Maternal Hypertension and Mortality in Small for Gestational Age 22- to 29-Week Infants

Abstract

Infants born before 30 weeks gestational age (GA) to mothers with hypertension (HTN) experience lower rates of mortality and serious morbidities when corrected for maternal and infant characteristics. Growth restriction and maternal HTN are often associated. We sought to determine if small for gestational age (SGA) infants have similarly decreased mortality risk when born to mothers with HTN. We identified 6897 singleton SGA, 22 + 0 to 29 + 6 weeks GA infants born between 2008 and 2011, cared for at 578 North American centers in the Vermont Oxford Network. Chromosomal abnormalities and birth defects were excluded. Mortality rates prior to discharge were compared between 4317 HTN and 2580 comparison infants. Logistic regression was used to adjust for birth weight, infant sex, maternal race, inborn/outborn, antenatal steroid exposure, prenatal care, and GA. Small for gestational age HTN infants were older (mean: 26.9 [1.9] vs 26.6 [2.2] weeks; P < .001) and larger (HTN = 584 [159] g vs 562 [156] g; P < .001) than comparison infants. Death prior to discharge occurred in 29% of HTN and 43% of comparison infants. Univariate analyses revealed lower mortality for HTN infants (odds ratio [OR] = 0.54, 95% confidence interval [CI]: 0.48-0.60). After adjustment, mortality remained lower when compared to non-HTN infants (OR = 0.60, 95% CI: 0.52-0.69). Extremely preterm SGA infants face high rates of mortality. Although maternal HTN is associated with SGA, SGA infants born to mothers with HTN have decreased risk of mortality compared to non-HTN SGA infants, prior to and after adjustment for antenatal and maternal characteristics. This may reflect detrimental physiologic effects associated with alternative mechanisms for fetal growth restriction and is important for parental counseling.

Keywords

preeclampsia hypertension infant premature mortality growth restriction small for gestational age

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References

Bernstein

Horbar

Badger

Ohlsson

Golan

. Morbidity and mortality among very-low-birth-weight neonates with intrauterine growth restriction. The Vermont Oxford Network. Am J Obstet Gynecol. 2000;182(1 pt 1):198–206.

Baschat

Hecher

. Fetal growth restriction due to placental disease. Semin Perinatol. 2004;28(1):67–80.

Ott

. Intrauterine growth retardation and preterm delivery. Am J Obstet Gynecol. 1993;168(6 pt 1):1710–1715; discussion 5-7.

Ghidini

. Idiopathic fetal growth restriction: a pathophysiologic approach. Obstet Gynecol Surv. 1996;51(6):376–382.

Matthews

MacDorman

Thoma

. Infant Mortality Statistics From the 2013 Period Linked Birth/Infant Death Data Set. Natl Vital Stat Rep. 2015;64(9):1–30.

Chiswick

. Intrauterine growth retardation. Br Med J (Clin Res Ed). 1985;291(6499):845–848.

Kristensen

Salihu

Keith

Kirby

Fowler

Pass

. SGA subtypes and mortality risk among singleton births. Early Hum Dev. 2007;83(2):99–105.

Weiler

Tong

Palmer

. Is fetal growth restriction associated with a more severe maternal phenotype in the setting of early onset pre-eclampsia? A retrospective study. PLoS One. 2011;6(10):e26937.

Odegard

Vatten

Nilsen

Salvesen

Austgulen

. Preeclampsia and fetal growth. Obstet Gynecol. 2000;96(6):950–955.

10.

Jain

. Effect of pregnancy-induced and chronic hypertension on pregnancy outcome. J Perinatol. 1997;17(6):425–427.

11.

Hutcheon

Lisonkova

Joseph

. Epidemiology of pre-eclampsia and the other hypertensive disorders of pregnancy. Best Pract Res Clin Obstet Gynaecol. 2011;25(4):391–403.

12.

McBride

Bernstein

Badger

Horbar

Soll

. The effect of maternal hypertension on mortality in infants 22, 29 weeks gestation. Pregnancy Hypertens. 2015;5(4):362–366.

13.

The Vermont-Oxford Trials Network: very low birth weight outcomes for 1990. Investigators of the Vermont-Oxford Trials Network Database Project. Pediatrics. 1993;91(3):540–545.

14.

Vermont Oxford Network: Manual of Operations: Release 12.0. Burlington: Vermont Oxford Network; 2007.

15.

Horbar

. The Vermont-Oxford Neonatal Network: integrating research and clinical practice to improve the quality of medical care. Semin Perinatol. 1995;19(2):124–131.

16.

Horbar

Leahy

. An assessment of data quality in the Vermont-Oxford Trials Network database. Control Clin Trials. 1995;16(1):51–61.

17.

Martin

Kochanek

Strobino

Guyer

MacDorman

. Annual summary of vital statistics—2003. Pediatrics. 2005;115(3):619–634.

18.

Tyson

Younes

Verter

Wright

. Viability, morbidity, and resource use among newborns of 501- to 800-g birth weight. National institute of child health and human development neonatal research network. JAMA. 1996;276(20):1645–1651.

19.

Vohr

Wright

Dusick

. Center differences and outcomes of extremely low birth weight infants. Pediatrics. 2004;113(4):781–789.

20.

Zeitlin

El Ayoubi

Jarreau

. Impact of fetal growth restriction on mortality and morbidity in a very preterm birth cohort. J Pediatr. 2010;157(5):733–739.e1.

21.

Garite

Clark

Thorp

. Intrauterine growth restriction increases morbidity and mortality among premature neonates. Am J Obstetr Gynecol. 2004;191(2):481–487.

22.

Chen

Wen

Smith

Yang

Walker

. Pregnancy-induced hypertension is associated with lower infant mortality in preterm singletons. BJOG. 2006;113(5):544–551.

23.

McCowan

Roberts

Dekker

. Risk factors for small-for-gestational-age infants by customised birthweight centiles: data from an international prospective cohort study. BJOG. 2010;117(13):1599–1607.

24.

Bernstein

Meyer

Capeless

. “Fetal growth charts”: comparison of cross-sectional ultrasound examinations with birth weight. J Matern Fetal Med. 1994;3(4):182–186.

25.

Bernstein

Mohs

Rucquoi

Badger

. Case for hybrid “fetal growth curves”: a population-based estimation of normal fetal size across gestational age. J Matern Fetal Med. 1996;5(3):124–127.

26.

Fry

Bernstein

Badger

. Comparison of fetal growth estimates based on birth weight and ultrasound references. J Matern Fetal Neonatal Med. 2002;12(4):247–252.

27.

Zaw

Gagnon

da Silva

. The risks of adverse neonatal outcome among preterm small for gestational age infants according to neonatal versus fetal growth standards. Pediatrics. 2003;111(6 pt 1):1273–1277.

28.

Lackman

Capewell

Richardson

daSilva

Gagnon

. The risks of spontaneous preterm delivery and perinatal mortality in relation to size at birth according to fetal versus neonatal growth standards. Am J Obstet Gynecol. 2001;184(5):946–953.