title: Severe acute maternal morbidity in multiple pregnancies: a nationwide cohort study.
abstract: BACKGROUND
  Adverse neonatal outcomes in multiple pregnancies have been documented extensively, in particular those associated with the increased risk of preterm birth. Paradoxically, much less is known about adverse maternal events. The combined risk of severe acute maternal morbidity in multiple pregnancies has not been documented previously in any nationwide prospective study.
  
  
  OBJECTIVE
  The objective of the study was to assess the risk of severe acute maternal morbidity in multiple pregnancies in a high-income European country and identify possible risk indicators.
  
  
  METHODS
  In a population-based cohort study including all 98 hospitals with a maternity unit in The Netherlands, pregnant women with severe acute maternal morbidity were included in the period Aug. 1, 2004, until Aug. 1, 2006. We calculated the incidence of severe acute maternal morbidity in multiple pregnancies in The Netherlands using The Netherlands Perinatal Registry. Relative risks (RR) of severe acute maternal morbidity in multiple pregnancies compared with singletons were calculated. To identify possible risk indicators, we also compared age, parity, method of conception, onset of labor, and mode of delivery for multiple pregnancies using The Netherlands Perinatal Registry as reference.
  
  
  RESULTS
  A total of 2552 cases of severe acute maternal morbidity were reported during the 2 year study period. Among 202 multiple pregnancies (8.0%), there were 197 twins (7.8%) and 5 triplets (0.2%). The overall incidence of severe acute maternal morbidity was 7.0 per 1000 deliveries and 6.5 and 28.0 per 1000 for singletons and multiple pregnancies, respectively. The relative risk of severe acute maternal morbidity compared with singleton pregnancies was 4.3 (95% confidence interval [CI], 3.7-5.0) and increased to 6.2 (95% CI 2.5-15.3) in triplet pregnancies. Risk indicators for developing severe acute maternal morbidity in women with multiple pregnancies were age of ≥ 40 years, (RR, 2.5 95% CI, 1.4-4.3), nulliparity (RR, 1.8, 95% CI, 1.4-2.4), use of assisted reproductive techniques (RR, 1.9, 95% CI, 1.4-2.5), and nonspontaneous onset of delivery (RR, 1.6, 95% CI, 1.2-2.1). No significant difference was found between mono- and dichorionic twins (RR, 0.8, 95% CI, 0.6-1.2).
  
  
  CONCLUSIONS
  Women with multiple pregnancies in The Netherlands have a more than 4 times elevated risk of sustaining severe acute maternal morbidity as compared with singletons.
authors.affiliation: Department of Obstetrics, Leiden University Medical Center, Leiden, The Netherlands. Electronic address: tom.witteveen@gmail.com.
authors.forename: Tom
authors.initials: T
authors.lastname: Witteveen
authors.affiliation: Department of Obstetrics, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Thomas
authors.initials: T
authors.lastname: Van Den Akker
authors.affiliation: Department of Obstetrics, Leiden University Medical Center, Leiden, The Netherlands; Department of Obstetrics and Gynecology, Deventer Ziekenhuis, Deventer, The Netherlands.
authors.forename: Joost J
authors.initials: JJ
authors.lastname: Zwart
authors.affiliation: Department of Obstetrics, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Kitty W
authors.initials: KW
authors.lastname: Bloemenkamp
authors.affiliation: Department of Obstetrics, Leiden University Medical Center, Leiden, The Netherlands; Athena Institute, VU University Amsterdam, Amsterdam, The Netherlands.
authors.forename: Jos
authors.initials: J
authors.lastname: Van Roosmalen
mesh_terms: D002585:Cesarean Section; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007230:Infant, Low Birth Weight; D007231:Infant, Newborn; D007362:Intensive Care Units; D007751:Labor, Induced; D007902:Length of Stay; D008423:Maternal Age; D009426:Netherlands / Q000453:epidemiology; D010298:Parity; D010343:Patient Admission; D011247:Pregnancy; D011248:Pregnancy Complications / Q000453:epidemiology*; D059286:Pregnancy, Triplet; D059285:Pregnancy, Twin; D027724:Reproductive Techniques, Assisted
keywords: maternal health; maternal mortality; multiple pregnancy; obstetrics; quality of care; reproductive health; severe acute maternal morbidity