Overview :

A variety of risk factors have been implicated in identifying pregnant women who are at risk for preterm delivery. A woman with one or more risk factors may benefit from more aggressive monitoring and early interventions.

Preterm delivery: delivery prior to end of the 37th week of gestation from last menstrual period

Risk factors include:

(1) age - younger (< 18) or older (> 40)

(2) alcohol abuse

(3) anemia, including hemoglobinopathy

(4) Black race

(5) bleeding in first or second trimester

(6) cervical insufficiency

(7) congenital anomalies in fetus

(8) diabetes mellitus

(9) drug abuse

(10) high altitude

(11) history of hypertension

(12) history of previous preterm delivery

(13) history of spontaneous abortion

(14) hyperemesis

(15) hypertension during pregnancy, including pre-eclampsia

(16) hypotension during pregnancy

(17) inadequate antenatal care

(18) infection, including bacterial vaginosis, bacteriuria, rubella, CMV, STD

(19) isoimmunization

(20) low education

(21) low socioeconomic status

(22) low weight increase during pregnancy

(23) multiple gestation (twins, triplets, etc)

(24) oligohydramnios, polyhydramnios

(25) placenta previa or abruptio placentae

(26) poor nutrition

(27) primipara or multipara with more than 4 deliveries

(28) short interval between pregnancies (less than 1 year)

(29) smoking

(30) spontaneous premature rupture of membranes

(31) toxins in environment

(32) underweight or overweight

(33) unmarried

(34) uterine anomaly

(35) uterine contractions

Some risk factors carry more significance than others. For example, the presence of a previous preterm delivery or spontaneous abortion is associated with a significant risk for recurrence.

Adams MM, Elam-Evans LD, et al. Rates and factors associated with recurrence of preterm delivery. JAMA. 2000; 283: 1591-1596

American College of Obstetrics and Gynecology (ACOG) Committee on Obstetric Practice. Bacterial vaginosis screening for prevention of preterm delivery. Committee Opinion. February, 1998, Number 198.

Carey JC, Klebanoff MA., et al. Metronidazole to prevent preterm delivery in pregnant women with asymptomatic bacterial vaginosis. N Engl J Med. 2000; 342: 534-540.

Carlini L, Somigliana E, et al. Risk factors for spontaneous preterm birth: A Northern Italian multicenter case-control study. Gynecol Obstet Invest. 2002; 53: 174-180.

Di Stefano L, Carta G, et al. Preterm delivery: predictive value of cervico-vaginal fetal fibronectin. Clin Exp Obstet & Gynecol. 1999; 26: 187-189

Goldenberg RL, Iams JD, et al. The Preterm Prediction Study: Sequential cervical length and fetal fibronectin testing for the prediction of spontaneous preterm birth. Am J Obstet Gynecol. 2000; 182: 636-643.

Iams JD, Newman RB, et al. Frequency of uterine contractions and the risk of spontaneous preterm delivery. N Engl J Med. 2002; 346: 250-255.

Institute of Medicine. Preventing Low Birthweight. National Academy Press (books.nap.edu). 1985, pages 4-14.

Lam CM, Wong SF. Risk factors for preterm delivery in women with placenta praevia and antepartum haemorrhage: retrospective study. Hong Kong Medical Journal. 2002; 8: 163-166.

Mercer BM, Goldenberg RL, et al. The Preterm Prediction Study: Effect of gestational age and cause of preterm birth on subsequent obstetric outcome. Am J Obstet Gynecol. 1999; 181: 1216-1221.