Preterm birth risk at high altitude in Peru

Published:September 04, 2014DOI:


      High altitude has been implicated in a variety of adverse pregnancy outcomes including preeclampsia and stillbirth. Smaller studies show conflicting data on the association between high altitude and preterm birth (PTB). The objective of this study was to assess the association between altitude and PTB.

      Study Design

      A retrospective cohort study was performed using data from the Perinatal Information System, which includes deliveries from 43 hospitals in Peru from 2000 through 2010. Altitude was classified into the following categories: low (0-1999 m), moderate (2000-2900 m), and high (3000-4340 m). The primary outcome was PTB (delivery <37 weeks). Secondary outcomes were cesarean delivery and small for gestational age (SGA). Deliveries less than 23 weeks are not included in the database. χ2 analyses were performed to compare categorical variables, and a logistic regression was used to calculate the odds ratios and control for confounders. Clustering by hospital was accounted for using generalized estimating equations.


      A total of 550,166 women were included (68% low, 15% moderate, 17% high altitude). The overall PTB rate was 5.9%, with no difference in the PTB rate among the 3 altitudes (5.6%, 6.2%, 6.8%, P = .13). There was a significant difference in cesarean rates (28.0%, 26.6%, 20.6%, P < .001) with a 34% decreased risk at high vs low altitude adjusted for confounders (adjusted odds ratio, 0.66; 95% confidence interval, 0.51–0.85). There was a difference in SGA (3.3%, 3.6%, 5.0%, P = .02) with a 51% increased risk at high vs low altitude adjusted for confounders (adjusted odds ratio, 1.49; 95% confidence interval, 1.14–1.93).


      High altitude is not associated with PTB. At high altitude, the cesarean rate was reduced and the SGA rate was increased.

      Key words

      To read this article in full you will need to make a payment

      Purchase one-time access:

      Academic & Personal: 24 hour online accessCorporate R&D Professionals: 24 hour online access
      One-time access price info
      • For academic or personal research use, select 'Academic and Personal'
      • For corporate R&D use, select 'Corporate R&D Professionals'


      Subscribe to American Journal of Obstetrics & Gynecology
      Already a print subscriber? Claim online access
      Already an online subscriber? Sign in
      Institutional Access: Sign in to ScienceDirect


        • Hill K.
        • Choi Y.
        Neonatal mortality in the developing world.
        Demogr Res. 2006; 14: 429-452
      1. Neonatal and perinatal mortality. Available at: Accessed Dec. 1, 2013.

      2. World Health Organization. Department of Making Pregnancy Safer, Annual Report 2007. Available at: Accessed Sept. 16, 2014.

      3. World Health Organization. Peru: country profile. Available at: Accessed Dec. 1, 2013.

      4. Millennium development goals. Available at: Accessed Dec. 1, 2013.

        • Villar J.
        • Valladares E.
        • Wojdyla D.
        • et al.
        Caesarean delivery rates and pregnancy outcomes: the 2005 WHO global survey on maternal and perinatal health in Latin America.
        Lancet. 2006; 367: 1819-1829
        • Bloom S.L.
        • Yost N.P.
        • McIntire D.D.
        • Leveno K.J.
        Recurrence of preterm birth in singleton and twin pregnancies.
        Obstet Gynecol. 2001; 98: 379-385
        • Esplin M.S.
        • O’Brien E.
        • Fraser A.
        • et al.
        Estimating recurrence of spontaneous preterm delivery.
        Obstet Gynecol. 2008; 112: 516-523
        • Iams J.D.
        • Goldenberg R.L.
        • Meis P.J.
        • et al.
        The length of the cervix and the risk of spontaneous premature delivery. Eunice Kennedy Shriver National Institute of Child Health and Human Development Maternal Fetal Medicine Unit Network.
        N Engl J Med. 1996; 334: 567
        • Zhu B.P.
        • Rolfs R.T.
        • Nangle B.E.
        • Horan J.M.
        Effect of the interval between pregnancies on perinatal outcomes.
        N Engl J Med. 1999; 340: 589-594
        • Conde-Agudelo A.
        • Rosas-Bermudez A.
        • Kafury-Goeta A.C.
        Birth spacing and risk of adverse perinatal outcomes: a meta-analysis.
        JAMA. 2006; 295: 1809-1823
        • Blackmore-Prince C.
        • Kieke Jr., B.
        • Kugaraj K.A.
        • et al.
        Racial differences in the patterns of singleton preterm delivery in the 1988 National Maternal and Infant Health Survey.
        Matern Child Health J. 1999; 3: 189-197
        • Knottnerus J.A.
        • Delgado L.R.
        • Knipschild P.G.
        • Essed G.G.
        • Smits F.
        Haematologic parameters and pregnancy outcome. A prospective cohort study in the third trimester.
        J Clin Epidemiol. 1990; 43: 461-466
        • Rasmussen K.
        Is there a causal relationship between iron deficiency or iron-deficiency anemia and weight at birth, length of gestation and perinatal mortality?.
        J Nutr. 2001; 131: 590S-601S
        • Gonzales G.F.
        • Steenland K.
        • Tapia V.
        Maternal hemoglobin level and fetal outcome at low and high altitudes.
        Am J Physiol Regul Integr Comp Physiol. 2009; 297: R1477-R1485
        • Lichty J.A.
        • Ting R.Y.
        • Bruns P.D.
        • Dyar E.
        Studies of babies born at high altitude.
        AMA J Dis Child. 1957; 93: 666-669
        • Jensen G.M.
        • Moore L.G.
        The effect of high altitude and other risk factors on birthweight: independent or interactive effects?.
        Am J Public Health. 1997; 87: 1003-1007
        • Lorna G. Moore
        Human genetic adaptation to high altitude.
        High Alt Med Biol. 2001; 2: 257-259
        • Zamudio S.
        • Wu Y.
        • Ietta F.
        • et al.
        Human placental hypoxia-inducible factor-1α expression correlates with clinical outcomes in chronic hypoxia in vivo.
        Am J Path. 2007; 170: 2171-2179
        • Julian C.G.
        • Wilson M.J.
        • Lopez M.
        • et al.
        Augmented uterine artery blood flow and oxygen delivery protect Andeans from altitude-associated reductions in fetal growth.
        Am J Physiol Regul Integr Comp Physiol. 2009; 296: R1564-R1575
        • Unger A.
        • Weiser J.K.
        • McCullough R.E.
        • Keefer A.
        • Grindlay Moore L
        Altitude, low birth weight, and infant mortality in Colorado.
        JAMA. 1988; 259: 3427-3432
        • Zamudio S.
        The placenta at high altitude.
        High Alt Med Biol. 2003; 4: 171-191
        • Gonzales G.F.
        • Tapia V.
        • Carrillo C.E.
        Stillbirth rates in Peruvian populations at high altitude.
        Int J Gynecol Obstet. 2008; 100: 221-227
        • Zamudio S.
        High-altitude hypoxia and preeclampsia.
        Front Biosci. 2007; 12: 2967-2977
        • Ali K.Z.
        • Ali M.E.
        • Khalid M.E.M.
        High altitude and spontaneous preterm birth.
        Int J Gynaecol Obstet. 1996; 54: 11-15
        • Naeye R.L.
        Pregnancy hypertension, placental evidence of low uteroplacental blood flow and spontaneous preterm delivery.
        Hum Pathol. 1989; 20: 441-444
        • Gonzales G.F.
        • Tapia V.
        Birth weight charts for gestational age in 63,620 healthy infants born in Peruvian public hospitals at low and at high altitude.
        Acta Paediatr. 2009; 98: 454-458
        • Kung-Yee Liang
        • Scott Zeger
        Longitudinal data analysis using generalized linear models.
        Biometrika. 1986; 73: 13-22
      5. NCHS Data Brief, number 39. Available at: . Accessed Aug. 29, 2013.

      6. Births: Preliminary Data for 2011. Available at: . Accessed Aug. 29, 2013.

        • Hamilton B.E.
        • Hoyert D.L.
        • Martin J.A.
        • Strobino D.M.
        • Guyer B.
        Annual summary of vital statistics: 2010-2011.
        Pediatrics. 2013; 131: 548-558
        • Gonzales G.F.
        Peruvian contributions to the study on human reproduction at high altitude: from the chronicles of the Spanish conquest to the present.
        Respir Physiol Neurobiol. 2007; 158: 172-179