Beta We are building this new website to better deliver information. Learn more about this site.
Pregnancy Care Guidelines

23 Risk of preterm birth

While there are many known and unknown causes of preterm birth, women identified as being at risk may benefit from advice about risk and protective factors.

23.1 Background

Preterm birth is defined as birth before 37 completed weeks of pregnancy (WHO 2012). Sub-categories of preterm birth are based on weeks of gestational age: early preterm (<34 weeks), very preterm (28 to <32 weeks) and extremely preterm (<28 weeks). This section is concerned with spontaneous preterm birth as opposed to planned preterm birth.

23.1.1 Incidence of preterm birth

In Australia in 2014 (AIHW 2016):

  • overall, 8.6% of babies were born preterm, with most of these births occurring at gestational ages between 32 and 36 completed weeks
  • the average gestational age for all preterm births was 33.3 weeks
  • babies whose mothers smoked during pregnancy were more likely to be born preterm (13%) than those whose mothers did not smoke during pregnancy (8%).
  • other characteristics associated with increased likelihood of preterm birth included:
    • babies born in multiple births: 63% of twins and all (100%) of other multiples (triplets and higher) were preterm, compared with 7% of singleton babies
    • babies born to mothers usually residing in more remote areas: 13% in very remote areas compared with 8% in major cities
    • babies of younger (<20 years) and older (≥40 years) mothers: 11% and 12% were preterm, compared with 8% of babies with mothers aged 20–39 years.

Nationally in 2014, approximately 14% of babies of Indigenous mothers were born preterm, compared with 8% of babies of non-Indigenous mothers (AIHW 2016); similar rates were found in an earlier West Australian study (14.8 and 7.6%) (Langridge et al 2010). However, a study in a Melbourne hospital found no significant difference in risk of preterm birth between Indigenous and non-Indigenous babies and mothers (Indigenous babies aOR 1.19, 95%CI 0.77 to 1.87, Indigenous mothers aOR 0.97 95%CI 0.52 to 1.80) (Whish-Wilson et al 2016).

23.1.2 Risks associated with preterm birth

Preterm birth is associated with perinatal mortality, long-term neurological disability (including cerebral palsy), admission to neonatal intensive care, severe morbidity in the first weeks of life, prolonged hospital stay after birth, readmission to hospital in the first year of life and increased risk of chronic lung disease (WHO 2012). Preterm birth can have a serious emotional impact on the family. In Australia in 2014 (AIHW 2016):

  • preterm babies were more likely to be admitted to a special care nursery or neonatal intensive care unit (72%) than babies born at term (10%) or post-term (13%)
  • spontaneous preterm birth accounted for 14% of all perinatal deaths and one third (33%) of perinatal deaths of babies of Indigenous mothers.

23.2 Identifying women at increased risk of giving birth preterm

A range of risk and protective factors influence the likelihood of preterm birth. While many risk factors are not modifiable during a woman’s current pregnancy, addressing modifiable risk factors may reduce risk of preterm birth. It should also be noted that many women who experience preterm birth have no risk factors.

23.2.1 Significant risk factors

There is a significant association between preterm birth and:

  • social disadvantage (OR 1.27, 95%CI: 1.16 to 1.39) (Ncube et al 2016) and lower levels of maternal education (RR 1.48; 95%CI 1.29 to 1.69) (Ruiz et al 2015)
  • previous preterm birth (absolute recurrence rate among women with a singleton pregnancy and previous preterm singleton birth 20%, 95% CI 19.9–20.6) (Kazemier et al 2014)
  • pre-existing (p=0.002) (Kock et al 2010) or gestational diabetes (AIHW 2010)
  • current urogenital infections: eg chlamydia [OR 1.60; 90%CI 1.01 to 2.5] (John Hopkins Study Team 1989), bacterial vaginosis [OR 1.85; 95%CI 1.62 to 2.11] (Flynn et al 1999)
  • alcohol consumption (OR 1.34; 95%CI 1.28 to 1.41) (Aliyu et al 2010), in a dose-response fashion (Sokol et al 2007; Patra et al 2011)
  • smoking at the first antenatal visit (aOR 1.42, 95%CI 1.27 to 1.59) (Bickerstaff et al 2012) and active smoking during pregnancy (aOR 1.53, 95%CI 1.05 to 2.21) (Fantuzzi et al 2007), with risk further increased among women smoking more than 10 cigarettes a day compared to those smoking 1–9 cigarettes per day (aOR 1.69 vs 1.54) (Fantuzzi et al 2007).

23.2.2 Other factors

Systematic reviews of RCTs found:

  • women who were overweight and obese who participated in aerobic exercise for 30–60 minutes three to seven times per week had a lower risk of preterm birth <37weeks (RR 0.62, 95% CI 0.41 to 0.95) compared to controls (Magro-Malosso et al 2016)
  • no clear difference in risk of preterm birth <37 weeks with treatment of periodontal disease (RR 0.87; 95%CI 0.70 to 1.10; low quality evidence) (Iheozor-Ejiofor et al 2017).

Systematic reviews of observational studies show the following associations with preterm birth:

  • country of origin/ethnicity: odds of very preterm birth among East African immigrants were higher than among Australian-born women (aOR 1.55, 95%CI 1.27 to 1.90) (Belihu et al 2016) and higher among African American women than among Caucasian women (pooled OR 2.0; 95%CI 1.8 to 2.2), with no significant association for Asian or Hispanic ethnicity (Schaaf et al 2013)
  • weight: risk was increased among women who were obese and gained more than the IOM recommendations (aOR 1.54; 95% CI 1.09 to 2.16) (Faucher et al 2016)
  • emotional health and wellbeing: increased risk was associated with low social support compared to high social support (OR 1.22, 95%CI 0.84 to 1.76); stress (OR 1.52, 95%CI 1.18, to 1.97) (Hetherington et al 2015); untreated depression (OR 1.56; 95%CI 1.25 to 1.94) (Jarde et al 2016) and anxiety (RR 1.50, 95%CI 1.33 to 1.70) (Ding et al 2014), (OR 1.70, 95%CI 1.33 to 2.18) (Rose et al 2016) but not with maternal personality traits (Chatzi et al 2013)
  • exposure to antidepressants: risk was increased among women exposed to antidepressants during pregnancy compared to women with depression but without antidepressant exposure (OR 1.17, 95%CI 1.10 to 1.25) (Eke et al 2016), (RR 2.85, 95%CI 2.00 to 4.07) (Huang et al 2014a); and risk was significantly increased with exposure in the third trimester (aOR 1.96, 95%CI 1.62 to 2.38) but not in the first trimester (aOR 1.16, 95%CI 0.92 to 1.45) (Huybrechts et al 2014)
  • environmental factors: increased risk was associated with high environmental temperature (Beltran et al 2013), especially heat stress (Carolan-Olah & Frankowska 2014); exposure to passive smoke in any place (OR 1.20, 95%CI 1.07 to 1.34) or at home (OR 1.16, 95%CI 1.04 to 1.30) (Cui et al 2016); risk associated with exposure to fine particulate matter was unclear due to significant heterogeneity between studies (Sun et al 2015)
  • pre-existing conditions: risk of preterm birth was increased among women with hepatitis C (OR 1.62, 95%CI 1.48 to 1.76, P < 0.001) (Huang et al 2015), human papilloma virus (OR 2.12, 95%CI 1.51 to 2.98, P<0.001) (Huang et al 2014c), hypothyroidism (OR 1.19, 95%CI 1.12 to 1.26; P < 0.00001) and hyperthyroidism (OR, 1.24, 95%, CI 1.17- 1.31; P < .00001) (Sheehan et al 2015) but not hepatitis B (OR 1.12, 95%CI 0.94 to 1.33) (Huang et al 2014b).
  • lifestyle factors: incidence of preterm birth (4.5% vs 4.4%; RR 1.01, 95%CI 0.68 to 1.50) was similar among women in the normal BMI category undertaking aerobic exercise during pregnancy and controls (Di Mascio et al 2016); risk was increased among women with serum vitamin D levels lower than 50 nmol/L (OR 1.29, 95%CI 1.16 to 1.45) (Qin et al 2016); and there was no clear or statistically significant relationship between preterm birth and shift work (van Melick et al 2014), multivitamin use (Johnston et al 2016) or influenza vaccination during pregnancy (Fell et al 2015)
  • history of gynaecological procedures: risk was increased among women with a history of dilatation and curettage (D&C) (OR 1.29, 95% CI 1.17 to 1.42) or multiple D&Cs (OR 1.74, 95%CI 1.10 to 2.76) (Lemmers et al 2016); surgically induced termination of pregnancy (OR 1.52, 95%CI 1.08 to 2.16); surgically managed miscarriage (OR 1.19, 95%CI 1.03 to 1.37) (Saccone et al 2016); loop electrosurgical excision procedure compared to women with no history of cervical dysplasia (pooled RR 1.61, 95%CI 1.35 to 1.92) but not when compared to women with a history of cervical dysplasia but no cervical excision (pooled RR 1.08, 95%CI 0.88 to 1.33) (Conner et al 2014); and treatment for cervical intraepithelial neoplasia before (OR 1.4, 95%CI 0.85 to 2.3) or during pregnancy (OR 6.5, 95%CI 1.1 to 37) (Danhof et al 2015).


  • Consensus-based
  • XXI

When women are identified as being at risk of giving birth preterm based on the presence of risk factors, provide advice about modifiable risk factors.

Approved by NHMRC in October 2017; expires October 2022

23.3 Prediction and prevention

23.3.1 Cervical length measurement

Systematic reviews of randomised controlled trials found:

  • among women with threatened preterm labour, those whose cervical length had been measured had a significantly lower rate of preterm birth <37 weeks (22.1 vs 34.5%; RR 0.64; 95%CI 0.44 to 0.94; 3 studies); management of women with a cervical length lower than the study threshold differed between studies (further observation in one study and administering tocolytics and antenatal corticosteroids in the other studies) (Berghella et al 2016)
  • no difference in incidence of maternal and neonatal infection among women with preterm premature rupture of the membranes who did or did not undergo transvaginal ultrasound of cervical length measurement (Berghella et al 2013).

Systematic reviews of observational studies were heterogeneous in terms of population and cut-off thresholds used but suggest that preterm birth is better predicted at 14 to 20 weeks rather than later, using a shorter cervical length as the cut-off threshold (Crane & Hutchens 2008; Domin et al 2010; Honest et al 2012; Conde-Agudelo & Romero 2015).

The evidence on cervical length measurement is emerging and will be reviewed as part of the next update of these Guidelines (anticipated for release in late 2019).

23.3.2 Holistic preventive strategies

Systematic reviews that evaluated holistic models of care and their effect on preterm birth found:

  • a significant effect in reducing risk of preterm birth among women receiving midwifery-led care compared to other models of care for childbearing women and their infants (average RR 0.76, 95%CI 0.64 to 0.91; n=13,238; 8 studies; high quality) (Sandall et al 2016)
  • no significant difference among:
    • women receiving group antenatal care compared to those receiving standard care (RR 0.87, 95%CI 0.70 to 1.09; 11 studies) (Carter et al 2016) and (RR 0.75, 95%CI 0.57 to 1.00; 3 3 studies; n=1,888, moderate quality) (Catling et al 2015)
    • women randomised to specialist preterm birth programs compared to those receiving standard care (RR 0.92, 95%CI 0.76 to 1.12; 15 RCTs) (Fernandez Turienzo et al 2016)
    • low risk women receiving a reduced number of antenatal visits (RR 1.02, 95%CI 0.94 to 1.11; 7 studies, n=53,661, moderate quality) (Dowswell et al 2015)
    • women receiving additional social support compared to those receiving standard care (RR 0.92, 95%CI 0.83 to 1.01; 11 RCTs; n=10,429) (Hodnett et al 2010), including adolescent women (RR 0.67; 95%CI 0.42 to 1.05; 4 studies; n=684) (Sukhato et al 2015)
    • women receiving telephone support during pregnancy compared to women receiving routine care or other support (RR 0.91, 95%CI 0.77 to 1.08, 4 RCTs; n=3,992) (Lavender et al 2013)
    • women in preterm labour using relaxation techniques compared to those not using relaxation techniques (RR 0.95; 95%CI 0.57 to 1.59; 11 RCTs; n=833) (Khianman et al 2012)
  • successful approaches to increasing access to antenatal care and reducing preterm birth among Aboriginal and Torres Strait Islander women include community-based collaborative antenatal care and community-based support (Rumbold & Cunningham 2008) and partnership between Aboriginal grandmothers, Aboriginal Health Officers, midwives and existing antenatal care services (Bertilone & McEvoy 2015).

23.4 Discussing risk of giving birth preterm

When risk of preterm birth is increased, modifiable risk factors should be addressed (Freak-Poli et al 2009; Kiran et al 2010; Carter et al 2011). Based on the evidence discussed in Section 23.2, discussion with women at risk of preterm birth can include the benefits of:

  • having adequate social and emotional support
  • quitting tobacco smoking and avoiding exposure to passive smoke
  • not drinking alcohol during pregnancy
  • having tests for urogenital infections
  • participating in regular exercise, particularly if they are overweight or obese.

Women can also be advised that risk is not reduced by supplementing with Vitamins C or E (Rumbold et al 2015a; Rumbold et al 2015b) or probiotics (Othman et al 2007; Hauth et al 2010).

A Cochrane review found no evidence to support or refute bed rest for prevention of preterm birth (Sosa et al 2015). A subsequent cohort study found that, among women at high risk of preterm birth, activity restriction was associated with increased risk of preterm birth (Levin et al 2017).

23.5 Practice summary: risk of preterm birth


A woman has identified risk factors for giving birth preterm


  • Midwife
  • GP
  • obstetrician
  • Aboriginal and Torres Strait Islander Health Practitioner
  • Aboriginal and Torres Strait Islander Health Worker
  • multicultural health worker


Discuss lifestyle factors associated with preterm birth
  • Explain that smoking during pregnancy makes it more likely that the baby will be born preterm and also causes other serious risks to the pregnancy.
  • Explain that not drinking alcohol during pregnancy is the safest option.
  • Offer testing for urogenital infection if the woman has risk factors for preterm birth. If results are positive, consider counselling, contact tracing, partner testing and treatment, and repeat testing.
Discuss protective factors
  • Explain that moderate physical activity during pregnancy has a range of health benefits, particularly for women who are overweight or obese.
Take a holistic approach
  • Provide information on relevant community supports (eg smoking cessation programs, drug and alcohol services, physical activity groups).
  • Consider whether a woman may be at increased risk if she has recently arrived from a country with a high prevalence of preterm birth.
  • Provide social and emotional support and access to continuity of carer, where possible


  • AIHW (2010) Diabetes in Pregnancy: It’s Impact on Australian Women and their Babies. Diabetes series no. 14. Cat. no. CVD 52. Canberra: Australian Institute of Health and Welfare.
  • AIHW (2016) Australia’s mothers and babies 2014—in brief. Canberra: Australian Institute of Health and Welfare.
  • Aliyu MH, Lynch O, Belogolovkin V et al (2010) Maternal alcohol use and medically indicated vs. spontaneous preterm birth outcomes: a population-based study. Eur J Public Health 20(5): 582–87.
  • Belihu FB, Davey MA, Small R (2016) Perinatal health outcomes of East African immigrant populations in Victoria, Australia: a population based study. BMC Pregnancy Childbirth 16: 86.
  • Beltran AJ, Wu J, Laurent O (2013) Associations of meteorology with adverse pregnancy outcomes: a systematic review of preeclampsia, preterm birth and birth weight. Int J Environ Res Public Health 11(1): 91-172.
  • Berghella V, Baxter JK, Hendrix NW (2013) Cervical assessment by ultrasound for preventing preterm delivery. Cochrane Database Syst Rev(1): CD007235.
  • Berghella V, Palacio M, Ness A et al (2016) Cervical length screening for prevention of preterm birth in singleton pregnancy with threatened preterm labor: systematic review and meta-analysis of randomized controlled trials using individual patient-level data. Ultrasound Obstet Gynecol.
  • Bertilone C & McEvoy S (2015) Success in Closing the Gap: favourable neonatal outcomes in a metropolitan Aboriginal Maternity Group Practice Program. Med J Aust 203(6): 262 e1-7.
  • Bickerstaff M, Beckmann M, Gibbons K et al (2012) Recent cessation of smoking and its effect on pregnancy outcomes. Aust N Z J Obstet Gynaecol52(1): 54–58.
  • Carolan-Olah M & Frankowska D (2014) High environmental temperature and preterm birth: a review of the evidence. Midwifery 30(1): 50-9.
  • Carter EB, Temming LA, Akin J et al (2016) Group Prenatal Care Compared With Traditional Prenatal Care: A Systematic Review and Meta-analysis. Obstet Gynecol 128(3): 551-61.
  • Carter MF, Fowler S, Holden A et al (2011) The late preterm birth rate and its association with comorbidities in a population-based study. Am J Perinatol 28(9): 703-7.
  • Catling CJ, Medley N, Foureur M et al (2015) Group versus conventional antenatal care for women. Cochrane Database Syst Rev(2): CD007622.
  • Chatzi L, Koutra K, Vassilaki M et al (2013) Maternal personality traits and risk of preterm birth and fetal growth restriction. Eur Psychiatry 28(4): 213-8.
  • Conde-Agudelo A & Romero R (2015) Predictive accuracy of changes in transvaginal sonographic cervical length over time for preterm birth: a systematic review and metaanalysis. Am J Obstet Gynecol 213(6): 789-801.
  • Conner SN, Frey HA, Cahill AG et al (2014) Loop electrosurgical excision procedure and risk of preterm birth: a systematic review and meta-analysis. Obstet Gynecol 123(4): 752-61.
  • Crane JM & Hutchens D (2008) Transvaginal sonographic measurement of cervical length to predict preterm birth in asymptomatic women at increased risk: a systematic review. Ultrasound Obstet Gynecol 31(5): 579-87.
  • Cui H, Gong TT, Liu CX et al (2016) Associations between Passive Maternal Smoking during Pregnancy and Preterm Birth: Evidence from a Meta-Analysis of Observational Studies. PLoS One 11(1): e0147848.
  • Danhof NA, Kamphuis EI, Limpens J et al (2015) The risk of preterm birth of treated versus untreated cervical intraepithelial neoplasia (CIN): a systematic review and meta-analysis. Eur J Obstet Gynecol Reprod Biol 188: 24-33.
  • Di Mascio D, Magro-Malosso ER, Saccone G et al (2016) Exercise during pregnancy in normal-weight women and risk of preterm birth: a systematic review and meta-analysis of randomized controlled trials. Am J Obstet Gynecol 215(5): 561-71.
  • Ding XX, Wu YL, Xu SJ et al (2014) Maternal anxiety during pregnancy and adverse birth outcomes: a systematic review and meta-analysis of prospective cohort studies. J Affect Disord 159: 103-10.
  • Domin CM, Smith EJ, Terplan M (2010) Transvaginal ultrasonographic measurement of cervical length as a predictor of preterm birth: a systematic review with meta-analysis. Ultrasound Q 26(4): 241-8.
  • Dowswell T, Carroli G, Duley L et al (2015) Alternative versus standard packages of antenatal care for low-risk pregnancy. Cochrane Database Syst Rev(7): CD000934.
  • Eke AC, Saccone G, Berghella V (2016) Selective serotonin reuptake inhibitor (SSRI) use during pregnancy and risk of preterm birth: a systematic review and meta-analysis. BJOG 123(12): 1900-07.
  • Fantuzzi G, Aggazzotti G, Righi E et al (2007) Preterm delivery and exposure to active and passive smoking during pregnancy: a case-control study from Italy. Paediatr Perinat Epidemiol 21(3): 194–200.
  • Faucher MA, Hastings-Tolsma M, Song JJ et al (2016) Gestational weight gain and preterm birth in obese women: a systematic review and meta-analysis. BJOG 123(2): 199-206.
  • Fell DB, Platt RW, Lanes A et al (2015) Fetal death and preterm birth associated with maternal influenza vaccination: systematic review. BJOG 122(1): 17-26.
  • Fernandez Turienzo C, Sandall J, Peacock JL (2016) Models of antenatal care to reduce and prevent preterm birth: a systematic review and meta-analysis. BMJ Open 6(1): e009044.
  • Flynn CA, Helwig AL, Meurer LN (1999) Bacterial vaginosis in pregnancy and the risk of prematurity: a meta-analysis. J Fam Pract 48(11): 885-92.
  • Freak-Poli R, Chan A, Tucker G et al (2009) Previous abortion and risk of pre-term birth: a population study. J Matern Fetal Neonatal Med 22(1): 1-7.
  • Hauth JC, Clifton RG, Roberts JM et al (2010) Vitamin C and E supplementation to prevent spontaneous preterm birth: a randomized controlled trial. Obstet Gynecol 116(3): 653-8.
  • Hetherington E, Doktorchik C, Premji SS et al (2015) Preterm Birth and Social Support during Pregnancy: a Systematic Review and Meta-Analysis. Paediatr Perinat Epidemiol 29(6): 523-35.
  • Hodnett ED, Fredericks S, Weston J (2010) Support during pregnancy for women at increased risk of low birthweight babies. Cochrane Database Syst Rev(6): CD000198.
  • Honest H, Hyde CJ, Khan KS (2012) Prediction of spontaneous preterm birth: no good test for predicting a spontaneous preterm birth. Curr Opin Obstet Gynecol 24(6): 422-33.
  • Huang H, Coleman S, Bridge JA et al (2014a) A meta-analysis of the relationship between antidepressant use in pregnancy and the risk of preterm birth and low birth weight. Gen Hosp Psychiatry 36(1): 13-8.
  • Huang QT, Wei SS, Zhong M et al (2014b) Chronic hepatitis B infection and risk of preterm labor: a meta-analysis of observational studies. J Clin Virol 61(1): 3-8.
  • Huang QT, Zhong M, Gao YF et al (2014c) Can HPV vaccine have other health benefits more than cancer prevention? A systematic review of association between cervical HPV infection and preterm birth. J Clin Virol 61(3): 321-8.
  • Huang QT, Huang Q, Zhong M et al (2015) Chronic hepatitis C virus infection is associated with increased risk of preterm birth: a meta-analysis of observational studies. J Viral Hepat 22(12): 1033-42.
  • Huybrechts KF, Sanghani RS, Avorn J et al (2014) Preterm birth and antidepressant medication use during pregnancy: a systematic review and meta-analysis. PLoS One 9(3): e92778.
  • Iheozor-Ejiofor Z, Middleton P, Esposito M et al (2017) Treating periodontal disease for preventing adverse birth outcomes in pregnant women. Cochrane Database Syst Rev 6: CD005297.
  • Jarde A, Morais M, Kingston D et al (2016) Neonatal Outcomes in Women With Untreated Antenatal Depression Compared With Women Without Depression: A Systematic Review and Meta-analysis. JAMA Psychiatry 73(8): 826-37.
  • John Hopkins Study Team (1989) Association of Chlamydia trachomatis and Mycoplasma hominis with intrauterine growth retardation and preterm delivery. The John Hopkins Study of Cervicitis and Adverse Pregnancy Outcome. Am J Epidemiol 129(6): 1247-57.
  • Johnston EO, Sharma AJ, Abe K (2016) Association Between Maternal Multivitamin Use and Preterm Birth in 24 States, Pregnancy Risk Assessment Monitoring System, 2009-2010. Matern Child Health J 20(9): 1825-34.
  • Kazemier BM, Buijs PE, Mignini L et al (2014) Impact of obstetric history on the risk of spontaneous preterm birth in singleton and multiple pregnancies: a systematic review. BJOG 121(10): 1197-208; discussion 209.
  • Khianman B, Pattanittum P, Thinkhamrop J et al (2012) Relaxation therapy for preventing and treating preterm labour. Cochrane Database Syst Rev(8): CD007426.
  • Kiran P, Ajay B, Neena G et al (2010) Predictive value of various risk factors for preterm labor. J Obstet Gynecol India 60(2): 141–45.
  • Kock K, Kock F, Klein K et al (2010) Diabetes mellitus and the risk of preterm birth with regard to the risk of spontaneous preterm birth. J Matern Fetal Neonatal Med 23(9): 1004-8.
  • Langridge AT, Nassar N, Li J et al (2010) Social and racial inequalities in preterm births in Western Australia, 1984 to 2006. Paediatr Perinat Epidemiol24(4): 352-62.
  • Lavender T, Richens Y, Milan SJ et al (2013) Telephone support for women during pregnancy and the first six weeks postpartum. Cochrane Database Syst Rev(7): CD009338.
  • Lemmers M, Verschoor MA, Hooker AB et al (2016) Dilatation and curettage increases the risk of subsequent preterm birth: a systematic review and meta-analysis. Hum Reprod 31(1): 34-45.
  • Levin HI, Sciscione A, Ananth CV et al (2017) Activity restriction and risk of preterm delivery. J Matern Fetal Neonatal Med: 1-5.
  • Magro-Malosso ER, Saccone G, Di Mascio D et al (2016) Exercise during pregnancy and risk of preterm birth in overweight and obese women: a systematic review and meta-analysis of randomized controlled trials. Acta Obstet Gynecol Scand.
  • Ncube CN, Enquobahrie DA, Albert SM et al (2016) Association of neighborhood context with offspring risk of preterm birth and low birthweight: A systematic review and meta-analysis of population-based studies. Soc Sci Med 153: 156-64.
  • Othman M, Neilson JP, Alfirevic Z (2007) Probiotics for preventing preterm labour. Cochrane Database Syst Rev(1): CD005941.
  • Patra J, Bakker R, Irving H et al (2011) Dose-response relationship between alcohol consumption before and during pregnancy and the risks of low birthweight, preterm birth and small for gestational age (SGA)-a systematic review and meta-analyses. BJOG 118(12): 1411-21.
  • Qin LL, Lu FG, Yang SH et al (2016) Does Maternal Vitamin D Deficiency Increase the Risk of Preterm Birth: A Meta-Analysis of Observational Studies. Nutrients 8(5).
  • Rose MS, Pana G, Premji S (2016) Prenatal Maternal Anxiety as a Risk Factor for Preterm Birth and the Effects of Heterogeneity on This Relationship: A Systematic Review and Meta-Analysis. Biomed Res Int 2016: 8312158.
  • Ruiz M, Goldblatt P, Morrison J et al (2015) Mother’s education and the risk of preterm and small for gestational age birth: a DRIVERS meta-analysis of 12 European cohorts. J Epidemiol Community Health 69(9): 826-33.
  • Rumbold A, Ota E, Hori H et al (2015a) Vitamin E supplementation in pregnancy. Cochrane Database Syst Rev(9): CD004069.
  • Rumbold A, Ota E, Nagata C et al (2015b) Vitamin C supplementation in pregnancy. Cochrane Database Syst Rev(9): CD004072.
  • Rumbold AR & Cunningham J (2008) A review of the impact of antenatal care for Australian Indigenous women and attempts to strengthen these services. Matern Child Health J 12(1): 83-100.
  • Saccone G, Perriera L, Berghella V (2016) Prior uterine evacuation of pregnancy as independent risk factor for preterm birth: a systematic review and metaanalysis. Am J Obstet Gynecol 214(5): 572-91.
  • Sandall J, Soltani H, Gates S et al (2016) Midwife-led continuity models versus other models of care for childbearing women. Cochrane Database Syst Rev4: CD004667.
  • Schaaf JM, Liem SM, Mol BW et al (2013) Ethnic and racial disparities in the risk of preterm birth: a systematic review and meta-analysis. Am J Perinatol 30(6): 433-50.
  • Sheehan PM, Nankervis A, Araujo Junior E et al (2015) Maternal Thyroid Disease and Preterm Birth: Systematic Review and Meta-Analysis. J Clin Endocrinol Metab 100(11): 4325-31.
  • Sokol RJ, Janisse JJ, Louis JM et al (2007) Extreme prematurity: an alcohol-related birth effect. Alcohol Clin Exp Res 31(6): 1031–37.
  • Sosa CG, Althabe F, Belizan JM et al (2015) Bed rest in singleton pregnancies for preventing preterm birth. Cochrane Database Syst Rev(3): CD003581.
  • Sukhato K, Wongrathanandha C, Thakkinstian A et al (2015) Efficacy of additional psychosocial intervention in reducing low birth weight and preterm birth in teenage pregnancy: A systematic review and meta-analysis. J Adolesc 44: 106-16.
  • Sun X, Luo X, Zhao C et al (2015) The association between fine particulate matter exposure during pregnancy and preterm birth: a meta-analysis. BMC Pregnancy Childbirth 15: 300.
  • van Melick MJ, van Beukering MD, Mol BW et al (2014) Shift work, long working hours and preterm birth: a systematic review and meta-analysis. Int Arch Occup Environ Health 87(8): 835-49.
  • Whish-Wilson T, Tacey M, McCarthy E et al (2016) Indigenous birth outcomes at a Victorian urban hospital, a retrospective 5-year cohort study 2010-2014. Aust N Z J Obstet Gynaecol 56(3): 238-44.
  • WHO (2012) Born Too Soon. The Global Action Report on Preterm Birth. Geneva: World Health Organization.
Last updated: 
21 November 2018