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Published in: BMC Pregnancy and Childbirth 1/2016

Open Access 01-12-2016 | Research article

Elective cesarean section or not? Maternal age and risk of adverse outcomes at term: a population-based registry study of low-risk primiparous women

Authors: Lina Herstad, Kari Klungsøyr, Rolv Skjærven, Tom Tanbo, Lisa Forsén, Thomas Åbyholm, Siri Vangen

Published in: BMC Pregnancy and Childbirth | Issue 1/2016

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Abstract

Background

Maternal age at delivery and cesarean section rates are increasing. In older women, the decision on delivery mode may be influenced by a reported increased risk of surgical interventions during labor and complications with increasing maternal age. We examined the association between maternal age and adverse outcomes in low-risk primiparous women, and the risk of adverse outcomes by delivery modes, both planned and performed (elective and emergency cesarean section, operative vaginal delivery, and unassisted vaginal delivery) in women aged ≥ 35 years.

Methods

A population-based registry study was conducted using data from the Medical Birth Registry of Norway and Statistics Norway including 169,583 low-risk primiparas with singleton, cephalic labors at ≥ 37 weeks during 1999 − 2009. Outcomes studied were obstetric blood loss, maternal transfer to intensive care units, 5-min Apgar score, and neonatal complications. We adjusted for potential confounders using relative risk models and multinomial logistic regression.

Results

Most adverse outcomes increased with increasing maternal age. However, the increase in absolute risks was low, except for moderate obstetric blood loss and transfer to the neonatal intensive care unit (NICU). Operative deliveries increased with increasing maternal age and in women aged ≥ 35 years, the risk of maternal complications in operative delivery increased. Neonatal adverse outcomes increased mainly in emergency operative deliveries. Moderate blood loss was three times more likely in elective and emergency cesarean section than in unassisted vaginal delivery, and twice as likely in operative vaginal delivery. Low Apgar score and neonatal complications occurred two to three times more often in emergency operative deliveries than in unassisted vaginal delivery. However, comparing outcomes after elective cesarean section and planned vaginal delivery, only moderate blood loss (higher in elective cesarean section), neonatal transfer to NICU and neonatal infections (both higher in planned vaginal delivery) differed significantly.

Conclusions

Most studied adverse outcomes increased with increasing maternal age, as did operative delivery. Although emergency operative procedures were associated with an increased risk of adverse outcomes, the absolute risk difference in complications between the modes of delivery was low for the majority of outcomes studied.
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Literature
3.
go back to reference Ulset E, Undheim R, Malterud K. Er fedmeepidemien kommet til Norge [Has the obesity epidemic reached Norway? In Norwegian]. Tidsskr Nor Laegeforen. 2007;127:34–7.PubMed Ulset E, Undheim R, Malterud K. Er fedmeepidemien kommet til Norge [Has the obesity epidemic reached Norway? In Norwegian]. Tidsskr Nor Laegeforen. 2007;127:34–7.PubMed
4.
go back to reference Ludford I, Scheil W, Tucker G, Grivell R. Pregnancy outcomes for nulliparous women of advanced maternal age in South Australia, 1998-2008. Aust N Z J Obstet Gynaecol. 2012;52:235–41.CrossRefPubMed Ludford I, Scheil W, Tucker G, Grivell R. Pregnancy outcomes for nulliparous women of advanced maternal age in South Australia, 1998-2008. Aust N Z J Obstet Gynaecol. 2012;52:235–41.CrossRefPubMed
5.
go back to reference Luke B, Brown MB. Elevated risks of pregnancy complications and adverse outcomes with increasing maternal age. Hum Reprod. 2007;22:1264–72.CrossRefPubMed Luke B, Brown MB. Elevated risks of pregnancy complications and adverse outcomes with increasing maternal age. Hum Reprod. 2007;22:1264–72.CrossRefPubMed
6.
go back to reference Timofeev J, Reddy UM, Huang CC, Driggers RW, Landy HJ, Laughon SK. Obstetric complications, neonatal morbidity, and indications for cesarean delivery by maternal age. Obstet Gynecol. 2013;122:1184–95.CrossRefPubMedPubMedCentral Timofeev J, Reddy UM, Huang CC, Driggers RW, Landy HJ, Laughon SK. Obstetric complications, neonatal morbidity, and indications for cesarean delivery by maternal age. Obstet Gynecol. 2013;122:1184–95.CrossRefPubMedPubMedCentral
7.
go back to reference Bayrampour H, Heaman M. Advanced maternal age and the risk of cesarean birth: a systematic review. Birth. 2010;37:219–26.CrossRefPubMed Bayrampour H, Heaman M. Advanced maternal age and the risk of cesarean birth: a systematic review. Birth. 2010;37:219–26.CrossRefPubMed
8.
go back to reference Herstad L, Klungsoyr K, Skjaerven R, Tanbo T, Forsen L, Abyholm T, et al. Maternal age and emergency operative deliveries at term: a population-based registry study among low-risk primiparous women. BJOG. 2014;122:1642–51.CrossRefPubMed Herstad L, Klungsoyr K, Skjaerven R, Tanbo T, Forsen L, Abyholm T, et al. Maternal age and emergency operative deliveries at term: a population-based registry study among low-risk primiparous women. BJOG. 2014;122:1642–51.CrossRefPubMed
9.
go back to reference Klemetti R, Gissler M, Sainio S, Hemminki E. Associations of maternal age with maternity care use and birth outcomes in primiparous women: a comparison of results in 1991 and 2008 in Finland. BJOG. 2014;121:356–62.CrossRefPubMed Klemetti R, Gissler M, Sainio S, Hemminki E. Associations of maternal age with maternity care use and birth outcomes in primiparous women: a comparison of results in 1991 and 2008 in Finland. BJOG. 2014;121:356–62.CrossRefPubMed
10.
go back to reference Waldenstrom U, Gottvall K, Rasmussen S. Caesarean section in nulliparous women of advanced maternal age has been reduced in Sweden and Norway since the 1970s: a register-based study. BJOG. 2012;119:1591–6.CrossRefPubMed Waldenstrom U, Gottvall K, Rasmussen S. Caesarean section in nulliparous women of advanced maternal age has been reduced in Sweden and Norway since the 1970s: a register-based study. BJOG. 2012;119:1591–6.CrossRefPubMed
11.
go back to reference Bell JS, Campbell DM, Graham WJ, Penney GC, Ryan M, Hall MH. Can obstetric complications explain the high levels of obstetric interventions and maternity service use among older women? A retrospective analysis of routinely collected data. BJOG. 2001;108:910–8.PubMed Bell JS, Campbell DM, Graham WJ, Penney GC, Ryan M, Hall MH. Can obstetric complications explain the high levels of obstetric interventions and maternity service use among older women? A retrospective analysis of routinely collected data. BJOG. 2001;108:910–8.PubMed
12.
go back to reference Herstad L, Klungsoyr K, Skjaerven R, Tanbo T, Eidem I, Forsen L, et al. Maternal age and elective cesarean section in a low-risk population. Acta Obstet Gynecol Scand. 2012;91:816–23.CrossRefPubMed Herstad L, Klungsoyr K, Skjaerven R, Tanbo T, Eidem I, Forsen L, et al. Maternal age and elective cesarean section in a low-risk population. Acta Obstet Gynecol Scand. 2012;91:816–23.CrossRefPubMed
13.
go back to reference Waldenstrom U, Aasheim V, Nilsen AB, Rasmussen S, Pettersson HJ, Schytt E. Adverse pregnancy outcomes related to advanced maternal age compared with smoking and being overweight. Obstet Gynecol. 2014;123:104–12.CrossRefPubMed Waldenstrom U, Aasheim V, Nilsen AB, Rasmussen S, Pettersson HJ, Schytt E. Adverse pregnancy outcomes related to advanced maternal age compared with smoking and being overweight. Obstet Gynecol. 2014;123:104–12.CrossRefPubMed
15.
go back to reference RCOG. Operative vaginal delivery: Guideline No. 26. London: Royal College of Obstetricians and Gynaecology; 2011. RCOG. Operative vaginal delivery: Guideline No. 26. London: Royal College of Obstetricians and Gynaecology; 2011.
16.
go back to reference Petrou S, Glazener C. The economic costs of alternative modes of delivery during the first two months postpartum: results from a Scottish observational study. BJOG. 2002;109:214–7.CrossRefPubMed Petrou S, Glazener C. The economic costs of alternative modes of delivery during the first two months postpartum: results from a Scottish observational study. BJOG. 2002;109:214–7.CrossRefPubMed
17.
go back to reference Nilsen AB, Waldenstrom U, Hjelmstedt A, Rasmussen S, Schytt E. Characteristics of women who are pregnant with their first baby at an advanced age. Acta Obstet Gynecol Scand. 2012;91:353–62.CrossRefPubMed Nilsen AB, Waldenstrom U, Hjelmstedt A, Rasmussen S, Schytt E. Characteristics of women who are pregnant with their first baby at an advanced age. Acta Obstet Gynecol Scand. 2012;91:353–62.CrossRefPubMed
18.
go back to reference Allen VM, O’Connell CM, Liston RM, Baskett TF. Maternal morbidity associated with cesarean delivery without labor compared with spontaneous onset of labor at term. Obstet Gynecol. 2003;102:477–82.PubMed Allen VM, O’Connell CM, Liston RM, Baskett TF. Maternal morbidity associated with cesarean delivery without labor compared with spontaneous onset of labor at term. Obstet Gynecol. 2003;102:477–82.PubMed
19.
go back to reference Hansen AK, Wisborg K, Uldbjerg N, Henriksen TB. Risk of respiratory morbidity in term infants delivered by elective caesarean section: cohort study. BMJ. 2008;336:85–7.CrossRefPubMed Hansen AK, Wisborg K, Uldbjerg N, Henriksen TB. Risk of respiratory morbidity in term infants delivered by elective caesarean section: cohort study. BMJ. 2008;336:85–7.CrossRefPubMed
20.
go back to reference Kolas T, Saugstad OD, Daltveit AK, Nilsen ST, Oian P. Planned cesarean versus planned vaginal delivery at term: comparison of newborn infant outcomes. Am J Obstet Gynecol. 2006;195:1538–43.CrossRefPubMed Kolas T, Saugstad OD, Daltveit AK, Nilsen ST, Oian P. Planned cesarean versus planned vaginal delivery at term: comparison of newborn infant outcomes. Am J Obstet Gynecol. 2006;195:1538–43.CrossRefPubMed
21.
go back to reference Wax JR, Cartin A, Pinette MG, Blackstone J. Patient choice cesarean: an evidence-based review. Obstet Gynecol Surv. 2004;59:601–16.CrossRefPubMed Wax JR, Cartin A, Pinette MG, Blackstone J. Patient choice cesarean: an evidence-based review. Obstet Gynecol Surv. 2004;59:601–16.CrossRefPubMed
22.
go back to reference Liu S, Liston RM, Joseph KS, Heaman M, Sauve R, Kramer MS. Maternal mortality and severe morbidity associated with low-risk planned cesarean delivery versus planned vaginal delivery at term. CMAJ. 2007;176:455–60.CrossRefPubMedPubMedCentral Liu S, Liston RM, Joseph KS, Heaman M, Sauve R, Kramer MS. Maternal mortality and severe morbidity associated with low-risk planned cesarean delivery versus planned vaginal delivery at term. CMAJ. 2007;176:455–60.CrossRefPubMedPubMedCentral
23.
go back to reference Ministry of Health and Care. Used with permission from WHO. The International Statistical Classification of Diseases and Related Health Problems, ICD-10, 10th revision. Norwegian edition, Oslo: Elanders Publishing AS; 1998. p. 2005. Ministry of Health and Care. Used with permission from WHO. The International Statistical Classification of Diseases and Related Health Problems, ICD-10, 10th revision. Norwegian edition, Oslo: Elanders Publishing AS; 1998. p. 2005.
24.
go back to reference Ministry of Health and Care. Used with permission from the NOMESCO classification of surgical prosedures. The Classification of Medical and Surgical Procedures. Norwegian edition, Trondheim: Bjærum AS; 2006 Ministry of Health and Care. Used with permission from the NOMESCO classification of surgical prosedures. The Classification of Medical and Surgical Procedures. Norwegian edition, Trondheim: Bjærum AS; 2006
26.
27.
go back to reference Borthen I, Eide MG, Veiby G, Daltveit AK, Gilhus NE. Complications during pregnancy in women with epilepsy: population-based cohort study. BJOG. 2009;116:1736–42.CrossRefPubMed Borthen I, Eide MG, Veiby G, Daltveit AK, Gilhus NE. Complications during pregnancy in women with epilepsy: population-based cohort study. BJOG. 2009;116:1736–42.CrossRefPubMed
28.
go back to reference Skomsvoll J, Ostensen M, Baste V, Irgens L. Validity of a rheumatic disease diagnosis in the Medical Birth Registry of Norway. Acta Obstet Gynecol Scand. 2002;81:831–4.CrossRefPubMed Skomsvoll J, Ostensen M, Baste V, Irgens L. Validity of a rheumatic disease diagnosis in the Medical Birth Registry of Norway. Acta Obstet Gynecol Scand. 2002;81:831–4.CrossRefPubMed
29.
go back to reference Stene LC, Eidem I, Vangen S, Joner G, Irgens LM, Moe N. The validity of the diabetes mellitus diagnosis in the Medical Birth Registry of Norway. Norsk Epidemiologi. 2007;17:165–74. Stene LC, Eidem I, Vangen S, Joner G, Irgens LM, Moe N. The validity of the diabetes mellitus diagnosis in the Medical Birth Registry of Norway. Norsk Epidemiologi. 2007;17:165–74.
30.
go back to reference Schorn MN. Measurement of blood loss: review of the literature. J Midwifery Womens Health. 2010;55:20–7.CrossRefPubMed Schorn MN. Measurement of blood loss: review of the literature. J Midwifery Womens Health. 2010;55:20–7.CrossRefPubMed
31.
go back to reference O’Donnell CP, Kamlin CO, Davis PG, Carlin JB, Morley CJ. Interobserver variability of the 5-min Apgar score. J Pediatr. 2006;149:486–9.CrossRefPubMed O’Donnell CP, Kamlin CO, Davis PG, Carlin JB, Morley CJ. Interobserver variability of the 5-min Apgar score. J Pediatr. 2006;149:486–9.CrossRefPubMed
32.
go back to reference Scott-Pillai R, Spence D, Cardwell CR, Hunter A, Holmes VA. The impact of body mass index on maternal and neonatal outcomes: a retrospective study in a UK obstetric population, 2004-2011. BJOG. 2013;120:932–9.CrossRefPubMed Scott-Pillai R, Spence D, Cardwell CR, Hunter A, Holmes VA. The impact of body mass index on maternal and neonatal outcomes: a retrospective study in a UK obstetric population, 2004-2011. BJOG. 2013;120:932–9.CrossRefPubMed
33.
go back to reference Arrowsmith S, Robinson H, Noble K, Wray S. What do we know about what happens to myometrial function as women age? J Muscle Res Cell Motil. 2012;33:209–17.CrossRefPubMedPubMedCentral Arrowsmith S, Robinson H, Noble K, Wray S. What do we know about what happens to myometrial function as women age? J Muscle Res Cell Motil. 2012;33:209–17.CrossRefPubMedPubMedCentral
34.
go back to reference Zwart JJ, Dupuis JR, Richters A, Ory F, van RJ. Obstetric intensive care unit admission: a 2-year nationwide population-based cohort study. Intensive Care Med. 2010;36:256–63.CrossRefPubMed Zwart JJ, Dupuis JR, Richters A, Ory F, van RJ. Obstetric intensive care unit admission: a 2-year nationwide population-based cohort study. Intensive Care Med. 2010;36:256–63.CrossRefPubMed
35.
go back to reference Battin M, Sadler L. Neonatal intensive care utilization and neonatal outcome of infants born to women aged 40 years and over in New Zealand. Acta Paediatr. 2010;99:219–24.CrossRefPubMed Battin M, Sadler L. Neonatal intensive care utilization and neonatal outcome of infants born to women aged 40 years and over in New Zealand. Acta Paediatr. 2010;99:219–24.CrossRefPubMed
36.
go back to reference Ehrenstein V, Pedersen L, Grijota M, Nielsen GL, Rothman KJ, Sorensen HT. Association of Apgar score at five minutes with long-term neurologic disability and cognitive function in a prevalence study of Danish conscripts. BMC Pregnancy Childbirth. 2009;9:14.CrossRefPubMedPubMedCentral Ehrenstein V, Pedersen L, Grijota M, Nielsen GL, Rothman KJ, Sorensen HT. Association of Apgar score at five minutes with long-term neurologic disability and cognitive function in a prevalence study of Danish conscripts. BMC Pregnancy Childbirth. 2009;9:14.CrossRefPubMedPubMedCentral
37.
go back to reference Lie KK, Groholt EK, Eskild A. Association of cerebral palsy with Apgar score in low and normal birthweight infants: population based cohort study. BMJ. 2010;341:c4990.CrossRefPubMedPubMedCentral Lie KK, Groholt EK, Eskild A. Association of cerebral palsy with Apgar score in low and normal birthweight infants: population based cohort study. BMJ. 2010;341:c4990.CrossRefPubMedPubMedCentral
38.
go back to reference Balchin I, Whittaker JC, Lamont RF, Steer PJ. Maternal and fetal characteristics associated with meconium-stained amniotic fluid. Obstet Gynecol. 2011;117:828–35.CrossRefPubMed Balchin I, Whittaker JC, Lamont RF, Steer PJ. Maternal and fetal characteristics associated with meconium-stained amniotic fluid. Obstet Gynecol. 2011;117:828–35.CrossRefPubMed
39.
go back to reference Naeye RL. Maternal age, obstetric complications, and the outcome of pregnancy. Obstet Gynecol. 1983;61:210–6.PubMed Naeye RL. Maternal age, obstetric complications, and the outcome of pregnancy. Obstet Gynecol. 1983;61:210–6.PubMed
40.
go back to reference Puopolo KM, Escobar GJ. Early-onset sepsis: a predictive model based on maternal risk factors. Curr Opin Pediatr. 2013;25:161–6.CrossRefPubMed Puopolo KM, Escobar GJ. Early-onset sepsis: a predictive model based on maternal risk factors. Curr Opin Pediatr. 2013;25:161–6.CrossRefPubMed
41.
go back to reference Dani C, Reali MF, Bertini G, Wiechmann L, Spagnolo A, Tangucci M, et al. Risk factors for the development of respiratory distress syndrome and transient tachypnoea in newborn infants. Italian Group of Neonatal Pneumology. Eur Respir J. 1999;14:155–9.CrossRefPubMed Dani C, Reali MF, Bertini G, Wiechmann L, Spagnolo A, Tangucci M, et al. Risk factors for the development of respiratory distress syndrome and transient tachypnoea in newborn infants. Italian Group of Neonatal Pneumology. Eur Respir J. 1999;14:155–9.CrossRefPubMed
42.
go back to reference Ekeus C, Hogberg U, Norman M. Vacuum assisted birth and risk for cerebral complications in term newborn infants: a population-based cohort study. BMC Pregnancy Childbirth. 2014;14:36.CrossRefPubMedPubMedCentral Ekeus C, Hogberg U, Norman M. Vacuum assisted birth and risk for cerebral complications in term newborn infants: a population-based cohort study. BMC Pregnancy Childbirth. 2014;14:36.CrossRefPubMedPubMedCentral
44.
go back to reference Karlstrom A, Lindgren H, Hildingsson I. Maternal and infant outcome after caesarean section without recorded medical indication: findings from a Swedish case-control study. BJOG. 2013;120:479–86.CrossRefPubMed Karlstrom A, Lindgren H, Hildingsson I. Maternal and infant outcome after caesarean section without recorded medical indication: findings from a Swedish case-control study. BJOG. 2013;120:479–86.CrossRefPubMed
45.
go back to reference Allen VM, O’Connell CM, Baskett TF. Maternal morbidity associated with cesarean delivery without labor compared with induction of labor at term. Obstet Gynecol. 2006;108:286–94.CrossRefPubMed Allen VM, O’Connell CM, Baskett TF. Maternal morbidity associated with cesarean delivery without labor compared with induction of labor at term. Obstet Gynecol. 2006;108:286–94.CrossRefPubMed
46.
go back to reference Holm C, Langhoff-Roos J, Petersen KB, Norgaard A, Diness BR. Severe postpartum haemorrhage and mode of delivery: a retrospective cohort study. BJOG. 2012;119:596–604.CrossRefPubMed Holm C, Langhoff-Roos J, Petersen KB, Norgaard A, Diness BR. Severe postpartum haemorrhage and mode of delivery: a retrospective cohort study. BJOG. 2012;119:596–604.CrossRefPubMed
47.
go back to reference Stock O, Beckmann M. Why group & save? Blood transfusion at low-risk elective caesarean section. Aust N Z J Obstet Gynaecol. 2014;54:279–82.CrossRefPubMed Stock O, Beckmann M. Why group & save? Blood transfusion at low-risk elective caesarean section. Aust N Z J Obstet Gynaecol. 2014;54:279–82.CrossRefPubMed
48.
go back to reference Geller EJ, Wu JM, Jannelli ML, Nguyen TV, Visco AG. Neonatal outcomes associated with planned vaginal versus planned primary cesarean delivery. J Perinatol. 2010;30:258–64.CrossRefPubMed Geller EJ, Wu JM, Jannelli ML, Nguyen TV, Visco AG. Neonatal outcomes associated with planned vaginal versus planned primary cesarean delivery. J Perinatol. 2010;30:258–64.CrossRefPubMed
49.
go back to reference Hansen AK, Wisborg K, Uldbjerg N, Henriksen TB. Elective caesarean section and respiratory morbidity in the term and near-term neonate. Acta Obstet Gynecol Scand. 2007;86:389–94.CrossRefPubMed Hansen AK, Wisborg K, Uldbjerg N, Henriksen TB. Elective caesarean section and respiratory morbidity in the term and near-term neonate. Acta Obstet Gynecol Scand. 2007;86:389–94.CrossRefPubMed
50.
go back to reference Saunders RA, Milner AD. Pulmonary pressure/volume relationships during the last phase of delivery and the first postnatal breaths in human subjects. J Pediatr. 1978;93:667–73.CrossRefPubMed Saunders RA, Milner AD. Pulmonary pressure/volume relationships during the last phase of delivery and the first postnatal breaths in human subjects. J Pediatr. 1978;93:667–73.CrossRefPubMed
52.
go back to reference Allen VM, Baskett TF, O’Connell CM, McKeen D, Allen AC. Maternal and perinatal outcomes with increasing duration of the second stage of labor. Obstet Gynecol. 2009;113:1248–58.CrossRefPubMed Allen VM, Baskett TF, O’Connell CM, McKeen D, Allen AC. Maternal and perinatal outcomes with increasing duration of the second stage of labor. Obstet Gynecol. 2009;113:1248–58.CrossRefPubMed
53.
go back to reference Nystedt A, Hildingsson I. Diverse definitions of prolonged labour and its consequences with sometimes subsequent inappropriate treatment. BMC Pregnancy Childbirth. 2014;14:233.CrossRefPubMedPubMedCentral Nystedt A, Hildingsson I. Diverse definitions of prolonged labour and its consequences with sometimes subsequent inappropriate treatment. BMC Pregnancy Childbirth. 2014;14:233.CrossRefPubMedPubMedCentral
54.
go back to reference Brouwer AJ, Groenendaal F, Koopman C, Nievelstein RJ, Han SK, de Vries LS. Intracranial hemorrhage in full-term newborns: a hospital-based cohort study. Neuroradiology. 2010;52:567–76.CrossRefPubMedPubMedCentral Brouwer AJ, Groenendaal F, Koopman C, Nievelstein RJ, Han SK, de Vries LS. Intracranial hemorrhage in full-term newborns: a hospital-based cohort study. Neuroradiology. 2010;52:567–76.CrossRefPubMedPubMedCentral
56.
go back to reference National Collaborating Centre for Women’s and Children’s Health. Intrapartum care for healthy women and their babies during childbirth. Commissioned by the National Institute for Health and Clinical Excellence (NICE). London: RCOG Press; 2007. National Collaborating Centre for Women’s and Children’s Health. Intrapartum care for healthy women and their babies during childbirth. Commissioned by the National Institute for Health and Clinical Excellence (NICE). London: RCOG Press; 2007.
Metadata
Title
Elective cesarean section or not? Maternal age and risk of adverse outcomes at term: a population-based registry study of low-risk primiparous women
Authors
Lina Herstad
Kari Klungsøyr
Rolv Skjærven
Tom Tanbo
Lisa Forsén
Thomas Åbyholm
Siri Vangen
Publication date
01-12-2016
Publisher
BioMed Central
Published in
BMC Pregnancy and Childbirth / Issue 1/2016
Electronic ISSN: 1471-2393
DOI
https://doi.org/10.1186/s12884-016-1028-3

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