Table 5.
Multivariable logistic regression analysis of IVF associated with SMM
| Variables in the models | Model 1 (all pregnancies) aOR (95% CI) | Model 2 (all pregnancies) aOR (95% CI) | Model 3 (all pregnancies) aOR (95% CI) | Model 4 (singletons) aOR (95% CI) |
| Dependent variable | SMM | Multiple gestations | SMM | SMM |
| Mode of conception | ||||
| IVF versus spontaneous | 1.54 (1.03 to 2.29) | 14.75 (11.38 to 19.10) | 0.89 (0.58 to 1.36) | 0.70 (0.37 to 1.32) |
| Multiple gestations | – | – | 5.92 (4.48 to 7.83) | – |
| Maternal age, years | ||||
| ≥35 vs <35 | 1.54 (1.26 to 1.88) | 1.41 (1.07 to 1.86) | 1.52 (1.24 to 1.86) | 1.62 (1.31 to 2.00) |
| Prepregnancy BMI | ||||
| Underweight versus normal weight | 0.78 (0.10 to 5.77) | – | 0.81 (0.11 to 6.04) | 0.78 (0.10 to 5.78) |
| Overweight versus normal weight | 1.03 (0.83 to 1.27) | 1.48 (1.06 to 2.07) | 1.00 (0.81 to 1.24) | 0.96 (0.77 to 1.19) |
| Obese versus normal weight | 1.48 (1.19 to 1.84) | 2.84 (2.04 to 3.96) | 1.38 (1.10 to 1.72) | 1.27 (1.02 to 1.60) |
| Residence location | ||||
| Rural area versus urban area | 1.19 (1.02 to 1.38) | 1.23 (1.00 to 1.51) | 1.17 (1.00 to 1.36) | 1.20 (1.03 to 1.40) |
| Parity | ||||
| Multiparity versus nulliparity | 1.41 (1.19 to 1.67) | 0.83 (0.64 to 1.07) | 1.45 (1.22 to 1.71) | 1.46 (1.23 to 1.75) |
| Smoking before pregnancy | ||||
| Yes versus no | 0.56 (0.38 to 0.83) | 0.30 (0.15 to 0.60) | 0.60 (0.40 to 0.88) | 0.63 (0.43 to 0.94) |
| IDA | ||||
| Yes versus no | 3.22 (2.54 to 4.09) | – | 3.10 (2.44 to 3.95) | 3.00 (2.32 to 3.87) |
| HBV infection | ||||
| Yes versus no | 1.59 (1.19 to 2.13) | – | 1.59 (1.18 to 2.13) | 1.61 (1.18 to 2.20) |
| Hypertension | ||||
| Yes versus no | 4.83 (3.49 to 6.69) | – | 4.76 (3.43 to 6.62) | 4.91 (3.48 to 6.90) |
| Cardiac diseases | ||||
| Yes versus no | 4.00 (2.81 to 5.70) | – | 3.87 (2.70 to 5.55) | 4.07 (2.81 to 5.90) |
| GDM | ||||
| Yes versus no | 1.17 (0.92 to 1.49) | – | 1.13 (0.88 to 1.44) | 1.21 (0.94 to 1.56) |
| Gynaecological diseases | ||||
| Yes versus no | 0.90 (0.68 to 1.20) | – | 0.88 (0.66 to 1.18) | 0.90 (0.66 to 1.22) |
| Individuals | 22 368 | 22 368 | 22 368 | 21 941 |
| Number of variables | 14 | 7 | 15 | 14 |
| Likelihood ratio χ2 | 314.8 | 381.4 | 433.5 | 273.1 |
Model 1 estimated the association between IVF and SMM by multivariable logistic regression analysis without the variable of multiple gestations in all pregnant women.
Model 2 estimated the association between IVF and multiple gestations by multivariable logistic regression analysis in all pregnant women.
Model 3 estimated the association between IVF and SMM by multivariable logistic regression analysis including the variable of multiple gestations in all pregnant women.
Model 4 estimated the association between IVF and SMM by multivariable logistic regression analysis without the variable of multiple gestations in a subset of singletons.
BMI, body mass index; GDM, gestational diabetes mellitus; HBV, hepatitis B virus; IDA, iron deficiency anaemia; IVF, in vitro fertilisation; SMM, severe maternal morbidity.