Association of maternal pre-pregnancy body mass index with neonatal respiratory outcomes: a nationwide population-based cohort study – Nature

Executive Summary

A nationwide, population-based cohort study was conducted in South Korea to assess the association between maternal pre-pregnancy body mass index (BMI) and neonatal respiratory morbidities. Utilizing linked mother-infant records from 2014–2021, the study analyzed 779,091 live births. The findings reveal a significant dose-response relationship: elevated maternal BMI is associated with an increased risk of respiratory distress syndrome (RDS), transient tachypnea of the newborn (TTN), and bronchopulmonary dysplasia (BPD), while maternal underweight is associated with a reduced risk. These results underscore the critical importance of maternal weight management as a key strategy for improving neonatal health outcomes, directly contributing to the achievement of Sustainable Development Goal 3 (Good Health and Well-being), particularly Target 3.2, which aims to end preventable deaths of newborns.

Introduction: Aligning Maternal Health with Sustainable Development Goals

The Global Context of Maternal Obesity and SDG 3

Maternal pre-pregnancy obesity has become a significant public health challenge, directly impacting the achievement of Sustainable Development Goal 3 (Good Health and Well-being). The rising global prevalence of obesity, a non-communicable disease (NCD), among women of reproductive age is linked to adverse pregnancy outcomes that compromise both maternal and infant health. This creates an obesogenic intrauterine environment that can disrupt fetal development, increasing the risk of neonatal complications. Addressing maternal weight is therefore essential for making progress on SDG Target 3.2 (end preventable deaths of newborns) and Target 3.4 (reduce premature mortality from NCDs).

Nutritional Challenges and SDG 2

The study’s focus on the full spectrum of maternal BMI—from underweight to obese—highlights the dual burden of malnutrition, a core concern of Sustainable Development Goal 2 (Zero Hunger). SDG Target 2.2 aims to end all forms of malnutrition by 2030. Both maternal underweight and obesity represent forms of malnutrition that can negatively influence fetal programming and neonatal health. This research provides critical evidence on how maternal nutritional status, reflected by BMI, affects neonatal respiratory function, reinforcing the need for integrated strategies that promote healthy nutrition for women before and during pregnancy.

Methodology: A Population-Based Approach to Assessing Neonatal Health

Study Design and Population

This cross-sectional study utilized a large-scale, nationwide dataset from the Korean National Health Insurance Service (NHIS) for birth cohorts between 2014 and 2021. After exclusions, the final analysis included 779,091 matched mother-infant dyads, providing a robust population base to assess public health trends and contribute to evidence-based policy aligned with the SDGs.

Key Variables and Outcome Measures

The primary exposure variable was maternal pre-pregnancy BMI, categorized according to Asia-Pacific criteria:

• Underweight (
• Normal weight (18.5–22.9 kg/m², reference group)
• Overweight (23.0–24.9 kg/m²)
• Obese Class I (25.0–29.9 kg/m²)
• Obese Class II/III (≥ 30 kg/m²)

The primary outcomes were neonatal respiratory morbidities, including:

1. Respiratory Distress Syndrome (RDS)
2. Transient Tachypnea of the Newborn (TTN)
3. Bronchopulmonary Dysplasia (BPD)

Statistical Analysis

To mitigate confounding factors and strengthen the validity of the findings, inverse probability of treatment weighting (IPTW) was applied using propensity scores. Weighted generalized linear models were used to calculate relative risks (RRs) and 95% confidence intervals (CIs), adjusting for maternal and newborn characteristics. This rigorous analytical approach ensures that the identified associations are reliable for informing public health interventions.

Key Findings: The Impact of Maternal BMI on Neonatal Respiratory Outcomes

Increased Risk Associated with Maternal Obesity

After adjusting for confounders, the study demonstrated a clear and significant increase in the risk of neonatal respiratory morbidities for infants born to mothers with a BMI ≥ 30 kg/m² compared to those with a normal BMI. This directly threatens progress toward SDG 3.

1. Respiratory Distress Syndrome (RDS): Risk increased by 160% (RR 2.598).
2. Transient Tachypnea of the Newborn (TTN): Risk increased by 15% (RR 1.154).
3. Moderate-to-Severe Bronchopulmonary Dysplasia (BPD): Risk increased by over 500% (RR 6.070).

Reduced Risk Associated with Maternal Underweight

Conversely, maternal underweight (BMI

1. Respiratory Distress Syndrome (RDS): Risk was reduced by 13% (RR 0.873).
2. Transient Tachypnea of the Newborn (TTN): Risk was reduced by 5% (RR 0.951).
3. All cases of Bronchopulmonary Dysplasia (BPD): Risk was reduced by 63% (RR 0.371).

Implications for SDG Target 3.2

The strong, graded relationship between maternal BMI and neonatal respiratory illness identifies maternal weight as a critical, modifiable risk factor. Interventions aimed at optimizing maternal BMI before conception can directly contribute to reducing neonatal morbidity, a cornerstone of achieving SDG Target 3.2, which seeks to end preventable deaths of newborns and children under five years of age.

Discussion: Pathways to Achieving Health-Related SDGs

Biological Mechanisms and Clinical Significance

The increased risk of respiratory complications in neonates of obese mothers is likely mediated by biological pathways including chronic systemic inflammation, hormonal imbalances, and metabolic dysregulation, which can impair fetal lung maturation. From a public health perspective, while absolute risks at an individual level are modest, the consistent, graded pattern across a large population highlights a significant opportunity for preventative action that aligns with the preventative health focus of the SDGs.

The Role of Preconception Care in Advancing SDG 3 and SDG 5

The findings strongly advocate for the integration of weight management into preconception counseling. Such interventions are a primary prevention strategy for improving neonatal outcomes, directly supporting SDG 3 (Good Health and Well-being). Furthermore, providing women with the knowledge and resources to manage their health before pregnancy empowers them, contributing to SDG 5 (Gender Equality) by ensuring their right to health and well-being.

Addressing Malnutrition for Sustainable Development (SDG 2)

This study reinforces the importance of addressing all forms of malnutrition, as outlined in SDG 2 (Zero Hunger). The results for both underweight and obese mothers emphasize that deviations from a normal, healthy BMI have consequences for the next generation. Public health policies should focus on promoting balanced nutrition and healthy lifestyles for women of reproductive age to prevent the intergenerational transmission of health risks.

Conclusion and Recommendations for Policy and Practice

Summary of Evidence

This large-scale study provides compelling evidence of a dose-response relationship between maternal pre-pregnancy BMI and the risk of neonatal respiratory morbidities. Both maternal obesity and underweight status are associated with significant changes in neonatal respiratory health outcomes. These findings highlight maternal nutritional status as a key determinant of child health, with profound implications for achieving global health and development targets.

Strategic Recommendations for SDG Attainment

To accelerate progress towards the Sustainable Development Goals, particularly SDG 2 and SDG 3, the following actions are recommended:

• Integrate Preconception Counseling: Health systems should systematically integrate weight optimization and nutritional support into routine primary care for women of reproductive age.
• Launch Public Health Campaigns: Promote awareness of the importance of maintaining a healthy BMI before pregnancy through targeted public health initiatives focused on nutrition and physical activity.
• Strengthen Maternal Health Services: Enhance antenatal and postnatal care to include comprehensive nutritional assessment and support, addressing both undernutrition and overnutrition.
• Foster Further Research: Encourage continued research to elucidate the causal pathways and develop effective, scalable interventions to mitigate the risks associated with non-optimal maternal BMI.

Analysis of Sustainable Development Goals (SDGs) in the Article

1. Which SDGs are addressed or connected to the issues highlighted in the article?

• SDG 3: Good Health and Well-being

  This goal is central to the article, which investigates the direct link between maternal health (pre-pregnancy BMI) and neonatal health outcomes. The study’s purpose is “to enhance neonatal health outcomes” by understanding risk factors like maternal obesity, which is described as a “critical public health issue with profound implications for both maternal and neonatal health.” The research focuses on specific neonatal respiratory morbidities (RDS, TTN, BPD) and associated maternal complications like gestational diabetes and hypertensive disorders, all of which fall under the purview of ensuring healthy lives and promoting well-being for all ages.

• SDG 2: Zero Hunger

  This goal aims to end all forms of malnutrition. The article addresses this by examining the health consequences of both extremes of the nutritional spectrum: maternal underweight (BMI

2. What specific targets under those SDGs can be identified based on the article’s content?

1. Target 3.2: End preventable deaths of newborns and children under 5 years of age.

   The article directly contributes to this target by investigating major causes of neonatal morbidity. It analyzes the risk factors for severe respiratory conditions such as Respiratory Distress Syndrome (RDS), Transient Tachypnea of the Newborn (TTN), and Bronchopulmonary Dysplasia (BPD). These conditions are significant contributors to neonatal illness, the need for intensive care (“admission to neonatal intensive care units (NICU)”), and potential mortality. By identifying maternal pre-pregnancy BMI as a “modifiable risk factor,” the study provides evidence for preventative strategies to improve neonatal survival and health.

2. Target 3.4: Reduce by one-third premature mortality from non-communicable diseases (NCDs) through prevention and treatment and promote mental health and well-being.

   Maternal obesity is a non-communicable disease and a primary focus of the article. The study highlights the rising global prevalence of obesity and its association with “adverse pregnancy outcomes, including gestational diabetes mellitus, hypertensive disorder of pregnancy.” By demonstrating a “dose–response relationship between maternal BMI and multiple neonatal respiratory outcomes,” the research underscores the importance of preventing and managing obesity in women of reproductive age as a key strategy to reduce the burden of NCDs for both mothers and their offspring.

3. Target 2.2: By 2030, end all forms of malnutrition… and address the nutritional needs of adolescent girls, pregnant and lactating women.

   The article’s core analysis is based on maternal nutritional status, as measured by pre-pregnancy Body Mass Index (BMI). It examines the health impacts of being “underweight,” “overweight,” and “obese” compared to a normal weight. This directly addresses the challenge of ending “all forms of malnutrition,” which includes both undernutrition and overnutrition. The study’s focus on “women of reproductive age” and its conclusion calling for “preconception counseling aimed at weight optimization and nutritional support” align perfectly with addressing the nutritional needs of pregnant women to improve health outcomes.

3. Are there any indicators mentioned or implied in the article that can be used to measure progress towards the identified targets?

• Indicators for Target 3.2 (End preventable deaths of newborns):

  The article provides several direct and proxy indicators for measuring neonatal health and well-being.

  • Incidence of Neonatal Respiratory Morbidities: The study measures the relative risk (RR) and absolute risk differences (RDs) for specific conditions, including Respiratory Distress Syndrome (RDS), Transient Tachypnea of the Newborn (TTN), and Bronchopulmonary Dysplasia (BPD).
  • Rate of Neonatal Intensive Care Unit (NICU) Admission: The article notes that “infants born to obese mothers were significantly more likely to require… admission to neonatal intensive care units (NICU).” This is a key indicator of severe neonatal illness.
  • Need for Respiratory Support: The study assesses the risk of newborns requiring “ventilator support” and “supplemental oxygen therapy,” which are direct measures of the severity of respiratory distress.

• Indicators for Target 3.4 (Reduce mortality from NCDs):

  The article uses the prevalence of a key NCD (obesity) and its related complications as primary variables.

  • Prevalence of Maternal Overweight and Obesity: The study categorizes maternal BMI into groups, including “overweight (23–24.9 kg/m²),” “obese class I (25–29.9 kg/m²),” and “obese class II/III (≥ 30 kg/m²).” Tracking the prevalence of these categories among women of reproductive age serves as an indicator for this target.
  • Prevalence of Pregnancy-Related Complications: The article measures the frequency of NCDs during pregnancy, noting that obese mothers “more frequently experienced pregnancy-related complications, such as gestational diabetes and hypertensive disorders of pregnancy.”

• Indicators for Target 2.2 (End all forms of malnutrition):

  The article’s main exposure variable is a direct indicator of maternal nutritional status.

  • Prevalence of Maternal Malnutrition (by BMI): The study’s classification of maternal pre-pregnancy BMI into “underweight (

4. Table of SDGs, Targets, and Indicators

Source: nature.com