Experts are still trying to piece together what factors contribute to the development of autism. Recent research suggests that changes that occur during conception, pregnancy, and possibly even delivery may increase the risk of autism in children who are genetically predisposed to the disorder. Here's what experts are learning and what you need to know.
A 2014 study in the American Journal of Epidemiology found that children born to iron-deficient mothers are five times more likely to develop autism. The risk increases when the mother is age 35 or older or has a metabolic condition such as obesity, high blood pressure or diabetes. Iron is crucial to fetal brain development, yet up to half of all pregnant women don't get enough of it.
Researchers looked at the iron intake of close to 900 women during three critical stages: three months prior to becoming pregnant, throughout pregnancy and after delivery while breastfeeding. The mothers of children with autism were significantly less likely to take iron supplements before, during and/or after their pregnancies than the mothers whose children were developing typically.
Should you be concerned? This study is the first to examine the relationship between maternal iron intake and autism risk. To confirm a connection and the study's validity, more researchers need to replicate the findings in larger research groups. "While there's no clear indication that iron deficiency during pregnancy causes autism, we know that iron is critical to the in utero development of a baby's nervous system," says Raphael Bernier, Ph.D., clinical director of the Autism Center at Seattle Children's Hospital. That's why it's important to get enough iron in your diet via foods, such as meats, seafood, eggs and iron-fortified breads and cereal, and to take an iron-fortified prenatal supplement when you're trying to conceive and when you're expecting.
A 2014 French study conducted on mice and published in the journal Science suggests that the use of spinal anesthesia during labor results in higher concentrations of chloride or salt in the brains of newborn mice. The authors hypothesize that this may increase the risk of autism in humans.
High chloride levels are essential to a baby's brain development while in utero. During labor and delivery, a baby is exposed to oxytocin, the hormone that brings on contractions. Oxytocin acts as a diuretic and naturally lowers an infant's chloride levels. Researchers believe epidurals may interfere with the release of oxytocin causing chloride levels to remain high after birth.
What you need to know: The study seems to support earlier findings from a 2012 clinical trial of 60 children with autism who saw some improvements in their behaviors after taking a diuretic that lowered their chloride levels. However, the Science study on epidurals and chloride was conducted solely on mice. While animal studies are important, the findings don't always translate to people. "For one thing, animals don't have symptoms of autism in the same way that people do," says Susan Hyman, M.D., division chief of neurodevelopmental and behavioral pediatrics at the University of Rochester Medical Center in New York and chair of the American Academy of Pediatrics' (AAP) Council of Children with Disabilities Autism Subcommittee.
What's more, the study didn't address what happens when a mother's labor is induced with pitocin, a synthetic version of oxytocin. "As a mother, I know that epidurals made my deliveries more comfortable," says Dr. Hyman. "I don't think it's prudent to deviate from a helpful obstetrical practice based on one animal study."
Research from the University of Utah published in the November 2013 issue of Pediatrics suggests a potential link between excess pregnancy pounds and autism risk. The American Congress of Obstetricians and Gynecologists (ACOG) recommends women gain no more than 35 pounds during pregnancy (it's 25 pounds if you're already overweight). In the study, incremental 5-pound increases in weight above ACOG's recommendation were linked to a slightly higher, yet significant risk for autism.
What you need to know: Previous studies indicate a possible connection to a woman's pre-pregnancy body mass index (BMI), pregnancy weight gain, and a child's risk of autism. One theory is that excess body fat may change a woman's hormone levels or cause inflammation that affects fetal brain development. "Obesity rates and autism rates have both gone up over the past decades, yet that doesn't mean the two are connected," says Anna Maria Wilms Floet, M.D., a behavioral developmental pediatrician at the Kennedy Krieger Institute's Center for Autism and Related Disorders in Baltimore. The bottom line: "Women should watch their weight gain during pregnancy to prevent problems like diabetes and high blood pressure," says Dr. Wilms Floet.
An April 2015 study in the Journal of the American Medical Association (JAMA) found that mothers-to-be who are diagnosed with gestational diabetes by their 26th week of pregnancy are 63 percent more likely to have a child with autism. That means for every 1,000 women with gestational diabetes, seven of them may have a child with autism. Researchers speculate that in utero exposure to high blood sugar may affect a baby's brain development and heighten the risk for developmental disorders.
What you need to know: Earlier studies also have shown a possible connection between high blood sugar during pregnancy and autism risk. The key factor may be how high blood sugar levels get. Interestingly, the JAMA study found that babies born to mothers who had type 2 diabetes before getting pregnant didn't have a higher risk of autism, perhaps because the women were taking medication to control their blood sugar levels.
Gestational diabetes poses a number of problems for infants, including preterm labor, large birth-weight and an increased risk of obesity and type 2 diabetes later in life. Moms-to-be have a higher risk of developing high blood pressure, preeclampsia and type 2 diabetes, as well. "All expectant women should strive to keep their blood sugar under control, regardless of these study findings," says Dr. Wilms Floet.
A 2011 Epidemiology study found that taking prenatal vitamins three months before conception and during at least the first month of pregnancy halves a child's autism risk. Women with a strong genetic link to the disorder who didn't take vitamins were up to seven times more likely to have a child with autism. Additional studies suggest high levels of folic acid, a B vitamin important for brain development, are key.
What you need to know: All women of childbearing age (even those who aren't trying to conceive) should get between 400 to 800 micrograms (mcg) of folic acid every day. Most women get about 150 mcg of daily folic acid from fortified foods such as breads and cereal. A 2012 American Journal of Clinical Nutrition study suggests that women need at least four times that amount -- 600 mcg -- to lower autism risk. Check your vitamin's nutrient label, and if necessary, discuss upping your folic acid intake with your doctor, and add more foods rich in folate (like lentils, spinach, and broccoli) to your diet.
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