Although there is no doubt that breastfeeding suppresses ovarian activity, the
reasons for the immense variability in the duration of this suppression and the
mechanisms by which the suckling stimulus causes it remain unclear.
In mammals lactation is associated with an inhibition of ovulation of variable
duration. Throughout evolutionary history, lactation has been a necessary condition
for the survival of their young. It provides adequate nutriments and serves the
equally important role of birth-spacing.
There is little doubt that, considered worldwide, lactational infertility is one of
the more important factors controlling birth-spacing intervals and thus, in a broader
sense, in limiting population growth.
The disruptive effects of undernutrition and intensive physical work on female
reproductive ability are well documented. Undernutrition and weight loss delay
menarche and cause cessation of already established ovulatory cycles (1—3).
Ample data exist to show that lactation prolongs postpartum amenorrhoea and
provides some degree of protection against pregnancy (1,2). There are, however,
marked variations in the duration of lactational infertility among women of different
countries and women in different communities in the same country (1,2).
To identify likely determinants of postpartum infecundity and to understand their
relative importance in free-living populations, data must be collected from many
women. Under such circumstances, a battery of biochemical and endocrinological
tests is not feasible.
As a demographer, my competence to assess some of the papers for this workshop,
especially the endocrinological ones, is quite limited.
(A) All agreed that the suckling stimulus to the nipple is mediated by neural
pathways to the brain and that the result is suppression of the pulsatile release of
gonadotrophin-releasing hormone (GnRH), which is necessary for release of the
luteinizing hormone (LH), which in turn promotes follicular maturation, ovulation,
and the luteinization required for maintenance of pregnancy.
Age, baby's, and ovarian activity, 9,14
Age, maternal, and postpartum
lactational, see Lactational