OBJECTIVES: This report presents 1997 data on U.S. births according to a wide variety of characteristics. Data are presented for maternal demographic characteristics including age, live-birth order, race, Hispanic origin, marital status, and educational attainment; maternal lifestyle and health characteristics (medical risk factors, weight gain, and tobacco and alcohol use); medical care utilization by pregnant women (prenatal care, obstetric procedures, complications of labor and/or delivery, attendant at birth, and method of delivery); and infant health characteristics (period of gestation, birthweight, Apgar score, abnormal conditions, congenital anomalies, and multiple births). Also presented are birth and fertility rates by age, live-birth order, race, Hispanic origin, and marital status. Selected data by mother's State of residence are shown including teenage birth rates and total fertility rates, as well as data on month and day of birth, sex ratio, and age of father. Trends in fertility patterns and maternal and infant characteristics are described and interpreted. METHODS: Descriptive tabulations of data reported on the birth certificates of the 3.9 million births that occurred in 1997 are presented. RESULTS: Birth and fertility rates declined very slightly in 1997. Birth rates for teenagers fell 3 to 5 percent. Rates for women in their twenties changed very little, whereas rates for women in their thirties rose 2 percent. The number of births and the birth rate for unmarried women each declined slightly in 1997 while the percent of births that were to unmarried women was unchanged. Smoking by pregnant women overall dropped again in 1997, but continued to increase among teenagers. Improvements in prenatal care utilization continued. The cesarean delivery rate increased slightly after declining for 7 consecutive years. The proportion of multiple birth continued to rise; higher order multiple births (e.g., triplets, quadruplets) rose by 14 percent in 1997, following a 20 percent rise from 1995 to 1996. Key measures of birth outcome--the percents of low birthweight and preterm births--increased, with particularly large increases in the preterm rate. These changes are in large part the result of increases in multiple births. (+info)
Natural variation in the human sex ratio.
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Analysis of the effect of multiple birth, birth order, age of parents and the sexes of preceding siblings on the secondary sex ratio was performed for 815 891 children, born in Denmark, 1980-1993. The proportion of males was analysed as a function of multiple birth, birth order, age of parents and the sexes of preceding siblings, using contingency tables, chi(2) tests and logistic regression analysis. The secondary sex ratio decreased with increased number of children per plural birth and with paternal age, whereas no independent effect was observed for maternal age, birth order, the sex of the preceding child, or the combination of sexes of previously born children in the family. (+info)
Cerebral palsy and multiple births in China.
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BACKGROUND: A population-based study on prevalence of cerebral palsy in multiple births has not been carried out in China. The purpose of this paper was to determine the prevalence of cerebral palsy in multiple births and to explore the influence of multiple pregnancy on cerebral palsy after controlling for birthweight. METHODS: A cross-sectional study of cerebral palsy was carried out among 388,192 children aged <7 years in seven cities of Jiangsu province in China. Information about birthweight and plurality was obtained from routine health care records. Pediatricians at city level diagnosed all cases. All the doctors involved had taken part in a training programme held by Beijing Medical University. Stratified analysis by birthweight and its standard normal deviate was employed to compare the prevalence of cerebral palsy in multiples and singletons. RESULTS: The prevalence of cerebral palsy for children aged <7 years in multiples was 9.7 per 1000 children (95% confidence interval [CI]: 6.5-14.0), which was 6.5 times that in singletons (95% CI: 4.4-9.3). The overall neonatal mortality rate was 60.9 per 1000 liveborn multiples, being highest (944.4 per 1000) in the 500-999 g birthweight groups. Most liveborn multiples weighing <1500 g at birth probably died from diseases related to very low birthweight prior to this study. The prevalence of cerebral palsy in multiple births was likely to be higher than that reported in developed countries for children weighing 1500-2499 g even though our data were from a cross-sectional study. When stratified by birthweight, the prevalence of cerebral palsy in multiples weighing <2500 g had tended to be lower than that of singletons in the same birthweight group. In contrast, in normal birthweight categories multiple births had a higher prevalence of cerebral palsy than singletons. When stratified by birthweight normal deviate, the prevalence of cerebral palsy in multiple births was uniformly higher than that in singletons in all birthweight strata and the prevalence of cerebral palsy among multiples appeared to be augmented as birthweight increased. CONCLUSION: The prevalence of cerebral palsy in multiples, 9.7 per 1000 children, is 6.5 times that in singletons. Survival of low birthweight infants is lower in China than in developed countries and survival quality of Chinese children weighing 1500-2499 g needs to be further improved. In terms of birthweight multiples and singletons may be heterogeneous. It might be difficult to directly use actual birthweight specific prevalence to compare the prevalence of cerebral palsy in multiples and singletons. Birthweight normal deviate specific prevalence of cerebral palsy suggests that multiple pregnancy is an independent risk factor for cerebral palsy in all birthweight groups. Multiples are in adverse circumstances very early in gestation and as the foetus matures the risk of cerebral palsy increases. (+info)
Multiple births and risk of epithelial ovarian cancer.
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BACKGROUND AND METHODS: Prevailing hypotheses about the causes of ovarian carcinogenesis predict that women with a history of multiple births (twins, triplets, etc.) should be at increased risk of epithelial ovarian cancer. However, the scant available evidence suggests that they may actually be at lower risk. To resolve this issue, we pooled data from eight studies involving 2859 parous women with epithelial ovarian cancer (case patients) and 7434 parous women without ovarian cancer (control women). In addition to assessing their history of multiple births (and the sex of the children, where available), we obtained information on age, parity, oral contraceptive use, and other reproductive factors for each woman. Details of tumor histology were available for all case patients. We estimated the relative risks of various histologic types of ovarian cancers associated with multiple births by using multivariable logistic regression analysis, adjusting for matching and confounding variables. RESULTS: Among these parous women, 73 case patients (2. 6%) and 257 control women (3.5%) had a history of multiple births. The adjusted summary odds ratio (OR) for developing all types of epithelial ovarian cancer that are associated with multiple births was 0.81 (95% confidence interval [CI] = 0.61-1.08). We found no evidence that risks associated with multiple births differed among women with borderline or invasive tumors and among women with same-sex and opposite-sex offspring from multiple births. The risk reductions appeared specific for nonmucinous tumors (n = 2453; summary adjusted OR = 0.71 [95% CI = 0.52-0.98]); in contrast, associations with mucinous tumors (n = 406) were heterogeneous across studies. CONCLUSIONS: Parous women with nonmucinous ovarian cancer are no more likely to have a history of multiple births than other parous women, counter to the predictions of current hypotheses for causes of ovarian cancer. (+info)
Contribution of assisted reproductive technology and ovulation-inducing drugs to triplet and higher-order multiple births--United States, 1980-1997.
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In the United States, pregnancies associated with assisted reproductive technology (ART) or ovulation-inducing drugs are more likely to result in multiple births than spontaneously conceived pregnancies (1). In addition, triplet and higher-order multiple births are at greater risk than singleton births to be preterm (< or = 37 completed weeks' gestation), low birthweight (LBW) (i.e., < or = 2500 g), or very low birthweight (i.e., < 1500 g), resulting in higher infant morbidity and mortality (2). Because preterm and LBW infants often require costly neonatal care and long-term developmental follow-up, the continuing increase in triplet and higher-order multiple births causes concern among health-care providers and policymakers (3). This report provides estimates of the contribution of ART and ovulation-inducing drugs to these birth outcomes for 1996 and 1997, and summarizes trends during 1980-1997, which indicate that the ratio of triplet and higher-order multiple births has more than quadrupled and that a large proportion of this increase can be attributed to ART or the use of ovulation-inducing drugs. (+info)
Offspring risk and sibling risk for multilocus traits.
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The recurrence risk of a trait in a relative of type R is the probability that an individual who is in relationship of type R to an affected proband has the trait. It is intuitively clear that closer relationships lead to higher recurrence risks. However, no exact analysis of this phenomenon has been presented for multilocus traits. We prove a theorem that shows how recurrence risks are influenced by the degree of closeness of the relationship R. For example, our theorem implies that sibling risk is always higher than offspring risk. The loci influencing the trait are assumed to be autosomal and unlinked, but arbitrary epistasis between the loci is allowed. We give a detailed proof of the theorem by using stochastic matrices. A shorter proof based on the additive and dominance genetic variances is also sketched. Additionally, we also give some empirical results and discuss generalizations of the theorem. (+info)
Live-birth rates and multiple-birth risk of assisted reproductive technology pregnancies conceived using thawed embryos, USA 1999-2000.
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BACKGROUND: Increasing use of assisted reproductive technology treatments has been associated with the current rise in multiple births in the USA. Embryo cryopreservation and subsequent thawed embryo transfer may favourably impact the multiple-birth risk by relieving some pressure that patients and providers may feel to transfer several embryos in a single cycle. The study objective was to examine both live-birth rates and multiple-birth risk in thawed cycles. METHODS: The authors used a population-based sample of 21 555 assisted reproductive technology procedures performed in US clinics in 1999 and 2000 that used thawed embryos derived from the patient's oocytes. RESULTS: Both patient age and the number of embryos transferred were independent predictors of live birth. Even among women aged 20-29 years, the transfer of three embryos resulted in an increase in the live-birth rate compared with cycles in which one or two embryos were transferred. This increase in success was accompanied by an increased multiple-birth risk. In all age groups up to 40 years, the transfer of just two embryos resulted in a multiple-birth risk of 16-17%. The multiple-birth risk increased with the number of embryos transferred. CONCLUSIONS: Patient age and the number of embryos transferred significantly affect live-birth and multiple-birth rates among women who use thawed embryos. (+info)
PROBLEM/CONDITION: In 1996, CDC initiated data collection regarding assisted reproductive technology (ART) procedures performed in the United States to determine medical center-specific pregnancy success rates, as mandated by the Fertility Clinic Success Rate and Certification Act (FCSRCA) (Public Law 102-493, October 24, 1992). ART includes fertility treatments in which both eggs and sperm are handled in the laboratory (i.e., in vitro fertilization and related procedures). Patients who undergo ART treatments are more likely to deliver multiple-birth infants than women who conceive naturally. Multiple births are associated with increased risk for mothers and infants (e.g., pregnancy complications, premature delivery, low-birthweight infants, and long-term disability among infants). REPORTING PERIOD COVERED: 2000. DESCRIPTION OF SYSTEM: CDC contracts with a professional society, the Society for Assisted Reproductive Technology (SART), to obtain data from fertility medical centers located in the United States. Since 1997, CDC has compiled data related to ART procedures. The Assisted Reproductive Technology Surveillance System was initiated by CDC in collaboration with the American Society for Reproductive Medicine, the Society for Assisted Reproductive Technology, and RESOLVE: The National Infertility Association. RESULTS: In 2000, a total of 25,228 live-birth deliveries and 35,025 infants resulting from 99,629 ART procedures were reported to CDC from 383 medical centers that performed ART in the United States and U.S. territories. Nationally, 75,516 (76%) of ART treatments were freshly fertilized embryos using the patient's eggs; 13,312 (13%) were thawed embryos using the patient's eggs; 7,919 (8%) were freshly fertilized embryos from donor eggs; and 2,882 (3%) were thawed embryos from donor eggs. The national live-birth delivery per transfer rate was 30.8%. The five states that reported the highest number of ART procedures were California (13,194), New York (11,239), Massachusetts (8,041), Illinois (7,323), and New Jersey (5,506). These five states also reported the highest number of live-birth deliveries and infants born as a result of ART. Overall, 47% of women undergoing ART-transfer procedures using freshly fertilized embryos from their own eggs were aged <35 years; 23% were aged 35-37 years; 19% were aged 38-40 years; 7% were aged 41-42 years; and 4% were aged >42 years. Among ART treatments in which freshly fertilized embryos from the patient's eggs were used, substantial variation in patient age, infertility diagnoses, history of past infertility treatment, and past births was observed. Nationally, live-birth rates were highest for women aged <35 years (38%). The risk for a multiple-birth delivery was highest for women who underwent ART-transfer procedures using freshly fertilized embryos from either donor eggs (40%) or from their own eggs (35%). Among women who underwent ART-transfer procedures using freshly fertilized embryos from their own eggs, further variation by patient age and number of embryos transferred was observed. Of the 35,025 infants born, 44% were twins, and 9% were triplet and higher order multiples, for a total multiple-infant birth rate of 53%. Patient's residing in states with the highest number of live-birth deliveries also reported the highest number of infants born in multiple-birth deliveries. INTERPRETATION: Whether an ART procedure was successful (defined as resulting in a pregnancy and live-birth delivery) varied according to different patient and treatment factors. Patient factors included the age of the woman undergoing ART, whether she had previously given birth, whether she had previously undergone ART, and the infertility diagnosis of both the female and male partners. Treatment factors included whether eggs were from the patient or a woman serving as an egg donor, whether the embryos were freshly fertilized or previously frozen and thawed, how long the embryos were kept in culture, how many embryos were transferred, and whether various specialized treatment procedures were used in conjunction with ART. ART poses a major risk for multiple births. This risk varied according to the patient's age, the type of ART procedure performed, and the number of embryos transferred. In addition, the increased risk for multiple births has a notable population impact in certain states. PUBLIC HEALTH ACTIONS: As use of ART and ART success rates continue to increase, ART-related multiple births are an increasingly important public health problem nationally and in many states. The proportion of infants born through ART in 2000 that were multiple births (53%) was substantially higher than in the general U.S. population during the same period. Data in this report indicate a need to reduce multiple births associated with ART. Efforts should be made to limit the number of embryos transferred for patients undergoing ART. In addition, continued research and surveillance is key to understanding the effect of ART on maternal and child health. (+info)