- Steven Ringer, MD, PhD
Steven Ringer, MD, PhD
- Associate Professor of Pediatrics
- Geisel School of Medicine
Postterm infants are born at a gestational age (GA) greater than 42 weeks or 294 days from the first day of the last menstrual period. Postterm infants have higher rates of morbidity and mortality than term infants.
The epidemiology, clinical manifestations, neonatal management, and outcome of postterm infants will be reviewed here.
The incidence of postterm births varies with different patient populations and is dependent on a number of factors, such as the percentage of primigravid women, and local practice patterns regarding the rates of scheduled cesarean delivery and routine labor induction. In the United States, postterm births have decreased from 11 percent of all births in 1990 to 5.5 percent of births in 2009 . In a population-based Norwegian study, the reported incidence of postterm deliveries was 7.6 percent from 1989 to 1999 .
In the United States, the decline in postterm births is the result of the widespread practice of inducing labor once pregnancies reach 41 weeks, a specific effort to avoid the delivery of postterm infants. (See "Postterm pregnancy", section on 'Management'.)
The etiology of most postterm pregnancies is unknown. Risk factors for postterm births are discussed separately and include the following (see "Postterm pregnancy", section on 'Etiology and risk factors'):
- Martin JA, Hamilton BE, Ventural SJ, et al. Births:Final Data for 2009. Natl Vital Stat Rep 2011; 60:1. http://www.cdc.gov/nchs/data/nvsr/nvsr60/nvsr60_01.pdf (Accessed on November 08, 2011).
- Nakling J, Backe B. Pregnancy risk increases from 41 weeks of gestation. Acta Obstet Gynecol Scand 2006; 85:663.
- O'Sullivan J, Iyer S, Taylor N, Cheetham T. Congenital adrenal hyperplasia due to 21-hydroxylase deficiency is associated with a prolonged gestational age. Arch Dis Child 2007; 92:690.
- Mori R, Ota E, Middleton P, et al. Zinc supplementation for improving pregnancy and infant outcome. Cochrane Database Syst Rev 2012; :CD000230.
- Mannino F. Neonatal complications of postterm gestation. J Reprod Med 1988; 33:271.
- Vorherr H. Placental insufficiency in relation to postterm pregnancy and fetal postmaturity. Evaluation of fetoplacental function; management of the postterm gravida. Am J Obstet Gynecol 1975; 123:67.
- Shime J, Librach CL, Gare DJ, Cook CJ. The influence of prolonged pregnancy on infant development at one and two years of age: a prospective controlled study. Am J Obstet Gynecol 1986; 154:341.
- Spellacy WN, Miller S, Winegar A, Peterson PQ. Macrosomia--maternal characteristics and infant complications. Obstet Gynecol 1985; 66:158.
- Rosen MG, Dickinson JC. Management of post-term pregnancy. N Engl J Med 1992; 326:1628.
- Lu Y, Zhang J, Lu X, et al. Secular trends of macrosomia in southeast China, 1994-2005. BMC Public Health 2011; 11:818.
- McLean FH, Boyd ME, Usher RH, Kramer MS. Postterm infants: too big or too small? Am J Obstet Gynecol 1991; 164:619.
- Divon MY, Haglund B, Nisell H, et al. Fetal and neonatal mortality in the postterm pregnancy: the impact of gestational age and fetal growth restriction. Am J Obstet Gynecol 1998; 178:726.
- CLIFFORD SH. Postmaturity, with placental dysfunction; clinical syndrome and pathologic findings. J Pediatr 1954; 44:1.
- Jovanovic-Peterson L. What is so bad about a prolonged pregnancy? J Am Coll Nutr 1991; 10:1.
- Feldman GB. Prospective risk of stillbirth. Obstet Gynecol 1992; 79:547.
- De Los Santos-Garate AM, Villa-Guillen M, Villanueva-García D, et al. Perinatal morbidity and mortality in late-term and post-term pregnancy. NEOSANO perinatal network's experience in Mexico. J Perinatol 2011; 31:789.
- Morken NH, Klungsøyr K, Skjaerven R. Perinatal mortality by gestational week and size at birth in singleton pregnancies at and beyond term: a nationwide population-based cohort study. BMC Pregnancy Childbirth 2014; 14:172.
- Bruckner TA, Cheng YW, Caughey AB. Increased neonatal mortality among normal-weight births beyond 41 weeks of gestation in California. Am J Obstet Gynecol 2008; 199:421.e1.
- Hannah ME. Postterm pregnancy: should all women have labour induced? A review of the literature. Fetal and Maternal Medicine Review 1993; 5:3.
- Hilder L, Sairam S, Thilaganathan B. Influence of parity on fetal mortality in prolonged pregnancy. Eur J Obstet Gynecol Reprod Biol 2007; 132:167.
- Haavaldsen C, Sarfraz AA, Samuelsen SO, Eskild A. The impact of maternal age on fetal death: does length of gestation matter? Am J Obstet Gynecol 2010; 203:554.e1.
- Eden RD, Seifert LS, Winegar A, Spellacy WN. Perinatal characteristics of uncomplicated postdate pregnancies. Obstet Gynecol 1987; 69:296.
- Heimstad R, Romundstad PR, Eik-Nes SH, Salvesen KA. Outcomes of pregnancy beyond 37 weeks of gestation. Obstet Gynecol 2006; 108:500.
- Hernández-Díaz S, Van Marter LJ, Werler MM, et al. Risk factors for persistent pulmonary hypertension of the newborn. Pediatrics 2007; 120:e272.
- Seo IS, Gillim SE, Mirkin LD. Hyaline membranes in postmature infants. Pediatr Pathol 1990; 10:539.
- Moster D, Wilcox AJ, Vollset SE, et al. Cerebral palsy among term and postterm births. JAMA 2010; 304:976.
- Ehrenstein V, Pedersen L, Holsteen V, et al. Postterm delivery and risk for epilepsy in childhood. Pediatrics 2007; 119:e554.
- Field TM, Dabiri C, Hallock N, Shuman HH. Developmental effects of prolonged pregnancy and the postmaturity syndrome. J Pediatr 1977; 90:836.
- El Marroun H, Zeegers M, Steegers EA, et al. Post-term birth and the risk of behavioural and emotional problems in early childhood. Int J Epidemiol 2012; 41:773.
- Seikku L, Gissler M, Andersson S, et al. Asphyxia, Neurologic Morbidity, and Perinatal Mortality in Early-Term and Postterm Birth. Pediatrics 2016; 137.
- Ting RV, Wang MH, Scott TF. The dysmature infant. Associated factors and outcome at 7 years of age. J Pediatr 1977; 90:943.
- Figlio DN, Guryan J, Karbownik K, Roth J. Long-term Cognitive and Health Outcomes of School-Aged Children Who Were Born Late-Term vs Full-Term. JAMA Pediatr 2016; 170:758.