Having just one abortion could raise the risk of potentially life-threatening problems in future pregnancies, young women were warned last night.

Those who terminate their first pregnancy could be risking not only their own health but that of their next baby, a study has found.

They are at higher risk of a range of problems, from their next child being born prematurely to pre-eclampsia, a complication of pregnancy that can be fatal to mother and baby.

Crucially, just one abortion appeared to be enough to do the damage, with subsequent terminations not being any more dangerous.

This differs from previous studies that found the risks rise with each abortion.

Most of the risks were linked to surgical abortions and not those that use pills, which are becoming increasingly common.

Almost 200,000 abortions are carried out in England and Wales each year, with the highest rates among women in their late teens and early 20s. In Scotland, 40 per cent of around 13,000 abortions are carried out in the under-25s.

Abortion has been linked to premature births before but some previous studies have been small and the results have been mixed.

To build a clearer picture, researchers at Aberdeen University analysed the medical records of more than 600,000 Scottish women, including many who had aborted their first baby.

The data, spanning three decades, showed a woman who had an abortion the first time she conceived was 37 per cent more likely to give birth prematurely the next time she became pregnant, compared with one who was having her first child.

She was also 67 per cent more likely to give birth early than a woman who had already started her family.

However, the risks were still lower than those faced by a woman who had suffered a miscarriage, the British Science Festival in Aberdeen heard.

A woman who aborted her first pregnancy was also at higher risk of having a baby of low weight and of developing pre-eclampsia than one who was pregnant for the first time or already had a child.

Pre-eclampsia causes high blood pressure, blood clots and kidney damage, and leads to the deaths of up to 1,000 babies and at least six mothers a year.

Medical abortions using pills are normally used early in pregnancy and account for almost half of terminations in England and Wales, and 70 per cent in Scotland.

Researcher Professor Siladitya Bhattacharya said surgical abortions may be more likely to damage the womb, leading to later problems.

He added women seeking abortions should be made aware of the potential risks and medical terminations should be available to all who would benefit from them.

The British Pregnancy Advisory Service, which carries out almost a third of abortions in the UK, says the leaflets it gives to patients mention the link with premature birth.

But they do not say abortion is the cause because some of the reasons women choose to terminate a pregnancy such as unemployment, smoking or poor diet are also linked to early births.

However, Philippa Taylor of the Christian Medical Fellowship said: 'This study confirms many previous findings... that all show a clear link between abortion and an increased risk of a later pre-term birth.'

Organic produce and meat typically isn't any better for you than conventional varieties when it comes to vitamin and nutrient content, according to a new review of the evidence.

But organic options may live up to their billing of lowering exposure to pesticide residue and antibiotic-resistant bacteria, researchers from Stanford University and the Veterans Affairs Palo Alto Health Care System found.

"People choose to buy organic foods for many different reasons. One of them is perceived health benefits," said Dr. Crystal Smith-Spangler, who led the new study.

"Our patients, our families ask about, 'Well, are there health reasons to choose organic food in terms of nutritional content or human health outcomes?'"

To try to answer that question, she and her colleagues reviewed over 200 studies that compared either the health of people who ate organic or conventional foods or, more commonly, nutrient and contaminant levels in the foods themselves.

Those included organic and non-organic fruits, vegetables, grains, meat, poultry, eggs and milk.

Many of the studies didn't specify their standards for what constituted "organic" food - which can cost as much as twice what conventional food costs - the researchers wrote Monday in the Annals of Internal Medicine.

According to United States Department of Agriculture standards, organic farms have to avoid the use of synthetic pesticides and fertilizers, hormones and antibiotics. Organic livestock must also have access to pastures during grazing season.

Many conventional farms in the U.S., in contrast, use pesticides to ward off bugs and raise animals in crowded indoor conditions with antibiotics in their feed to promote growth and ward off disease. The Food and Drug Administration has been examining that type of antibiotic use and its contribution to drug-resistant disease in humans.

SAME VITAMINS

Smith-Spangler and her colleagues found there was no difference in the amount of vitamins in plant or animal products produced organically and conventionally - and the only nutrient difference was slightly more phosphorus in the organic products.

Organic milk and chicken may also contain more omega-3 fatty acids, they found - but that was based on only a few studies.

There were more significant differences by growing practice in the amount of pesticides and antibiotic-resistant bacteria in food.

More than one-third of conventional produce had detectable pesticide residues, compared to seven percent of organic produce samples. And organic chicken and pork was 33 percent less likely to carry bacteria resistant to three or more antibiotics than conventionally-produced meat.

Smith-Spangler told Reuters Health it was uncommon for either organic or conventional foods to exceed the allowable limits for pesticides, so it's unclear whether a difference in residues would have an effect on health.

But Chensheng Lu, who studies environmental health and exposure at the Harvard School of Public Health in Boston, said that while the jury is still out on those effects, people should consider pesticide exposure in their grocery-shopping decisions.

"If I was a smart consumer, I would choose food that has no pesticides," Lu, who wasn't involved in the new study, told Reuters Health. "I think that's the best way to protect your health."

He said more research is necessary to fully explore the potential health and safety differences between organic and conventional foods, and that it's "premature" to conclude organic meat and produce isn't any healthier than non-organic versions.

"Right now I think it's all based on anecdotal evidence," Lu said.

UCLA researchers have discovered a type of cell that is the "missing link" between bone marrow stem cells and all the cells of the human immune system.

The finding may help explain how a healthy immune system is produced and how disease can lead to poor immune function.

The studies were done using human bone marrow, which contains all the stem cells that produce blood during postnatal life.

The research team was "intrigued to find this particular bone marrow cell because it opens up a lot of new possibilities in terms of understanding how human immunity is produced from stem cells throughout life," said study senior author Dr. Gay Crooks, co-director of the Eli and Edythe Broad Center of Regenerative Medicine and a co-director of the Cancer and Stem Cell Biology program at UCLA's Jonsson Comprehensive Cancer Center.

Understanding the process of normal blood formation in human adults is a crucial step in shedding light on what goes wrong during the process that results in leukemia, or cancer of the blood.

Before this study, researchers had a fairly good idea of how to find and study the blood stem cells of the bone marrow. The stem cells live forever, reproduce themselves and give rise to all the cells of the blood. In the process, the stem cells divide and produce intermediate stages of development called progenitors, which make various blood lineages like red blood cells or platelets.

Crooks was most interested in the creation of the progenitors that form the entire immune system, which consists of many different cells called lymphocytes, each with a specialized function to fight infection.

"Like the stem cells, the progenitor cells are also very rare, so before we can study them we needed to find the needle in the haystack." said Lisa Kohn, a member of the UCLA Medical Scientist Training Program and first author in the paper.

Previous work had found a fairly mature type of lymphocyte progenitor with a limited ability to differentiate, but the new work describes a more primitive type of progenitor primed to produce the entire immune system, Kohn said

Once the lymphoid primed progenitor had been identified, Crooks and her team studied how gene expression changed during the earliest stages of its production from stem cells.

"The gene expression data convinced us that we had found a unique stage of development in the immune system. There was a set of genes that the lymphoid-primed cell shares with the bone marrow stem cells and a unique gene expression of its own once it becomes active. This data provided us with an understanding of what genes are important in creating all the cells of the immune system," said Crooks, a professor of pathology and pediatrics.

"The information could allow us to manipulate bone marrow to help create a stronger immune system," he noted.

The study appeared in the early online edition of Nature Immunology.

Two studies by University of Alabama at Birmingham researchers have suggested that deep-brain stimulation (DBS) may stop uncontrollable shaking in patients with Parkinson's disease and essential tremor by imposing its own rhythm on the brain.

DBS uses an electrode implanted beneath the skin to deliver electrical pulses into the brain more than 100 times per second. Although this technology was approved by the Food and Drug Administration more than 15 years ago, it remains unclear how it reduces tremor and other symptoms of movement disorders.

With the help of electroencephalography or EEG - electrodes placed on the scalp - study authors used new techniques to suppress the electrical signal associated with the DBS electrode. That enabled the first clear, non-invasive EEG measurements of the underlying brain response during clinically effective, high-frequency brain stimulation in humans.

The results showed that nerves in the cerebral cortex, the outer layer of the brain, fire with rapid and precise timing in response to individual stimulus pulses. This suggests that DBS may synchronize the firing of nerve cells and break the abnormal rhythms associated with involuntary movements in Parkinson's disease and essential tremor.

The newly identified rhythm was captured during effective DBS treatment, so it could represent a new physiological measure of the stimulation dose, said the authors. If validated, such a yardstick could help to guide the fine-tuning of DBS stimulator settings in patients for more lasting relief, fewer side effects and less-frequent battery-replacement surgeries.

"Though it's clear that more work is needed to better understand these initial observations, we're very excited by our findings because they may provide a biological marker for improvement in the symptoms of these patients," said Harrison Walker, M.D., assistant professor in the UAB Department of Neurology's Division of Movement Disorders and lead author of the study.

In current clinical practice, stimulator settings are adjusted by trial and error, requiring careful observation of changes in symptoms over multiple clinic visits. But such immediate, visual feedback may not be available as DBS is applied to neurological or psychiatric conditions such as epilepsy, severe depression or obsessive compulsive disorder.

In these diseases, an effective dose measurement could be especially useful in optimizing DBS therapy.

In both studies, EEG data revealed that nerve cells in the cerebral cortex discharged about one one-thousandth of a second, or one millisecond, after each stimulus pulse was delivered into the brain.

The authors argue that this rapid response on the brain's surface most likely represented "backfiring" along extensions of cortical nerve cells called axons that connect them to deeper regions within the brain where the DBS electrodes were placed. Interestingly, this rapid response on the brain surface was present in both studies, regardless of the stimulation target or the disease state of the patient.

Although prior studies had hinted at these brain responses, they were unable to measure them directly because of interference from the competing electrical signal emitted by the DBS pulse itself. Walker and his team reversed the polarity of the stimulation pulse, in effect subtracting the DBS signal and leaving only the EEG signal associated with the brain activity.

The new technique also enabled the researchers to show that the size of the brain response at one millisecond after a DBS pulse is dependent on the intensity or voltage of the stimulus pulse, and that larger brain responses were closely associated with improvement in tremor.

"While early, this work has tremendous implications for the understanding of brain mechanisms responsible for a number of neurological and psychiatric diseases," said co-author Barton Guthrie, M.D., in the Division of Neurosurgery.

"Further studies are planned to confirm these measures and mechanisms and we believe this insight will soon make valuable contributions to the next generation of DBS treatments," he added.

The studies were published recently in the journal Movement Disorders.

Children whose mothers are in full-time employment are at greater risk of obesity even if their father is a stay-at-home parent, according to experts.

Their study highlights that men about the house fail to realise the importance of their child's eating habits.

Study authors say that it is important for both parents to discuss day-to-day responsibilities, including food preparation and mealtimes.

John Cawley, from Cornell University and Feng Liu used data on almost 25,000 families from a yearly survey of how Americans spend their time.

Data showed that on average women who worked spent 127 fewer minutes per day with their children than stay-at-home mothers.

However stay-at-home fathers failed to offset the difference "We're not trying to say men are scum," Cawley told BuzzFeed.

Cawley and Liu noted that preparing meals from scratch and eating as a family could decrease a child's risk of obesity.

They also suggest that schools could offer healthier food and better physical education.

The study is published in the June issue of Economics and Human Biology.