Table 2

Pregnancy outcomes in patients with and without a history of pregnancy termination

OutcomeHistory of termination of pregnancies (%)Reference group (%)Risk differenceNNHcOR (95% CI)aOR (95% CI)
Cervical incompetence treated by cerclage39 (0.2)712 (0.1)0.110004.60 (3.33 to 6.36)4.58 (2.93 to 7.15)
SPTB781 (4.9)57019 (4.3)0.61671.15 (1.07 to 1.23)1.11 (1.02 to 1.20)
 SPTB <32 weeks150 (0.9)7788 (0.6)0.33331.61 (1.37 to 1.89)1.52 (1.26 to 1.85)
 SPTB <28 weeks85 (0.5)3984 (0.3)0.25001.78 (1.43 to 2.21)1.67 (1.30 to 2.15)
PIRP571 (3.6)35822 (2.7)0.91111.35 (1.25 to 1.47)1.32 (1.21 to 1.43)
 Placenta praevia41 (0.3)1315 (0.1)0.25002.62 (1.92 to 3.58)2.48 (1.80 to 3.42)
 Placental abruption22 (0.1)1074 (0.1)01.72 (1.13 to 2.62)1.56 (1.02 to 2.39)
 Retained placenta512 (3.2)33521 (2.5)0.71421.30 (1.19 to 1.42)1.26 (1.15 to 1.38)
Postpartum haemorrhage760 (5)53571 (4.1)0.91111.22 (1.14 to 1.32)1.16 (1.08 to 1.25)
Any listed adverse outcome1750 (10.9)124586 (9.3)1.6631.20 (1.14 to 1.26)1.15 (1.09 to 1.22)
Any listed adverse outcome other than cervical incompetence treated by cerclage1726 (10.8)124119 (9.2)1.6631.19 (1.13 to 1.25)1.14 (1.08 to 1.21)
  • p Value for all outcomes <0.001.

  • aOR are adjusted for known confounders for the given outcome. SPTB and cervical incompetence treated by cerclage are adjusted for maternal age, ethnicity, SES, parity, smoking, drug dependence, pyelitis, polyhydramnios, history of SPTB, history of cervical incompetence or Shirodkar procedure, history of uterine myoma and history of cervical surgery.

  • aOR of PIRP, placenta praevia, placental abruption and retained placenta are adjusted for maternal age, ethnicity, SES, parity, smoking, drug dependence, history of caesarean section and history of PIRP.

  • aOR of PPH is adjusted for maternal age, ethnicity, SES, parity, polyhydramnios, history of PPH and history of uterine myoma.

  • aOR of composite outcome is adjusted for all the above-mentioned parameters.

  • aOR, adjusted OR; cOR, crude OR; NNH, number needed to harm; PIRP, placental implantation or retention problems; PPH, postpartum haemorrhage; SES, socioeconomic status; SPTB, spontaneous preterm birth (gestational age from 20 to 37 weeks).