Table 5.

Relation between physical work load, weekly hours standing/walking and iatrogenic PTB stratified by hypertensive status in employed women only (n=4865)

		N	Iatrogenic PTB	Adjusted*
			OR (95% CI)
			Crude
	Physical work load
Hypertension during pregnancy	Low (ref)	2124	1.0	1.0
No	Moderate	1370	1.92 (0.79–4.64)	1.74 (0.69–4.38)
	High	415	1.15 (0.23–5.32)	1.10 (0.22–5.55)
Pre-existent hypertension	Low	79	1.0	1.0
	Moderate	54	0.76 (0.28–3.17)	0.75 (0.14–4.12)
	High	25	1.08 (0.20–5.77)	0.94 (0.12–7.34)
PIH	Low	403	1.0	1.0
	Moderate	268	3.46 (1.05–11.36)	3.25 (0.96–10.98)
	High	62	7.09 (1.72–29.19)	6.44 (1.21–29.76)

Goodness of fit tests showed no evidence of lack of fit (p>0.51 for the adjusted logistic model).

Bold values indicate statistically significance at the level of p<0.05.

*Model adjusted for: parity, smoking, previous PTB, ethnicity, maternal educational level, maternal age and maternal pre-pregnancy BMI.

BMI, body mass index; PIH, pregnancy-induced hypertension; PTB, preterm birth.