Early rapid growth, early birth: Accelerated fetal growth and spontaneous late preterm birth

Michelle Lampl, Juan Pedro Kusanovic, Offer Erez, Jimmy Espinoza, Francesca Gotsch, Luis Goncalves, Sonia Hassan, Ricardo Gomez, Jyh Kae Nien, Edward A. Frongillo, Roberto Romero

Research output: Contribution to journalArticlepeer-review

24 Scopus citations


The past two decades in the United States have seen a 24% rise in spontaneous late preterm delivery (34-36 weeks) of unknown etiology. This study tested the hypothesis that fetal growth was identical prior to spontaneous preterm (n = 221, median gestational age at birth 35.6 weeks) and term (n = 3706) birth among pregnancies followed longitudinally in Santiago, Chile. The hypothesis was not supported: Preterm-delivered fetuses were significantly larger than their term-delivered peers by mid-second trimester in estimated fetal weight, head, limb, and abdominal dimensions, and they followed different growth trajectories. Piecewise regression assessed time-specific differences in growth rates at 4-week intervals from 16 weeks. Estimated fetal weight and abdominal circumference growth rates slowed at 20 weeks among the preterm-delivered, only to match and/or exceed their term-delivered peers at 24-28 weeks. After an abrupt growth rate decline at 28 weeks, fetuses delivered preterm did so at greater population-specific sex and age-adjusted birth weight percentiles than their peers from uncomplicated pregnancies (P < 0.01). Growth rates predicted birth timing: one standard score of estimated fetal weight increased the odds ratio for late preterm birth from 2.8 prior to 23 weeks, to 3.6 (95% confidence interval, 1.82-7.11, P < 0.05) between 23 and 27 weeks. After 27 weeks, increasing size was protective (OR: 0.56, 95% confidence interval, 0.38-0.82, P = 0.003). These data document, for the first time, a distinctive fetal growth pattern across gestation preceding spontaneous late preterm birth, identify the importance of mid-gestation for alterations in fetal growth, and add perspective on human fetal biological variability.

Original languageEnglish
Pages (from-to)141-150
Number of pages10
JournalAmerican Journal of Human Biology
Issue number2
StatePublished - 11 May 2009
Externally publishedYes

ASJC Scopus subject areas

  • Anatomy
  • Ecology, Evolution, Behavior and Systematics
  • Anthropology
  • Genetics


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