Parity Correlates with the Timing of Developing Endometrial Cancer, But Not Subtype of Endometrial Cancer.

Parity is one of well-known risk factors of endometrial cancer, but it is less clear whether parity is associated with the timing of developing endometrial cancer, and with the incidence of subtype of endometrial cancer. Data on 902 patients including age at diagnosis, age at menarche and menopause, parity and age at last birth from two obstetrics and gynaecology hospitals in China was analysed. 5.6% patients were nulliparous, 53.4% patients had one live birth, 27.7% patients had two live births and 13.3% patients had three or more live births. Patients at diagnosis who had three or more live births were significantly older than patients who were nulliparous or had one or two live births with the median age at diagnosis of 63 versus 51 or 52 or 59 years respectively. The percentage of patients with three or more live births at diagnosis before menopause was significantly lower than patients who were nulliparous, had one live birth or had two live births (10% versus 52%, or 51.9% or 22.4%). Furthermore, time from last birth to endometrial cancer was significantly longer in patients who had three or more live births than patients who had two live births or had one live birth (35 versus 31, or 24 years). However, there was no difference in the incidence of subtypes of endometrial cancer according to parity. Our data suggests parity is negatively correlated with the time onset of endometrial cancer and not associated with the incidence of endometrial cancer subtypes.