Lack of catch-up in weight gain may intermediate between pregnancies with hyperemesis gravidarum and reduced fetal growth: the Japan Environment and Children’s Study

Table 1 Background characteristics of study participants (91,313 singleton pregnancies)

	n	%
Maternal age, years
< 25	10,337	11
25–34	58,927	65
35 ≤	22,049	24
Parity
0	36,774	40
1 or more	54,539	60
Pre-pregnancy BMI
< 18.5 kg/m²	14,783	16
18.5–24.9 kg/m²	67,217	74
25 kg/m² ≤	9,313	10
Household income (per year)
< 2 million	4,790	5
2 to < 4 million	29,386	32
4 to < 6 million	28,243	31
6 to < 8 million	13,634	15
8 million ≤	9,249	10
No answer	6,011	7
Maternal education
High school or less	33,030	36
Vocational school	22,383	25
2-year college	16,116	18
University or higher	19,784	22
Smoking status
Never smoked	52,819	58
Stopped before pregnancy	21,905	24
Stopped because of pregnancy	12,402	14
Current smoker	4,187	5
Infant sex
Male	46,758	51
Female	44,555	49
Weight change from pre-pregnancy to 1^st trimester (7–14 weeks)
> + 3%	24,975	27
> 0 to + 3%	29,525	32
> -3 to 0%	25,601	28
> -5 to -3%	6,018	7
≤ -5%	5,196	6
	mean	SD
Height, cm	158.1	5.4
Pre-pregnancy weight, kg	21.1	3.0

10,840 (11.9%) measurements of weight gain at 7–14 weeks were imputed based on other characteristics; numbers of participants for weight change from pre-pregnancy to 1^st trimester (7–14 weeks) add up to 91,315 due to rounding after multiple imputation
BMI Body mass index, SD Standard deviation

ISSN: 1471-2393