Ongoing Lactation Research Articles

Breast-feeding and infant mortality in Norway 1860–1930

Using medical records from maternity clinics in the two Norwegian cities Oslo and Bergen, the effect of lactation on infant mortality during the period 1860-1930 is examined, comparing those who were and were not breast-fed in a total of about 6900 live born infants. The mortality of children not breast-fed was nearly three times that of those who were breast-fed. In a Cox regression analysis the infant's year of birth and the mother's marital status were found to influence mortality in addition to lactation. Children born to unmarried mothers experienced a mortality about twice that of those born to married mothers, both during on-going lactation and in the absence of lactation, up to about 1915. Children born in Oslo had a slightly higher mortality than those born in Bergen. The duration of lactation was found to have a continuing protective effect on infant survival after weaning--the longer the duration, the lower the mortality after cessation of lactation.

Lactation and post-partum amenorrhoea: a study based on data from three Norwegian cities 1860-1964.

SummaryMedical records from maternity clinics in three Norwegian cities, Oslo, Bergen and Trondheim, have been used to study the relationship between lactation and post-partum amenorrhoea during the period 1860–1964. Resumption of menses after a period of post-partum amenorrhoea has been examined separately during lactation, after cessation of lactation, and in the absence of lactation, in 5250 cases. During ongoing lactation the median duration of post-partum amenorrhoea was found by survival analysis to be 12 months for women who had given birth before 1900 and 6 months for women who had given birth after 1900. In a Cox regression analysis, age of menarche and parity were found to influence the duration of post-partum amenorrhoea, in addition to the child's birth year. With a later age of menarche there was longer amenorrhoea, and primiparae resumed menses earlier than multiparae. After cessation of breast-feeding the median duration of amenorrhoea was 1 month, the only variable significantly influencing it being the age of menarche, a younger age showing a shorter duration. In the absence of lactation the survivor function started to decline after 3–4 weeks, and had a half-life of 2 months.None of the variables indicating the woman's social condition seemed to influence the duration of amenorrhoea. The decline in the duration of post-partum amenorrhoea during ongoing lactation from 1860 until today is therefore probably caused by a changed breast-feeding pattern rather than by improved nutrition for women giving birth.