‘Pregnant women particularly susceptible to the harmful effects of air pollution’

Does the foetus inhale pollutants which penetrate the placenta?

Air pollution, both indoor and outdoor, has significant adverse health effects, especially in vulnerable segments like pregnant women and neonates, explains Dr Divya Awasthi, senior consultant, Obstetrics and Gynaecology, Fortis Hospital, Mohali. Pollutants include greenhouse gases and particulate matter of different sizes. Particulate matter of less than 2.5 microns is of greater concern as it can reach the blood circulation system through the alveoli of the lungs. These minute particles can even cross the placenta, entering foetal circulation. Air pollution may indirectly harm lung development by causing low birth weight, preterm birth, or inadequate immune system development. The exposure during the prenatal period may interfere with organ development and organogenesis.

“Pregnant women are particularly susceptible to the harmful effects of air pollution because of the normal physiological changes that happen in pregnancy. There is a 20% increase in oxygen requirement, increased respiratory rate with 40% to 50% increase in minute ventilation, and 40% increase in cardiac output. These changes increase the amount of pollutants that get inhaled.”

Lungs of newborn exposed to air pollution may be smaller

There is now enough scientific evidence to accept that severe air pollution harms the foetus, newborn babies, infants and children and changes how lungs develop and work after birth, explains Dr Diljot Singh Bedi, Senior Consultant, Department of Paediatrics.

What severe air pollution does to newborns and children: Before even birth, when a pregnant woman is exposed to air pollution, she develops a high risk of premature birth and delivering a low-birth-weight newborn. The lungs of this newborn baby may be smaller and function poorly throughout life. After birth in infants and children, air pollution causes increased risk of hospital visits and admissions with pneumonia, wheezing and asthma. Babies who are born premature are at the greatest risk of hospital visits and admissions with pneumonia, wheezing and asthma as their lungs are not fully developed.

What happens in the lungs of foetus and children exposed to air pollution?

Air pollution damages foetal and child lungs in several ways. Before birth, air pollutant particles have been found in the human placenta and foetal tissues. These pollutants cause inflammation of the placenta and changes in gene expression that further lead to disturbance in foetal growth, so the foetus may develop smaller lungs or a different immune response. Exposure after birth to air-polluting particles provokes local airway inflammation, which narrows the airways, injures airway lining cells, and increases the risk of infection. This leads to symptoms of cough, wheezing and asthma. The overall development of the lung during childhood is impaired.

How this translates into clinical presentations in infants/newborns

Common presentations and conditions linked to high pollution exposure

Newborn/neonatal period: Higher risk of being born premature or low birth weight; these babies are at higher risk of respiratory problems immediately after birth and hence need NICU (Neonatal Intensive Care Unit) admission. If the placenta is affected, there may be foetal growth reduction and thus less mature lungs at birth, which need medical interventions like ventilator support for these newborn babies.

Early infancy (first months): More frequent respiratory infections like pneumonia and more severe episodes requiring oxygen or admission in highly polluted areas. Reduced measured lung function, smaller airway diameter, and lower lung volumes. In infants who were born very prematurely, expect more frequent exacerbations and readmissions on high pollution days.

Young children: Increased wheeze and diagnosed asthma, slower lung growth into childhood and adolescence, meaning pollution exposure in early life transforms into chronic respiratory disease risk. These children have poor weight gain if chronic asthma develops.

How pollution affects breathing in babies, those with compromised lungs

Preterm infants or babies with congenital lung disease: pollution exacerbates the baseline problems, increases episodes of lower oxygenation, more hospital visits, worse clinical status during respiratory infections, and delays recovery. Studies show ambient pollution is associated with higher outpatient visits and rehospitalisation in very premature populations.

Does the foetus inhale pollutants or do pollutants cross the placenta?

The foetus does not breathe air (no pulmonary gas exchange before birth), so foetal exposure is not by inhalation of outside air; it’s mediated by the mother.

Two main exposure routes to the foetus:

Indirect — maternal systemic inflammation / altered placental function: maternal inflammation or placental dysfunction (from inhaled particles) changes nutrient/oxygen delivery and signalling to the foetus (affecting growth and organ development).

Possible direct transfer / placental deposition: Several human studies have found black carbon/ultrafine particles on the fetal side of the placenta, and experimental work and some human tissue work show particles can translocate into foetal tissues. So small particles can at least reach the placenta, and in some reports, they are present on the foetal side, whether and how much reaches foetal organs in every pregnancy is variable and under study.

Effects on organs beyond the lungs

Evidence links prenatal and early-life air pollution to:

Brain/neurodevelopmental risks (associations with lower IQ and autism risk).

Cardiac effects (increased blood pressure).

Diabetes and obesity (altered glucose/lipid metabolism later).

Higher risk of stillbirth and infant death in areas with very high pollution.

Practical clinical implications and what to do for infants or pregnant patients

For pregnant people:

Reduce exposure where possible (monitor AQI, avoid outdoor activity during “very unhealthy/hazardous” days, use well-fitting masks if exposure is unavoidable, improve indoor air with HEPA filters). Population-level interventions are the mainstay, but personal risk reduction helps.

For newborns/infants, especially preterm or very premature:

Minimise indoor pollution (no indoor smoking, use clean cooking/ventilation, HEPA air cleaners if available). Consider closer follow-up after discharge for infants from high-exposure areas (monitor growth, feeding, respiratory symptoms).

Prompt attention to respiratory symptoms (early assessment of breathing effort, pulse-oximetry, consider lower threshold for clinic / OPD Review in high AQI periods). Studies show higher illness from pollution in very premature infants.

Public-health level: reducing community and traffic pollution is the only way to eliminate the root cause, individual measures help but do not remove the population risk.