Table 1 Characteristics of the participating mother and twins in the quantitative study (63 / 126) and qualitative study (14 / 28)

Mother

 Vaginal birth

16

73%

35

85%

0.253

9

62%

 Married / living with partner

20

95%

36

95%

>  0.05

14

100%

 Maternal age, mean (SD)

>  0.05

 Household income / month (ISK)

>  0.05

  < 400.000

6

28%

5

13%

  4–800.000

10

48%

18

49%

  > 800.000

5

24%

14

38%

 Highest educational level

>  0.05

  University

11

55%

30

79%

10

71%

  High school

7

35%

5

13%

4

29%

  Elementary

2

10%

2

8%

0

0%

  Depression

3

14%

4

10%

0.637

0

0%

  Anxiety

3

14%

4

10%

0.637

2

14%

 EPDS at 1 month, mean (SD)

<  0.05

 EPDS at 4 months, mean (SD)

>  0.05

 Multipara

10

45%

26

65%

>  0.05

11

79%

  Have breastfed before

10

100%

24

92%

>  0.05

11

100%

Infant

 NICU

21

48%

0

0

<  0.001

16

57%

  < 24 hours

0

0

4

5%

0.133

0

0%

  1 to 6 days

25

57%

72

89%

<  0.001

14

50%

  7 to 13 days

17

39%

2

2%

<  0.001

14

50%

  14 to 28 days

0

0

2

2%

0.347

0

0%

  > 29 days

0

0

0

0

>  0.05

0

0%

  34 + 0–34 + 6

10

23%

6

21%

  35 + 0–35 + 6

12

27%

10

36%

  36 + 0–36 + 6

22

50%

12

43%

  37 + 0–37 + 6

68

83%

  38 + 0–38 + 6

12

15%

  39 + 0–39 + 6

2

2%

  ≥ 40

0

0%

  First breastfeeding

n

%

n

%

n

%

   < 6 hours

22

52

71

89

<  0.001

11

39

   6–24 hours

13

31

6

7

<  0.001

7

25

   > 24 hours

7

17

0

0

<  0.001

10

36

   Did not breastfeed at the hospital

0

0

3

4

0.181

0

0

   < 6 hours

4

19

4

10

0.317

   6–24 hours

16

76

13

32

0.001

   > 24 hours

1

5

12

30

0.022

   Did not pump at the hospital

0

0

11

28

0.006

 Gestational age at birth in days, mean (SD)

<  0.001

 Birth weight, grams, mean (SD)

<  0.001

 Apgar 5 min, median (SD)

>  0.05

 Girl

21

48%

35

43%

>  0.05

8

29%

 Weight at 1 month, grams, mean (SD)

<  0.05

 Weight at 4 months, grams, mean (SD)

>  0.05

 Age when answering at time 1, days, (SD) (range)

>  0.05

 Age when answering at time 2, days, (SD) (range)

>  0.05