State Study Finds No Gain in Fight Against Birth Defects

In the largest analysis of its kind ever undertaken anywhere, state officials have found that birth defects in California have not declined despite increases in prenatal care and screening programs.

The report by the California Birth Defects Monitoring Program suggests that prenatal care has little impact on reducing birth defects, because the cause of most anomalies is unknown. Nevertheless, the data does point to subtle but measurable racial, geographical and age differences.

Although screening tests are in widespread use for two defects--Down’s syndrome and neural tube defects--the impact of those relatively new tests is not yet apparent.

The study of 1.6 million births statewide found little change in overall rates from 1983 to 1990, the latest figures available.

“No one has ever had this kind of data before, so this is a benchmark study,” said Liz Stierman, regional coordinator of the monitoring system. “It’s surprising how common birth defects are--one in every 33 births. It’s tragic for families and it has an incredible impact economically.”

Babies with birth defects are 16 times more likely to die before age 1.

“Think about the loss of potential years,” said Dr. Robin Dawn Clark, director of prenatal diagnosis at Childrens Hospital in Los Angeles. “We are certainly not putting the kind of research dollars we need to into investigating the cause of birth defects.”

The report suggests that birth defects will be difficult to eradicate without considerably more research into “micro environments,” such as a parent’s home, workplace and lifestyle. The monitoring program, which is highly regarded nationwide, is turning its focus toward these areas, Stierman said.

“We would like to be able to say, ‘This is the cause of a birth defect.’ But there are probably six or seven causes and there may be an interaction between risk factors,” she said. “This report gives us a road map so that we know where to home in.”

Since 15% of all U.S. births occur in California, the report’s findings can serve as a national benchmark as well, she said.

Birth defect rates varied somewhat among racial groups and geographic areas. The region bordering Mexico had the highest overall rate (36.3 defects per 1,000 births) while the coastal areas from Santa Cruz to Los Angeles had the lowest rate (less than 27 defects per 1,000 births).

The high rates along the border were found in all racial groups.

“We really can’t say what the cause is,” Stierman said. “We weren’t able to identify anything, environmentally, in that area.”

While people may fear that pesticides contribute to birth defects, she said, no difference was seen when comparing urban rates to rural rates.

Racial variations were also noted, although most differences were slight. African Americans had the highest overall rate, while Asians had the lowest rate.

One of the major findings of the report was that the rate of Down’s syndrome, the leading cause of mental retardation, among babies born to Latinas of all ages is significantly higher. In women over age 35, the rate for Latinas is 5.5 among 1,000 births, compared to 1.9 among whites and 3.1 among blacks.

The cause is unknown and is the subject of further study.

Before this study, little was known about birth defect rates among Latinos and Asian Americans, Stierman said.

“The racial and geographical variations are not great, but they give us an idea about where to go looking for causes,” she said.

Defects also varied slightly in relation to a mother’s age, with women under 20 and those over 34 showing higher rates. Among women over 34, the higher rate was due mostly to the well-known risk of chromosomal defects.

Even with knowledge of a cause, birth defects may be difficult to prevent. The study found that about 70 babies are diagnosed each year with fetal alcohol syndrome, even though 83% of their mothers had prenatal care.

The reason why rates for the syndrome remain high despite prenatal care is unknown. The mothers may have sought prenatal care too late or may have continued to drink despite warnings, Stierman said.

Moreover, while health professionals now know that folic acid supplements taken early in pregnancy can dramatically reduce the risk of neural tube defects, those defects have not declined significantly and still occur twice as frequently among Latino infants as among other groups. Studies are under way to see if folic acid supplements are equally effective in all ethnic groups.

One of the few large increases reported in the study was for another preventable defect. Rubella-related birth defects, such as congenital cataracts, soared in the late ‘80s due to a measles outbreak and the high number of unimmunized women throughout the state.

The report was reassuring on one note: It failed to turn up evidence of any major, new problem.

“The good news is that we didn’t see any epidemic, we don’t want to have another thalidomide (the medication taken during pregnancy that was blamed for an epidemic of limb defects in the 1960s),” Stierman said. “One of the reasons we do this kind of monitoring is to find new (birth defects). So this finding is very reassuring.”

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The Findings

A new study of birth defects in California suggests that the cause of most anomalies is complicated and may have to do with a combination of risk factors. The study contains the first analysis on Latinos and Asians, showing the lowest overall rate of defects among Asians. And, in a finding that should reassure older mothers, birth defect rates were only slightly higher for women over age 35, with most of the increase attributable to chromosomal defects.