It seems that in the case of women, fertility is not just an innate quality but also one adjusted by life conditions in early life.

This conclusion was reached by a team at University College London which analyzed hormone levels in women who migrated to the UK from Bangladesh at various life stages.

The researchers found that women brought up in UK, where they had enjoyed better sanitation and health care, and faced lower risks of disease, presented higher levels of sexual hormones than those who grew up in Bangladesh. The first category reached puberty earlier and displayed up to 103% higher levels of progesterone at adult age, compared with those brought up in Bangladesh or that did not leave the country.

Progesterone is a hormone implied in a woman's fertility but it can also come with side effects.

"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." said author Dr Gillian Bentley.

The role of the early childhood is determining the speed of girls' sexual maturation and their level of reproductive hormone levels during adulthood is explained by the body's monitoring of its environment (diet and general health) throughout childhood to assess the best timing and rhythm of maturation.

Girls who migrated early in life appeared too mature at earlier age.

"This is an advantage in evolutionary terms, as it makes the best of the resources and energy available for reproduction in any given circumstance." said lead researcher Dr Alejandra N￭ñez de la Mora.

That's crucial when energy is limited; the body must cope with all functions, so it can re-program reproduction to proper time.
The research was made on five groups of women, among whom those growing up in Bangladesh but moved to the UK as adults, those who migrated as children and women still residents where they were born, in either England or Bangladesh.

"This sounds like a reasonable idea and suggests evidence to support the fact that improved nutrition is likely to have a beneficial effect on fertility." said consultant gyneacologist Adrian Lower.