Mothers who breast feed for at least six months may have a somewhat lower risk of developing high blood pressure later on, new research suggests.
For the new study, researchers looked at the correlation between breast feeding and later risk of hypertension among close to 56,000 US mothers taking part in the long-running Nurses' Health Study II.
Over an average follow-up of 14 years, nearly 8,900 women were eventually diagnosed with hypertension. But the risk was 22% higher for women who did not breast feed their first child, versus women who'd exclusively breastfed for six months.
Similarly, women who'd either never breasted or done so for three months or less were almost one-quarter more likely to develop high blood pressure than women who'd breasted for at least a year.
Those were the findings after adjustment for other risk factors such as diet, exercise and smoking habits, according to an online report in the American Journal of Epidemiology.
Co-author Dr Alison M. Stuebe, of the University of North Carolina, Chapel Hill, says it's possible that some other factor both hindered women from breast feeding and contributed to their high blood pressure.
On the other hand, it's plausible that breast feeding has direct benefits, she said. Animal research has found that oxytocin, which is involved in breast feeding, has lasting effects on blood pressure.
It's also known that women tend to have a short-term blood pressure decrease immediately after breast feeding, Dr Stuebe noted.
Breast feeding protective
Her team estimates that if breast feeding is in fact protective, 12% of high blood pressure cases among women with children could be linked to "suboptimal" breast feeding. But, Dr Stuebe said, "the point here is not to exhort women to try harder."
"If this is a causal relationship," she said, "then taking away barriers to breast feeding could make a difference in women's health later on." One way to help more mothers breast feed successfully would be to get them off to a good start at the hospital, according to Dr Stuebe.
The World Health Organization encourages hospitals to take certain "baby-friendly" steps that have been shown to aid breast feeding – like not feeding newborns anything other than breast milk, avoiding pacifiers and allowing mom and baby to be together 24 hours a day.
But Dr Stuebe pointed to a 2008 study of 1,900 US mothers that found only 8% experienced all six recommended baby-friendly practices at their maternity hospital.
She also suggested some other steps breast feeding advocates have long called for, including better access to lactation counselling, which is often not covered by insurance; break time at work so women can pump breast milk, and paid maternity leave.
Right now, the US requires employers with 50 or more workers to offer 12 weeks of non-paid maternity leave.
(Reuters Health, Amy Norton, November 2011)