Placenta weight in pre-eclampsia

Authors

  • BERIT DAHLSTRØM,

    Corresponding author
    1. Faculty Division Akershus University Hospital, University of Oslo, Norway
    2. Department of Obstetrics and Gynecology, Akershus University Hospital, Lørenskog, Norway
      : Berit Dahlstrøm, Department of Obstetrics and Gynecology, Akershus University Hospital, N-1478, Lørenskog, Norway. E-mail: berit.dahlstrom@ahus.no
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  • PÅL ROMUNDSTAD,

    1. Department of Public Health, Norwegian University of Science and Technology, Trondheim, Norway
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  • PÅL ØIAN,

    1. Department of Obstetrics and Gynecology, University Hospital of North Norway, Tromsø, Norway
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  • LARS J. VATTEN,

    1. Department of Public Health, Norwegian University of Science and Technology, Trondheim, Norway
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  • ANNE ESKILD

    1. Faculty Division Akershus University Hospital, University of Oslo, Norway
    2. Department of Obstetrics and Gynecology, Akershus University Hospital, Lørenskog, Norway
    3. Division of Mental Health, Norwegian Institute of Public Health, Oslo, Norway
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: Berit Dahlstrøm, Department of Obstetrics and Gynecology, Akershus University Hospital, N-1478, Lørenskog, Norway. E-mail: berit.dahlstrom@ahus.no

Abstract

Objective. Preterm and term pre-eclampsia may differ in etiology. This could be reflected in differences in placenta weight. Therefore, we compared placenta weight in pregnancies with preterm or term pre-eclampsia to placenta weight in pregnancies without pre-eclampsia. Design. Population study. Setting. Medical Birth Registry of Norway. Population. All singleton pregnancies in Norway from 1999 through 2004 delivered at or after 21 weeks’ gestation (n = 317,688). Methods. Placenta weight in pregnancies without pre-eclampsia (n = 304,875) was compared to placenta weight in pregnancies with preterm pre-eclampsia (delivery before week 37 of pregnancy, n = 3,070) and term pre-eclampsia (delivery on or after week 37 of pregnancy, n = 9,743). Placenta weight z-scores were calculated to adjust for offspring sex and length of gestation, and grouped in tenths. Placenta weight according to pre-eclampsia status is presented as proportions within each tenth. Main outcome measures. Pre-eclampsia status. Results. In preterm pre-eclampsia, placentas were over-represented in the two lowest (33.8%; 95% CI 32.1–35.5) and under-represented in the two highest (13.1%; 95% CI 11.9–14.3) tenths of placenta weight compared to pregnancies without pre-eclampsia (20%). In term pre-eclampsia, placentas were over-represented in the two lowest (22.0%; 95% CI 21.2–22.8) and the two highest (22.7%; 95% CI 21.9–23.6) placenta weight groups. Mean placenta weight z-score was higher in term pre-eclampsia compared to pregnancies without pre-eclampsia. Conclusions. Small placentas were associated with pre-eclampsia, and more strongly with preterm than term pre-eclampsia. In term pre-eclampsia, the association with placenta weight was u-shaped, yielding higher proportions of both low and high placenta weight compared to pregnancies without pre-eclampsia.

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