Study of the Relationship between Body Mass Index and Birth Weight, Spontaneous Preterm Labor and Maternal Anemia in Shahid Akbarabadi Hospital, Tehran, 2008

Document Type : Original Article


1 . Assistant Professor of Obstetrics and Gynecology, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran.

2 Professor of Obstetrics and Gynecology, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran.

3 Resident of Obstetrics and Gynecology, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran.


Introduction: Recent studies have reported that high and low maternal pre-pregnancy weight is accompanied with adverse pregnancy outcome including preterm labor and low birth weight or macrosomia. The purpose of the present study is to find the relationship between maternal pre-pregnancy body mass index (BMI) and spontaneous preterm labor and birth weight.
Methods: This cohort study was performed on 576 pregnant women who referred to Shahid Akbarabadi hospital in Tehran in year 2008. 396 women finally finished the study. Maternal BMI was determined at the first prenatal visit (between 8-12 weeks of pregnancy) then the women were followed up to delivery. Gestational age at the time of delivery and neonatal weight were recorded and their results were investigated in four groups: underweight (BMI<20 kg/m2), normal weight (BMI=20-24.9 kg/m2), over weight (BMI=25-29.9 kg/m2) and obese (BMI=30-40 kg/m2). Data were analyzed using SPSS software (version 15), T-test, ANOVA, Chi-square and Pearson correlation tests and linear regression model. P less than 0.05 was considered statistically significant.
Results: The women in all BMI groups had no significant differences according to age, height, history of abortion and occupation. 21 women (5.3%) were underweight, 198 women (50%) had normal weight, 117 women (29.5%) were overweight and 60 (15.2%) were obese. No case of morbidly obese was seen.
Obesity had positive correlation with higher gestational age at the time of delivery (r=0.213, p=0.015) and more birth weight (r=0.361, p=0.008). In contrast, low birth weight had correlation with low maternal weight (r=0.157, p=0.041). Macrosomia was more in obese women (p=0.022) and BMI had positive correlation with macrosomia (r=0.224, p=0.034). Preterm labor showed a negative correlation with BMI (r=-0.124, p=0.004) and preterm labor was seen more in women with lower BMI (p=0.035).
Conclusion: Overweight women was more high risk for macrosomia, while, low birth weight (LBW) and spontaneous preterm labor were seen more in underweight mothers.


1. Carey C, Gibbs RS. Preterm labor and post-term delivery. In: Gibbs RS, Karlan BY, Haney AF, Nygaard IE.
Danforth’s obstetrics and gynecology. 10th ed. Philadelphia:Lippincott Williams & Wilkins;2008:165-85.
2. 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 Repord Biol 2009 Jun;144(2):119-23.
3. Borkowski W, Mielniczuk H. [Preterm delivery in relation to combined pregnancy weight gain and pre
pregnancy body mass] [Article in Polish]. Przegl Epidemiol 2007;61(3):577-84.
4. Honest H, Bachmann LM, Ngai C, Gupta JK, Kleijnen J, Khan KS. The accuracy of maternal anthropometry
measurements as predictors for spontaneous preterm birth a systematic review. Eur J Obstet Gynecol Repord Biol 2005
Mar 1;119(1):11-20.
5. Schieve LA, Cogswell ME, Scanlon KS, Perry E, Ferre C, Blackmore- Prince C, et al. Prepregnancy body mass
index and pregnancy weight gain: associations with preterm delivery. The NMIHS Collaborative Study Group.
Obstet Gynecol 2000 Aug;96(2):194-200.
6. Naeye RL. Maternal body weight and pregnancy outcome. Am J Clin Nutr 1990 Aug;52(2):273-9.
7. Sebire NJ, Jolly M, Harris J, Regan L, Robinson S. Is maternal underweight really a risk factor for adverse
pregnancy outcome? A population-based study in London. BJOG 2001 Jan;108(1):61-6.
8. Bhattacharya S, Campbell DM, Liston WA, Bhattacharya S. Effect of Body Mass Index on pregnancy outcome
in nulliparous women delivering singleton babies. BMC Public Health 2007 Jul 24;7:168.
9. Wise LA, Palmer JR, Heffner LJ, Rosenberg L. Prepregnancy body size, gestational weight gain, and risk of
preterm birth in African-American women. Epidemiology 2010 Mar;21(2):243-52.
10. Sahu MT, Agarwal A, Das V, Pandey A. Impact of maternal body mass index on obstetric outcome. J Obstet
Gynaecol Res 2007 Oct;33(5):655-9.
11. Khashan AS, Kenny LC. The effects of maternal body mass index on pregnancy outcome. Eur J Epidemiol
12. Rosenberg AG, Wang X, Xing H, Chen C, Chen D, Guang W, et al. Low preconception body mass index is
associated with birth outcome in a prospective cohort of Chinese women. J Nutr 2003 Nov;133(11):3449-55.
13. Sebire NJ, Jolly M, Harris JP, Wadsworth J, Joffe M, Beard RW, Regan L, Robinson S. Maternal obesity and pregnancy
outcome: a study of 287, 213 pregnancies in London. Int J Obes Relat Metab Disord 2001 Aug;25(8):1175-82.
14. Cedergren M. Effects of gestational weight gain and body mass index on obstetric outcome in Sweden. Int J
Gynaecol Obstet 2006 Jun;93(3):269-74.
15. Cedergren MI. Optimal gestational weight gain for body mass index categories. Obstet Gynecol 2007 Oct;110(4):359-64.
16. Nohr EA, Vaeth M, Baker JL, Sorensen Tla, Olsen J, Rasmussen KM. Combined associations of pre pregnancy body
mass index and gestational weight gain with the outcome of pregnancy. Am J Clin Nutr 2008 Jun;87(6):1750-9.
17. Nohr EA, Bech BH, Vaeth M, Rasmussen KM, Henriksen TB, Olsen J. Obesity, gestational weight gain and
preterm birth: a study within the Danish National Birth Cohort. Paediatr Perinat Epidemiol 2007 Jan;21(1):5-14.
18. Cnattingius S, Bergstrom R, Lipworth L, Kramer MS. Prepregnancy weight and the risk of adverse pregnancy
outcome. N Engl J Med 1998 Jan 15;338(3):147-52.
19. Reddy UM, Laughon SK, Sun L, Troendle J, Willinger M, Zhang J. Prepregnancy risk factors for antepartum
still birth in the United States. Obstet Gynecol 2010 Nov;116(5):1119-26.
20. Allen LH. Biological mechanisms that might underlie iron’s effects on fetal growth and preterm birth. J Nutr
2001 Feb;131(2S-2):581S-589S.
21. 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 Jan;126(1):146-53.
22. Ehrenberg HM, Dierker L, Milluzzi C, Mercer BM. Low maternal weight, failure to thrive in pregnancy, and
adverse pregnancy outcomes. AM J Obstet Gynecol 2003 Dec;189(6):1726-30.
23. Doherty DA, Magann EF, Francis J, Morrison JC, Newnham JP. Pre-pregnancy body mass index and pregnancy
outcome. Int J Gynaecol Obstet 2006 Dec;95(3):242-7.
24. Hendler I, Goldenberg RL, Mercer BM, Imas JD, Meis PJ, Moavad AH, et al. The preterm Prediction Study:
association between maternal body mass index and spontaneous and indicated preterm birth. Am J Obstet
Gynecol 2005 Mar;192(3):882-6.
25. Crane JM, White J, Murphy P, Burrage L, Hutchens D. The effect of gestational weight gain by body mass
index on maternal and neonatal outcomes. J Obstet Gynaecol Can 2009 Jan;31(1):28-35.
26. Oken E, Kleinman KP, Belfort MB, Hammitt JK, Gillman MW. Associations of gestational weight gain with
short- and longer term maternal and child health outcomes. Am J Epidemiol 2009 Jul 15;170(2):173-80.
27. Dickey RP, Xiong X, Gee RE, Pridjian G. Effect of maternal height and weight on risk of preterm birth in
singleton and twin births resulting from in vitro fertilization: a retrospective cohort study using the Society for
Assisted Reproductive Technology Clinic Outcome Reporting System. Fertil Steril 2012 Feb;97(2):349-54.
28. Mandal D, Manda S, Rakshi A, Dey RP, Biswas SC, Banerjee A. Maternal obesity and pregnancy outcome: a
prospective analysis. J Assoc Physicians India 2011 ASug;59:486-9.
29. Liabsuetrakul T; Southern Soil-Transmitted Helminths and Maternal Health Working Group. Is international or
Asian criteria-based body mass index associated with maternal anaemia, low birthweight, and preterm births
among Thai population? An observational study. J Health Popul Nutr 2011 Jun;29(3):218-28.