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Category: pregnancy and childbirth

Published on Leave a comment on Microbes Partially Restored To C-Section Babies

I posted about this amazing research while it was still ongoing (Jan. 16, 2015), but now a study has been published. The small well-done pilot study looked at the microbiome (microbial communities) and microbial differences between different groups of infants during the first 30 days of life. They found significant differences in the bacteria of C-section infants (not exposed to their mother's vaginal fluid in the birth canal) compared to C-section infants who were swabbed with a gauze pad right after birth with their mother's vaginal fluids. They found that the microbiota (community of microbes) is partially restored in the swabbed C-section infants and more similar to that of vaginally delivered infants (who were exposed to the maternal bacteria naturally in the birth canal). They found that the procedure restored some bacteria, such as Lactobacillus and Bacteroides, which were nearly absent in the skin and anal samples of non-swabbed C-section babies.

In the C-section group, four mothers who were free of infections that might harm the babies, incubated a sterile gauze in their vaginas for one hour before the operation (C-section). Then, within two minutes of birth, the babies were swabbed with the gauze first over their mouths, then their faces, and then the rest of their bodies. These results are important because it is thought that microbiome differences (depending on method of birth) are long-lasting (with higher incidence of some health problems later in life with C-sections), and because the baby's early microbiome helps educate the baby's developing immune system.

Rob Knight (a leading microbiologist and one of the researchers) pointed out that the study "provides the proof-of-concept that microbiome modification early in life is possible." Now we need to see if these microbial differences persist over time and if it makes a health difference. From Science Daily:

Vaginal microbes can be partially restored to c-section babies

In a small pilot study, researchers at University of California, San Diego School of Medicine and Icahn School of Medicine at Mount Sinai determined that a simple swab to transfer vaginal microbes from a mother to her C-section-delivered newborn can alter the baby's microbial makeup (microbiome) in a way that more closely resembles the microbiome of a vaginally delivered baby. 

Babies delivered by C-section differ from babies delivered vaginally in the makeup of the microbes that live in and on their bodies. These early microbiomes help educate the baby's developing immune system. Previous research suggests a link between C-section delivery and increased subsequent risk of obesity, asthma, allergies, atopic disease and other immune deficiencies. Many of these diseases have also been linked to the microbiome, though the role a newborn's microbiome plays in current or long-term health is not yet well-understood....Other research suggests that microbiome differences between vaginal and C-section babies can persist for years."

In the study, the researchers collected samples from 18 infants and their mothers, including seven born vaginally and 11 delivered by scheduled C-section. Of the C-section-delivered babies, four were exposed to their mothers' vaginal fluids at birth as part of this study. To do this, sterile gauze was incubated in the mothers' vaginas for one hour before the C-section. Within two minutes of their birth, the babies delivered by C-section were swabbed with the gauze starting with the mouth, then the face and the rest of the body.

Six times over the first month after birth, the researchers collected a total of 1,519 anal, oral and skin samples from the mothers and infants. Knight's team then used a gene sequencing technique to map the types and relative quantities of bacterial species present at each body site.

Here's what they found: the microbiomes of the four C-section-delivered infants exposed to vaginal fluids more closely resembled those of vaginally delivered infants than unexposed C-section-delivered infants, though the difference was more distinct in their oral and skin samples than in their anal samples. This partial microbial restoration could be due to the fact that the infants received only one surface application of maternal vaginal fluids, Knight said.

Yet the oral and skin microbiome differences between C-section-delivered infants who received the microbial transfer and those who did not was still noticeable one month after birth. The results were not due to diet differences, as all of the infants received breast milk either exclusively or supplemented with formula during the first month of life. In addition, consistent with previous studies, the babies' microbiome profiles did not correlate with the amount of breast milk they received.

"The present work is a pilot study -- we need substantially more children and a longer follow-up period to connect the procedure to health effects," said Knight...."This study points the way to how we would do that, and provides the proof-of-concept that microbiome modification early in life is possible. In fact, we already have more than 10,000 additional samples collected as part of this study that still await analysis."

Published on Leave a comment on Oral Contraceptives, Pregnancy, and Birth Defects

This is an issue that a lot of women I've known over the years have wondered about: if a woman gets pregnant while on birth control pills (oral contraceptives) - and many women do - does it mean higher rates of birth defects? This study says NO to higher rates of major birth defects which is very reassuring, but it doesn't answer the issue of more subtle effects (e.g., behavioral effects) from the hormones in the contraceptives. From Medical Xpress:

Oral contraceptive use not associated with increased birth defects risk

Oral contraceptives taken just before or during pregnancy do not increase the risk of birth defects, according to a new study by researchers from Harvard T.H. Chan School of Public Health and the Statens Serum Institut in Denmark. They found that the prevalence of major birth defects was consistent (about 25 per 1,000 live births) across all pregnant women in the study population regardless of contraceptive use.

Even though oral contraceptives are more than 99% effective with perfect use, almost 10% of women become pregnant within their first year of use. Many more women will stop using oral contraceptives when planning a pregnancy and conceive within a few months. Little is known about the potential health effects to children from in utero exposure to the hormones in oral contraceptives.

....Charlton and colleagues were able to tap into a wealth of data collected from multiple Danish health registries between 1997 and 2011 and linked by the unique personal identification number assigned to all Denmark residents. The researchers looked at 880,694 live-born infants, and the health of these children at one-year follow-up. Oral contraceptive use was estimated based on the date of the mother's most recently filled prescription.  Among the women in the study population, a fifth had never used oral contraceptives before becoming pregnant, and more than two-thirds had stopped using oral contraceptives at least three months before becoming pregnant. Eight percent had discontinued use within three months of becoming pregnant, and 1%, or well over 10,000 women, had used oral contraceptives after becoming pregnant.

The prevalence of birth defects was consistent across each category of oral contraceptive use, and remained so when the researchers added in pregnancies that ended as stillbirths or induced abortions.

Published on Leave a comment on Phthalates, Sperm, and Miscarriages

More and more negative news about phthalates: men with greater exposure to DEHP (a phthalate) have lower sperm motility (how the sperm move or their ability to swim), and pregnant women with higher levels of phthalates have a higher rate of pregnancy loss (miscarriages - mainly between 5 and 13 weeks of pregnancy). Phthalates are found in many plastics, are thought to be endocrine disruptors, and can be measured in urine. From Medical Xpress: Lower sperm motility in men exposed to common chemical

Men with higher exposure to the substance DEHP, a so-called phthalate, have lower sperm motility and may therefore experience more difficulties conceiving children, according to a Lund University study. Phthalates is an umbrella term for a group of substances based on phthalic acid, some of which are suspected to be endocrine disruptors. Many phthalates are found in soft plastics in our daily surroundings.... Since phthalate molecules leak out of plastics, we are exposed to it daily and absorb the chemicals through food, drink, skin contact and inhalation. 

"We have studied metabolite levels of the phthalate DEHP (diethylhexyl phthalate) in urine as an indicator of exposure, as well as the semen quality of 300 men between the ages of 18 and 20. The results show that the higher metabolite levels the men had, the lower their sperm motility was", says Jonatan Axelsson, researcher at the Department of Laboratory Medicine, Lund University. For the one quarter of the men with the lowest levels of exposure, 57 per cent of the sperm cells were moving forward, compared to 46 per cent for the quarter of the men with the highest levels of exposure.

As previous research has reported that there is a linear connection also between sperm motility and chances of becoming pregnant, the findings could indicate that the more exposed one is to DEHP, the smaller the chances are of having children.

From Medical Xpress:  Exposure to phthalates could be linked to pregnancy loss

A new study of more than 300 women suggests that exposure to certain phthalates—substances commonly used in food packaging, personal-care and other everyday products—could be associated with miscarriage, mostly between 5 and 13 weeks of pregnancy. 

Out of concern over the potential health effects of phthalates, the U.S. has banned six of these substances from use in certain products made for young children. But many are still included as ingredients in paints, medical tubes, vinyl flooring, soaps, shampoos and other items. Research on phthalates has shown that long-term exposure to low levels of the some of these compounds harms lab animals' health and can increase their risk for pregnancy loss. Additionally, at least one study found that female factory workers exposed to high levels of phthalates through their work were at a higher risk for miscarriage.

The researchers tested urine samples from 132 women who had miscarriages and 172 healthy pregnant women in China. They found pregnancy loss was associated with higher levels of urinary phthalate metabolites from diethyl phthalate (DEP), di-isobutyl phthalate (DiBP) and di-n-butyl phthalate (DnBP). Although this doesn't prove that phthalates cause pregnancy loss, the study suggests an association exists that the researchers say should be studied further.

Published on Leave a comment on Taking Antidepressants During Pregnancy and Autism

A large study found that using antidepressants during the second or third trimester of pregnancy increases the risk that the child will have autism by 87%,  especially if the mother takes selective serotonin reuptake inhibitors (SSRIs). A drawback was that the study looked at associations rather than actual cause (which would have meant randomly assigning women to either treatment or no treatment - which is unethical). From Medical Xpress:

Taking antidepressants during pregnancy increases risk of autism by 87 percent

Using antidepressants during pregnancy greatly increases the risk of autism, Professor Anick Bérard of the University of Montreal and its affiliated CHU Sainte-Justine children's hospital revealed today. Prof. Bérard, an internationally renowned expert in the fields of pharmaceutical safety during pregnancy, came to her conclusions after reviewing data covering 145,456 pregnancies.

"The variety of causes of autism remain unclear, but studies have shown that both genetics and environment can play a role," she explained. "Our study has established that taking antidepressants during the second or third trimester of pregnancy almost doubles the risk that the child will be diagnosed with autism by age 7, especially if the mother takes selective serotonin reuptake inhibitors, often known by its acronym SSRIs." Her findings were published today in JAMA Pediatrics.

Bérard and her colleagues worked with data from the Quebec Pregnancy Cohort and studied 145,456 children between the time of their conception up to age ten. In addition to information about the mother's use of antidepressants and the child's eventual diagnosis of autism, the data included a wealth of details that enabled the team to tease out the specific impact of the antidepressant drugs. 

"We defined exposure to antidepressants as the mother having had one or more prescription for antidepressants filled during the second or third trimester of the pregnancy. This period was chosen as the infant's critical brain development occurs during this time," Prof. Bérard said. "Amongst all the children in the study, we then identified which children had been diagnosed with a form of autism by looking at hospital records indicating diagnosed childhood autism, atypical autism, Asperger's syndrome, or a pervasive developmental disorder. Finally, we looked for a statistical association between the two groups, and found a very significant one: an 87% increased risk." 

The findings are hugely important as six to ten percent of pregnant women are currently being treated for depression with antidepressants. In the current study, 1,054 children were diagnosed with autism (0.72% of the children in the study), on average at 4.5 years of age. Moreover, the prevalence of autism amongst children has increased from 4 in 10,000 children in 1966 to 100 in 10,000 today. While that increase can be attributed to both better detection and widening criteria for diagnosis, researchers believe that environmental factors are also playing a part.

"It is biologically plausible that anti-depressants are causing autism if used at the time of brain development in the womb, as serotonin is involved in numerous pre- and postnatal developmental processes, including cell division, the migration of neuros, cell differentiation and synaptogenesis - the creation of links between brain cells," Prof. Bérard explained. "Some classes of anti-depressants work by inhibiting serotonin (SSRIs and some other antidepressant classes), which will have a negative impact on the ability of the brain to fully develop and adapt in-utero".

Published on Leave a comment on Endocrine Disrupting Chemicals and Male Infertility

Recent research looked at environmental causes of male infertility, specifically endocrine-disrupting chemicals. Poor semen quality contributes to increases in infertility and the use of assisted reproductive technology.The researchers also discuss the higher incidence of testicular cancer worldwide, lower levels of testosterone in men, and poor semen quality among men aged 20 to 25 (with the average man having up to 90% abnormal sperm). From Science Daily:

Endocrine-disrupting chemicals may be threatening fertility in industrialized countries

The birth rate is declining in all industrialised countries, and socioeconomic factors and women's age are not solely to blame. Male reproductive health and environmental factors are also significant, as concluded in a new scientific review article. ...Behind the article are fertility researchers from Denmark, the US and Finland. The researchers studied a number of factors related to fertility, and one of the main conclusions of their study was that poor semen quality contributed to increases in infertility and the use of assisted reproductive technology.

The study also revealed higher incidence of testicular cancer worldwide, with the greatest frequency among Caucasian populations. Moreover, the researchers also observed lower levels of testosterone in average men. "I was surprised that we found such poor semen quality among young men aged 20 to 25. The average man had up to 90% of abnormal sperm. Normally, there would be so many sperms that a few abnormal ones would not affect fertility. However, it appears that we are at a tipping point in industrialised countries where poor semen quality is so widespread that we must suspect that it results in low pregnancy rates," said first author of the article, Professor Niels E. Skakkebaek from the Department of Growth and Reproduction (EDMaRC) at Rigshospitalet and the University of Copenhagen.

"The article also demonstrates the impact of the increasing number of male reproductive problems on low birth rates. There is no doubt that environmental factors are playing a role. These are the correlations we are researching at the new research centre EDMaRC at Rigshospitalet," added Professor Anders Juul, who is the last author of the article.

Many of the male reproductive problems could be due to damage to the testes during embryonic development. While the reproductive problems could arise from genetic changes, "recent evidence suggests that most often they are related to environmental exposures of the fetal testes," the researcher team wrote."Since the disorders in male genitals have increased over a relatively short period of time, genetics alone cannot explain this development. There is no doubt that environmental factors are playing a role and that endocrine-disrupting chemicals, which have the same effect on animals, are under great suspicion. The exposure that young people are subjected to today can determine not only their own, but also their children's, ability to procreate," explained Professor Skakkebaek.

Published on Leave a comment on More Negative News About Hormone Disrupting Chemicals

More and more studies are finding negative health effects from hormone disrupting chemicals (which we are exposed to every single day, and subsequently which are in all of us), such as parabens, phthalates, Bisphenol-A (BPA), and chemical substitutes for BPA such as Bisphenol-S (BPS) and BPF. The following are a few recent studies and one article from my files. Also check out the other endocrine disrupting chemical studies I've posted (SEARCH: 'endocrine disruptors', and 'phthalates').

Bottom line: Read labels and try to minimize plastics in personal care products (e.g., lotion) and your food if possible (e.g., choose glass, stainless steel, wax paper, aluminum foil). This is especially important during pregnancy.  Even BPA alternatives (labeled BPA-free) should be viewed as the same as BPA - as endocrine disruptors. In other words, currently there are no good BPA substitutes. Don't microwave food in a plastic dish or container, or covered with plastic wrap. Eat fresh foods rather than packaged, processed foods. From Newsweek:

BPA Is Fine, If You Ignore Most Studies About It

Bisphenol-A (BPA) is either a harmless chemical that’s great for making plastic or one of modern society’s more dangerous problems. Depends whom you ask. BPA is in many types of plastics and the epoxy resins that line most aluminum cans, as well as thermal papers like receipts. It is an endocrine disruptor that mimics estrogen, a hormone especially important in sexual development, and the fact that it’s all over the place worries many people. Newsweek spoke with about 20 scientists, leaders in the field of BPA research, and the majority say it is likely (though not certain) that the chemical plays a role in a litany of health concerns: obesity, diabetes, problems with fertility and reproductive organs, susceptibility to various cancers and cognitive/behavioral deficits like ADHD.  ...continue reading "More Negative News About Hormone Disrupting Chemicals"

Published on Leave a comment on Missing Microbes in Infancy and Asthma

An interesting Canadian study that followed young children for 3 years found that young infants may be more likely to develop allergic asthma if they lack four beneficial bacteria in their gut. Children with low levels of Lachnospira, Veillonella, Faecalibacterium, and Rothia bacteria in their gut in their first 3 months were at higher risk for asthma and tended to receive more antibiotics than healthier children before they turned 1 year old.

Other studies have shown that the risk of developing asthma and allergies has been linked with such things as taking antibiotics, cesarean birth, bottle fed with formula, not living on a farm, and not having furry pets in the first year of life.

The researchers wrote: "Our findings indicate that in humans, the first 100 days of life represent an early-life critical window in which gut microbial dysbiosis {the microbial community being out of whack} is linked to the risk of asthma and allergic disease." How do the infants get these microbes? It is thought that infants get exposed to the mother's microbiome (microbial community) via vaginal birth, breast-milk, and mouth contact with the mother's skin.  From NPR News:

Missing Microbes Provide Clues About Asthma Risk

The composition of the microbes living in babies' guts appears to play a role in whether the children develop asthma later on, researchers reported Wednesday. The researchers sampled the microbes living in the digestive tracts of 319 babies, and followed up on the children to see if there was a relationship between their microbes and their risk for the breathing disorder. In the journal Science Translational Medicine, the researchers report Wednesday that those who had low levels of four bacteria were more likely to develop asthma by the time they were 3-years-old.

Specifically, the researchers focused on 22 children who showed early signs of asthma, such as wheezing, when they were 1-year-old. They were much more likely than the other children to have had low levels of the four bacteria when they were 3-months-old. By the time they turned 3, most had developed full-blown asthma."The bottom line is that if you have these four microbes in high levels you have a very low risk of getting asthma," says Brett Finlay, a microbiologist at the University of British Columbia who helped conduct the research. "If you don't have these four microbes or low levels of these microbes you have a much greater chance of asthma."

Asthma is a common and growing problem among children. Evidence has been accumulating that one reason may be a disruption in the healthful microbes children get early in life, Finlay says."There's all these smoking guns like, for example, if you breast-feed versus bottle feed you have less asthma," he says. "If you're born by C-section instead of vaginal birth you have a 20 percent higher rate of asthma. If you get antibiotics in the first year of life you have more asthma." The microbiomes of kids who aren't breast-fed and are born by Caesarean section may miss out on getting helpful bugs. Antibiotics can kill off the good bacteria that seem important for the development of healthy immune systems.

"What's become clear recently is that microbes play a major role in shaping how the immune system develops. And asthma is really an immune allergic-type reaction in the lungs," Finlay says. "And so our best guess is the way these microbes are working is they are influencing how our immune system is shaped really early in life."

To further test their theory, the researchers gave laboratory mice bred to have a condition resembling asthma in humans the four missing microbes. The intervention reduced the signs of levels of inflammation in their lungs, which is a risk factor for developing asthma.

The bacteria are from four genuses: Lachnospira, Veillonella, Faecalibacterium and Rothia. The researchers aren't exactly sure how the microbes may protect against asthma. But babies with few or none of them had low levels of a substance known as acetate, which is believed to be involved with regulating the immune system.

Published on Leave a comment on Home Pesticide Use Linked to Childhood Cancer

Children exposed to insecticides (pesticides) at home have an increased risk of developing leukemia or lymphoma, a new review finds.The analysis, of 16 studies done since the 1990s, found that children exposed to indoor insecticides had an elevated risk of developing the blood cancers. There was also a weaker link between exposure to weed killers and the risk of leukemia.

There is also evidence from studies linking pesticides with neurological consequences, such as lower IQ and attention deficit hyperactivity disorder. Note: insecticides and weed-killers (herbicides) are both pesticides. The article also gives some non-chemical approaches to treating pests with non-chemical means.

From CNN: Report: Pesticide exposure linked to childhood cancer and lower IQ

Pesticide use in homes may increase the risk of children developing leukemia or lymphoma, a new report suggests. Researchers combined data from 16 earlier studies that had compared pesticide exposure between children who developed leukemia or lymphoma and those who did not. These studies estimated the level of insecticides and herbicides both inside the home and in the yard and outdoor residential space.

The researchers concluded that children who had been exposed to insecticides indoors were 47% more likely to have leukemia and 43% more likely to have lymphoma. Although leukemia and lymphoma are rare -- leukemia affects about five in 100,000 children in the United States -- they are among the common types of childhood cancers. "Childhood cancers are increasing year by year in this country....  ...continue reading "Home Pesticide Use Linked to Childhood Cancer"

Published on Leave a comment on Are All These Prescription Meds During Pregnancy Really Necessary?

Disturbing results from a study looking at data from over 1 million women enrolled in Medicaid before pregnancy from 2000 to 2007. More than four of five (82.5%) pregnant women were prescribed at least one medication, and 42.0% were prescribed a drug that is potentially harmful to the developing fetus.From Medscape:

Prescription Meds Common in Pregnancy; Maybe Too Common

Although most physicians acknowledge the complexity of prescribing drugs to pregnant women, they nonetheless prescribe them frequently. More than four of five (82.5%) pregnant women were prescribed at least one medication, and 42.0% were prescribed a drug that is potentially harmful to the developing fetus, researchers found in a large, population-based study.The study, which details the type and timing of medications prescribed to pregnant Medicaid patients, presents a disturbing pattern, according to Kristin Palmsten, ScD, from the University of California, San Diego, in La Jolla, and colleagues. 

Dr Palmsten and colleagues found that the most commonly dispensed medications are those used to treat infections. They also report that dispensing is more common for younger pregnant women and white women. The researchers examined data for women enrolled in Medicaid before pregnancy (n = 1,106,757), using 2000 to 2007 Medicaid Analytic eXtract data for prospectively collected medication information. The analysis included over-the-counter medications dispensed by a pharmacist, but excluded medications purchased over the counter directly or prescribed during hospitalizations.

The most commonly dispensed medications were nitrofurantoin (21.6%), metronidazole (19.4%), amoxicillin (18.0%), azithromycin (19.9%), and promethazine (13.5%). Other frequently dispensed medications include promethazine cephalexin and codeine with acetaminophen.....The investigators also note that nine of the 20 most commonly dispensed medications are rated as having limited to fair data quality and quantity to inform human teratogenic risk assessments by the Teratogen Information System.

Dr Palmsten and colleagues also found that 42.0% of pregnant women filled a prescription for a former US Food and Drug Administration (FDA) category D or X drug during pregnancy. Category D medications are associated with evidence of human fetal risk based on adverse reaction data. The top five most commonly prescribed category D medications were codeine (11.9%), hydrocodone (10.2%), ibuprofen (4.9%), sulfamethoxazole (4.0%), and hydrocortisone (4.0%). The authors note that some of those agents are considered category B or C drugs, depending on the circumstances of use.

Class X medications have been tested in animals or humans and found to cause fetal abnormalities. The five most commonly prescribed category X drugs were hormonal contraceptives (4.9%), temazepam (0.11%), atorvastatin (0.07%), simvastatin (0.04%), and warfarin (0.04%).

Moreover, the researchers note that many of the most commonly dispensed medications have limited or low-quality data available regarding safety during pregnancy. “Lack of unambiguous safety information may lead to the use of medications with potential to cause adverse pregnancy outcomes, whereas beneficial medications may be avoided,” they write. Many opioids are category N, meaning the FDA has not classified the drug. 

Although the solution to the complex problem of drug use by pregnant women is not clear, the FDA has made a change that is designed to better inform healthcare providers and patients about the risks of drugs. As of June 30, 2015, the FDA has changed the way it labels human prescription medications and biologic preparations for use in pregnancy and lactation. The new labels will include a summary of the risks of the drug during pregnancy.

Published on

Several recent studies have found that constant exposure to high levels of air pollution has negative effects on the brain. The last post described negative effects on the gray matter in brains (resulting in smaller brain volumes) of elderly women from air pollution, but this study found negative effects (lower grade point averages) in young children from high air pollution. From Environmental Health News:

Bad air means lower grade point averages in Texas

Fourth and fifth graders in El Paso, Texas, are more likely to have lower grade point averages if heavily exposed to contaminated air at home, according to a new study.It bolsters a growing body of evidence that air pollution can impair success in school.

They found that for all types of air pollution sources, more exposure corresponded with lower grade point averages. Only one type of pollution—point sources such as factories—was not significantly linked to lower grade point averages.University of Texas at El Paso researchers analyzed the grade point averages of 1,895 children and, using their home location, estimated their exposure to air toxics—such as benzene, arsenic, lead, mercury, hydrochloric acid, toluene, vinyl bromide, xylenes, and diesel particulate matter—using federal data.

“Effects appear to be insidious, since they are mild, unlikely to be perceived, and, hence, unlikely to be addressed in any way … seemingly trivial effects on children’s development may translate into substantial impacts throughout the life course in terms of physical and mental health and personal success,” the authors wrote.The researchers did control for some other things that can affect children’s grades such as poverty, mother’s age, education and ability to speak English, and the child’s race and sex.

Still, the study doesn’t prove that dirty air makes kids do worse in school. It does, however, suggest children’s developing bodies are more susceptible to air pollution, which can harm their respiratory systems and brain.Air pollution might hamper kids’ grades via two primary ways: Illnesses, mostly respiratory, that would make them miss school, and developmental problems resulting from long-term exposure, said Sara Grineski, an associate professor of sociology at The University of Texas at El Paso and co-author of the new study.

Others have found similar links between air pollution and academic performance. Three months ago Columbia University's Perera and colleagues reported that New York City children born to mothers in poverty and exposed to certain air toxics during pregnancy had lower IQs.  Perera, tracking the mothers and children since before birth, said the pollution exposure prior to birth is more strongly linked to learning and behavioral problems. 

In the current study it’s unclear if the children were exposed in their mothers’ womb—an exposure window that is critical to brain development, Perera said....Other studies support this—in February Calderón-Garcidueñas and colleagues reported Mexico City smog was linked to impaired short-term memory and IQ in children.

The city is more than 80 percent Hispanic....Previous studies have shown that El Paso’s minorities are disproportionately impacted by toxics, Grineski said. The city of 675,000 is one of the worst when it comes to particulate matter—a mix of substances emitted by combustion sources, including cars, trucks, industrial plants and wood burning—especially coarse particulates, PM10, those between 2.5 and 10 micrometers (from about 25 to 100 times thinner than a human hair, according to the EPA). El Paso’s 24-hour PM10 average is about 233 micrograms per cubic meter of air, according to the latest EPA data from 2013, which was eighth highest among more than 500 U.S. cities. El Paso, along with Laredo, has the highest carbon monoxide levels in Texas.