Table 3.
Risk factors associated with miscarriage in women with either no malaria or a single malaria episode in the first trimester and known outcomes
| Miscarriage (3527) | Delivery (14 086) | Unadjusted odds ratio | Adjusted odds ratio* | Population attributable fraction | |
|---|---|---|---|---|---|
| Malaria symptoms† | |||||
| No malaria | 92% (3198) | 97% (13470) | Reference group | Reference group | .. |
| Asymptomatic malaria | 3% (104) | 2% (213) | 2·06 (1·62–2·61; p<0·0001) | 2·70 (2·04–3·59; p<0·0001) | 1·4% (1·0–1·9) |
| Symptomatic malaria | 5% (157) | 1% (172) | 3·84 (3·09–4·79; p<0·0001) | 3·99 (3·10–5·13; p<0·0001) | 2·6% (2·1–3·1) |
| Pregnancy | |||||
| Women in their first pregnancy | 15% (537) | 22% (3089) | Reference group | Reference group | .. |
| Women who have had more than one pregnancy‡ | 85% (2986) | 78% (10973) | 1·57 (1·42–1·73; p<0·001) | ..§ | .. |
| Smoking¶ | |||||
| Non-smoker | 62% (1817) | 72% (8253) | Reference group | Reference group | .. |
| Smoker | 38% (1129) | 28% (3191) | 1·61 (1·48–1·75; p<0·0001) | 1·26 (1·15–1·38; p<0·0001) | 5·8% (3·4–8·1) |
| Age‖ | |||||
| 13–20 years | 16% (558) | 23% (3309) | Reference group | Reference group | .. |
| 21–25 years | 19% (668) | 26% (3712) | 1·07 (0·94–1·21; p=0·295) | 0·97 (0·84–1·11; p=0·627) | .. |
| 26–30 years | 23% (825) | 26% (3604) | 1·36 (1·21–1·53; p<0·0001) | 1·21 (1·06–1·39; p=0·005) | 3·3% (1·0–5·5) |
| ≥31 years | 42% (1476) | 25% (3460) | 2·53 (2·27–2·82; p<0·0001) | 2·16 (1·90–2·46; p<0·0001) | 18·9% (15·9–21·8) |
| Number of previous miscarriages** | |||||
| None | 61% (2133) | 74% (10298) | Reference group | Reference group | .. |
| One | 24% (857) | 19% (2671) | 1·55 (1·42–1·69; p<0·0001) | 1·31 (1·18–1·45; p<0·0001) | 4·4% (2·7–6·1) |
| Two or more | 15% (518) | 7% (1029) | 2·43 (2·17–2·73; p<0·0001) | 1·89 (1·65–2·17; p<0·0001) | 5·3% (4·0–6·5) |
| Non-malaria febrile illness in the first trimester | |||||
| No | 96% (3402) | 99% (13903) | Reference group | Reference group | .. |
| Yes | 4% (125) | 1% (183) | 2·79 (2·22–3·52; p<0·0001) | 3·00 (2·34–3·84; p<0·0001) | 2·1% (1·6–2·7) |
Data are number (%), unadjusted or adjusted odds ratio (95% CI), or population attributable fraction (95% CI).
n=14 190 (results unchanged if smoking variable excluded from multivariable logistic regression model [n=17 207]).
Data missing for 68 patients in the miscarriage group and 231 patients in the delivery group.
Data missing for four patients in the miscarriage group and 24 patients in the delivery group.
Highly collinear with number of previous miscarriages since women in their first pregnancy cannot have a previous miscarriage; estimated adjusted odds ratios for the other variables were unchanged whether parity or number of previous miscarriages were adjusted for or not.
Data missing for 581 patients missing in the miscarriage group and 2642 in the delivery group.
Data missing for one patient in the miscarriage group.
Data missing for 19 patients in the miscarriage group and 88 patients in the delivery group.