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

Table 2 Distribution of gestational week according to NVP status

	Total	No NVP	Mild NVP	Moderate NVP	Severe NVP	P value
	n = 96,056	n = 16,596	n = 41,198	n = 27,744	n = 10,518	P value
Gestational week, Median (p5–p95), weeks
	39.4 (37.0–41.1)	39.4 (36.9–41.3)	39.4 (37.0–41.1)	39.4 (37.0–41.1)	39.4 (37.0–41.3)	0.006^a
Gestational week, n(%)
26–27 week	88	16 (0.10)	46 (0.11)	20 (0.07)	6 (0.06)	< 0.001^b
28–31 week	364	94 (0.6)	152 (0.4)	93 (0.3)	25 (0.2)
32–36 week	3929	743 (4.5)	1674 (4.1)	1089 (3.9)	423 (4.0)
37–41 week	91,454	15,694 (94.6)	39,224 (95.2)	26,495 (95.5)	10,041 (95.5)

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