Title of Thesis:  Stillbirth risk during the 1918 Influenza Pandemic in Arizona, USA. 

Thesis Chair: Dr. Gerardo Chowell

INTRODUCTION:  Influenza pandemic of 1918 was the most devastating pandemics till date, affecting approximately one-third of the population worldwide. The effect of influenza on adults are well studied but little is known about the impact of infection on pregnant mothers. Prior work documented the impact of influenza infection on pregnant mothers and pregnancy outcomes like birth defects, miscarriages or preterm births, but the impact of infection on stillbirth is not studied well. 

AIM: The objective of the study is to assess the stillbirth risk due to 1918 influenza pandemic in Arizona, USA.

METHODS: It is a retrospective study conducted to assess the impact of 1918 influenza pandemic on stillbirth risk. Approximately 21,334 birth records were retrieved for the Maricopa County, Arizona state from the years 1915-1925 from a publicly available genealogy database. Logistic regression using SAS statistical software was used to assess the impact of influenza on risk of stillbirth. Additionally, the study evaluated the risk of stillbirth with advanced maternal age. 

RESULTS: The results did not show significant impact of pandemic on stillbirth risk. January 1920 experienced the highest rate of stillbirths with 59 stillbirths per 1000 births, 9-10 months later the deadly second pandemic wave. The results show high rate of stillbirth in July 1919, with 49 stillbirths per 1000 births.
Additionally, there was a significant association between stillbirth and advanced maternal age (P-value 0.0030, at 0.05 level of significance) with stillbirth risk of 1.42 (95% Confidence interval: 1.17, 1.72) in younger women (<35 yrs.) compared to older women (≥35 yrs.). The results show least risk of stillbirth if the age of mother is approximately 26 years.

DISCUSSION: Though the results did not show significant impact of pandemic on stillbirth risk, but the study did observe higher rate of stillbirth in July 1919, consistent with natality decline reported in previous study in the same month in Arizona. Also, the results are in line with prior work and found that there is a high risk of stillbirths with advanced maternal age.