Only weak link seen between gestational pesticide exposure and gastroschisis

BELLEVUE, WASH. – Early gestational exposure to agricultural pesticides is only weakly linked to the risk of gastroschisis in offspring, suggests a case-control study conducted in California’s San Joaquin Valley, an area having among the highest levels of pesticide use nationwide.

Using data from the state and the National Birth Defects Prevention Study for the years 1997-2012, investigators led by Gary M. Shaw, Dr.P.H., assessed maternal exposure during early pregnancy to hundreds of chemicals as ascertained from state pesticide reporting data by geographic area and the women’s address of residence, obtained during interviews.

Analyses were based on 156 live births, fetal deaths, or pregnancy terminations affected by gastroschisis and 785 unaffected matched controls.

"Gastroschisis is a rather unique birth defect. It has a very unique epidemiology," noted Dr. Shaw, who is a professor of clinical research and a doctor of public health in the pediatrics department at Stanford (Calif.) University. "It’s one of a few or perhaps the only one that has been increasing around the world for the last 20-30 years, and it really looks like it’s a disease of young women from what we observe." Teenagers, for example, have a seven to nine times higher risk than do older women.

Overall, 35% of cases and 38% of controls had maternal pesticide exposure in early pregnancy, Dr. Shaw reported at the annual meeting of the Teratology Society. The most common chemical groups to which women had been exposed were poly-alkyl-oxy compounds, glycophosphates, organophosphorus insecticides, alcohols/ethers, and pyrethroids.

However, in adjusted analyses of 52 chemical groups restricted to those for which more than four cases or controls were exposed, only one – the triazine group – was associated with an increased risk of gastroschisis (odds ratio, 1.7), and that association was merely borderline significant, with the confidence interval including unity.

Similarly, in adjusted analyses of 233 individual chemicals restricted to those for which more than four cases or controls were exposed, only two – oxyfluorfen (OR, 1.6) and petroleum distillates (OR, 2.5) – showed an association with this risk; in these cases, the confidence intervals did not include unity.

"We basically got a general lack of association in a discovery, hypothesis-generating study. We have a detailed exposure assessment. ... We conducted many comparisons, and we’ve got modest sample sizes," Dr. Shaw concluded. "And the kicker is that none of the associations we looked at seemed to stand up for young maternal age."

"This is a useful negative study, and it is noteworthy that, even without correcting for multiple comparisons, there were no impressive positive findings," commented session cochair Dr. James Mills, an investigator with the Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, Md.

In additional study results, analyses of exposure to those chemicals classified as reproductive toxicants, ones listed in California’s Proposition 65 (which aims to eliminate carcinogenic and teratogenic agents from drinking water and consumer products), and known endocrine disruptors, either alone or in combinations, did not alter the findings, according to Dr. Shaw.

Furthermore, there was no significant association of the combination of pesticide exposure and air pollution exposure (any of either vs. none) and the risk of gastroschisis.

Dr. Shaw had no relevant conflicts of interest.

BELLEVUE, WASH. – Early gestational exposure to agricultural pesticides is only weakly linked to the risk of gastroschisis in offspring, suggests a case-control study conducted in California’s San Joaquin Valley, an area having among the highest levels of pesticide use nationwide.

Using data from the state and the National Birth Defects Prevention Study for the years 1997-2012, investigators led by Gary M. Shaw, Dr.P.H., assessed maternal exposure during early pregnancy to hundreds of chemicals as ascertained from state pesticide reporting data by geographic area and the women’s address of residence, obtained during interviews.

Analyses were based on 156 live births, fetal deaths, or pregnancy terminations affected by gastroschisis and 785 unaffected matched controls.

"Gastroschisis is a rather unique birth defect. It has a very unique epidemiology," noted Dr. Shaw, who is a professor of clinical research and a doctor of public health in the pediatrics department at Stanford (Calif.) University. "It’s one of a few or perhaps the only one that has been increasing around the world for the last 20-30 years, and it really looks like it’s a disease of young women from what we observe." Teenagers, for example, have a seven to nine times higher risk than do older women.

Overall, 35% of cases and 38% of controls had maternal pesticide exposure in early pregnancy, Dr. Shaw reported at the annual meeting of the Teratology Society. The most common chemical groups to which women had been exposed were poly-alkyl-oxy compounds, glycophosphates, organophosphorus insecticides, alcohols/ethers, and pyrethroids.

However, in adjusted analyses of 52 chemical groups restricted to those for which more than four cases or controls were exposed, only one – the triazine group – was associated with an increased risk of gastroschisis (odds ratio, 1.7), and that association was merely borderline significant, with the confidence interval including unity.

Similarly, in adjusted analyses of 233 individual chemicals restricted to those for which more than four cases or controls were exposed, only two – oxyfluorfen (OR, 1.6) and petroleum distillates (OR, 2.5) – showed an association with this risk; in these cases, the confidence intervals did not include unity.

"We basically got a general lack of association in a discovery, hypothesis-generating study. We have a detailed exposure assessment. ... We conducted many comparisons, and we’ve got modest sample sizes," Dr. Shaw concluded. "And the kicker is that none of the associations we looked at seemed to stand up for young maternal age."

"This is a useful negative study, and it is noteworthy that, even without correcting for multiple comparisons, there were no impressive positive findings," commented session cochair Dr. James Mills, an investigator with the Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, Md.

In additional study results, analyses of exposure to those chemicals classified as reproductive toxicants, ones listed in California’s Proposition 65 (which aims to eliminate carcinogenic and teratogenic agents from drinking water and consumer products), and known endocrine disruptors, either alone or in combinations, did not alter the findings, according to Dr. Shaw.

Furthermore, there was no significant association of the combination of pesticide exposure and air pollution exposure (any of either vs. none) and the risk of gastroschisis.

Dr. Shaw had no relevant conflicts of interest.

BELLEVUE, WASH. – Early gestational exposure to agricultural pesticides is only weakly linked to the risk of gastroschisis in offspring, suggests a case-control study conducted in California’s San Joaquin Valley, an area having among the highest levels of pesticide use nationwide.

Using data from the state and the National Birth Defects Prevention Study for the years 1997-2012, investigators led by Gary M. Shaw, Dr.P.H., assessed maternal exposure during early pregnancy to hundreds of chemicals as ascertained from state pesticide reporting data by geographic area and the women’s address of residence, obtained during interviews.

Analyses were based on 156 live births, fetal deaths, or pregnancy terminations affected by gastroschisis and 785 unaffected matched controls.

"Gastroschisis is a rather unique birth defect. It has a very unique epidemiology," noted Dr. Shaw, who is a professor of clinical research and a doctor of public health in the pediatrics department at Stanford (Calif.) University. "It’s one of a few or perhaps the only one that has been increasing around the world for the last 20-30 years, and it really looks like it’s a disease of young women from what we observe." Teenagers, for example, have a seven to nine times higher risk than do older women.

Overall, 35% of cases and 38% of controls had maternal pesticide exposure in early pregnancy, Dr. Shaw reported at the annual meeting of the Teratology Society. The most common chemical groups to which women had been exposed were poly-alkyl-oxy compounds, glycophosphates, organophosphorus insecticides, alcohols/ethers, and pyrethroids.

However, in adjusted analyses of 52 chemical groups restricted to those for which more than four cases or controls were exposed, only one – the triazine group – was associated with an increased risk of gastroschisis (odds ratio, 1.7), and that association was merely borderline significant, with the confidence interval including unity.

Similarly, in adjusted analyses of 233 individual chemicals restricted to those for which more than four cases or controls were exposed, only two – oxyfluorfen (OR, 1.6) and petroleum distillates (OR, 2.5) – showed an association with this risk; in these cases, the confidence intervals did not include unity.

"We basically got a general lack of association in a discovery, hypothesis-generating study. We have a detailed exposure assessment. ... We conducted many comparisons, and we’ve got modest sample sizes," Dr. Shaw concluded. "And the kicker is that none of the associations we looked at seemed to stand up for young maternal age."

"This is a useful negative study, and it is noteworthy that, even without correcting for multiple comparisons, there were no impressive positive findings," commented session cochair Dr. James Mills, an investigator with the Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, Md.

In additional study results, analyses of exposure to those chemicals classified as reproductive toxicants, ones listed in California’s Proposition 65 (which aims to eliminate carcinogenic and teratogenic agents from drinking water and consumer products), and known endocrine disruptors, either alone or in combinations, did not alter the findings, according to Dr. Shaw.

Furthermore, there was no significant association of the combination of pesticide exposure and air pollution exposure (any of either vs. none) and the risk of gastroschisis.

Dr. Shaw had no relevant conflicts of interest.