Clinical Research

The relationship between maternal body mass index and pregnancy outcomes in twin compared with singleton pregnancies



Women with twins have an a priori increased risk for many of the complications associated with maternal obesity. Thus, the impact of maternal obesity in twins may differ from that reported in singletons. In addition, given the increased metabolic demands in twin pregnancies, the impact of maternal underweight may be greater in twin compared with singleton gestations. Our objective was to test the hypothesis that the relationship between maternal pre-pregnancy body mass index (BMI) and adverse pregnancy outcomes differ between twin and singleton gestations.


This was a retrospective population-based study of all women who had a singleton or twin hospital birth in Ontario, Canada, between April 2012 and March 2016. Data were obtained from the Better Outcomes Registry & Network (BORN) Ontario. The relationship between maternal BMI category and pregnancy complications was assessed separately in twin and singleton gestations. The primary outcome was a composite variable that included any of the following complications: preeclampsia, gestational diabetes, or preterm birth before 320/7 weeks. Relative risk (aRR) and 95% confidence intervals (CI) for adverse outcomes for each BMI category as defined by WHO (using normal weight category as reference) were generated using modified Poisson regression, adjusting for maternal age, nulliparity, smoking, previous preterm birth, and fetal sex.


A total of 487,870 women with singleton (n = 480,010) and twin (n = 7860) pregnancies met the inclusion criteria. The risk of the composite primary outcome, preeclampsia, gestational diabetes, and cesarean delivery increased with high maternal BMI in both singleton and twin gestations, but these associations were weaker in twin compared with singleton gestations (association of BMI ≥ 40.0 kg/m2 with primary outcome: aRR = 3.10, 95%-CI 2.96–3.24 in singletons compared with aRR = 1.74, 95%-CI 1.37–2.20 in twins). In singleton pregnancies the risk of preterm birth at < 320/7 weeks increased with maternal BMI, mainly due to an increased risk of provider-initiated preterm birth. In twin gestations, however, underweight (but not overweight or obesity) was associated with the greatest risk of preterm birth at < 32 weeks (aRR 1.67, 95%-CI 1.17–2.37), mainly due to an increased risk of spontaneous preterm birth (aRR 2.10, 95%-CI 1.44–3.08).


In healthy women with twin pregnancies, underweight is associated with the greatest risk for preterm birth, while the association of maternal obesity with adverse pregnancy outcomes is weaker than that observed in singletons.

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  1. 1.

    Mission JF, Marshall NE, Caughey AB. Pregnancy risks associated with obesity. Obstet Gynecol Clin North Am. 2015;42:335–53.

    PubMed  Google Scholar 

  2. 2.

    Lu GC, Rouse DJ, DuBard M, Cliver S, Kimberlin D, Hauth JC. The effect of the increasing prevalence of maternal obesity on perinatal morbidity. Am J Obstet Gynecol. 2001;185:845–9.

    CAS  PubMed  Google Scholar 

  3. 3.

    Kim SY, Dietz PM, England L, Morrow B, Callaghan WM. Trends in pre-pregnancy obesity in nine states, 1993–2003. Obesity. 2007;15:986–93.

    PubMed  Google Scholar 

  4. 4.

    Obesity: preventing and managing the global epidemic. Report of a WHO consultation. World Health Organ Tech Rep Ser. 2000;894(i–xii):1–253.

  5. 5.

    Rasmussen KM, Yaktine AL, editors. Weight gain during pregnancy: reexamining the guidelines. The National Academies Collection: Reports funded by National Institutes of Health. Washington (DC); 2009.

  6. 6.

    ACOG Practice Bulletin No 156: obesity in pregnancy. Obstet Gynecol. 2015;126:e112–26.

  7. 7.

    Aamir AH. The obese pregnancy. J Pak Med Assoc. 2016;66(9Suppl 1):S65–8.

    CAS  PubMed  Google Scholar 

  8. 8.

    Doherty DA, Magann EF, Francis J, Morrison JC, Newnham JP. Pre-pregnancy body mass index and pregnancy outcomes. Int J Gynaecol Obstet. 2006;95:242–7.

    CAS  PubMed  Google Scholar 

  9. 9.

    Malik VS, Willett WC, Hu FB. Global obesity: trends, risk factors and policy implications. Nat Rev Endocrinol. 2013;9:13–27.

    PubMed  Google Scholar 

  10. 10.

    Orpana HM, Berthelot JM, Kaplan MS, Feeny DH, McFarland B, Ross NA. BMI and mortality: results from a national longitudinal study of Canadian adults. Obesity. 2010;18:214–8.

    PubMed  Google Scholar 

  11. 11.

    Viswanathan M, Siega-Riz AM, Moos MK, Deierlein A, Mumford S, Knaack J, et al. Outcomes of maternal weight gain. Evid Rep Technol Assess (Full Rep). 2008;168:1–223.

    Google Scholar 

  12. 12.

    Callaway LK, Prins JB, Chang AM, McIntyre HD. The prevalence and impact of overweight and obesity in an Australian obstetric population. Med J Aust. 2006;184:56–9.

    PubMed  Google Scholar 

  13. 13.

    Davies GA, Maxwell C, McLeod L, Gagnon R, Basso M, Bos H, et al. Obesity in pregnancy. J Obstet Gynaecol Can. 2010;32:165–73.

    PubMed  Google Scholar 

  14. 14.

    Robinson HE, O’Connell CM, Joseph KS, McLeod NL. Maternal outcomes in pregnancies complicated by obesity. Obstet Gynecol. 2005;106:1357–64.

    PubMed  Google Scholar 

  15. 15.

    Salihu HM, Dunlop AL, Hedayatzadeh M, Alio AP, Kirby RS, Alexander GR. Extreme obesity and risk of stillbirth among black and white gravidas. Obstet Gynecol. 2007;110:552–7.

    PubMed  Google Scholar 

  16. 16.

    Sebire NJ, Jolly M, Harris JP, Wadsworth J, Joffe M, Beard RW, et al. Maternal obesity and pregnancy outcome: a study of 287,213 pregnancies in London. Int J Obes Relat Metab Disord. 2001;25:1175–82.

    CAS  PubMed  Google Scholar 

  17. 17.

    Yogev Y, Catalano PM. Pregnancy and obesity. Obstet Gynecol Clin North Am. 2009;36:285–300. viii

    PubMed  Google Scholar 

  18. 18.

    Al Wattar BH, Pidgeon C, Learner H, Zamora J, Thangaratinam S. Online health information on obesity in pregnancy: a systematic review. Eur J Obstet Gynecol Reprod Biol. 2016;206:147–52.

    PubMed  Google Scholar 

  19. 19.

    Vinturache AE, Chaput KH, Tough SC. Pre-pregnancy body mass index (BMI) and macrosomia in a Canadian birth cohort. J Matern Fetal Neonatal Med. 2017;30:109–16.

    PubMed  Google Scholar 

  20. 20.

    Catalano PM, Shankar K. Obesity and pregnancy: mechanisms of short term and long term adverse consequences for mother and child. BMJ. 2017;356:j1.

    PubMed  PubMed Central  Google Scholar 

  21. 21.

    Avci ME, Sanlikan F, Celik M, Avci A, Kocaer M, Gocmen A. Effects of maternal obesity on antenatal, perinatal and neonatal outcomes. J Matern Fetal Neonatal Med. 2015;28:2080–3.

    PubMed  Google Scholar 

  22. 22.

    Dixit A, Girling JC. Obesity and pregnancy. J Obstet Gynaecol. 2008;28:14–23.

    CAS  PubMed  Google Scholar 

  23. 23.

    Chu SY, Callaghan WM, Kim SY, Schmid CH, Lau J, England LJ, et al. Maternal obesity and risk of gestational diabetes mellitus. Diabetes Care. 2007;30:2070–6.

    PubMed  Google Scholar 

  24. 24.

    Weiss JL, Malone FD, Emig D, Ball RH, Nyberg DA, Comstock CH, et al. Obesity, obstetric complications and cesarean delivery rate—a population-based screening study. Am J Obstet Gynecol. 2004;190:1091–7.

    PubMed  Google Scholar 

  25. 25.

    Gilead R, Yaniv Salem S, Sergienko R, Sheiner E. Maternal “isolated” obesity and obstetric complications. J Matern Fetal Neonatal Med. 2012;25:2579–82.

    PubMed  Google Scholar 

  26. 26.

    Kogan MD, Alexander GR, Kotelchuck M, MacDorman MF, Buekens P, Martin JA, et al. Trends in twin birth outcomes and prenatal care utilization in the United States, 1981–1997. JAMA. 2000;284:335–41.

    CAS  PubMed  Google Scholar 

  27. 27.

    Mathews TJ, MacDorman MF. Infant mortality statistics from the 2003 period linked birth/infant death data set. Natl Vital Stat Rep. 2006;54:1–29.

    CAS  PubMed  Google Scholar 

  28. 28.

    Chauhan SP, Scardo JA, Hayes E, Abuhamad AZ, Berghella V. Twins: prevalence, problems, and preterm births. Am J Obstet Gynecol. 2010;203:305–15.

    PubMed  Google Scholar 

  29. 29.

    Salihu HM, Bekan B, Aliyu MH, Rouse DJ, Kirby RS, Alexander GR. Perinatal mortality associated with abruptio placenta in singletons and multiples. Am J Obstet Gynecol. 2005;193:198–203.

    PubMed  Google Scholar 

  30. 30.

    Powers WF, Kiely JL. The risks confronting twins: a national perspective. Am J Obstet Gynecol. 1994;170:456–61.

    CAS  PubMed  Google Scholar 

  31. 31.

    American College of O, Gynecologists Committee on Practice B-O, Society for Maternal-Fetal M, Committee AJE. ACOG Practice Bulletin #56: Multiple gestation: complicated twin, triplet, and high-order multifetal pregnancy. Obstet Gynecol. 2004;104:869–83.

    Google Scholar 

  32. 32.

    Blickstein I. Growth aberration in multiple pregnancy. Obstet Gynecol Clin North Am. 2005;32:39–54. viii

    PubMed  Google Scholar 

  33. 33.

    Blondel B, Kogan MD, Alexander GR, Dattani N, Kramer MS, Macfarlane A, et al. The impact of the increasing number of multiple births on the rates of preterm birth and low birthweight: an international study. Am J Public Health. 2002;92:1323–30.

    PubMed  PubMed Central  Google Scholar 

  34. 34.

    Helmerhorst FM, Perquin DA, Donker D, Keirse MJ. Perinatal outcome of singletons and twins after assisted conception: a systematic review of controlled studies. BMJ. 2004;328:261.

    PubMed  PubMed Central  Google Scholar 

  35. 35.

    Kilpatrick SJ, Jackson R, Croughan-Minihane MS. Perinatal mortality in twins and singletons matched for gestational age at delivery at > or = 30 weeks. Am J Obstet Gynecol. 1996;174(1 Pt 1):66–71.

    CAS  PubMed  Google Scholar 

  36. 36.

    Luke B, Keith LG. The contribution of singletons, twins and triplets to low birth weight, infant mortality and handicap in the United States. J Reprod Med. 1992;37:661–6.

    CAS  PubMed  Google Scholar 

  37. 37.

    Lynch A, McDuffie R Jr., Murphy J, Faber K, Orleans M. Preeclampsia in multiple gestation: the role of assisted reproductive technologies. Obstet Gynecol. 2002;99:445–51.

    PubMed  Google Scholar 

  38. 38.

    Schwartz DB, Daoud Y, Zazula P, Goyert G, Bronsteen R, Wright D, et al. Gestational diabetes mellitus: metabolic and blood glucose parameters in singleton versus twin pregnancies. Am J Obstet Gynecol. 1999;181:912–4.

    CAS  PubMed  Google Scholar 

  39. 39.

    Seoud MA, Toner JP, Kruithoff C, Muasher SJ. Outcome of twin, triplet, and quadruplet in vitro fertilization pregnancies: the Norfolk experience. Fertil Steril. 1992;57:825–34.

    CAS  PubMed  Google Scholar 

  40. 40.

    Sibai BM, Hauth J, Caritis S, Lindheimer MD, MacPherson C, Klebanoff M, et al. Hypertensive disorders in twin versus singleton gestations. National Institute of Child Health and Human Development Network of Maternal-Fetal Medicine Units. Am J Obstet Gynecol. 2000;182:938–42.

    CAS  PubMed  Google Scholar 

  41. 41.

    Spellacy WN, Handler A, Ferre CD. A case-control study of 1253 twin pregnancies from a 1982–1987 perinatal data base. Obstet Gynecol. 1990;75:168–71.

    CAS  PubMed  Google Scholar 

  42. 42.

    Weissman A, Drugan A. Glucose tolerance in singleton, twin and triplet pregnancies. J Perinat Med. 2016;44:893–7.

    CAS  PubMed  Google Scholar 

  43. 43.

    Shinagawa S, Suzuki S, Chihara H, Otsubo Y, Takeshita T, Araki T. Maternal basal metabolic rate in twin pregnancy. Gynecol Obstet Invest. 2005;60:145–8.

    PubMed  Google Scholar 

  44. 44.

    Luke B. Nutrition in multiple gestations. Clin Perinatol. 2005;32:403–29. vii

    PubMed  Google Scholar 

  45. 45.

    Luke B. Improving multiple pregnancy outcomes with nutritional interventions. Clin Obstet Gynecol. 2004;47:146–62.

    PubMed  Google Scholar 

  46. 46.

    Fox NS, Roman AS, Saltzman DH, Klauser CK, Rebarber A. Obesity and adverse pregnancy outcomes in twin pregnancies. J Matern Fetal Neonatal Med. 2014;27:355–9.

    CAS  PubMed  Google Scholar 

  47. 47.

    Lucovnik M, Blickstein I, Verdenik I, Steblovnik L, Trojner Bregar A, Tul N. Impact of pre-gravid body mass index and body mass index change on preeclampsia and gestational diabetes in singleton and twin pregnancies. J Matern Fetal Neonatal Med. 2014;27:1901–4.

    CAS  PubMed  Google Scholar 

  48. 48.

    Lucovnik M, Blickstein I, Verdenik I, Trojner-Bregar A, Tul N. Maternal obesity in singleton versus twin gestations: a population-based matched case-control study. J Matern Fetal Neonatal Med. 2015;28:623–5.

    PubMed  Google Scholar 

  49. 49.

    Sung SJ, Lee SM, Kim S, Kim BJ, Park CW, Park JS, et al. The risk of spontaneous preterm birth according to maternal pre-pregnancy body mass index in twin gestations. J Korean Med Sci. 2018;33:e103.

    PubMed  PubMed Central  Google Scholar 

  50. 50.

    Vinturache A, McKeating A, Daly N, Sheehan S, Turner M. Maternal body mass index and the prevalence of spontaneous and elective preterm deliveries in an Irish obstetric population: a retrospective cohort study. BMJ Open. 2017;7:e015258.

    PubMed  PubMed Central  Google Scholar 

  51. 51.

    Aliyu MH, Alio AP, Lynch O, Mbah A, Salihu HM. Maternal pre-gravid body weight and risk for placental abruption among twin pregnancies. J Matern Fetal Neonatal Med. 2009;22:745–50.

    PubMed  Google Scholar 

  52. 52.

    Al-Obaidly S, Parrish J, Murphy KE, Maxwell C. Maternal pre-gravid body mass index and obstetric outcomes in twin gestations. J Perinatol. 2014;34:425–8.

    CAS  PubMed  Google Scholar 

  53. 53.

    Salihu HM, Alio AP, Belogolovkin V, Aliyu MH, Wilson RE, Reddy UM, et al. Prepregnancy obesity and risk of stillbirth in viable twin gestations. Obesity. 2010;18:1795–800.

    PubMed  Google Scholar 

  54. 54.

    Colletto GM, Segre CA. Lack of effect of maternal body mass index on anthropometric characteristics of newborns in twin gestations. Genet Mol Res. 2005;4:47–54.

    PubMed  Google Scholar 

  55. 55.

    Simoes T, Queiros A, Correia L, Rocha T, Dias E, Blickstein I. Gestational diabetes mellitus complicating twin pregnancies. J Perinat Med. 2011;39:437–40.

    PubMed  Google Scholar 

  56. 56.

    Suzuki S, Yoneyama Y, Sawa R, Shin S, Araki T. Clinical usefulness of maternal body mass index in twin pregnancies. Hypertens Pregnancy. 2000;19:273–9.

    CAS  PubMed  Google Scholar 

  57. 57.

    Suzuki S, Inde Y, Miyake H. Maternal obesity as a risk factor for very pre-term delivery in dichorionic twin pregnancies. J Obstet Gynaecol. 2010;30:354–6.

    CAS  PubMed  Google Scholar 

  58. 58.

    Kosinska-Kaczynska K, Szymusik I, Kaczynski B, Wielgos M. Observational study of associations between gestational weight gain and perinatal outcomes in dichorionic twin pregnancies. Int J Gynaecol Obstet. 2017;138:94–9.

    PubMed  Google Scholar 

  59. 59.

    White IR, Royston P, Wood AM. Multiple imputation using chained equations: Issues and guidance for practice. Stat Med. 2011;30:377–99.

    PubMed  Google Scholar 

  60. 60.

    Kramer MS, Platt RW, Wen SW, Joseph KS, Allen A, Abrahamowicz M, et al. A new and improved population-based Canadian reference for birth weight for gestational age. Pediatrics. 2001;108:E35.

    CAS  PubMed  Google Scholar 

  61. 61.

    Altman DG, Bland JM. Interaction revisited: the difference between two estimates. BMJ. 2003;326:219.

    PubMed  PubMed Central  Google Scholar 

  62. 62.

    Lynch AM, Hart JE, Agwu OC, Fisher BM, West NA, Gibbs RS. Association of extremes of prepregnancy BMI with the clinical presentations of preterm birth. Am J Obstet Gynecol. 2014;210:428 e1–9.

    Google Scholar 

  63. 63.

    Han Z, Mulla S, Beyene J, Liao G, McDonald SD, Knowledge Synthesis G. Maternal underweight and the risk of preterm birth and low birth weight: a systematic review and meta-analyses. Int J Epidemiol. 2011;40:65–101.

    PubMed  Google Scholar 

  64. 64.

    Shaw GM, Wise PH, Mayo J, Carmichael SL, Ley C, Lyell DJ, et al. Maternal prepregnancy body mass index and risk of spontaneous preterm birth. Paediatr Perinat Epidemiol. 2014;28:302–11.

    PubMed  Google Scholar 

  65. 65.

    Hoellen F, Hornemann A, Haertel C, Reh A, Rody A, Schneider S, et al. Does maternal underweight prior to conception influence pregnancy risks and outcome? In Vivo. 2014;28:1165–70.

    PubMed  Google Scholar 

  66. 66.

    Sharifzadeh F, Kashanian M, Jouhari S, Sheikhansari N. Relationship between pre-pregnancy maternal BMI with spontaneous preterm delivery and birth weight. J Obstet Gynaecol. 2015;35:354–7.

    CAS  PubMed  Google Scholar 

  67. 67.

    Luke B. The evidence linking maternal nutrition and prematurity. J Perinat Med. 2005;33:500–5.

    CAS  PubMed  Google Scholar 

  68. 68.

    Salihu HM, Mbah AK, Alio AP, Clayton HB, Lynch O. Low pre-pregnancy body mass index and risk of medically indicated versus spontaneous preterm singleton birth. Eur J Obstet Gynecol Reprod Biol. 2009;144:119–23.

    CAS  PubMed  Google Scholar 

  69. 69.

    Siega-Riz AM, Adair LS, Hobel CJ. Maternal underweight status and inadequate rate of weight gain during the third trimester of pregnancy increases the risk of preterm delivery. J Nutr. 1996;126:146–53.

    CAS  PubMed  Google Scholar 

  70. 70.

    Lechtig A, Yarbrough C, Delgado H, Martorell R, Klein RE, Behar M. Effect of moderate maternal malnutrition on the placenta. Am J Obstet Gynecol. 1975;123:191–201.

    CAS  PubMed  Google Scholar 

  71. 71.

    Hediger ML, Luke B, Gonzalez-Quintero VH, Martin D, Nugent C, Witter FR, et al. Fetal growth rates and the very preterm delivery of twins. Am J Obstet Gynecol. 2005;193:1498–507.

    PubMed  Google Scholar 

  72. 72.

    Bukowski R, Gahn D, Denning J, Saade G. Impairment of growth in fetuses destined to deliver preterm. Am J Obstet Gynecol. 2001;185:463–7.

    CAS  PubMed  Google Scholar 

  73. 73.

    Lysikiewicz A, Bracero LA, Tejani N. Sonographically estimated fetal weight percentile as a predictor of preterm delivery. J Matern Fetal Med. 2001;10:44–7.

    CAS  PubMed  Google Scholar 

  74. 74.

    Zhang Q, Ananth CV, Li Z, Smulian JC. Maternal anaemia and preterm birth: a prospective cohort study. Int J Epidemiol. 2009;38:1380–9.

    CAS  PubMed  Google Scholar 

  75. 75.

    Allen LH. Biological mechanisms that might underlie iron’s effects on fetal growth and preterm birth. J Nutr. 2001;131(2S-2):581S–9S.

    CAS  PubMed  Google Scholar 

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This study was funded by the Canadian Institute of Health Research (CIHR) (Grant#146442; Non-communicable Diseases in Obstetrics: Improving Quality of Care and Maternal-infant Outcomes Through an Obstetrical Research Network). Matched funding was provided by the Department of Obstetrics and Gynecology at the University of Toronto, McMaster University, Sunnybrook Research Institute, and Providence St. Joseph’s and St. Michael’s Healthcare. Dr. Sarah D. McDonald is supported by a Tier II Canada Research Chair. Dr. Beth Murray-Davis is supported by a Hamilton Health Sciences Early Career Award. None of the funding agencies had any role in the idea, design, analyses, interpretation of data, writing of the manuscript or decision to submit the manuscript.

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Ram, M., Berger, H., Lipworth, H. et al. The relationship between maternal body mass index and pregnancy outcomes in twin compared with singleton pregnancies. Int J Obes 44, 33–44 (2020).

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