title: Effect of Placenta Previa on Preeclampsia.
abstract: BACKGROUND
  The correlation between gestational hypertension-preeclampsia (GH-PE) and placenta previa (PP) is controversial. Specifically, it is unknown whether placenta previa has any effect on the various types of preeclampsia (PE), and the role PP with concurrent placenta accreta (PA) play in the occurrence of GH-PE are not well understood.
  
  
  OBJECTIVE
  The aim of this study was to identify the effects of PP on GH, mild and severe preeclampsia (MPE and SPE), and early- and late-onset preeclampsia (EPE and LPE). Another aim of the study was to determine if concurrent PA impacts the relationship between PP and GH-PE.
  
  
  METHODS
  A retrospective single-center study of 1,058 patients having singleton pregnancies with PP was performed, and 2,116 pregnant women were randomly included as controls. These cases were collected from a tertiary hospital and met the inclusion criteria for the study. Clinical information, including PP and the gestational age at the onset of GH-PE were collected. Binary and multiple logistic regression analyses were conducted after the confounding variables were controlled to assess the effects of PP on different types of GH-PE.
  
  
  RESULTS
  There were 155 patients with GH-PE in the two groups. The incidences of GH-PE in the PP group and the control group were 2.5% (26/1058) and 6.1% (129/2116), respectively (P = 0.000). Binary and multiple regression analyses were conducted after controlling for confounding variables. Compared to the control group, in the PP group, the risk of GH-PE was reduced significantly by 78% (AOR: 0.216; 95% CI: 0.135-0.345); the risks of GH and PE were reduced by 55% (AOR: 0.451; 95% CI: 0.233-0.873) and 86% (AOR: 0.141; 95% CI: 0.073-0.271), respectively; the risks of MPE and SPE were reduced by 73% (AOR: 0.269; 95% CI: 0.087-0828) and 88% (AOR: 0.123; 95% CI: 0.055-0.279), respectively; and the risks of EPE and LPE were reduced by 95% (AOR: 0.047; 95% CI: 0.012-0.190) and 67% (AOR: 0.330; 95% CI: 0.153-0.715), respectively. The incidence of concurrent PA in women with PP was 5.86%; PP with PA did not significantly further reduce the incidence of GH-PE compared with PP without PA (1.64% vs. 2.51%, P>0.05). Binary logistic regression analyses were conducted after controlling for confounding variables, compared with the non-PP + GH-PE group, and the AOR of FGR in the non-PP + non-GH-PE group was 0.206 (0.124-0.342). Compared with the PP + GH-PE group, the AOR of FGR in the PP + non-GH-PE group was 0.430 (0.123-1.500).
  
  
  CONCLUSIONS
  PP is not only associated with a significant reduction in the incidence of GH-PE, but also is associated with a reduction in incidence of various types of PE. Concurrent PA and PP do not show association with a reduction in incidence of GH-PE.
authors.affiliation: Department of Obstetrics, Shanghai First Maternity and Infant Hospital, Tongji University School of Medicine, Shanghai, China.
authors.forename: Hao
authors.initials: H
authors.lastname: Ying
authors.affiliation: Department of Obstetrics, Shanghai First Maternity and Infant Hospital, Tongji University School of Medicine, Shanghai, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Lu
authors.affiliation: Department of Obstetrics, Shanghai First Maternity and Infant Hospital, Tongji University School of Medicine, Shanghai, China.
authors.forename: Yi-Nuo
authors.initials: YN
authors.lastname: Dong
authors.affiliation: Department of Obstetrics, Shanghai First Maternity and Infant Hospital, Tongji University School of Medicine, Shanghai, China.
authors.forename: De-Fen
authors.initials: DF
authors.lastname: Wang
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D046110:Hypertension, Pregnancy-Induced / Q000453:epidemiology*; D015994:Incidence; D010921:Placenta Accreta / Q000453:epidemiology; D010923:Placenta Previa / Q000453:epidemiology*; D011225:Pre-Eclampsia / Q000453:epidemiology*; D011247:Pregnancy; D012189:Retrospective Studies; D012307:Risk Factors; D055815:Young Adult