Relation between perinatal outcome and gestational duration in term primiparous pregnancies stratified by body mass index

Abstract Introduction There is growing evidence that induction of labor at 41 completed weeks improves neonatal outcome, at least among primiparous women. This study was performed to investigate whether maternal body mass index (BMI) should be considered when deciding on timing of intervention in te...

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Main Authors: Lina Lindegren, Andrea Stuart, Andreas Herbst, Karin Källén
Format: Article
Language:English
Published: Wiley 2022-12-01
Series:Acta Obstetricia et Gynecologica Scandinavica
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Online Access:https://doi.org/10.1111/aogs.14465
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author Lina Lindegren
Andrea Stuart
Andreas Herbst
Karin Källén
author_facet Lina Lindegren
Andrea Stuart
Andreas Herbst
Karin Källén
author_sort Lina Lindegren
collection DOAJ
description Abstract Introduction There is growing evidence that induction of labor at 41 completed weeks improves neonatal outcome, at least among primiparous women. This study was performed to investigate whether maternal body mass index (BMI) should be considered when deciding on timing of intervention in term pregnancies. Material and methods The study design was a historical cohort study using data from the Swedish Medical Birth Register, singletons in cephalic presentation with births 39+0 to 41+6 weeks, with available information on maternal BMI 2005–2017 (n = 352 567). Modified Poisson regression analyses were used to investigate the association between gestational duration and stillbirth or death before 45 postmenstrual weeks (primary outcome) and Apgar score <7 at 5 minutes (secondary outcome) by BMI, respectively. Adjustments were made for maternal age, smoking, country of birth and educational level. Results The adjusted relative risk (ARR) of stillbirth or death before 45 weeks among infants born at 41+0 to 41+6 vs 40+0 to 40+6 weeks, was 1.26 with a 95% confidence interval (CI) of 1.07–1.48. Among women with BMI ≥30, the offspring mortality risk in pregnancies lasting 39+0 to 39+2 weeks was significantly above the corresponding risk among women of normal BMI who delivered at 41+0 to 41+2 weeks (ARR = 1.95; 95% CI 1.07–3.56) but no statistically significant heterogeneity was found regarding the magnitude of the association between gestational duration and offspring mortality. The ARR, for Apgar <7 at 5 minutes (41+0 to 41+6 vs 40+0 to 40+6 weeks, regardless of BMI), was 1.36 (95% CI 1.27–1.45). The risk for low Apgar score at 41+0 weeks was 1.5% among all children regardless of maternal BMI. Among children to women with BMI ≥30, this magnitude of risk was found already at 39+3 weeks. Conclusions In primiparous women with obesity the risk of stillbirth or death before 45 postmenstrual weeks were increased throughout all full‐term gestational age categories, compared with women with overweight or normal BMI. Children to obese women had the same risk for Apgar scores <7 at 5 minutes compared with women overall at earlier gestational age. The results suggest that maternal BMI needs to be considered when discussing timing of elective induction in term healthy pregnancies of primiparous women.
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spelling doaj-art-0ca5f7e68d2d40ca8cb44853697213fd2025-08-20T02:09:35ZengWileyActa Obstetricia et Gynecologica Scandinavica0001-63491600-04122022-12-01101121414142110.1111/aogs.14465Relation between perinatal outcome and gestational duration in term primiparous pregnancies stratified by body mass indexLina Lindegren0Andrea Stuart1Andreas Herbst2Karin Källén3Institution of Clinical Sciences, Department of Obstetrics and Gynecology Lund University Lund SwedenInstitution of Clinical Sciences, Department of Obstetrics and Gynecology Lund University Lund SwedenInstitution of Clinical Sciences, Department of Obstetrics and Gynecology Lund University Lund SwedenInstitution of Clinical Sciences, Department of Obstetrics and Gynecology Lund University Lund SwedenAbstract Introduction There is growing evidence that induction of labor at 41 completed weeks improves neonatal outcome, at least among primiparous women. This study was performed to investigate whether maternal body mass index (BMI) should be considered when deciding on timing of intervention in term pregnancies. Material and methods The study design was a historical cohort study using data from the Swedish Medical Birth Register, singletons in cephalic presentation with births 39+0 to 41+6 weeks, with available information on maternal BMI 2005–2017 (n = 352 567). Modified Poisson regression analyses were used to investigate the association between gestational duration and stillbirth or death before 45 postmenstrual weeks (primary outcome) and Apgar score <7 at 5 minutes (secondary outcome) by BMI, respectively. Adjustments were made for maternal age, smoking, country of birth and educational level. Results The adjusted relative risk (ARR) of stillbirth or death before 45 weeks among infants born at 41+0 to 41+6 vs 40+0 to 40+6 weeks, was 1.26 with a 95% confidence interval (CI) of 1.07–1.48. Among women with BMI ≥30, the offspring mortality risk in pregnancies lasting 39+0 to 39+2 weeks was significantly above the corresponding risk among women of normal BMI who delivered at 41+0 to 41+2 weeks (ARR = 1.95; 95% CI 1.07–3.56) but no statistically significant heterogeneity was found regarding the magnitude of the association between gestational duration and offspring mortality. The ARR, for Apgar <7 at 5 minutes (41+0 to 41+6 vs 40+0 to 40+6 weeks, regardless of BMI), was 1.36 (95% CI 1.27–1.45). The risk for low Apgar score at 41+0 weeks was 1.5% among all children regardless of maternal BMI. Among children to women with BMI ≥30, this magnitude of risk was found already at 39+3 weeks. Conclusions In primiparous women with obesity the risk of stillbirth or death before 45 postmenstrual weeks were increased throughout all full‐term gestational age categories, compared with women with overweight or normal BMI. Children to obese women had the same risk for Apgar scores <7 at 5 minutes compared with women overall at earlier gestational age. The results suggest that maternal BMI needs to be considered when discussing timing of elective induction in term healthy pregnancies of primiparous women.https://doi.org/10.1111/aogs.14465Apgar scorebody mass indexgestational durationobesityoverweightperinatal outcome
spellingShingle Lina Lindegren
Andrea Stuart
Andreas Herbst
Karin Källén
Relation between perinatal outcome and gestational duration in term primiparous pregnancies stratified by body mass index
Acta Obstetricia et Gynecologica Scandinavica
Apgar score
body mass index
gestational duration
obesity
overweight
perinatal outcome
title Relation between perinatal outcome and gestational duration in term primiparous pregnancies stratified by body mass index
title_full Relation between perinatal outcome and gestational duration in term primiparous pregnancies stratified by body mass index
title_fullStr Relation between perinatal outcome and gestational duration in term primiparous pregnancies stratified by body mass index
title_full_unstemmed Relation between perinatal outcome and gestational duration in term primiparous pregnancies stratified by body mass index
title_short Relation between perinatal outcome and gestational duration in term primiparous pregnancies stratified by body mass index
title_sort relation between perinatal outcome and gestational duration in term primiparous pregnancies stratified by body mass index
topic Apgar score
body mass index
gestational duration
obesity
overweight
perinatal outcome
url https://doi.org/10.1111/aogs.14465
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AT andreasherbst relationbetweenperinataloutcomeandgestationaldurationintermprimiparouspregnanciesstratifiedbybodymassindex
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