Verne Nelson

Hypospadias in California: Trends and Descriptive Epidemiology

Background The occurrence of hypospadias has been reported to be increasing. The objectives of this study were to extend the literature on the descriptive epidemiology of hypospadias and to determine whether its birth prevalence increased in California in recent years. We used actively ascertained, population-based data for which detailed clinical descriptions permitted careful phenotypic classifications. Methods We examined registry data on 5838 male live births and stillbirths that occurred in California from 1984 through 1997. To reduce pathogenic heterogeneity, cases were classified as mild, severe, or not otherwise specified based on the anatomic position of the urethral opening. We also classified cases as isolated or nonisolated based on the presence and type of accompanying malformations. We used multivariable Poisson regression analysis to examine time trends and risk factors. Results There was no evidence for an increase in prevalence of any of the case groups between 1989 and 1997. The adjusted relative risk (RR) for change in prevalence per year of isolated severe cases was 0.99 (95% confidence interval = 0.96–1.03). Adjusted RRs indicated increased risks for specific types of hypospadias with maternal non-Hispanic white race–ethnicity, higher education, older age, and nulliparity. Delivery before 37 weeks and multiple births tended either not to be associated with risk or to be associated with reduced risk. Lower birthweight was associated with increased risk for all case groups. Conclusions This study suggests that hypospadias prevalence has not been increasing in California in recent years. Differences by phenotype suggest that examining certain phenotypes separately could help to understand hypospadias etiology.

Marriage, divorce, and mortality: A life table analysis

The life status table, an analytical model which follows a birth cohort through life and through the never-married, presently married, widowed and divorced statuses, is developed and applied to data from four Western populations. Particular attention is given to recent marriage, remarriage, and divorce trends in California. California data for 1969 imply that 40 percent of all marriages will end in divorce, that each marrying male will marry an average of 12/3 times, and that every woman born can expect to spend 61/2 years in the divorced state. Rising divorce rates may be seen as signaling fundamental changes in both the nature of the American family and the structure of American society.

Schizencephaly: Heterogeneous etiologies in a population of 4 million California births

Schizencephaly is a rare congenital brain defect characterized by gray matter lined clefts of the cerebral mantle, frequently accompanied by other defects of the CNS such as absence of the corpus callosum. This study in a California population of >4 million births from 1985–2001 found a population prevalence of 1.54/100,000. Among 63 cases, there was an association with young parental age in isolated schizencephaly (RR 3.9 mothers; 5.8 fathers), which was also seen in mothers but not fathers of non‐isolated cases (RR 3.2). Monozygotic twins may also be at increased risk for schizencephaly (RR 2.1). One third of cases had a non‐CNS abnormality, over half of which could be classified as secondary to vascular disruption, including gastroschisis, bowel atresias, and amniotic band disruption sequence. Other apparent rare causes included chromosomal aneuploidy, non‐random associations, and unusual syndromes. Our observations suggest that schizencephaly has heterogeneous etiologies many of which are vascular disruptive in origin.

Occurrence of Low Birthweight and Preterm Delivery among California Infants before and after Compulsory Food Fortification with Folic Acid

Objectives. Studies suggest that folic acid intake influences the occurrence of low birthweight and preterm delivery. Since 1998, there has been compulsory fortification of flour and other grains with folic acid in the U.S. The objective of this study was to investigate the frequencies of low birthweight and preterm delivery after mandatory folic acid fortification among approximately six million California births. Methods. The authors investigated prevalences of low birthweight and preterm delivery before and after compulsory fortification among 5,916,630 singleton California live births that occurred from January 1990 through December 2000. Results. The unadjusted prevalences of very low birthweight, low birthweight, and preterm delivery did not substantially vary across birth years. That is, substantial decreased prevalences during the fortification period relative to the period preceding it were not observed. However, analyses that simultaneously adjusted for maternal age, parity, race/ethnicity, education, year of birth, and fortification period revealed the following relative risk ratios (RR) and 95% confidence intervals (CI): RR=0.91, CI 0.88, 0.94 for very low birthweight, RR=0.94; 95% CI 0.93, 0.96 for low birthweight, and RR=0.96; 95% CI 0.94, 0.97 for preterm delivery. Conclusion. Findings indicate small reductions in prevalences of these outcomes associated with the timing of fortification of the U.S. food supply.

Maternal occupational and hobby chemical exposures as risk factors for neural tube defects

In a case-control study, we investigated whether occupational and nonoccupational (hobbies) chemical exposures to women in the periconceptional period increased their risk for having neural tube defect-affected pregnancies. Women were asked about occupational tasks and hobbies performed during the 3

Food fortification with folic acid and twinning among California infants

This study sought to determine whether a change in twinning prevalence was associated with mandatory folic acid fortification. As of January 1998, it became mandatory in the United States that grain products be fortified with folic acid. The effectiveness of this fortification for neural tube defects has been explored, but other possible implications of fortification has not. We computed the prevalence of twinning among more than 2.5 million California births occurring from 1990 to 1999. The prevalence of twin births in California increased over the last decade with increases observed among most maternal race/ethnic, age, and parity groupings. Unadjusted prevalence measures did not reveal substantial increases in twinning prevalence among these groupings after the fortification period relative to the period immediately preceding it. Analyses that simultaneously adjusted for age, parity, race/ethnicity, sexes of twin pair (as a measure of zygosity), year of birth, and fortification period also did not reveal an association between fortification and twinning. Our results do not suggest a change in twinning prevalence associated with folic acid fortification of the US food supply among women delivering in California.

Maternal periconceptional use of electric bed-heating devices and risk for neural tube defects and orofacial clefts.

Electric and magnetic fields are of concern as risk factors for adverse reproductive outcomes, including congenital anomalies. Among residential exposures to electric and magnetic fields, electric bed-heating devices such as electric blankets may be a substantial source of such exposures, and their use is fairly common. Two population-based case-control studies were analyzed to investigate whether the periconceptional use of electric blankets, bed warmers, or electrically heated waterbeds increased the risk of women to deliver infants or fetuses with neural tube defects (NTDs) or orofacial clefts. We obtained information on bed-heating devices from 538 NTD cases and their 539 controls in one study, and 265 NTD cases and 481 controls and 652 orofacial cleft cases and their 734 controls from another study. Our results revealed a few modestly elevated risks of certain anomaly phenotypes with maternal use of certain bed-heating devices, but risks tended to be imprecise. In general, women who reported more frequent use of a bed-heating device, or longer duration of use, did not appear to have a higher risk for delivering offspring with anomalies than were women who reported less frequent or shorter-duration use.

Intermarriage among Spanish surnamed Californians 1962-1974

The nature and extent of outgroup marriage among Mexican Americans in California during the 1962–1974 period is analyzed here through marriage records coded to indicate the Spanish surname status of the bride and groom. A high level of outmarriage was found, on the order of one-third to two-fifths of those marrying. Differentials in outmarriage proportions by age and sex were examined and tended to be relatively small. More substantial differentials were found with regard to marriage order, where higher order marriages of Spanish surnamed persons were more likely than first marriages to involve a non-Spanish surnamed partner. The largest differentials were generational, with Spanish surnamed persons not born in Mexico much more likely to outmarry than were those born in Mexico.

Risks for severe mental retardation occurring in isolation and with other developmental disabilities

Individual and maternal characteristics as potential risk factors for having severe mental retardation (SMR) occurring with and without cerebral palsy (CP), epilepsy, or a pervasive developmental disorder (PDD) were explored among a cohort of 119,404 children without Down syndrome born in the California Central Valley in 1992 and 1993. Unadjusted and adjusted relative risks (RRs) and their 95% confidence intervals (CIs) based on the Poisson distribution were used to estimate the risks associated with each individual and maternal factor studied for each SMR diagnostic category. The most notable increased risks for SMR occurring in isolation or with CP or epilepsy was for children born low‐birth‐weight or preterm who were at a substantially increased risk (RRs 2.6–9.9). In contrast, the risk of SMR occurring with a PDD was the greatest among males compared to females (RR = 3.4, 95% CI 1.5, 7.9), Blacks compared to Whites (RR = 5.1, 95% CI 1.7, 15.5), and Asians compared to Whites (RR = 3.9, 95% CI 1.3, 12.0). Etiologic heterogeneity when SMR occurs with a PDD was suggested.