Table 1

Characteristics of women and infants

	Preterm (n=15 889, 5.00%)		Full-term (n=301 574, 95.00%)		p Value
	n	%	n	%	p Value
Age at delivery
<25	3091	3.62	82 224	96.38	<0.001
25–34	11 055	5.17	202 692	94.83
≥35	1743	9.47	16 658	90.53
Education level
Less than high school	3519	4.55	73 737	95.45	<0.001
High school	5010	4.71	101 458	95.29
College	7360	5.50	126 379	94.50
Offspring sex
Male	9188	5.41	160 671	94.59	<0.001
Female	6701	4.54	140 903	95.46	<0.001
Parity
Nullipara	11 948	4.65	245 121	95.35	<0.001
Multipara	3941	6.53	56 453	93.47	<0.001
Gravidity
<3	11 471	4.59	238 259	95.41	<0.001
≥3	4418	6.52	63 315	93.48	<0.001
Pre-pregnancy BMI (kg/m²)
Underweight (<18.5)	3118	4.21	70 916	95.79	<0.001
Normal (18.5–23.9)	11 083	5.03	209 246	94.97
Overweight (24–27.9)	1360	6.94	18 226	93.06
Obese (≥28)	328	9.33	3186	90.67
Vomiting
Yes	4978	5.25	89 879	94.75	<0.001
No	10 911	4.90	211 695	95.10	<0.001

BMI, body mass index.