Seasonality of low birthweight in indigenous Australians: an increase in pre-term birth or intrauterine growth retardation?

We have analysed birthweights of 4,508 Aboriginal and Torres Strait Islander livebirths in the Kimberley region of Western Australia from 1981-93. Mean birthweight varied significantly according to month of birth (F(11) = 2.57, p = 0.003) and low birthweight babies were more common during the wet season. A significant increase in the proportion of very low birthweight (VLBW) babies was observed during the wet season compared with the dry season (OR 2.73; 95% CI 2.3-3.67; p < 0.001); whereas babies weighing 1,500-2,499 g were not significantly more common during the wet season (OR 1.06; 95% CI 0.96-1.17; p = ns). The results indicate that adverse environmental conditions may be associated with increased risk of VLBW. Since newborns weighing less than 1500 g are very likely to be pre-term (< 37 weeks' gestation), the findings also suggest that seasonality of birthweight may be due to an increase in pre-term births rather than an increase in intrauterine growth retardation. Further research is required to identify the underlying causes of an increase in VLBW babies during the wet season.

Births of Hispanic origin, 1989-95

OBJECTIVES

This report presents trend data on births in the United States to women of Hispanic and non-Hispanic origin, from 1989 to 1995, for a wide variety of characteristics. Hispanic women data are presented where possible separately for Mexican, Puerto Rican, Cuban, Central and South American, and other Hispanic women while for non-Hispanic women data are shown for white and black women. Maternal demographic characteristics include age, marital status, live-birth order, educational attainment, and mother's place of birth. Health care utilization items include timing of prenatal care, cesarean delivery rate, place of birth and midwife attendance. Infant health characteristics include percents born preterm, low birthweight, very low birthweight, and percent born in multiple births. Trend data for the number of births by State are also presented.

METHODS

Descriptive tabulations of births of Hispanic origin of the mother for births that occurred from 1989 through 1995 are presented.

RESULTS

The number of births born to Hispanic women has risen every year from 1989 to 1995. In addition in 1989 Hispanic women had 14 percent of births in the United States and in 1995 they represented 18 percent. While Hispanic women as a group continue to have higher fertility rates than non-Hispanics, Mexican women in particular have dramatically higher rates. While increases in early prenatal care were observed for all women in the United States, increases were particularly substantial for Hispanic women. The cesarean section rate has been dropping in the United States; yet while rates for Cuban women have also been dropping, the rates are nearly 50 percent higher than those for any other population subgroup.

The risk for recurrence of premature births to African-American and white women

Preterm birth rates are higher for African Americans than for whites, but the risk for recurrence is not well defined. We tested the hypothesis that the base and recurrence rates for premature births are higher for African Americans than for whites. We recruited a cohort of African-American and white women giving birth to singleton infants between 1988 and 1993 at Perinatal Network, a Midwest urban teaching hospital. These women had known reproductive history, delivered two or more singletons, and had no planned abortions, miscarriages, or induced preterm labor. Premature infants were born at less than 37 completed weeks of gestation. The total preterm birth rate among African Americans was 24.5%, significantly higher than the 11.1% for whites (relative risk, 2.22; confidence interval, 1.79 to 2.75). The preterm birth rate among African Americans for the second pregnancy was 30.6%, significantly higher than the rate of 18.2% for the first pregnancy and 24.5% for the third and fourth pregnancies. The preterm birth rates for whites were 11.7% for the first pregnancy, 9.8% for the second, and 12.9% for the third and fourth pregnancies, which were not significantly different from each other. Considering only the first two pregnancies, recurrence accounted for 32.6% of all premature births for both African Americans and whites. After the second pregnancy, 68% of African-American and 41.7% of white premature babies were born to women who had previous preterm infants. We conclude that preterm births are relatively common for African Americans and whites in the first two pregnancies. Women, particularly African-American women with a previous preterm birth at either the first or second pregnancy, require more specific management to prevent recurrence of preterm birth.

State-specific birth rates for teenagers--United States, 1990-1996

During the late 1980s, birth rates for teenagers in the United States increased sharply. Although rates have declined steadily since 1991 (1,2), age-, race-, ethnicity-, and state-specific rates have varied substantially. Despite recent declines, the U.S. birth rate for teenagers remains high compared with other industrialized countries. In 1996, an estimated 505,514 females aged <20 years gave birth; two thirds of births to teenagers are unintended (3). The adverse consequences of teenage childbearing include increased poverty for both mother and child. This report presents state-specific birth rates for females aged 15-19 years for 1991 and 1995 and compares race/ethnicity-specific birth rates for U.S. females aged <20 years for 1990-1996. These findings indicate that, during 1991-1995, birth rates among teenagers declined significantly in all but five states and the District of Columbia, and declines nationwide during 1991-1996 were especially large for teenagers aged 15-17 years and for black teenagers. Recent declines in abortions and abortion rates forteenagers, coupled with the trends described in this report for birth rates for teenagers, indicate that, since 1991, pregnancy rates for teenagers also have declined.

Consanguinity and its relationship to differential fertility and mortality in the Kotia: a tribal population of Andhra Pradesh, India

Data on patterns of marriage, differential fertility and mortality were collected from 211 Kotia women residing in Visakhapatnam district of Andhra Pradesh, India. Consanguineous marriages made up just over a quarter of the total, and of these, father's sister's daughter (FSD) were more common than mother's brother's daughter (MBD). The mean inbreeding coefficient for the sample (F) was 0.0172. Women in consanguineous marriages had a lower mean number of total conceptions, live births and living offspring (net fertility) than women in non-consanguineous marriages. Significant heterogeneity was found in the means of living offspring for FSD, MBD and non-consanguineous couples, but not for conceptions and live births.

Education and the changing age pattern of American fertility: 1963-1989

Using pooled data from the 1980, 1985, and 1990 Current Population Surveys, we describe fertility trends by age and education for the period 1963-1989. Interest focuses on whether the effects of education have changed across this period. We show that women with college degrees experienced dramatic shifts toward later ages of childbearing. This shift is consistent with arguments we develop about the increased opportunity for women to pursue careers and about changes in the availability of child care.

A decomposition of trends in the nonmarital fertility ratios of blacks and whites in the United States, 1960-1992

We use a method of standardization and decomposition developed by Das Gupta to update Smith and Cutright's analysis of demographic factors responsible for increases in the nonmarital fertility ratio (illegitimacy ratio) among blacks and whites in the United States. We create standardized rates for each year between 1960 and 1992, and consistent, exhaustive decompositions of the nonmarital fertility ratio for any interval during this period in terms of four components: (1) the age distribution of women of reproductive age, (2) the proportion of women unmarried at each age, (3) the age-specific birth rates of married women, and (4) the age-specific birth rates of unmarried women. Nonmarital fertility ratios are much higher among blacks than among whites, but both increased monotonically from 1960 to 1992. During the last 10 years, each increased by nearly 10 percentage points. Increases in the proportion of women not married, at all ages, account for the preponderance of the increase in black nonmarital fertility ratios. Increasing rates of unmarried childbearing, however, have played a role during the most recent decade (1983-1992). For whites, from 1960 until 1975, declines in marital fertility were most important in producing increases in the proportion of children born out of wedlock. Since then, these proportions have increased primarily because of increases in unmarried women's birth rates, and secondarily because of declines in the proportion of women who are married. These trends are consistent with arguments that emphasize declining economic incentives to marry and reduced access to, and acceptability of, abortion.

Racial fertility differences: the role of female employment and education in wanted and unwanted childbearing

This paper employs data from a merged sample of the National Surveys of Family Growth to examine how female employment status conditions the relationship between education and wanted and unwanted births among African American and white women. A rationale is presented for why a minority group status hypothesis that posits lower fertility among more highly educated African American women as compared to similar white women might find support in the case of wanted births and among certain women, including earlier birth cohorts. Our results provide some evidence for these ideas as well as evidence for a social characteristics hypothesis that predicts convergence of childbearing with rising education. However, persistently higher levels of unwanted births among African American women of all educational levels suggest that the dynamics of racial fertility differences are more complex than either of the hypotheses imply.

Ethnic comparison of twinning rates in California

A meaningful comparison of the twinning rates of different populations can be hindered by several factors that may influence the rates. Chief among these factors are the sources of data from which the rates are derived and the maternal age structure of the populations. The effects of such factors were minimal when the twinning rates of 14 ethnic groups in California were compared. After standardization for maternal age, twinning rates per 1000 maternities for the main ethnic groups were 13.20 for blacks, 10.05 for whites, and 7.18 for Asians. There were significant differences within the Asian group. The highest rate was for Cambodians (8.57). This rate compares with rates of approximately 6 for Koreans, Thai, and Vietnamese. These rates are similar to those found in Asia but lower than those for Californian Chinese, Japanese, and Filipinos, who have been established in the state for longer. In general, the results provide support for previous reports that twinning rates are modified by both migration and interethnic mixing. Rates for Indians from India were lower than those reported from the Indian subcontinent, whereas the twinning rates for Native Americans (10.15) and Pacific Islanders (10.60) were similar to the rate for US whites.

Proportional differences in births and infant mortality rates among the triethnic population in Texas from 1984 through 1986

Birth at preterm gestation and/or with low birth weight is a major predictor of the infant mortality rate, which is twice as high in African-American as in Anglo and Hispanic infants in Texas. This study examined the relative proportions of Anglo, African-American, and Hispanic births that occurred in Texas at specific gestational ages and birth weights, and the neonatal, postneonatal, and infant mortality rates associated with those births. African-American infants showed a systematic tendency to be born at earlier gestational ages and with lower birth weights than did Anglo infants, while Hispanic-Anglo differences were limited to a small excess of preterm but not low weight Hispanic births. Preterm and low-birth-weight African-American infants had neonatal and infant mortality rates that were lower than those of Anglo infants, but that benefit was inadequate to compensate for the greater proportion of African-American births that were at risk. No consistent difference could be identified between Hispanic and Anglo infant mortality rates. We conclude that the birth weight and gestational age predictors of infant mortality reflect the combined effects of two ethnic-specific factors: the mortality rates at specific birth weights and gestational ages, and the proportions of births that are at risk. The biological and/or sociological causes for these ethnic differences in pregnancy outcomes and mortality risk need to be identified if the mortality rate of African-American infants in Texas is to be reduced.

The state of South Dakota's child: 1994

This annual report reviews natality and infant mortality data and also reviews teenage pregnancy in South Dakota. Data for 1993 again document a declining rate of birth for South Dakota with a 3% decline in the number of births since 1990 and an 18% decline since 1980. An identical number of infants (102) died in 1993 as 1992 with neonatal mortality slightly declining and post neonatal mortality slightly increasing for the state. Rates of perinatal causes of infant death are lower in South Dakota than they are nation-wide, but are higher for congenital anomalies, sudden infant death, pneumonia/influenza, and injuries/homicide. The 1993 birth rate per 1,000 teenagers 15-19 years of age in South Dakota was 44.5 compared to the 1992 rate of 60.7 for the United States. In South Dakota the rate of teen births for American Indian mothers is over four times higher than that for whites. The American Indian rate is also higher than that observed for Indians nation-wide. Alternately, the South Dakota white rate of birth to this age group is lower than the national rate. For all babies born to teenage mothers, 69% of the fathers are beyond their teen years. The need to examine teen pregnancy as a societal, and not just an adolescent problem, is emphasized.

Comparing the changing suicide rate in Singapore with the rates in England/Wales and the USA, 1950-1985

Whereas marriage and birth rates were significantly associated with the time-series annual suicide rate from 1950 to 1985 in England and Wales and birth rates were associated with the annual suicide rate in the USA, neither variable was significantly associated with the annual suicide rate in Singapore. It seems that different theories of suicide may have to be proposed in order to account for the societal suicide rate in Asian nations.

Trends in multiple births

Since the early 1970s, the number and rate of multiple births have increased fairly steadily. Of the 4,110,907 babies born in the United States in 1991, 98,125 (2.4 percent) were twins, triplets or other higher order plural births. The 1991 rate of 23.9 multiple births per 1,000 live births--the highest recorded in this country in the last 50 years--was 1.3 percent higher than that in 1990, and 14 percent higher than the rate in 1985. The twins proportion of all multiple births has been slowly decreasing--97.6 percent in 1985, 96.9 percent in 1990 and 96.6 percent in 1991. Rates of multiple births continue to be higher among black women than white (2.8 and 2.3 per 1,000 live births, respectively, in 1991) and are more prevalent among older women. In 1991 the rates were higher through each age group to a high of 3.4 for white and 3.6 for black mothers aged 35-39 before dropping to 1.9 and 0.5, respectively, among 45- to 49-year-olds. Incidence of low birthweight (< 2,500 grams) and of very low birthweight (< 1,500 grams) babies were more frequent among multiple births than singletons and were more common among black than white infants. The median weight for white singleton births was 3,420 grams versus 2,260 grams for black plural births. The District of Columbia, Michigan and Massachusetts registered the highest percentage of multiple births in 1991 (2.9 to 2.7 percent) and the lowest rates were recorded in New Mexico and Wyoming (1.9 percent).

Recent fertility decline in Dariusleut Hutterites: an extension of Eaton and Mayer's Hutterite fertility study

A church book that has been routinely updated by the Dariusleut Hutterites enabled us to update some fertility tables presented by Eaton and Mayer in the 1950s. The age-specific (nuptial) fertility rates and the total fertility rates (TFRs) were calculated for every 5-year period from 1901-1905 to 1981-1985. Our calculations for Dariusleut, one of the three sects of the Hutterites, gave slightly lower age-specific nuptial fertility rates before 1951 compared with the figures given by Eaton and Mayer (1953) for all Hutterites in the corresponding time periods. The recent decline in Hutterite fertility, especially at higher maternal ages, was confirmed in this study. The TFR, given as a sum of 5-year-grouped age-specific nuptial fertility rates from 15 to 49 years of maternal age, was higher (8.80-9.83) in the years 1946-1965, but it declined to 8.13 in 1966-1970, to 7.22 in 1971-1975, to 6.39 in 1976-1980, and to 6.29 in 1981-1985. For the age groups 35-39 years and older the age-specific nuptial fertility rate in 1981-1985 decreased by more than 50% compared with the rate during the peak period of 1951-1955. The probability of a married woman having a live birth at each age from 15 to 49 years still peaked around the twentieth year of life, as found by Eaton and Mayer (1953), but it decreased more rapidly from the late twenties among the recently married women, most evidently in their thirties.

Sudden infant death syndrome in aboriginal and non-aboriginal infants

This study, based on routinely recorded data, was designed to compare the epidemiology of sudden infant death syndrome (SIDS) in Aboriginal and non-Aboriginal infants in Western Australia (WA). All cases of SIDS occurring in infants born in WA from 1980 to 1988 were included in the study. There were 66 Aboriginal (6.1 per 1000 live births) and 337 non-Aboriginal (1.7 per 1000 live births) infants who died from SIDS. It was found that there was a significant linear increase in the Aboriginal SIDS rate over the study period while the non-Aboriginal rate remained relatively constant. For non-Aboriginal infants, there was an elevated risk of SIDS for young maternal age, single marital status and male gender but this was not found for Aboriginal infants. There was a significant difference in the age at death distribution for the two populations. Low birthweight and preterm birth were risk factors for both Aboriginal and non-Aboriginal infants. There may be differences in the aetiology and/or classification of SIDS between the two populations.

Trends in cohort fertility of the Dariusleut Hutterite population

A church book containing vital information on Dariusleut Hutterite families enabled us to trace the life course of individual women. We conducted a retrospective cohort study on the women born in the Dariusleut sect for the period 1901-1965, focusing on their marriage and reproductive histories. The subjects were grouped into 5-year birth cohorts from 1901-1905 to 1961-1965. The marital age-specific fertility rate (MASFR) increased from the 1901-1905 cohort to the 1926-1930 cohort and then began to decrease, particularly at the ages of 30-39 years. The initial increase in MASFR was not reflected directly in the cohort mean of the total number of children per woman because of a concurrent delay in age at marriage. Marriage delay, however, could not explain the drastic decrease, which started in the 1931-35 cohort, in the total number of children per woman; the decrease in MASFR at the ages of 30 years and older was considered a major reason for the recent changes in Hutterite fertility. The causes of the recent fertility decrease of Hutterites at higher ages remain to be investigated.

Geographical differences and time trends in the seasonality of birth in Japan

Seasonal variations of births in six different prefectures in Japan are analysed using Vital Statistics from 1974 to 1983. First births show a bimodal pattern with two peaks, one in winter (December-February) and the other in summer to early autumn (August-September). The seasonality of first births is statistically significantly correlated with the seasonality of marriages with 9 + 12*n (n = 0, 1, 2, 3) lag months. For subsequent births, the seasonal pattern is unimodal and there is also a geographical trend in seasonality of these births with a late spring peak in the northernmost prefecture of Japan giving way to an early autumn peak in the southernmost prefecture. These findings suggest that seasonal variations in marriage play some role in the seasonality of first births, while other features such as environmental factors could be associated with the seasonal variations of subsequent births. Changes in the seasonality of both births and marriages over time suggest that the modernization of Japanese society after the second World War could be responsible for the drastic changes in the pattern and degree of seasonality of births.

Evaluation of the Consensus Health Status Indicator for assessing adolescent pregnancies and births

The authors used vital statistics and population data for DeKalb County, GA, in an evaluation of the accuracy of the Consensus Health Status Indicator for assessing adolescent pregnancies and births. The indicator used was the number of births to females 10-17 years of age, expressed as a percentage of all births in the population. The investigators found no significant changes in the proportions of births to adolescents for the period 1982-90. Births to adolescents were 5.3 percent of all births during 1982-84 and 5.2 percent during 1988-90. However, the pregnancy rate for adolescents in those years increased significantly, from 27.9 per 1,000 births for 1982-84 to 33.1 per 1,000 for 1988-90. The results indicate that, in localities with substantial changes in the age distribution of the population, the health status indicator does not adequately reflect trends in pregnancies among those 10-17 years of age.

Surveillance for pregnancy and birth rates among teenagers, by state--United States, 1980 and 1990

PROBLEM/CONDITION

In the United States in 1990, there were an estimated 1 million pregnancies and 521,826 births among women ages 15-19 years. Rates of teenage pregnancy and birth rates by state in 1990 exceeded those in most developed countries. An estimated 95% of teenage pregnancies are unintended (i.e., they occur sooner than desired or are not wanted at any time).

REPORTING PERIOD COVERED

This report summarizes and reviews surveillance data for pregnancies, abortions, and births among women ages 15-19, 15-17, and 18-19 years reported by CDC for 1980 and 1990.

DESCRIPTION OF SYSTEM

Data for births and abortions were reported to state health departments and other health agencies and sent to CDC. The data from each state included the total number of births and abortions by age and race/ethnicity.

RESULTS

Data in this report indicate that pregnancy rates by state among U.S. teenagers ages 15-19 years have changed little since 1980. Moreover, many states have reported increases in birth rates that are probably related to concurrent decreases in abortion rates. Pregnancy rates range from 25 to 75 per 1,000 for 15- to 17-year-olds and from 92 to 165 per 1,000 for 18- to 19-year-olds.

INTERPRETATION

States with low rates of teenage pregnancy or birth may have developed and used prevention strategies directed at the needs of both younger and older teenagers; these programs may serve as models for other states where birth rates have remained high or have increased since 1980.

ACTIONS TAKEN

CDC will continue to conduct surveillance of and analyze data for pregnancies, abortions, and births among teenagers to monitor progress toward national goals and to assist in targeting program efforts for reducing teenage pregnancy.