Cesarean Delivery And Risk Of Infant Leukemia

RICHARDSON M. ¹ , ROESLER M. ¹ , SPECTOR L. ¹

Introduction. Recent case-control studies have reported increased risks of pediatric acute lymphoblastic leukemia (ALL) among children born by cesarean delivery (CD). However, an association of CD with childhood leukemia has not been conclusively established and no previous study has examined the impact of CD on risk of infant leukemia specifically.
Methods. 443 infants diagnosed with acute leukemia, including both ALL and acute myeloid leukemia (AML), were identified at Children’s Oncology Group (COG) institutions between January 1996 and December 2006. 324 controls frequency matched by year of birth were identified through random digit dialing and random selection from US birth registries. Mothers of cases and controls completed an interview including questions on mode of birth, information on labor and delivery, and birth characteristics. Odds ratios (OR) and 95% confidence intervals (CI) for risk of ALL and AML were estimated using multivariable unconditional logistic regression models, adjusted for year of birth, breastfeeding, birth weight, and maternal race.
Results. We observed a statistically significant association between CD and ALL (OR and 95% CI: 1.64 [1.09, 2.46]). We did not observe an association between CD and AML (OR and 95% CI: 1.20 [0.73, 1.98]).
Conclusions. Our analysis suggests an increased risk of infant leukemia following CD. Cortisol exposure is reduced among infants born by CD, particularly infants born by pre-labor CD, compared to those born vaginally. Cortisol may be beneficial among infants susceptible to ALL due to induction of apoptosis among preleukemic cells. Therefore, reduced cortisol levels in the first days of life among infants born by CD should be considered as a potential mechanism underlying this association. Additional mechanistic studies are needed to confirm causality and further understand the role of cortisol in reducing risk of infant leukemia.