Context
A recent nationwide study based on National Family Health Survey (NFHS-5) data has established a significant association between prolonged exposure to extreme heat during pregnancy and adverse birth outcomes such as low birth weight, preterm birth and stillbirth.
Key Findings of the Study
- The study analysed data of 209,266 births recorded between 2015 and 2020.
- It linked NFHS-5 (2019–21) birth records with high-resolution India Heat Index estimates to measure maternal heat exposure.
- Researchers used “consecutive sweltering days” instead of average temperature to estimate heat stress.
- First trimester heat exposure showed the strongest association with preterm births.
- Second trimester exposure was more strongly associated with low birth weight.
- Third trimester exposure was linked to a higher risk of stillbirth.
- The risk was greater among:
- Women with low Body Mass Index (BMI <18.5).
- Women from lower educational and poorer socioeconomic backgrounds.
- Urban areas recorded relatively higher rates of low birth weight.
- Mountainous and humid subtropical climatic regions showed stronger associations between heat stress and adverse pregnancy outcomes.
Why Does Extreme Heat Affect Pregnancy?
High ambient temperatures can:
- Increase maternal core body temperature.
- Cause heat stress and dehydration.
- Reduce uterine blood flow, limiting oxygen and nutrient supply to the fetus.
- Impair fetal growth and development.
- Increase the likelihood of uterine contractions, raising the risk of preterm delivery.
What is Heat Stress?
- Heat stress is the physiological strain experienced by the human body when exposed to high temperatures, humidity and solar radiation, reducing the body’s ability to maintain a normal temperature.
Major Factors Influencing Heat Stress
- Air temperature
- Relative humidity
- Solar radiation
- Wind speed
- Duration of exposure
- Individual health and hydration status
What is the India Heat Index?
The India Heat Index is a high-resolution heat exposure dataset that combines:
- Air temperature,
- Relative humidity,
- Solar radiation, and
- Wind conditions
To estimate the actual heat stress experienced by people, rather than temperature alone.
| Important CTC from This Article for UPSC 1. National Family Health Survey (NFHS) 2. Heat Index |
Q. With reference to the National Family Health Survey (NFHS), consider the following statements:
1. It is conducted under the Ministry of Health and Family Welfare with the International Institute for Population Sciences (IIPS) as the nodal agency.
2. It provides district-level information on population, health and nutrition indicators.
3. NFHS collects information only on maternal and child health.
Which of the statements given above is/are correct?
(a) 1 and 2 only
(b) 2 and 3 only
(c) 1 only
(d) 1, 2 and 3
Answer: (a)
• Statement 1 is Correct: NFHS is conducted under the Ministry of Health and Family Welfare (MoHFW), with IIPS, Mumbai as the nodal agency.
• Statement 2 is Correct: It provides district-level data on population, health and nutrition indicators across India.
• Statement 3 is Incorrect: NFHS covers fertility, family planning, nutrition, mortality, anaemia, domestic violence and other health indicators, not just maternal and child health.