The historically low birthrate, explained in 3 charts

US women are having fewer and fewer babies. In some ways, it’s a sign of progress

American women are having so few babies these days that the fertility rate has hit a historic low, according to stunning provisional data just published by the Centers for Disease Control and Prevention.

The number of births in the US dropped by 2 percent between 2016 and 2017, to 60.2 births per 1,000 women ages 15 to 44, continuing a general downturn that started with the Great Recession of 2008. It’s the lowest the fertility rate has been in 30 years. Read more.

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Scientists may be closer to understanding a mysterious but common cause of female infertility

For a condition that affects up to 10% of reproductive-age women worldwide, polycystic ovary syndrome (PCOS) remains mysterious. It’s a leading cause of female infertility and often boosts the risk of metabolic problems such as type 2 diabetes. It’s also highly heritable: The sister of an affected woman has at least a 20% chance of developing it herself, and the risk for identical twins is even higher. Read more.

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FDA just approved the first drug to prevent migraines. Here’s the story of its discovery—and its limitations

*Update, 18 May, 10 a.m.: Yesterday, the U.S. Food and Drug Administration approved the first in a new class of drugs designed to prevent migraines. This feature, originally published on 8 January 2016, describes the history of these drugs, the powerful relief they can bring some patients, and the limitations that still exist with them. Read more.

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Why getting old gives you itchy skin

Getting old can be a real itch. In addition to having memory and muscle loss, many elderly people develop supersensitive skin that gets itchy at the lightest touch. Scientists don’t know what causes this miserable condition, called alloknesis, or how to treat it. Now, however, a study in mice has revealed a counterintuitive mechanism for the disorder: a loss of pressure-sensing cells in the skin. Although the findings have yet to be replicated in humans, the study raises the possibility that boosting the function of these cells could treat chronic itch in people, both young and old. Read more.

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More than half your body is not human

Human cells make up only 43% of the body’s total cell count. The rest are microscopic colonists.

Understanding this hidden half of ourselves – our microbiome – is rapidly transforming understanding of diseases from allergy to Parkinson’s.

The field is even asking questions of what it means to be “human” and is leading to new innovative treatments as a result.

“They are essential to your health,” says Prof Ruth Ley, the director of the department of microbiome science at the Max Planck Institute, “your body isn’t just you”. Read more.

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