In a study published in Neurology, 397 women with MS or its precursor, clinically isolated syndrome, were compared to 433 controls matched for race and age. The women were given in-person questionnaires about pregnancies, breastfeeding, hormonal contraceptive use and other factors.
Women who had breastfed for a cumulative amount of 15 months or more with one or more children, were 53 per cent less likely to develop MS or clinically isolated syndrome than women who had a total of 0-4 months of breastfeeding. Women who were age 15 or older at the time of their first menstrual cycle were 44 per cent less likely to develop MS than women who were 11 years old or younger at the time of their first menstruation.
The number of years a woman ovulated was not associated with MS risk. No association was seen with number of pregnancies, use of hormonal contraceptives or age at first birth.