Does pregnancy induce the shedding of premalignant ovarian cells?
BACKGROUND
High parity is associated with reduced risk of ovarian cancer. One hypothesis is that pregnancy is associated with clearance of a fraction of the genetically modified (premalignant) cells from the ovaries.


METHODS
We evaluated this hypothesis using a model that estimates the cell clearance fraction at first and second pregnancy according to age at pregnancy. The model was fitted using reproductive history data from a cohort of 1.5 million Danish women born between 1935 and 1978 and followed for 28.7 million person-years. During this follow-up period, 2,035 developed invasive ovarian cancer.


RESULTS
We found the model to have a satisfactory fit despite the very few parameters involved. The model estimated similar cell clearance fractions for the first and second pregnancy and decreasing clearance with later age at pregnancy.


CONCLUSIONS
The relation of pregnancy history to risk of ovarian cancer can be well described by a cell clearance model that allows the cell clearance fraction to decrease with age at pregnancy.
Rostgaard
Klaus
K
Department of Epidemiology Research, Danish Epidemiology Science Centre, Statens Serum Institut, Copenhagen, Denmark. klp@ssi.dk
Wohlfahrt
Jan
J
Andersen
Per Kragh
PK
Hjalgrim
Henrik
H
Frisch
Morten
M
Westergaard
Tine
T
Melbye
Mads
M
D000328:Adult; D003718:Denmark / Q000453:epidemiology; D005260:Female; D006801:Humans; D008423:Maternal Age; D015233:Models, Statistical; D010051:Ovarian Neoplasms / Q000453:epidemiology / Q000473:pathology*; D010298:Parity; D011247:Pregnancy; D012042:Registries; D012307:Risk Factors