Causes & risk factors

Preterm birth occurs for a variety of reasons [6,7]. The majority of preterm births happen spontaneously. Experts have identified several factors which may increase the risk of preterm birth.

Some risk factors are “modifiable,” meaning they can be changed to help reduce the risk, while others cannot be changed. However, in about 50% of cases no cause for the baby born too early can be identified.

Medical conditions

Pregnancy historyFor example a mother having born a preterm baby before is at higher risk for another preterm birth within the next pregnancy.
Multiple pregnancyThe most common complication of a multiple pregnancy is preterm birth.
Assisted technologyReproductive treatments are linked to multiple pregnancies and hence to preterm birth.
Uterine or cervical abnormalitiesFor example, a short cervix might favour preterm birth: during pregnancy, the cervix gradually softens, decreases in length as the baby grows to prepare birth. As consequence the cervix might begin to open too soon.
Infections and chronic conditionsInfections of the uterus (e.g. through urinary tract infections or bacterial vaginosis , an imbalance of the bacteria that are normally present in the vagina) or non-communicable diseases such as for example diabetes, high blood pressure, asthma or renal and cardiac disorders.
Pregnancy complicationsGestational diabetes and pre-eclampsia are two examples of typical pregnancy complications. Due to preeclampsia women may need to give birth early to avoid serious health problems for both, the mother and the baby.
Genetic influeceSpecific foetal and maternal genotypes (a person’s type of genes for a particular inheritable trait) are associated with the risk of preterm delivery.

Modifiable lifestyle risk factors

Lifestyle patternsFactors like an unbalanced diet, underweight or overweight (obesity), smoking, alcohol or drug consumption, a high stress level and exposure to environmental pollutants.
HealthcareNo or late antenatal care might inhibit identification and therapy measures at an early stage.

Demographic factors

AgeParticularly young (< 17) or older women (> 35) are at higher risk for preterm birth.
Sociodemographic determinantsSocioeconomic disadvantages (low education level, low income, few social support) might play a role for preterm birth.
EthnicallyThere are higher preterm birth rates reported in black than white women [7, US data].


[6] Goldenberg R, Culhane J, Iams JD, Romero R. Epidemiology and causes of preterm birth. 2008. The Lancet. 371(9606): 75–84.

[7] Keller M, Saugstad O, van Steenbrugge G, Mader S, Thiele N. European Foundation for the Care of Newborn Infants. Caring for Tomorrow. EFCNI White Paper on Maternal and Newborn Health and Aftercare Services.Munich 2011.