REPRODUCTIVE AND MENSTRUAL FACTORS IN RELATION TO MAMMOGRAPHIC PARENCHYMAL PATTERNS AMONG PERIMENOPAUSAL WOMEN

The relationship between mammographic patterns and reproductive and me nstrual factors was examined in 3640 Norwegian women, aged 40-56 years , participating in the Third Tromso study conducted in 1986-87. Epidem iological data were obtained from questionnaires. The mammograms were categorised into five groups. This categorisation is based on anatomic -mammographic correlations, following three-dimensional (thick slice t echnique) histopathologic-mammographic comparisons, rather than simple pattern reading. Patterns 1-3 were combined into a low-risk group and patterns 4 and 5 into a high-risk group for analysis. Women who had m ore than four children were 90% less likely to have a high-risk patter n than nulliparous women (OR = 0.09, 95% CI 0.04-0.16) controlling for age, weight, height and menopausal status. Furthermore, those who fir st gave birth over 34 years of age were more than twice as likely to h ave a high-risk pattern than those giving birth in their teens (OR = 2 .37, 95% CI 1.23-4.56) adjusting for parity. Among post-menopausal wom en, age at menarche was negatively (P for trend = 0.015) and late age at menopause positively (P for trend = 0.072) related to high-risk pat terns. Among premenopausal women, age at menarche was positively relat ed to high-risk patterns (P for trend = 0.001). Also, menopausal statu s rather than age was associated with high-risk patterns. These findin gs support the opinion that reproductive and menstrual factors are inv olved in determining the mammographic parenchymal pattern among perime nopausal women.