Impact of Climate Change on Pregnancy and Reproductive Outcomes

Climate change and pregnancy: effects on maternal, foetal, and neonatal outcomes.

Climate impacts on pregnancy health can be conceptualized to involve:

Ø Direct impacts via discrete environmental disasters, such as wildfires, extreme heat, drought, hurricanes, floods, etc,. The primary stressors here are extreme ambient air temperature and direct physical harm to pregnant women and the newborn.

Ø Indirect impacts through changes in the natural environment (air quality, food and water quality and availability, disease vector and pathogen distribution).

Ø Indirect impacts through changes in the social environment (conflicts due to resource scarcity, forced migration where pregnant women are less likely to seek prenatal care).

Exposure to high temperature is associated with:

Ø An increase in adverse pregnancy outcomes, the most significant of which are preterm births and stillbirths. Associations between temperature and birth outcomes appear especially pronounced among women in low socioeconomic groups. This suggests that pregnant women in low and middle income countries could be at particular risk from heat exposure.

Ø Adverse foetal outcomes including:

1. Association between high temperatures and congenital heart defects (CHD). Maternal exposure to a maximum daily temperature of 30^oC was significantly associated with an increased risk of multiple and noncritical congenital heart defects. The risk for noncritical CHD further increased with extreme summer heat exposures.

2. Neural tube defects (spina bifida and anencephaly) show a weak positive association with high temperatures (>30^oC) - elevated temperature may be a risk factor for neural tube defects .

3. Reduced Placental Weight and Volume. Negative association between high temperatures and placental weight and volume, and a positive association with placental efficiency.

Ø Adverse neonatal outcomes such as:

1. Increase neonatal morbidity: Heatwaves increased risk of foetal distress, necessity for ventilator-associated breathing for more than 30 min, and meconimum aspiration syndrome.

2. Higher International Normalised Ratio (INR) of neonates. Seasonal variations were evident - higher INR in summer vs. winter. Outdoor temperature significantly influenced the INR values (positive correlation).

3. Shorter Newborn Telomere Length: Higher temperature (>19.5^oC) was associated with shorter cord blood telomere length.

4. Significant positive correlation coefficients were demonstrated between mean monthly temperature and conception rate for those developing schizophrenia, suggesting that higher temperatures at conception were associated with more conceptions of offspring who developed schizophrenia. Some evidence also supports a role for early pregnancy maternal exposure to extreme ambient heat in the development of psychiatric disorders.

Ø Adverse maternal outcomes:

1. Gestational diabetes mellitus (GDM). Increased prevalence of GDM, the likelihood of GDM diagnosis, and serum glucose levels was correlated with elevated temperatures, especially in the summer season. Each 10^oC increase in mean 30-day temperature was associated with a 6–9% relative increase in the risk of GDM.

2. Hypertensive disorders. Maternal exposure to heatwaves and high average temperature increased the risk of preeclampsia, eclampsia, and gestational hypertension.

3. Premature Rupture of Membrane (PROM). PROM occurs due to the natural weakening of the foetal membrane, which triggers the foetal membrane’s rupture without labour onset. Elevated temperatures are associated with a higher risk of PROM.

4. Placental abruption. High risk for placental abruption associated with high-temperature exposures during the pregnancy period. Elevated temperature (>30^oC) in warm seasons increases the risk of placental abruption by 7%. Placental abruption plays a role in the association between elevated temperature and stillbirth.

5. Maternal stress. Extreme temperature increases maternal stress during pregnancy.

6. Cardiovascular risk at labour. Exposure to 1^oC increases in temperature during the last week of pregnancy increases the cardiovascular risk by 7% and that the risk was more evident on days closer to delivery.

7. Bacteriuria. Increased maternal risk with significant bacteriuria, with high ambient monthly temperature, potentially leading to kidney infection, premature labour, and/or low birth weight.

In terms of indirect impacts of climate change on pregnancy, maternal stress and mental health appear to be major issues. Climate change may directly affect mental health through exposure of its victims to trauma and indirectly through primary effects on physical health and community wellbeing. Prenatal maternal stress leads to adverse pregnancy, newborn, and generational outcomes.