Table 2 Stratum-specific odds ratios of effect modifiers to the association of gravidity as a multi-level variable and placental malaria, among Ghanaian mothers aged 14–49, estimated by logistic regression fitted with interaction parameters after adjustment^a,b for confounders

Stratified by area (N = 1823)

Urban

Multigravidae

29.5% (59/200)

1^a

Secundigravidae

35.9% (33/92)

1.04 (0.60–1.81)^a

Primigravidae

57.7% (52/90)

2.09 (1.17–3.71)^a

Rural

Multigravidae

25.8% (240/930)

1^a

Secundigravidae

47.8% (119/249)

1.87 (1.34–2.62)^a

Primigravidae

68.7% (180/262)

3.79 (3.61–5.51)^a

Stratified by wealth index (N = 1823)

Higher

Multigravidae

23.1% (98/424)

1^b

Secundigravidae

32.9% (51/155)

1.21 (0.79–1.86)^b

Primigravidae

52.0% (78/150)

2.14 (1.38–3.35)^b

Lower

Multigravidae

28.5% (201/706)

1^b

Secundigravidae

54.3% (101/186)

2.05 (1.41–2.98)^b

Primigravidae

76.2% (154/202)

4.73 (3.08–7.25)^b

Stratified by ITN use (N = 1782)

Don’t use

Multigravidae

23.9% (137/573)

1^a

Secundigravidae

43.3% (62/143)

1.83 (1.20–2.79)^a

Primigravidae

70.0% (100/145)

4.22 (2.68–6.67)^a

Use

Multigravidae

29.6% (158/532)

1^a

Secundigravidae

45.6% (87/191)

1.39 (0.95–2.04)^a

Primigravidae

62.6% (124/198)

2.36 (1.54–3.60)^a

Doses of Fansidar (IPTp) (N = 1820)

0

Multigravidae

16.1% (10/62)

1

Secundigravidae

38.1% (8/21)

2.00 (0.63–6.27)

Primigravidae

69.2% (9/13)

7.13 (1.76–28.81)

1

Multigravidae

26.6% (37/139)

1

Secundigravidae

38.6% (17/44)

1.28 (0.61–2.69)

Primigravidae

78.4% (40/51)

5.50 (2.46–12.32)

2

Multigravidae

25.5% (72/282)

1

Secundigravidae

48.3% (42/87)

2.09 (1.22–3.56)

Primigravidae

71.0% (64/90)

4.86 (2.71–8.73)

3

Multigravidae

27.8% (179/645)

1

Secundigravidae

45.0% (85/189)

1.56 (1.07–2.28)

Primigravidae

60.4% (119/197)

2.38 (1.59–3.57)