De­liv­er­ing a baby in­creases - then low­ers - risk of breast can­cer

The Borneo Post - Nature and health - - Front Page - by Gene Emery

Hav­ing a baby tem­po­rar­ily in­creases the risk of breast can­cer by about 80 per cent com­pared with the risk in women who have never given birth, re­searchers be­hind a new study have con­cluded. But the 80 per cent-higher breast can­cer risk is not as scary as it first sounds be­cause “for­tu­nately, breast can­cer is un­com­mon in young women,” chief au­thor Dr Hazel Ni­chols told Reuters Health in a tele­phone in­ter­view. Ni­chols and col­leagues found that the breast can­cer risk peaks 4.6 years after a woman’s most re­cent birth but then be­gins to fall. After an­other 19 years, the risk re­turns to the same level as a woman who has never given birth. And from there, it con­tin­ues to drop. By 34.5 years after birth of the youngest child, the breast can­cer risk is 23 per cent lower than the risk in women who had never been preg­nant. While a 45-year-old woman who had never given birth had a 0.62 per cent chance of be­ing di­ag­nosed with breast can­cer up to that point in her life, the breast can­cer odds for a woman of the same age who had given birth in the past three to seven years were only slightly higher, at 0.66 per cent. Sim­i­larly, by age 50, the odds of be­ing di­ag­nosed with breast can­cer were 1.95 per cent for the child­less women and 2.20 per cent for women with a re­cent preg­nancy, a dif­fer­ence of only one quar­ter of a per­cent­age point. Women who had given birth to their first child be­fore age 25 did not have any el­e­vated risk at all. “This should not dic­tate when women de­cide to have their chil­dren be­cause while we are see­ing this ex­tra risk after child­birth, this is a pe­riod of time when risk over­all is ex­cep­tion­ally low,” said Ni­chols. “This is not trans­lat­ing to a large num­ber of ad­di­tional breast can­cers.” Mia Gaudet, sci­en­tific di­rec­tor for epi­demi­ol­ogy re­search at the Amer­i­can Can­cer So­ci­ety, agreed. The find­ings “shouldn’t change women’s be­hav­iour with re­gard to when a woman de­cides to have a first child,” Gaudet told Reuters Health in a tele­phone in­ter­view. “It may per­haps change how and when a woman be­gins to be screened for breast can­cer,” added Gaudet, who was not in­volved in the study. The con­ven­tional wis­dom has been that preg­nancy and child­birth pro­tect women from breast can­cer, but that be­lief had come from look­ing at the can­cer rates among women age 60 and older. In fact, half of women with breast can­cer are di­ag­nosed be­fore age 62. The new find­ings, re­ported in the An­nals of In­ter­nal Medicine, come from com­bin­ing data from 15 stud­ies of nearly 890,000 women of vary­ing ages across three con­ti­nents. They con­firm what smaller stud­ies have sug­gested. Said Ni­chols: “We are not the first to see the short-term in­crease in risk after child­birth, but we are now able to see whether or not other fac­tors like breast­feed­ing your chil­dren make a dif­fer­ence. When it came to breast­feed­ing, it did not.” But Gaudet of the Can­cer So­ci­ety said the breast­feed­ing con­clu­sion is ques­tion­able be­cause the Ni­chols study only looked at whether breast­feed­ing ever oc­curred. That’s im­por­tant be­cause “prior stud­ies have shown that it’s the du­ra­tion of breast­feed­ing, not whether they ever breast fed or not” that’s key, she said. Those stud­ies show that breast­feed­ing low­ers the breast can­cer risk. The Ni­chols team also found that women with the most chil­dren and those who had chil­dren later in life had high­est risks.– Reuters

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