Risk and Protective Factors for Preterm Birth
A number of factors can affect the health of pregnant people and their babies. These factors can sometimes increase or decrease the risk of preterm birth or other complications.
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"Risk Factors" are generally thought to be those that increase a person's risk for an outcome like preterm birth.
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"Protective Factors" are generally thought to decrease a person's risk for an outcome like preterm birth.
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HELLO EGG founders and partners recently published data on patterns of preterm birth and related risk and protective factors in the journal JAMA Open.
Click on this link to read this study entitled:
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You can also read related commentary by clicking on this link:
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While our discussion of risk and protection is largely driven by this recent article and related research from the group and others over the past decade, there are other risk and protective factors that are not discussed in detail here and are not measured by the HELLO EGG Healthy Pregnancy Questionnaire (HPQ). It is critical that you discuss your health with your prenatal provider and develop a plan together for addressing risk and having your healthiest pregnancy possible.
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Information provided through this site and HELLO EGG is for information purposes only and should not be interpreted as health advice.
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Risk Factors
Some risk factors for preterm birth and related complications are addressable through interventions and some are more helpful for understanding risk but do not have specific known interventions. For example, managing hypertension and stopping smoking are examples of factors with clear interventions, while a factor like years of education does not have a clear intervention attached to it but may be associated with some increased risk.
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It's also important to note that some social factors affect pregnancy health including racial identity and associated experiences of racism and discrimination as well as income and place of birth, which have strong influences on the type of services and resources available to a person. You can read more about social determinants of health and "mommy blaming" HERE.
Below are a list of risk factors for preterm birth where a substantial amount of research has been done showing that each factor is associated with increased risk across populations. There are many additional risk factors not outlined here. More information about preterm birth and risk factors can be found on the websites of the CDC and the US National Institute of Health.​
It is critical that all pregnant women and expectant mothers be seeing a prenatal provider who can help them better understand their pregnancy health and risk. Prenatal providers are able to work with women and expectant mothers to develop a personalized care plan that is specific to their needs.
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You can search for a provider and other resources in your community on the EGG HP website HERE.
EGG HP discussion of risk factors for preterm birth are divided into topic grouping starting with factors that have been shown to reliably predict risk for preterm birth in the first trimester. This discussion aligns with how we have developed the EGG HP Healthy Pregnancy Questionnaire (the HPQ) which currently focuses on first trimester risk. You can read more about the HPQ HERE. We also present information about risk factors that may emerge later in pregnancy so that women and expectant mothers who want this information have it.
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SPECIFIC FIRST TRIMESTER RISK FACTORS FOR PRETERM BIRTH (more detail for each of these groupings and factors can be accessed by clicking each of the title groupings below).
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​Pregnancy History
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Nulliparity (no previous live birth)
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previous preterm birth
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previous cesarean section
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short or long time since last pregnancy (less than 18-months or 60 months (5 years) or more)
Social and Demographic Factors​​
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expected age at delivery less than 18-years of age
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expected age at delivery more than 34-years of age
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less than 12 years of education
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12 years of education only
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race/ethnicity
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public insurance for prenatal care
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Mother born in United States
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Health and Diagnoses Present Before Pregnancy -
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Weight, Diabetes, and Hypertension
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high body mass index (before pregnancy)
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low body mass index (before pregnancy)
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diabetes (diagnosed before pregnancy)
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hypertension (diagnosed before pregnancy)
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Other Conditions
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sickle cell anemia
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mental health condition (e.g. anxiety, depression)
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Exposures
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smoking, vaping, or ingesting nicotine or cannabis
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other drug or alcohol use
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ADDITIONAL SECOND AND THIRD TRIMESTER RISKS FOR PRETERM BIRTH (you can read more about these risk factors and related interventions HERE).
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All of the first trimester risk factors listed above are also associated with increased risk in the second trimester. Additional risks include, for example,
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Conditions
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diabetes (diagnosed during pregnancy)
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hypertension (diagnosed during pregnancy)
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anemia (non-sickle cell)
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asthma
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dislipidemia (abnormally high or low cholesterol, low density lipoproteins (LDLs), high density lipoproteins (HDLs), triglycerides)
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autoimmune disorder (for example, rheumatoid arthritis, psoriasis/psoriatic arthritis, multiple sclerosis, systemic lupus erythematosus, other)
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malignancy/ cancer
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infection during pregnancy (COVID-19 or another infection like the flu, a urinary tract infection, or a sexually transmitted infection)
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Wellness and Care
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< 3 prenatal care visits
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As noted above, there are many additional risk factors not outlined here. More information about preterm birth and risk factors can be found on the websites of the CDC and the US National Institute of Health.
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​Read More -
More information about risks and related interventions