January 25th, 2010 
Babies of women who smoked during pregnancy have blood pressure problems at birth that persisted through the first year of life, a new study finds.
“What is of concern is that the problems are present at birth and get worse over time,” said Gary Cohen, a senior research scientist in the department of women and child health at the Karolinska Institute in Stockholm, and lead author of a report in the Jan. 25 online edition of Hypertension.
The study led by Cohen compared 19 infants of nonsmoking couples with 17 infants born to women who smoked an average of 15 cigarettes a day during pregnancy. At one week of age, the infants of nonsmoking mothers experienced a 2 percent increase in blood pressure when tilted upright, with a 10 percent increase at one year. The pattern for the children of smoking mothers was reversed: a 10 percent blood pressure increase at one week, a 4 percent increase at one year.
And the heart rate response to tilting of the children of mothers who smoked was abnormal and exaggerated, the report said.
It’s not possible to say whether the abnormalities seen in the babies will lead to trouble later in life, Cohen said. But, he noted, “the extent of the condition at one year suggests that it is not going to disappear quickly.”
The reason why exposure to tobacco in the womb affects blood pressure is not clear, Cohen said. A leading possibility is that “smoking might damage the structure and function of blood vessels,” he said, mainly by damaging the endothelium, the delicate layer of cells that line the interior of blood vessels.
Whether that damage will persist is not known. “We’re only up to 12 months at the moment,” he said. “We plan to follow them.”
The damage seen in the Karolinska study is similar to that observed in babies born to mothers whose pregnancies were marked by such abuses as drug use, said Barry M. Lester, a professor of psychiatry and pediatrics at Brown Medical School, and director of the Brown Center for the Study of Children at Risk.
“Early kinds of natal insults can cause reprogramming of brain circuitry,” Lester explained. He has led studies of the long-term effects of cocaine and amphetamine use during pregnancy. Many women who take such drugs also smoke, Lester added.
“When we isolated tobacco effects, we showed that there are inborn neural effects of tobacco exposure similar to what we see in cocaine and methamphetamine abuse,” he said.
Some research has connected such problems to overproduction of cortisol, a “stress hormone” that plays an important role in regulation of blood pressure and the immune system, Lester said. “Cortisol overexposure is one hypothesis,” he said. “There is a lot of evidence showing that too much cortisol is damaging.”
It is a reasonable hypothesis, Cohen said. Babies born preterm have problems with blood pressure that have been linked to overproduction of cortisol by the adrenal glands, he noted, “and there are some parallels between tobacco smoke exposure and preterm babies of the same age.”
Whatever the mechanism of damage, treatment to eliminate the problems after birth does not seem possible, Cohen added.
“What we know from studies in older kids is that even if you remove them from an environment of exposure to tobacco smoke, it is unlikely you will get full restoration of normal function,” he said. “The best intervention to solve these problems is prevention. Women who are pregnant need to avoid exposure to tobacco smoke in the air. Passive smoke exposure can be as bad as being an active smoker.”
Related
- Exposure to passive smoking during pregnancy ‘increase children’s risk of cancer in later life’
Pregnant women subjected to passive smoking give birth to babies with an increased, lifelong susceptibility to cancer, research reveals.
Passive smoking causes the same type of genetic damage in unborn infants as that found in adult smokers with cancerous tumors.
Researchers said the abnormalities in newborns were indistinguishable from those found in babies of mothers who were active smokers.
And they may affect survival, birth weight and lifelong susceptibility to diseases like cancer, according to the study published online in the Open Paediatric Medicine Journal.
Dr Stephen Grant and colleagues at the University of Pittsburgh in the U.S. found a smoke-induced mutation in an oncogene, a gene which transforms normal cells into cancerous tumors.
The mutation was the same level and type in newborns of mothers who were active smokers as those in babies born to non-smoking mothers exposed to tobacco smoke.
The mutations were also discernible in newborns of women who had stopped smoking during their pregnancies, but who did not actively avoid second-hand smoke.
The study confirms previous research in which Dr Grant discovered evidence of genetic abnormalities in babies whose mothers were exposed to environmental tobacco smoke.
There is also evidence that maternal exposure to passive smoke, as well as a history of paternal cigarette smoke exposure, is linked with an increased risk of childhood cancer, especially leukaemias and lymphomas in children under five.
Dr Grant said: ‘These findings back up our previous conclusion that passive, or secondary, smoke causes permanent genetic damage in newborns that is very similar to the damage caused by active smoking.
‘By using a different laboratory test, we were able to pick up a completely distinct yet equally important type of genetic mutation that is likely to persist throughout a child’s lifetime.
‘Pregnant women should not only stop smoking, but be aware of their exposure to tobacco smoke from other family members, work and social situations.’
- Lead associated with high blood pressure during pregnancy
A French study reports that higher lead levels measured in women halfway through their pregnancy are associated with pregnancy-induced high blood pressure.
A recent study links higher blood lead levels with high blood pressure in pregnant women, suggesting that lead exposure may increase the risk of developing hypertension during pregnancy.
All of the women in the study had blood levels below the level considered “acceptable” by most health agencies. The association suggests that the level – 10 micrograms per deciliter (µg/dL) – may need to be lowered.
Prior studies have associated elevated lead levels with hypertension and other indicators of vascular disease in women during late-pregnancy or those who are not pregnant. This new study is the first to find a similar relationship in mid-pregnancy.
Lead was measured in blood collected from 971 women between the 24th and the 28th week of gestation. Women were placed into the case or control groups based on monthly blood pressure measurements.
Of the subjects, 106 developed pregnancy-induced hypertension. Lead levels were significantly higher in those women when compared to the other women in the study.
Researchers reported that women with pregnancy-induced hypertension (PIH) had mean blood lead levels of 2.2 µg/dL relative to 1.9 µg/dL in women with normal blood pressure. According to national data (National Health and Nutrition Examination Survey), more than 25 percent of women have blood lead levels above 2.2 µg/dL in the United States.
In addition, every 1 µg/dL increase in blood concentration was associated with a 3-fold increase in the likelihood of PIH. The blood lead levels were weakly, but significantly, associated with systolic blood pressure.
Blood levels of other metals – cadmium, manganese and selenium – were also measured but only elevated lead levels were significantly correlated with blood pressure. This relationship persisted even after controlling for potential confounders, including dietary habits, smoking history, and socio-economic status.
Blood pressure normally rises in mid-pregnancy but approximately 10 percent of mothers-to-be develop PIH. The condition Increases the risk of preeclampsia which is characterized by high blood pressure during pregnancy accompanied by measureable proteins in the urine. It is also a risk factor for intrauterine growth retardation (abnormally slow fetal growth) and stillbirth. Preeclampsia can also lead to maternal seizures (also named eclampsia).
Lead exposure varies by region in the United States. It is higher in places with older buildings, because they are more likely to contain lead-based paint and plumbing capable of leaching lead. Areas with numerous industrial sites also can have higher environmental lead levels.
Lead can cause other health problems when exposure occurs at low levels, including memory impairment and increased risk of cancer.
- High blood pressure in pregnancy a heart risk
Women who had an increase in blood pressure during pregnancy are likely to develop heart disease at an earlier age than women who maintained normal blood pressure while they were pregnant, Chilean researchers report.
Dr. Gloria Valdes of Pontificia Universidad Catolica, Santiago and colleagues studied 217 women with an average age of about 61 years, who underwent a coronary artery examination about 30 years after their last pregnancy.
As reported in the medical journal Hypertension, 146 women had had normal blood pressure during their pregnancies while 71 women had hypertension during at least one pregnancy.
About half of all the participants were found to have significant coronary artery disease. Valdes told Reuters Health that women with hypertensive pregnancies developed significant narrowing in their coronary arteries about three years sooner than women with normal blood pressure during pregnancy.
Furthermore, during 10 years of follow-up, there was a significantly greater increase in the number of clogged arteries in the hypertensive group (28 percent) than in the normal blood pressure group (22 percent).
“Gestational hypertension represents a positive stress test for future cardiovascular risk, which should prompt early management of cardiovascular risks,” Valdes commented.
She added, “Obstetricians need to identify women with a family history of premature cardiovascular disease, as this doubles the risk of a hypertensive pregnancy.”
- High blood pressure in pregnancy a heart risk
Women who had an increase in blood pressure during pregnancy are likely to develop heart disease at an earlier age than women who maintained normal blood pressure while they were pregnant, Chilean researchers report.
Dr. Gloria Valdes of Pontificia Universidad Catolica, Santiago and colleagues studied 217 women with an average age of about 61 years, who underwent a coronary artery examination about 30 years after their last pregnancy.
As reported in the medical journal Hypertension, 146 women had had normal blood pressure during their pregnancies while 71 women had hypertension during at least one pregnancy.
About half of all the participants were found to have significant coronary artery disease. Valdes told Reuters Health that women with hypertensive pregnancies developed significant narrowing in their coronary arteries about three years sooner than women with normal blood pressure during pregnancy.
Furthermore, during 10 years of follow-up, there was a significantly greater increase in the number of clogged arteries in the hypertensive group (28 percent) than in the normal blood pressure group (22 percent).
“Gestational hypertension represents a positive stress test for future cardiovascular risk, which should prompt early management of cardiovascular risks,” Valdes commented.
She added, “Obstetricians need to identify women with a family history of premature cardiovascular disease, as this doubles the risk of a hypertensive pregnancy.”
- Pot smoking during pregnancy may stunt fetal growth
Women who smoke marijuana during pregnancy may impair their baby’s growth and development in the womb, a new study suggests.
Poor fetal growth and reduced head circumference at birth are linked to an increased risk of problems with thinking, memory and behavior in childhood. Cigarette smoking during pregnancy is known to impair fetal growth, but studies on the potential effects of marijuana have been inconclusive.
For the new study, researchers in the Netherlands followed more than 7,000 pregnant women, 3 percent of whom acknowledged smoking marijuana at least during early pregnancy. They found that babies born to marijuana users tended to weigh less and have smaller heads than other infants.
What’s more, the study found, the longer a woman had used marijuana during pregnancy, the stronger the impact on birth size – suggesting that the drug itself was to blame.
And while most marijuana users in the study also smoked cigarettes, the drug appeared to have effects over and above those of tobacco. In fact, marijuana showed stronger effects on birth size than tobacco, the investigators report in the Journal of the American Academy of Child and Adolescent Psychiatry.
The findings suggest that marijuana use, even restricted to early pregnancy, may have irreversible effects on fetal growth, write the researchers, led by Hannan El Marroun of Erasmus University Medical Center in Rotterdam.
The study included almost 7,500 pregnant women who were surveyed on their use of alcohol, tobacco and drugs, and had ultrasounds to chart fetal growth during the first, second and third trimesters.
Overall, 214 women said they had used marijuana before and during early pregnancy; 81 percent quit after learning they were pregnant, but 41 women continued to smoke marijuana throughout pregnancy.
The researchers found that, on average, marijuana users gave birth to smaller babies, particularly those who had used throughout pregnancy.
Women who had smoked only during early pregnancy had babies who were 156 grams — about 5.5 ounces — lighter than infants born to women who had not used the drug. Women who had continued to smoke past early pregnancy had babies who were 277 grams, or nearly 10 ounces, smaller.
Based on ultrasound, marijuana use only in early pregnancy impaired fetal growth by about 11 grams per week, while use throughout pregnancy slowed fetal growth by roughly 14 grams per week. That compared with a deficit of 4 grams per week with tobacco use, the researchers found.
Similar patterns were seen when the researchers looked at fetal head circumference.
According to El Marroun’s team, mothers’ marijuana use could stunt fetal growth for several reasons. Like tobacco smoking, it may deprive the fetus of oxygen. It is also possible that the byproducts of marijuana directly affect the developing nervous and hormonal systems of the fetus.
Finally, the researchers note, pregnant women who use marijuana may have other factors in their lives – such as a less-than-healthy diet or chronic stress — that could contribute to poor fetal growth.
