Table 3: Risk factors for surgical site infection before and after discharge following cesarean delivery
Risk factorNo infection, no. of deliveries*Infection before dischargeInfection after discharge
No. of deliveries*Adjusted OR
(95% CI)
No. of deliveries*Adjusted OR
(95% CI)
Institution-related
No. of cesarean deliveries per hospital per year
    < 130807051Reference104Reference
    130-94968931253.16 (2.26-4.44)1571.76 (1.34-2.30)†
    950-124987871422.46 (1.73-3.51)1701.58 (1.20-2.08)
    ≥ 12508223591.76 (1.16-2.67)951.26 (0.92-1.73)
Area-level
Quintile of neighbourhood-level income
    1 (lowest)6349971.22 (0.95-1.57)1621.54 (1.25-1.90)
    25784701.03 (0.78-1.36)1021.15 (0.91-1.46)
    3-519 840210Reference262Reference
Maternal demographic characteristics
Age, yr
    < 255876821.08 (0.81-1.43)1421.18 (0.93-1.49)
    25-3419 719211Reference295Reference
     356378841.41 (1.08-1.83)891.08 (0.84-1.38)
Prepregnancy weight, kg
    < 53.02593271.04 (0.67-1.60)341.08 (0.72-1.60)
    53.0-66.9946392Reference102Reference
    67.0-76.95410511.02 (0.72-1.45)821.46 (1.09-1.97)
    77.0-86.93868461.29 (0.90-1.85)621.53 (1.11-2.12)
    87.0-97.92480371.70 (1.15-2.51)481.97 (1.38-2.81)
    ≥ 98.02954713.07 (2.21-4.25)1144.06 (3.02-5.45)
    Missing5205531.06 (0.68-1.67)841.95 (1.28-2.97)
Marital status3868
    Married/common-law23 323250Reference323Reference
Single/divorced/separated/widowed70441111.34 (1.03-1.75)1721.28 (1.03-1.58)
    Missing1606161.26 (0.73-2.18)321.07 (0.72-1.60)
Smoking during pregnancy
    No25 151282Reference361Reference
    Yes6822950.94 (0.73-1.21)1651.39 (1.13-1.70)†
Maternal medical conditions
Nonobstetric preexisting health conditions affecting pregnancy
    No25 941278Reference393Reference
    Yes6032991.37 (1.08-1.75)1331.22 (0.99-1.50)
Diabetes
    No29 923335Reference467Reference
    Preexisting19462.29 (0.96-5.48)51.28 (0.52-3.16)
    Gestational1856361.50 (1.05-2.15)541.47 (1.09-1.98)
Depression during pregnancy
    No30 567357Reference490Reference
    Yes1406201.44 (0.91-2.29)361.45 (1.01-2.08)
Anticoagulation therapy during pregnancy
    No31 700365Reference515Reference
    Yes273123.94 (2.02-7.70)111.93 (1.03-3.63)
Pregnancy history
Parity
    Primiparous15 723208Reference329Reference
    Multiparous16 2501690.87 (0.69-1.08)1970.75 (0.61-0.93)
Pregnancy characteristics
Weight gain during pregnancy, kg
    < 10.05353620.83 (0.61-1.12)930.80 (0.62-1.05)
    10.0-19.913 468140Reference208Reference
    20.0-29.94341611.40 (1.02-1.90)801.14 (0.87-1.48)
     30.0599182.98 (1.79-4.96)191.68 (1.02-2.75)
    Missing8212961.43 (1.01-2.02)1260.92 (0.65-1.29)
Chorioamnionitis
    No31 307352Reference496Reference
    Yes666253.30 (2.11-5.16)302.47 (1.67-3.63)
Diagnostic and/or therapeutic procedure(s) performed in woman
    No31 049365Reference500Reference
    Yes924120.88 (0.49-1.57)261.52 (1.01-2.29)
Labour
Stage of labour before cesarean delivery
    None15 645155Reference172Reference
    First10 1591321.00 (0.77-1.29)2171.40 (1.11-1.77)
    Second6169901.35 (1.02-1.79)1371.66 (1.28-2.15)
Delivery
Year of delivery
    1997-200068911725.69 (4.01-8.07)1631.30 (1.01-1.68)†
    2001-200485321022.91 (2.00-4.25)880.63 (0.48-0.84)†
    2005-20088670631.52 (1.03-2.25)1300.88 (0.69-1.12)†
    2009-2012788040Reference145Reference
Antibiotic therapy during labour and delivery
    Yes20 185187Reference316Reference
    No11 7881901.48 (1.18-1.84)2101.17 (0.97-1.41)
Maternal blood transfusion
    No31 675367Reference511Reference
    Yes298102.80 (1.43-5.48)152.66 (1.53-4.62)
Fetal or neonatal
No. of fetuses
    130 939350Reference515Reference
     21034271.78 (1.13-2.80)110.64 (0.34-1.20)†
Gestational age
    < 37 wk3057621.42 (1.02-1.96)541.21 (0.88-1.66)
    37 wk to 39 wk  + 6 d18331191Reference248Reference
    ≥ 40 wk105851240.98 (0.77-1.24)2241.19 (0.98-1.46)

Note: CI = confidence interval, OR = odds ratio.

*A total of 32 876 cesarean deliveries were included in the analysis; 1115 deliveries were excluded because of missing values for neighbourhood-level income (n = 724), smoking (n = 283), stage of labour (n = 1) and/or gestational age (n = 118).

p < 0.05 for association between risk factor and timing of infection (before v. after discharge).