Joyce A. Martin

Annual summary of vital statistics: 2006.

US births increased 3% between 2005 and 2006 to 4265996, the largest number since 1961. The crude birth rate rose 1%, to 14.2 per 1000 population, and the general fertility rate increased 3%, to 68.5 per 1000 women 15 to 44 years. Births and birth rates increased among all race and Hispanic-origin groups. Teen childbearing rose 3% in 2006, to 41.9 per 1000 females aged 15 to 19 years, the first increase after 14 years of steady decline. Birth rates rose 2% to 4% for women aged 20 to 44; rates for the youngest (10–14 years) and oldest (45–49) women were unchanged. Childbearing by unmarried women increased steeply in 2006 and set new historic highs. The cesarean-delivery rate rose by 3% in 2006 to 31.1% of all births; this figure has been up 50% over the last decade. Preterm and low birth weight rates also increased for 2006 to 12.8% and 8.3%, respectively. The 2005 infant mortality rate was 6.89 infant deaths per 1000 live births, not statistically higher than the 2004 level. Non-Hispanic black newborns continued to be more than twice as likely as non-Hispanic white and Hispanic infants to die in the first year of life in 2004. For all gender and race groups combined, expectation of life at birth reached a record high of 77.9 years in 2005. Age-adjusted death rates in the United States continue to decline. The crude death rate for children aged 1 to 19 years decreased significantly between 2000 and 2005. Of the 10 leading causes of death for children in 2005, only the death rate for cerebrovascular disease was up slightly from 2000, whereas accident and chronic lower respiratory disease death rates decreased. A large proportion of childhood deaths, however, continue to occur as a result of preventable injuries.

Annual summary of vital statistics: 2005

The general fertility rate in 2005 was 66.7 births per 1000 women aged 15 to 44 years, the highest level since 1993. The birth rate for teen mothers (aged 15 to 19 years) declined by 2% between 2004 and 2005, falling to 40.4 births per 1000 women, the lowest ever recorded in the 65 years for which there are consistent data. The birth rates for women ≥30 years of age rose in 2005 to levels not seen in almost 40 years. Childbearing by unmarried women also increased to historic record levels for the United States in 2005. The cesarean-delivery rate rose by 4% in 2005 to 30.2% of all births, another record high. The preterm birth rate continued to rise (to 12.7% in 2005), as did the rate for low birth weight births (8.2%). The infant mortality rate was 6.79 infant deaths per 1000 live births in 2004, not statistically different from the rate in 2003. Pronounced differences in infant mortality rates by race and Hispanic origin continue, with non-Hispanic black newborns more than twice as likely as non-Hispanic white and Hispanic infants to die within 1 year of birth. The expectation of life at birth reached a record high in 2004 of 77.8 years for all gender and race groups combined. Death rates in the United States continued to decline, with death rates decreasing for 9 of the 15 leading causes. The crude death rate for children aged 1 to 19 years did not decrease significantly between 2003 and 2004. Of the 10 leading causes of death for 2004 in this age group, only the rates for influenza and pneumonia showed a significant decrease. The death rates increased for intentional self-harm (suicide), whereas rates for other causes did not change significantly for children. A large proportion of childhood deaths continue to occur as a result of preventable injuries.

Annual Summary of Vital Statistics: 2010–2011

The number of births in the United States declined by 1% between 2010 and 2011, to a total of 3 953 593. The general fertility rate also declined by 1% to 63.2 births per 1000 women, the lowest rate ever reported. The total fertility rate was down by 2% in 2011 (to 1894.5 births per 1000 women). The teenage birth rate fell to another historic low in 2011, 31.3 births per 1000 women. Birth rates also declined for women aged 20 to 29 years, but the rates increased for women aged 35 to 39 and 40 to 44 years. The percentage of all births to unmarried women declined slightly to 40.7% in 2011, from 40.8% in 2010. In 2011, the cesarean delivery rate was unchanged from 2010 at 32.8%. The preterm birth rate declined for the fifth straight year in 2011 to 11.72%; the low birth weight rate declined slightly to 8.10%. The infant mortality rate was 6.05 infant deaths per 1000 live births in 2011, which was not significantly lower than the rate of 6.15 deaths in 2010. Life expectancy at birth was 78.7 years in 2011, which was unchanged from 2010. Crude death rates for children aged 1 to 19 years did not change significantly between 2010 and 2011. Unintentional injuries and homicide were the first and second leading causes of death, respectively, in this age group. These 2 causes of death jointly accounted for 47.0% of all deaths of children and adolescents in 2011.

Annual Summary of Vital Statistics: 2009

The number of births in the United States decreased by 3% between 2008 and 2009 to 4 130 665 births. The general fertility rate also declined 3% to 66.7 per 1000 women. The teenage birth rate fell 6% to 39.1 per 1000. Birth rates also declined for women 20 to 39 years and for all 5-year groups, but the rate for women 40 to 44 years continued to rise. The percentage of all births to unmarried women increased to 41.0% in 2009, up from 40.6% in 2008. In 2009, 32.9% of all births occurred by cesarean delivery, continuing its rise. The 2009 preterm birth rate declined for the third year in a row to 12.18%. The low-birth-weight rate was unchanged in 2009 at 8.16%. Both twin and triplet and higher order birth rates increased. The infant mortality rate was 6.42 infant deaths per 1000 live births in 2009. The rate is significantly lower than the rate of 6.61 in 2008. Linked birth and infant death data from 2007 showed that non-Hispanic black infants continued to have much higher mortality rates than non-Hispanic white and Hispanic infants. Life expectancy at birth was 78.2 years in 2009. Crude death rates for children and adolescents aged 1 to 19 years decreased by 6.5% between 2008 and 2009. Unintentional injuries and homicide, the first and second leading causes of death jointly accounted for 48.6% of all deaths to children and adolescents in 2009.

Fetal and neonatal mortality among twin gestations in the United States: the role of intrapair birth weight discordance

OBJECTIVE To examine the association of intrapair birth weight discordance with fetal and neonatal mortality. METHODS We used the United States (1995–1997) Matched Multiple Birth File (n = 297,155). RESULTS Among twin live births and stillborn fetuses, 29.9% had less than 5% birth weight discordance, 24.2% had 5–9%, 29.6% had 10–19%, 11.1% had 20–29%, 3.4% had 30–39%, and 1.8% had 40% or more. The stillborn fetus rate increased progressively with increasing birth weight discordance for smaller and larger twins of the same sex. Compared with the less than 5% birth weight discordance category, the adjusted odds ratios (OR) (95% confidence intervals [CIs]) for stillborn fetus associated with 5–9%, 10–19%, 20–29%, 30–39%, and 40% or more birth weight discordance, respectively, were 0.81 (95% CI 0.58, 1.11), 1.41 (95% CI 1.07, 1.84), 1.74 (95% CI 1.28, 2.35), 3.06 (95% CI 2.21, 4.24), and 4.29 (95% CI 3.05, 6.04) for smaller twins. The corresponding ORs (95% CIs) for larger twins were 0.78 (95% CI 0.57, 1.08), 1.26 (95% CI 0.96, 1.66), 1.77 (95% CI 1.27, 2.46), 3.38 (95% CI 2.33, 4.92), and 2.91 (95% CI 1.89, 4.47). Similar associations were observed among smaller but not larger twins of opposite sex. Among larger but not smaller twins of the same sex, increasing birth weight discordance was associated with overall neonatal deaths. This association was not apparent among smaller and larger twins of opposite sex. However, increasing birth weight discordance was associated with neonatal deaths related to congenital malformations among smaller and larger twins. CONCLUSION The results provide evidence that increased twin birth weight discordance was associated with increased risk of intrauterine death and malformation‐related neonatal deaths.

The Rise in Multiple Births in the United States: Who, What, When, Where, and Why

Introduction In 2001, there were nearly 129,000 multiples born in the United States, the highest number ever recorded. The number of multiple births has risen dramatically just since 1980, with a 77% increase in twins and a 459% increase in triplet and higher-order births (quadruplets and quintuplets) (Table 1, Figure 1). Although triplets and higherorder multiples are increasing at a faster rate, twins account for 94% of all multiple births each year. Multiple pregnancy is associated with significantly higher maternal and neonatal morbidity and mortality. Women pregnant with multiples are nearly six times more likely to be hospitalized during pregnancy, more than twice as likely to be admitted to the adult intensive care unit, and to die compared with women with singleton pregnancies. Maternal length of stay during the birth admission is 60% to 70% higher for multiple versus singleton births, even when matched for gestational age. Hospital costs for the mother’s birth admission are 37% higher, primarily due to a longer length of stay both before and after delivery, and more complications. The rise in multiple births in the United States is a phenomena occurring in developed countries around the world. Factors that have contributed to this change include a trend toward delayed childbearing and advances in reproductive technology. The purpose of this chapter is to Correspondence: Barbara Luke, ScD, MPH, RD, Department of Epidemiology and Public Health, University of Miami School of Medicine, Highland Professional Bldg., 1801 NW 9 Avenue (Room 200H), Miami, FL 33136. E-mail: bluke@med.miami.edu CLINICAL OBSTETRICS AND GYNECOLOGY Volume 47, Number 1, 118–133

Supplemental Analyses of Recent Trends in Infant Mortality

U.S. preliminary data for 2002 show a significant increase in the infant mortality rate to 7.0 infant deaths per 1,000 live births, the first rise in the infant mortality rate since 1958. The increase in infant mortality was concentrated in the neonatal period, particularly in deaths occurring within seven days of birth. Partially edited fetal death data suggest that the increase in neonatal mortality was accompanied by a decline in the late fetal mortality rate, and thus it appears that the 2002 perinatal mortality rate will remain level. Potential explanatory factors for the changes in the infant mortality rate are examined, including causes of infant death, percentage of births that are preterm, and low birthweight. Data from the 2002 linked birth and infant death file will allow an assessment of the contribution of maternal and infant factors such as multiple births and management of labor and delivery.

Explaining the 2001-2002 infant mortality increase in the United States: data from the linked birth/infant death data set.

The U.S. infant mortality rate (IMR) increased from 6.8 infant deaths per 1,000 live births in 2001 to 7.0 in 2002, the first increase in more than 40 years. From 2001 to 2002, IMR increased for very low birthweight infants as well as for preterm and very preterm infants. Although IMR for very low birthweight infants increased, most of the increase in IMR from 2001 to 2002 was due to a change in the distribution of births by birthweight and, more specifically, to an increase in infants born weighing less than 750 grams. The majority of infants born at less than 750 grams die within the first year of life; thus, these births contribute disproportionately to overall IMR. Increases in births at less than 750 grams occurred for non-Hispanic white, non-Hispanic black, and Hispanic women. Most of the increase occurred among mothers 20 to 34 years of age. Although multiple births contributed disproportionately, most of the increase in births at less than 750 grams occurred among singletons. Three hypotheses were evaluated to assess their possible impact on the increase in less than 750-gram births: possible changes in (1) the reporting of births or fetal deaths, (2) the risk profile of births, and (3) medical management of pregnancy. Although each of these factors may have contributed to the increase, the relative effects of these and other factors remain unclear. More detailed studies are needed to further explain the 2001–2002 infant mortality increase.

Annual summary of vital statistics: 2013-2014

This article presents US final natality and mortality data for 2013 and 2014 by demographic and medical characteristics. The number of births in the United States increased by 1% between 2013 and 2014, to a total of 3 988 076. The general fertility rate rose 1% to 62.9 births per 1000 women. The total fertility rate also rose 0.3% in 2014, to 1862.5 births per 1000 women. The teenage birth rate fell to another historic low in 2014, 24.2 births per 1000 women. The percentage of all births to unmarried women declined to 40.2% in 2014, from 40.6% in 2013. In 2014, the cesarean delivery rate declined to 32.2% from 32.7% in 2013. The preterm birth rate declined for the seventh straight year in 2014 to 9.57%; the low birth weight rate was unchanged at 8.00%. The infant mortality rate decreased to a historic low of 5.82 infant deaths per 1000 live births in 2014. The age-adjusted death rate for 2014 was 7.2 deaths per 1000 population, down 1% from 2013. Crude death rates for children aged 1 to 19 years did not change significantly between 2013 and 2014. Unintentional injuries and suicide were, respectively, the first and second leading causes of death in this age group. These 2 causes of death jointly accounted for 46.5% of all deaths to children and adolescents in 2014.