Errata: Vol. 33, No. 29

p. 421. In the article, "Mumps Outbreak - New Jersey," the last sentence of the first paragraph of the Editorial Note on page 429 should read: "Cases in 1982 decreased by 38% from 1982 (5,270 cases) and by 98% from 1967." The 5,310 cases given was the provisional total for 1982.

Vol. 33, No. 28

p. 408. In the article, "Chromosomally Mediated Resistant Neisseria gonorrhoeae-United States," the third sentence of the third paragraph should read: Gonococcal isolates that grew on media containing 1.6 μg/ml of penicillin or produced a zone of inhibition less than 26 mm, with a 10-Unit penicillin disk, were submitted to CDC for confirmation of resistance.

The Morbidity and Mortality Weekly Report is prepared by the Centers for Disease Control, Atlanta, Georgia, and available on a paid subscription basis from the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402, (202) 783-3238.

The data in this report are provisional, based on weekly reports to CDC by state health departments. The reporting week concludes at close of business on Friday; compiled data on a national basis are officially released to the public on the succeeding Friday.

The editor welcomes accounts of interesting cases, outbreaks, environmental hazards, or other public health problems of current interest to health officials. Such reports and any other matters pertaining to editorial or other textual considerations should be addressed to: ATTN: Editor, Morbidity and Mortality Weekly Report, Centers for Disease Control, Atlanta, Georgia 30333.

The Ur

of Michigan Public Health Library

Vietnam Veterans' Risks for Fathering Babies with Birth Defects

Vietnam veterans' risks for fathering babies born with serious structural birth defects were assessed using a case-control study. Case-group babies-those with serious structural defects-were born during 1968 through 1980 and registered by CDC's Metropolitan Atlanta Congenital Defects Program (MACDP). This program registers babies born with structural defects to women who are residents of the five-county metropolitan Atlanta area. To be included in the registry, a baby's defects must have been diagnosed during the first year of life and recorded on a hospital chart by a physician. The use of MACDP as the source of cases precluded analysis of other reproductive outcomes in the fathers or functional deficits, such as mental retardation, in the babies.

Control-group babies-those born without defects-were chosen from among 323,421 babies who were born in the same metropolitan area to resident mothers during the same period. They were frequency-matched to the case-group babies by race, year of birth, and hospital of birth. A total of 7,133 case-group babies and 4,246 control-group babies were eligible for the study. The decision to include fewer control-group babies than case-group babies was based on a review of the anticipated statistical power of the study.

In all, 4,929 mothers of case-group babies and 3,029 mothers of control-group babies completed interviews; fewer fathers completed interviews-3,977 from the case group and 2,426 from the control group. The major reason for parents' not participating in the study was that they could not be located after extensive searching.

Information about paternal military service in Vietnam was obtained during 1982 and 1983 through telephone interviews with the parents of the case- and control-group babies. Vietnam veteran fathers were asked if they believed they had been exposed to herbicides, such as Agent Orange. In addition, a five-level "Exposure Opportunity Index" (EOI) was defined based on activities that may have provided an opportunity for exposure to Agent Orange. Vietnam veteran fathers were given subjective scores by the staff of the Army Agent Orange Task Force reflecting their presumed opportunities for exposure to Agent Orange; the EOI scores were assigned on the basis of times and places of service in Vietnam and occupational duties. Scores were assigned without knowledge of the case/control status of the fathers. Both parents were questioned about a wide variety of other potential risk factors for birth defects. In addition, Vietnam veteran fathers were asked whether they had contracted malaria in Vietnam and whether they had taken malaria chemoprophylaxis there.

Defects occurring among the case-group babies were divided into 96 diagnostic categories for data analysis. Most of the 96 categories were comprised of specific defects, such as anencephaly, ventricular septal defect, and Down syndrome. Some categories were formed by grouping specific types of defects; one comprised all types of defects combined (i.e., the complete case series).

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES / PUBLIC HEALTH SERVICE

US DEPOSITORY

SEP 10 1984

Birth Defects - Continued

For each of these 96 categories, four hypotheses were tested: (1) whether veterans, excluding Vietnam veterans, were at different risk than nonveterans for fathering babies with birth defects; (2) whether Vietnam veterans were at different risk for fathering babies with birth defects; (3) whether Vietnam veterans who were judged by the Army Agent Orange Task Force to have had greater opportunities for exposure to Agent Orange had different risks for fathering babies with defects; and (4) whether Vietnam veterans who said during the interview that they had been exposed to herbicides, such as Agent Orange, were at different risk. Testing the first hypothesis determined whether, for the tests of the remaining three hypotheses, Vietnam veterans' risks should be compared with those of other veterans or with those of other veterans and nonveterans combined. Testing the second hypothesis was the main focus of this study.

Fathers of 428 case-group babies were Vietnam veterans; fathers of 268 control-group babies were Vietnam veterans. Fathers of 4,387 case-group babies and fathers of 2,699 control-group babies were not Vietnam veterans.

The estimated relative risk of Vietnam veterans' fathering babies with defects when all types of defects are combined was 0.97 (95% confidence limits 0.83-1.14). With few exceptions, the estimated relative risks of Vietnam veterans' fathering babies with defects in the remaining 95 defect groups were similar. Similarly, there was little evidence of different risks for Vietnam veterans who had been assigned higher Agent Orange EOI scores or for Vietnam veterans who had stated during the interview that they believed they had been exposed.

It was determined that, for most defect groups, Vietnam veterans' risks were neither higher nor lower than those of other fathers. In any large study in which multiple statistical tests are done, some exceptions are expected. Some of this study's exceptions are noted below. The estimated risks for fathering babies with spina bifida (imperfectly formed spinal cord) were higher for Vietnam veteran fathers who received higher EOI scores. Vietnam veterans who had higher scores had higher estimated risks for fathering babies with cleft lip with or without cleft palate. Vietnam veterans who received higher scores had higher estimated risks for fathering babies with defects classified as "Other Neoplasms," which include teratomas, neuroblastomas, hamartomas, dermoid cysts, lipomas, central nervous system tumors, Wilms tumor, and miscellaneous benign tumors. Vietnam veterans, in general, had a lower risk for fathering babies with cardiovascular defects classified as "complex" defects (two or more cardiovascular defects). Vietnam veterans who stated they had contracted malaria while in Vietnam had a higher estimated risk for fathering babies born with hypospadias.

No associations between risks of defects and use of malaria chemoprophylaxis were found.

Reported by Chronic Diseases Div, Center for Environmental Health, CDC. Editorial Note: The most important conclusion to be drawn from this study is that the data collected contain no evidence to indicate that Vietnam veterans have had a greater risk than other men for fathering babies with defects when all types of serious structural birth defects are combined. This study cannot prove that some factor associated with service in Vietnam was or was not associated with the occurrence of rare types of defects, defects in the babies of selected individuals, or defects in the babies of small groups of veterans. The conclusion, however, that Vietnam veterans in general have not fathered, at higher rates than other men, babies with defects when all types of birth defects are combined is based on relatively strong evidence.

All parents are at some risk of having a baby born with birth defects. Because this risk is always there, it is called a "background risk." All men, whether Vietnam veterans or not, who father babies, have the same background risk-about two or three chances out of 100 that their babies will have serious structural birth defects.

Assessing Vietnam veterans' risks associated with exposure to Agent Orange is difficult.

Birth Defects - Continued

The measures of exposure that can be obtained today are imperfect, at best. The ability of Vietnam veterans to give valid reports of exposure is unknown, and the records used for the assignment of EOI scores were made for military purposes, not for health studies. This limitation makes it particularly difficult to assess whether the few statistically significant associations found in this study between defects and greater opportunity for exposure to Agent Orange are likely to reflect true effects of exposure or whether they are merely chance

Occurrences.

Moreover, the estimated relative risks for the exceptions presented here are rather low. These exceptions could conceivably be due to unmeasured confounding factors and may not be biologically significant. The same reasoning can be applied to the statistically significant association of malaria and hypospadias and the statistically significant association observed for babies with complex cardiovascular defects being fathered by Vietnam veterans.

A summary report of this study has recently been published (1), and a more comprehensive report is available from CDC. Copies of these reports can be obtained from CDC's Chronic Diseases Division, Center for Environmental Health.

Reference

1. Erickson JD, Mulinare J, McClain PW, et al. Vietnam veterans' risks for fathering babies with birth defects. JAMA 1984:252;903-12.

International Notes

Update: Incidence of Low Birth Weight

The birth weight of an infant is the single most important determinant of its chances of survival and healthy growth and development. Because birth weight is conditioned by the health and nutritional status of the mother, the proportion of infants born with low birth weights (LBW) closely reflects the health status of the communities into which they are born. LBW has been defined as a birth weight of less than 2,500 g. It can be caused either by premature delivery (short gestation) or by fetal growth retardation. In countries where the proportion of LBW infants is low, most are preterm. In countries where the proportion is high, the majority of LBW infants suffer from fetal growth retardation. The causes of fetal growth retardation are multiple and interrelated and include low maternal food intake, hard physical work during pregnancy, and illness, especially infections. Short maternal stature, very young age, high parity, and close birth spacing are all associated factors.

It is clear from the many causes that there is no single solution to LBW. Interventions have to be cause-specific. Prenatal care, nutrition programs, health education on the needs of pregnant women, family planning, and measures aimed at improving the health and nutrition of young girls all factor in the solution.

At the Thirty-fourth World Health Assembly, the Member States of the World Health Organization (WHO) adopted, as part of the global strategy for health for all by the year 2000, the proportion of infants born with an LBW as one of a number of global indicators with which to monitor progress.

Associated with the use of this indicator, however, are a number of practical problems. In developed countries, most infants are weighed at birth; in developing countries, usually only those born in institutions are weighed. These infants constitute a small-usually privileged-minority. A recent survey has shown that only about one-third of births in the developing world take place in institutions; in some countries, the proportion is lower than one-fifth. Even when records of birth weights exist at the institutional level, they are rarely collated at the national level.

Low Birth Weight - Continued

For these reasons, and to obtain an approximate global picture of the availability of data and the extent of the problem of LBW, the Division of Family Health, WHO, Geneva, undertook in 1979 a widespread search of all available sources of information. The results of this search and details of the methodology employed have been published (1). At that time, it was estimated that 21 million LBW infants were born in 1979.

The present review updates that search. A new search, carried out at the end of 1983, yielded some new information on 90 countries, including 20 for which no previous information was available. This brings the total number of countries for which some information is available to 112. The new information was compared to that of the previous search and new estimates made where the data seemed to warrant it."

Taken as a whole, the data would tend to indicate a slight decrease in the incidence of LBW. It is estimated that, of the 127 million infants born in 1982, 16.0%-some 20 million-had an LBW. This constitutes a decrease in both relative and absolute terms when compared to the estimates for 1979-21 million LBW infants making up 16.8% of the 122 million born that year. For developing countries only, the proportion has fallen from 18.4% to 17.6%.

'Details of the studies on which the estimates are based are available from the Division of Family Health, WHO, 1211 Geneva 27, Switzerland.

(Continued on page 465)

TABLE 1. Summary-cases specified notifiable diseases, United States