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

Table 3 Odds ratio of 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)	0.88	0.81–0.95	0.002	0.84	0.76–0.91	< 0.001	0.83	0.74–0.94	0.002
Adjusted Odds ratio^a	1(reference)	0.87	0.80–0.95	0.002	0.85	0.78–0.93	0.001	0.84	0.74–0.95	0.004

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