Reproductive function in women shaped by childhood environment

A recent research has found that female reproductive function is influenced by childhood environment.

Washington, May 15 : A recent research has found that female reproductive function is influenced by childhood environment.

The study, led by researchers at UCL (University College London), suggests that there is a crucial window of time from about 0-8 years of age that establishes the rate at which girls physically grow and how high their reproductive hormone levels reach as adults.

Published today in PLoS Medicine, the study compares reproductive hormone levels of groups of Bangladeshi women who migrated at different periods of their life.

It finds that women who migrated from Bangladesh to the UK during babyhood and early childhood reach puberty earlier, are taller, and have up to 103 per cent higher levels of the hormone progesterone as adults in comparison to women who migrated at a later age, as well as those who had remained in Bangladesh. These higher hormone levels could potentially boost a woman's capability to conceive.

"The findings point to the period before puberty as a sensitive phase when changes in environmental conditions positively impact on key developmental stages. Put very simply, the female body seems to monitor its environment throughout childhood and before puberty, to gauge when and at what rate it will be best to mature. It then sets development, including reproductive hormone levels, accordingly. This is an advantage in evolutionary terms, as it makes the best of the resources and energy available for reproduction in any given circumstance," Lead author Dr Alejandra N£�ez de la Mora, UCL Department of Anthropology, said.

"Girls who migrate at a young age seem to mature more quickly when they find themselves in an environment where the body has more access to energy. In other words, when they're under less physical strain due to factors like a better diet and general health. When energy is a limited resource, it must be allocated between maintenance, growth, and reproductive functions - the body makes trade-offs within the constraints it experiences. When conditions are better, these constraints are relaxed and more energy is diverted towards reproduction," Dr Alejandra added.

The results of this study are significant not only to Bangladeshi groups, but to other nomad groups and populations in transition worldwide. These findings add to amassing evidence that humans have a developed ability to react to constant environmental conditions during growth and to make decisions about how to allocate energy between reproductive and other bodily functions.

Five groups of women were selected and compared for the study. These included women who had matured in Bangladesh but migrated to the UK as adults; those who had moved to the UK as children; second generation Bangladeshi women living in the UK; women who were born and raised in Bangladesh; and a comparison group of women of European descent who were born and raised in the UK. Bangladeshi migrants were selected for this study because of the elongated and on-going history of migration to the UK and the general disparity in conditions between the two countries.

The subjects in each group gave their saliva samples over an extended period, to gauge levels of the female hormones progesterone and oestradiol. These are key fertility hormones, affecting the female menstrual cycle, pregnancy and embryonic development.

"The theory that early environmental factors may affect reproductive function has been suggested previously by anthropologists*, but this field study is the first to use measurements of hormone levels to demonstrate a link between childhood environment and reproductive maturation and function. However, hormone levels are not just relevant to reproduction. The significant increase in progesterone levels that we document in migrant women may result, for example, in higher breast cancer risks in subsequent generations of this community. The potential health implications are far-reaching," co-author Dr Gillian Bentley, UCL Department of Anthropology, who directed the project, said.

Bangladesh is one of the most thickly populated countries in the world. The Bangladeshis who participated in the study were middle class women from the Sylhet District. Although a comparatively prosperous area of the country, residents still undergo higher immune challenges, mainly due to poor hygiene and inadequate access to healthcare. These facets of the environment in Bangladesh are thought to be accountable for the slower development of the Bangladeshi women who grew up there.

ANI