Preterm birth, defined as delivery before 37 weeks of gestation, presents a major global health challenge. It affects approximately 13 million infants each year and significantly contributes to neonatal morbidity and mortality [1].

The incidence of preterm birth varies widely across populations and regions, with disparities linked to maternal characteristics, socio-economic status, and environmental conditions [2]. Understanding these risk factors is essential for developing effective prevention strategies and improving health outcomes for both mothers and infants.

Preterm birth can be influenced by a variety of risk factors, many of which are unique to each individual. Understanding these factors is crucial for prevention and management strategies.

A mother’s health history plays a crucial role in preterm birth risk. Women who have previously delivered preterm or experienced preterm labor face a higher likelihood of future preterm births [3]. Certain health conditions, including diabetes, high blood pressure, and heart disease, also elevate the risk, even when well managed [4, 5]. Additionally, maternal mental health conditions, such as depression and anxiety, have been identified as key contributors to preterm labor [2].

Pre-existing maternal health conditions further impact preterm birth risk. Hypertension and infections account for a significant proportion of cases, with studies attributing 22% of preterm births to hypertension and 17% to infections [1]. Chronic diseases and inadequate prenatal care can worsen these risks [1].

Maternal age significantly affects preterm birth risk. Women younger than 20 or older than 40 face higher risks, particularly during their first pregnancy. Teenage mothers often struggle with inadequate nutrition and lack of early prenatal care, increasing their likelihood of preterm delivery [4, 6, 7]. Older mothers frequently contend with pre-existing health conditions or prior obstetric complications, further raising their risk [4].

Genetics also plays a role in preterm birth. Variations in genes associated with inflammation, immune response, and uterine contractility can make women more susceptible to preterm labor. Research indicates that women with a family history of preterm births are more likely to experience them, highlighting a hereditary component to this risk [8].

Several maternal conditions and characteristics increase the risk of preterm birth, including:

• Cervical Incompetence: An inability of the cervix to maintain a pregnancy to term significantly raises the likelihood of extremely preterm and very preterm births [9].

   

• Previous Preterm Births: A history of prior preterm births is one of the strongest predictors of future preterm deliveries. Women with a history of preterm deliveries face a much higher recurrence risk [10].

   

• MultiplePregnancies: Carrying more than one fetus (e.g., twins or triplets) increases preterm birth risk due to greater uterine stretching and physiological strain [9].

   

• Gestational Health Issues: Conditions like pre-eclampsia, gestational diabetes, and placental disorders can induce preterm labor due to increased physiological stress [10].

   

• Assisted Reproductive Technology: Pregnancies conceived through in vitro fertilization (IVF) or other fertility treatments show a higher likelihood of preterm delivery [11].

Fetal characteristics also influence preterm birth risk. Growth restrictions or abnormal fetal positioning can lead to early delivery. Certain fetal health conditions, such as an isolated single umbilical artery, have been directly linked to increased preterm birth risk [10, 12].

Maternal alcohol consumption during pregnancy, especially heavy use, has been associated with an increased risk of preterm birth. increases the risk of preterm birth. Research links heavy drinking to adverse obstetric and neonatal outcomes, including small-for-gestational-age infants and preterm delivery [13]. Studies show that heavy alcohol consumption during the second and third trimesters significantly raises the likelihood of preterm birth [14]. These findings highlight maternal alcohol use as a major behavioral risk factor for preterm delivery.

Smoking also contributes to preterm birth risk. While numerous studies confirm its impact, variability in study designs and sample sizes makes it difficult to quantify the precise effect [2].

Environmental factors significantly influence preterm birth risk. Women living in areas with high pollution levels face a greater likelihood of preterm delivery compared to those in cleaner environments [15, 16].

Beyond pollution, additional environmental stressors, such as extreme temperatures and high-altitude living conditions, can increase preterm birth risk. These factors contribute to chronic stress and hormonal imbalances that may trigger early labor [8].

Certain medical conditions elevate the risk of preterm birth. Complications such as pre-eclampsia, eclampsia, and intrauterine growth restriction often require induced preterm delivery to protect the mother and fetus [5, 17, 18]. Additionally, infections in the uterus or vagina can trigger premature labor. Studies also link periodontal disease to an increased risk of preterm birth [19, 20].

Socio-economic status plays a significant role in influencing health outcomes, including preterm birth rates. Research indicates that factors such as maternal education and income affect the risk of preterm birth, though the extent of their impact varies across populations and contexts.

While higher education levels are generally associated with better health outcomes, studies show mixed findings regarding their direct effect on preterm birth rates. In certain populations—such as in Kazakhstan—high baseline education levels may help reduce disparities in maternal health outcomes related to education [21].

Low family income is consistently linked to an increased risk of preterm birth. Studies associate lower social class, poverty, and financial stress with a higher likelihood of preterm birth [21, 22].

Additional contributing factors include unstable housing, inadequate nutrition, and poor living conditions, all of which elevate the risk. To improve maternal and infant health outcomes, it is essential to implement targeted policies that address socioeconomic disparities [21, 22].

Ethnicity significantly affects preterm birth rates, with disparities observed across racial and ethnic groups. In the United States, for example, preterm birth rates are notably higher among Black women (14.6%) compared to white (9.4%) and Hispanic (10.1%) women, highlighting racial and ethnic inequalities in birth outcomes [23]. These disparities extend beyond the U.S., as Black, Asian, and minority ethnic women in various high-income countries face disproportionately high maternal mortality and adverse birth outcomes [24].

Community and societal factors also influence preterm birth risk. In the U.S., African-American mothers face the highest risk, followed by Hispanic and Caucasian mothers, while Asian mothers have the lowest risk [4]. Improving overall maternal health, particularly in high-risk communities, could help reduce these disparities [11]. A deeper understanding of these risk factors enables healthcare providers to implement targeted interventions that lower preterm birth rates and improve outcomes for mothers and newborns.

Preterm birth leads to numerous complications for newborns due to underdeveloped organs and systems. These complications often cause immediate health challenges and can impact long-term development.

Preterm infants frequently struggle with feeding due to an immature gastrointestinal tract, which affects their ability to coordinate sucking and swallowing [25]. These difficulties can lead to inadequate nutritional intake, requiring specialized feeding methods such as tube feeding or fortified human milk to support growth and development [25].

Necrotizing Enterocolitis (NEC), a serious condition affecting preterm infants, involves inflammation and bacterial infection of the bowels, which can lead to tissue death. This life-threatening complication demands immediate medical intervention to prevent severe health risks [26, 27].

Preterm infants face a higher risk of infections due to their immature immune systems and lower immunoglobulin levels. This vulnerability increases the likelihood of conditions like sepsis, which can have severe consequences if not treated promptly. Strict infection control measures are essential in neonatal care to reduce these risks [28-30].

Preterm infants are more susceptible to neurological issues, including intraventricular hemorrhage (IVH) and cerebral palsy. IVH, characterized by bleeding in the brain’s ventricular system, commonly affects very low birth weight infants [11]. Preterm birth also increases the risk of long-term neurological impairments, such as developmental delays and learning disabilities, particularly in cases involving brain injury during or after birth [31].

Respiratory Distress Syndrome (RDS) remains one of the most critical complications of preterm birth. Immature lungs lacking adequate surfactant struggle to maintain proper function, leading to breathing difficulties, low oxygen levels, and potential lung tissue damage [11]. RDS contributes significantly to morbidity in preterm infants and often requires immediate medical intervention, including supplemental oxygen, positive airway pressure, or mechanical ventilation [32].

Bronchopulmonary Dysplasia (BPD), another serious respiratory condition, results from chronic lung injury and inflammation. Infants with BPD often experience respiratory distress, tachypnea, labored breathing, and accessory muscle use [33]. BPD impairs pulmonary function, affecting gas exchange and increasing the risk of chronic respiratory issues [34, 35].

BPD is a leading cause of chronic lung disease in preterm infants, contributing to long-term respiratory and neurodevelopmental complications. Infants who require prolonged respiratory support, supplemental oxygen, or mechanical ventilation face a higher risk of developing BPD. Diagnosis typically occurs after postnatal day 28 and/or at 36 weeks corrected age, complicating early intervention [36, 37].

Preterm infants have a higher risk of developing vision and hearing impairments. Retinopathy of Prematurity (ROP) can occur, requiring monitoring and, in severe cases, surgical intervention [38, 39]. Hearing screenings are typically conducted within one month of birth or at term-equivalent age to identify early auditory issues that may require intervention [40].

The effects of preterm birth extend beyond infancy, increasing the risk of chronic respiratory conditions and noncommunicable diseases later in life [31]. Preterm infants face a higher likelihood of developing asthma, growth failure, obesity, and cardiovascular diseases, emphasizing the need for lifelong medical monitoring and intervention [31, 41].