Table 2.

Characteristics according to quartile of seaweed consumption in 1745 pregnant women

	Quartile
Variable	1 (Lowest) (n = 436)	2 (n = 436)	3 (n = 436)	4 (Highest) (n = 437)	Pfor trend a
Age, years, mean	30.8	31.1	31.6	31.3	0.04
Gestation, weeks, mean	18.5	18.4	18.5	18.7	0.67
Region of residence, %					0.31
Fukuoka Prefecture	56.4	59.2	54.1	52.9
Other than Fukuoka Prefecture in Kyushu	34.6	30.7	36.0	34.3
Okinawa Prefecture	8.9	10.1	9.9	12.8
Number of children, %					0.77
0	39.2	42.0	37.4	42.6
1	39.2	39.0	44.7	35.2
≥ 2	21.6	19.0	17.9	22.2
Nuclear family structure, %	85.8	83.9	85.8	82.4	0.28
History of depression, %	5.5	4.8	4.4	4.6	0.48
Family history of depression, %	10.3	11.5	8.7	9.6	0.45
Having ever smoked,%	37.2	36.0	27.1	28.8	0.0007
Ever experiencing secondhand smoke exposure at home, %	78.2	76.6	72.5	74.1	0.08
Ever experiencing secondhand smoke exposure at work, %	64.9	64.5	62.2	62.0	0.29
Job typeb, %					0.03
Unemployed	38.1	41.7	40.8	41.0
Professional or technical	21.1	23.6	28.0	27.0
Clerical or related occupation	22.7	17.0	17.9	17.6
Sales	6.0	4.6	5.1	3.4
Service	6.7	7.6	5.5	6.6
Production	3.9	3.9	1.6	2.3
Othersc	1.6	1.6	1.2	2.1
Household income, yen/year, %					0.11
< 4,000,000	41.3	35.6	32.3	35.7
4,000,000 − 5,999,999	33.3	35.8	34.9	37.8
≥ 6,000,000	25.5	28.7	32.8	26.5
Education, years, %					0.10
< 13	28.0	23.9	23.2	23.1
13 − 14	31.9	32.3	36.7	31.4
≥ 15	40.1	43.8	40.1	45.5
Body mass index, kg/m2, mean	21.7	21.4	21.4	21.4	0.11
Fish, g, meand	40.3	45.7	49.2	51.8	< 0.0001
Yogurt, g, meand	32.4	32.4	36.4	38.1	0.01

^aFor continuous variables, a linear trend test was used; for categorical variables, a Mantel-Haenszel χ²-test was used.

^bEmployment status in the year when the first questionnaire was conducted or in the previous year.

^cManagement; protection services; farming, fishing, or forestry; transportation or communications; or construction.

^dFood intake was adjusted for total energy intake using the residual method.