Children whose mothers needed drugs to start giving birth are slightly more likely to have autism, US researchers say. 
 
 A study of 625,000 children, published in JAMA Pediatrics, showed the autism link was stronger in boys. 
 
 Scientists have called for more research to explain the difference as it is not clear why there would be a link. 
 
 Doctors said inducing labour was safe, necessary and could save a baby's life. 
 
 Autism is thought to be caused by a combination of family, or genetic, risk and conditions in the womb and early life while the child is developing. 
 
 Procedure could be life-saving 
 
 We don't want mothers to say, 'Under no circumstances do I want to be induced because I don't want a kid with autism'. That would be plain wrong Prof Simon Gregory, Duke University 
 
 The study of births in North Carolina showed 13 out of every 1,000 boys born, and four per 1,000 girls, developed autism. 
 
 However, the rate was a third higher in boys when their mother needed drugs to induce or assist the pregnancy, while any effect in girls was more muted. 
 
 Researchers said that two cases of autism in every 1,000 births might be prevented by stopping induction. However, they warned this would come at significant cost as the procedure could be life-saving. 
 
 Prof Simon Gregory, of Duke University, said there had been a lot of conflicting evidence on autism and inducing labour, but this study was the largest to look at the issue. 
 
 He told the BBC: "We don't want mothers to say, 'Under no circumstances do I want to be induced because I don't want a kid with autism'. That would be plain wrong. 
 
 "We've found an association and more research is needed. This allows us to focus on the factors around birth that may affect autism and how it develops." 
 
 The study only shows that the rates of autism are higher after being induced. It could be down to the drugs used to begin labour or something else influencing the pregnancy that leads to women needing to be induced and also affects the developing brain. 
 
 What is autism? Autism and Asperger's syndrome are part of a range of disorders that can cause difficulties with communication and social skills 
 
 The conditions can lead to isolation and emotional problems for those living with them 
 
 Conditions can vary from very mild, where the person can function easily, to so severe they cannot take part in normal society 
 
 The conditions are collectively known as autistic spectrum disorders and affect more than 580,000 people in the UK What are the symptoms of autism? 
 
 'Good medical reasons' 
 
 Labour is often induced when the pregnancy has gone on too long and the mother has missed the due date, normally by at least a week. 
 
 Michael Heard, of Hampshire Hospitals NHS Foundation Trust and the Royal College of Obstetricians and Gynaecologists spokesperson, said: "We induce to improve outcomes. You reduce the chance of losing the baby and the chance of mum and baby getting unwell. 
 
 "This is a preliminary statistical overview, with no clear reasoning why the two things should be linked. 
 
 "Induction is very common and is offered for good medical reasons and is extremely safe. But like most medical processes there is a small risk associated. 
 
 "This is another thing to consider in a long-term study, but not something I'd consider in my practice." 
 
 Carol Povey, of the National Autistic Society, said: "Autism is a complex condition and is thought to be the result of many different underlying physical and genetic factors. Its exact causes are still being investigated. 
 
 "The scientists who conducted this study acknowledge that further research is required before any hard and fast conclusions can be drawn. 
 
 "It's therefore important that people do not jump to conclusions about this study and its implications." ||||| Credit: Pregnancy photo via Shutterstock 
 
 Babies born to women whose labor was induced, or whose contractions were strengthened, with medical procedures such as hormone treatments, face an increased risk of autism, a new study suggests. 
 
 Using school records and birth databases in North Carolina, researchers looked at the birth records of more than 625,000 children born between 1990 and 1998, including 5,500 who were diagnosed with autism. 
 
 They found that children born to mothers whose labor was induced, augmented or both had a 27-percent increased risk of autism, compared with children born to mothers whose labors were not induced or augmented. 
 
 The link held when the researchers took into account other factors that could have influenced the rate of autism, such as mother's age, diabetes during pregnancy and pre-term labor. 
 
 Still, other factors that were not accounted for could have lay beneath both the need for hormones during labor and a baby's risk of autism. 
 
 "While the results are interesting, we are not drawing a cause-and-effect relationship," said study researcher Simon Gregory, professor of medicine at Duke University in Durham, N.C. 
 
 The researchers said women should not avoid receiving induction or augmentation treatment when it is recommended by their physicians due to concern for the woman's health or that of the fetus. [Beyond Vaccines: 5 Things That Might Really Cause Autism] 
 
 "The risk to the mother and the unborn child would be far greater" if the labor were not induced or augmented when necessary, Gregory said. 
 
 Labor induction is a medical procedure that stimulates uterine contractions before labor begins on its own. A doctor may recommend this treatment when a pregnancy is more than a week or two past the due date, or when the health of the mother or her unborn child is at risk if the pregnancy were to continue. Labor augmentation, on the other hand, is a procedure that speeds up a labor that has already started, but is progressing too slowly. 
 
 It is not clear whether it is the act of labor induction or augmentation that underlies the link with autism, or the medications used in these methods, the researchers said. Moreover, it might be that certain medical conditions during pregnancy that can lead to the need for labor induction or augmentation are also responsible for the link with autism, the researchers said. 
 
 It is possible that exposure to the hormone oxytocin, which is used for labor induction, could explain the link, the researchers said. It is estimated that 50 to 70 percent of women who undergo labor induction receive oxytocin. Oxytocin might affect the baby's nervous system, perhaps in ways that depend on genetics, but this idea needs further study, the researchers said. 
 
 In the study, children born to mothers whose labor was induced (but not augmented) had a 13 percent increase in risk of autism, and children born after augmented labor had 16 percent increased risk of autism. 
 
 The results were particularly pronounced in male children, the researchers said. Boys born to mothers who received both induction and augmentation faced a 35 percent increase in autism risk, according to the study. 
 
 The study also confirmed links between autism and other previously suggested risk factors, such as pre-term birth and diabetes in the mother. Children born before week 34 of pregnancy were 25 percent more likely to have autism, compared with children born at full term. Mothers with diabetes — including both those with gestational diabetes and those who had diabetes prior to their pregnancies — had a 23 percent increased risk of having a child with autism, compared to mothers without diabetes. 
 
 The study had some limitations, the researchers said. The databases did not include information about every possible risk factor, and the researchers could not take into account the fathers' age, the medications the mothers might have used, or the severity of the children's autism. 
 
 The study was published online today (Aug. 12) in the journal JAMA Pediatrics. 
 
 Email Bahar Gholipour or follow her @alterwired. Follow LiveScience @livescience, Facebook & Google+. Original article on LiveScience.com.
– A new study finds induced labor may be linked to an increased risk of autism, but doctors warn that more research is needed. The study of 625,000 children found that, overall, 13 out of every 1,000 boys and four out of every 1,000 girls developed autism. But, for boys, that rate was one-third higher when their mothers saw their labor induced or augmented, the BBC reports. (The effect was not as pronounced in female births.) LiveScience reports that such augmentations might include strengthening contractions with hormone treatments; it says the risk of autism was 13% higher when labor was induced, 16% higher when it was augmented, and 35% higher (in male births) when it was both induced and augmented. The study did account for other factors (mother's age, diabetes, pre-term labor) that could have affected the autism rate, but researchers say there could be still other factors that underlie both the need for induced labor and the increased occurrence of autism. "We are not drawing a cause-and-effect relationship," says one. All in all, halting induced labor could prevent two cases of autism out of every 1,000 births, according to the study. But there would be a cost, as induced labor (which is often recommended when a pregnancy extends more than a week or two beyond the due date) and augmented labor (which is often used when a birth is progressing too slowly) can save lives of both moms and babies.