Last reviewed: 2 Feb 2021
Last updated: 27 Jan 2021



History and exam

Key diagnostic factors

  • maternal last menstrual period (LMP)
  • distance from the maternal superior pubis to the uterine fundus
  • infant physical maturity score
  • infant neuromuscular maturity score
  • combined physical/neuromuscular score <10: gestational age <28 weeks
  • combined physical/neuromuscular score 11 to 19: gestational age 29 to 31 weeks
  • combined physical/neuromuscular score 20 to 24: gestational age 32 to 33 weeks
  • combined physical/neuromuscular score 25 to 33: gestational age 34 to 36 weeks

Other diagnostic factors

  • infant birth weight (appropriate for gestational age infants)

Risk factors

  • spontaneous preterm labor
  • intrauterine infection
  • preterm premature rupture of membranes (PPROM)
  • pre-eclampsia/pregnancy-induced hypertension
  • abruption/antepartum hemorrhage
  • abnormal amniotic fluid volume
  • severe bacterial vaginosis
  • multiple gestation
  • previous preterm birth
  • fetal abnormality
  • cervical incompetence/uterine abnormality
  • gestational diabetes
  • maternal surgery during pregnancy
  • chronic maternal illness
  • short interpregnancy time interval
  • drug use (tobacco, cocaine, heroin)
  • maternal pregnancy body mass index <19 or >35
  • stress/depression
  • nonwhite race

Diagnostic investigations

Treatment algorithm


Associate Professor

Section of Neonatology and Department of Pediatrics

Baylor College of Medicine




MP declares that he has no competing interests.

Dr Mohan Pammi would like to gratefully acknowledge Dr Stephen Welty and Dr James L. Wynn, previous contributors to this topic. 


SW and JLW declare that they have no competing interests.

Peer reviewersVIEW ALL

Consultant Obstetrician and Gynaecologist

Gloucestershire Royal Hospital




IB declares that he has no competing interests.

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