Seasonal patterns in perinatal mortality and preterm delivery

Area of Science:

• Obstetrics and Gynecology
• Perinatology
• Epidemiology

Background:

• Seasonal variations in preterm birth and perinatal mortality are not well understood.
• Environmental factors may influence pregnancy outcomes, but their specific role requires further investigation.

Purpose of the Study:

• To investigate potential seasonal patterns in preterm delivery and perinatal mortality.
• To explore the association between specific causes of death, such as infection, and seasonal trends.

Main Methods:

• Utilized linked birth, infant death, and fetal death records from Minnesota (1967-1973).
• Included over 400,000 white singleton births and stillbirths (≥29 weeks gestation).
• Constructed monthly cohorts to estimate probabilities of preterm delivery and perinatal death.

Main Results:

• A statistically significant increase in preterm delivery and perinatal mortality was observed in July, August, and September.
• Perinatal deaths attributed to maternal or fetal infection showed a marked increase in August and September.
• Fetal deaths occurring before labor exhibited a seasonal pattern similar to overall perinatal deaths.

Conclusions:

• Findings suggest environmental factors, potentially including ascending infections, may contribute more significantly to preterm delivery and perinatal mortality than previously recognized.
• The summer months, particularly August and September, are associated with heightened risks for adverse pregnancy outcomes.