
BMI 30–34.9	3.61 (1.40–9.27)	1.71 (1.3–2.24)
BMI > 35.0	2.99 (1.09–8.21)	2.2 (1.66–2.91)
Obesity
Obese	3.52 (2.34–5.3)	1.69 (1.38–2.07)	0.08
Non–obese	2.90 (1.45–5.8)	1
Recreational drug use (during pregnancy)
Yes	–	1.40 (0.83–2.37)	0.97
No	2.92 (2.05–4.15)	1
Smoking
Smoking (beyond first trimester)	6.32 (2.31–17.32)	1.99 (1.54–2.58)	0.86
Non-smoking	2.88 (1.98–4.2)	1
Pre-existing hypertension or diabetes
Yes	3.12 (0.19–51.78)	2.23 (1.28–3.88)	0.62
No	2.90 (2.04–4.12)	1
Fetal movement frequency (last two weeks)
Increased	2.49 (1.03–6.00)	1	0.40
Decreased	16.94 (7.60–37.76)	8.50 (6.19–11.67)
Same/unsure	10.50 (6.19–17.81)	2.91 (2.19–3.85)
Term (≥ 37 weeks') versus preterm (< 37 weeks') infant
Term	2.79 (1.72–4.53)	1	0.88
Preterm	2.78 (1.69–4.57)	0.95 (0.79–1.13)