Table 1 Baseline characteristics of the study participants with singleton birth in the second pregnancy (N = 5948)

Age [Mean, SD]

[28.3, 5.4]

[28.3, 5.4]

Maternal Age

 15–19

163

3.7

63

4.0

0.822

 20–29

2483

56.9

911

57.6

 30–39

1617

37.0

574

36.3

 ≥40

104

2.4

33

2.1

Education

 None formal

64

1.5

27

1.7

0.685

 Primary education

1844

42.2

689

43.6

 Secondary education

1126

25.8

398

25.2

 Higher education

1333

30.5

467

29.5

Religion

 Christian

3476

79.6

1243

78.6

0.604

 Muslim

865

19.8

326

20.6

 Others

26

0.6

12

0.8

Occupation

 Housewife

517

11.8

186

11.8

0.444

 Farmer

650

14.9

209

13.2

 Business

1454

33.3

554

35.0

 Employed

1376

31.5

490

31.0

 Others e.g. students, retired

370

8.5

142

9.0

Residency

 Urban

2584

59.2

937

59.3

0.947

 Rural

1783

40.8

644

40.7

Tribe

 Chagga

2242

51.3

793

50.2

0.857

 Pare

527

12.1

200

12.7

 Maasai

93

2.1

35

2.2

 Others

1505

34.5

553

35.0

Booking BMI (kg/m²)

 Underweight

131

3.0

70

4.4

 < 0.0001

 Normal

2058

47.1

649

41.0

 Overweight

1762

40.3

653

41.3

 Obesity

416

9.5

209

13.2

[Mean, SD]

[24.7, 3.5]

[25.3, 4.4]

ANC visit

 ≥4

2882

66.0

1057

66.9

0.535

 4

1485

34.0

524

33.1

Gestation age at delivery

 28–32

130

3.0

49

3.1

0.047

 33–36

829

19.0

345

21.8

 ≥37

3408

78.0

1187

75.1

[Mean, SD]

[37.9, 2.3]

[37.8, 2.3]

Inter-pregnancy Interval

  < 24 months

15

0.3

7

0.4

 < 0.0001

 24–36 months

1200

27.5

338

21.4

 37–60 months

2423

55.5

987

62.4

  > 60 months

729

16.7

249

15.7

Referral

 Home

3508

80.3

1227

77.6

0.566

 District hospital

707

16.2

289

18.3

 Regional hospital

152

3.5

65

4.1