Nausea and vomiting during pregnancy associated with lower incidence of preterm births: the Japan Environment and Children’s Study (JECS)

Table 4 Odds ratio of very preterm birth and extremely preterm birth in relation to NVP status

	No NVP	Mild NVP			Moderate NVP			Severe NVP
		OR	95% CI	P value	OR	95% CI	P value	OR	95% CI	P value
Crude Odds ratio	1(reference)	0.72	0.57–0.91	0.007	0.61	0.47–0.80	< 0.001	0.44	0.30–0.66	< 0.001
Adjusted Odds ratio^a	1(reference)	0.74	0.58–0.94	0.01	0.62	0.47–0.82	0.001	0.44	0.29–0.67	< 0.001

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