The shape of the placental surface at birth and colorectal cancer in later life.

OBJECTIVES

Many chronic diseases, including certain cancers, may originate through variations in the supply of nutrients to the fetus. These variations change gene expression and permanently set the structure and function of the body, a process known as programming. Fetal nutrition depends on the mother's metabolism and nutritional reserves, and on the placenta's ability to transfer nutrients from mother to baby. In this study, we examine how colorectal cancer is related to maternal and placental characteristics.

METHODS

We ascertained 275 cases of colorectal cancer among the 20,431 people in the Helsinki Birth Cohort, who were born during 1924-1944 and whose body size at birth was recorded, together with the shape and size of the placenta.

RESULTS

Hazard ratios for colorectal cancer increased as the placental surface became longer and more oval. The hazard ratio was 2.3 (95% CI 1.2-4.7) among people in whom the difference between the length and breadth of the surface exceeded 6 cm, compared with those in whom there was no difference. Colorectal cancer was unrelated to other placental measurements or to body size at birth.

CONCLUSION

An oval placental surface at birth is associated with later colorectal cancer. The shape of the placental surface is determined by events at around 8-12 weeks gestation. We speculate that, if the spiral arteries open prematurely, the surface becomes more oval and the fetus is at risk of oxidative damage at a time when the colon is differentiating.