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Table 1 Characteristics of participants according to breastfeeding period duration (n = 70,078)

From: Impact of breastfeeding during infancy on functional constipation at 3 years of age: the Japan Environment and Children’s Study

Variable

Breastfeeding period duration

Never

Up to 6 months

 ≥ 7 months

n = 1,623

n = 14,174

n = 54,281

Maternal age at delivery (years)

31 (27, 35)

31 (27, 35)

31 (28, 35)

Maternal age group, n (%)

 < 35 years

1,132 (69.7)

10,376 (73.2)

39,205 (72.2)

 ≥ 35 years

491 (30.3)

3,797 (26.8)

15,076 (27.8)

Pre-pregnancy BMI (kg/m2)

21.2 (19.3, 24.0)

20.8 (19.1, 23.2)

20.4 (19.1, 22.2)

Pre-pregnancy BMI group, n (%)

 Underweight (BMI < 18.5)

248 (15.3)

2,246 (15.9)

8,865 (16.3)

 Normal weight (BMI 18.5–24.9)

1,055 (65.1)

9,843 (69.5)

40,887 (75.4)

 Overweight (BMI 25.0–29.9)

242 (14.9)

1,531 (10.8)

3,604 (6.6)

 Obese (BMI ≥ 30.0)

75 (4.6)

550 (3.9)

891 (1.6)

Gestational weight gain (kg)

10.2 (7.6, 12.8)

10.3 (7.8, 13.0)

10.1 (8.0, 12.4)

Highest age of maternal education, n (%)

 < 16 years

178 (11.1)

918 (6.6)

1,380 (2.6)

 16 to < 19 years

759 (47.5)

5,907 (42.2)

13,986 (26.0)

 ≥ 19 years

662 (41.4)

7,181 (51.3)

38,479 (71.5)

Annual household incomea, n (%)

 < 2,000,000 JPY

164 (11.2)

1,067 (8.2)

1,983 (3.9)

 2,000,000–3,999,999 JPY

592 (40.6)

5,112 (39.5)

16,377 (32.1)

 4,000,000–5,999,999 JPY

451 (30.9)

4,019 (31.0)

17,580 (34.5)

 6,000,000–7,999,999 JPY

154 (10.6)

1,654 (12.8)

9,014 (17.7)

 ≥ 8,000,000 JPY

97 (6.7)

1,096 (8.5)

6,055 (11.9)

Marital status, n (%)

 Married

1,507 (94.0)

13,188 (94.1)

52,227 (96.9)

 Single

73 (4.6)

659 (4.7)

1,431 (2.7)

 Divorced

23 (1.4)

172 (1.2)

226 (0.4)

 Widowed

0 (0.0)

2 (0.0)

10 (0.0)

Parity, n (%)

 Primiparous

615 (38.7)

5,670 (40.9)

22,021 (41.6)

 Multiparous

975 (61.3)

8,187 (59.1)

30,959 (58.4)

Cesarean section at delivery, n (%)

 No

1,214 (75.0)

11,086 (78.3)

44,942 (83.0)

 Yes

405 (25.0)

3,066 (21.7)

9,216 (17.0)

Offspring gender (male), n (%)

824 (50.8)

7,256 (51.2)

27,587 (50.8)

Gestational age (weeks)

39 (38, 40)

39 (38, 40)

39 (38, 40)

Gestational age group, n (%)

 < 37 weeks

120 (7.4)

869 (6.1)

2,017 (3.7)

 37–41 weeks

1,497 (92.4)

13,263 (93.6)

52,115 (96.0)

 ≥ 42 weeks

3 (0.2)

37 (0.3)

128 (0.2)

Birth weight (g)

2,994 (2,720, 3,269)

3,000 (2,746, 3,268)

3,040 (2,798, 3,286)

Birth weight group, n (%)

  < 1,500

12 (0.7)

100 (0.7)

171 (0.3)

 1,500–2,499 g

183 (11.3)

1,320 (9.3)

3,545 (6.5)

 2,500–3,999 g

1,411 (87.1)

12,605 (89.0)

50,095 (92.3)

 ≥ 4000 g

14 (0.9)

142 (1.0)

439 (0.8)

Started solid baby food by 6 months of age, n (%)

 No

372 (23.0)

2,971 (21.0)

15,255 (28.2)

 Yes

1,246 (77.0)

11,172 (79.0)

38,925 (71.8)

  1. Continuous variables are expressed as the mean ± standard deviation or the median (interquartile range)
  2. Breastfeeding duration up to 12 months of age was defined as the period up to the last month between 1 and 12 months in which mothers checked selections for any breastfeeding, regardless of whether or not infant formula was used in combination
  3. Data were missing on maternal age (n = 1), pre-pregnancy BMI (n = 41), body weight gain during pregnancy (n = 637), maternal education level (n = 628), household income (n = 4,663), marital status (n = 560), parity (n = 1,651), mode of delivery (n = 149), birth weight (n = 41), gestational age (n = 29), and started solid baby food by 6 months of age (n = 137)
  4. BMI, body mass index; JPY, Japanese yen
  5. aThe average (median) annual Japanese household income in 2018 was 5,523,000 JPY (4,370,000 JPY). The currency exchange rates on January 25, 2023, were: 1 USD = 130 JPY and 1 EUR = 142 JPY
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International Breastfeeding Journal

ISSN: 1746-4358