Extrauterine neuromaturation of low risk preterm infants.

The objective of the study was to follow neuromaturation in preterm infants. From serial exams in 90 low risk very low birthweight infants, each infant's Maturity Scores (the sum of tone, reflex, and response items) were plotted against postmenstrual age (PMA) when examined. Each infant's estimated line of best fit provides two descriptors of that infant's neuromaturation: slope (Individual Maturity Slope) and y-value (Predicted Maturity Score at 32-wk PMA). We found that Maturity Scores increased with PMA; 96% had correlation coefficients >0.8. Mean Actual and Predicted Maturity Scores at 32-wk PMA were 60 and 58, respectively, in 65 infants. When stratified by gestational age, Mean Actual Maturity Score at 30-wk PMA were 50 whether infants were 1 or several weeks old when examined. Therefore, low risk preterm infants demonstrated individual variability in rate of neuromaturation. Tone, reflexes, and responses nonetheless emerged in a predictable pattern, whether neuromaturation was intrauterine or extrauterine. This unique tool that measures preterm neuromaturation requires expertise but no technology. It has an exciting potential for providing insight into how emerging central nervous system function and structure influence each other, as well as how the central nervous system recovers from injury.

Pregnancy spacing among women delaying initiation of childbearing.

INTRODUCTION: An increasing proportion of women in the US and other countries delay initiation of childbearing until their thirties. Little is known about their subsequent pregnancies, particularly with regard to pregnancy spacing. OBJECTIVES: To determine interpregnancy interval (IPI) patterns, factors associated with IPI among women delaying initiation of childbearing until their thirties, and ascertain if delay in initiation of childbearing is associated with increased likelihood for short interpregnancy interval of less than 6 months. METHODS: A retrospective cohort study was performed using the Missouri maternal linked file for 1978-1997, inclusive. Analysis was limited to mothers aged 20-50 years at first pregnancy, having a first and second pregnancy during the study period; the sample size included 242,559 mother-infant pairs. Analysis strategies included stratified analysis, and multivariable logistic regression. Interpregnancy interval was main outcome variable, and was grouped in seven categories: 0-5, 6-11, 12-17, 18-23, 24-59, 60-119, >or=120 months. RESULTS: The mean interpregnancy interval was significantly shorter for women delaying start of childbearing (>or=30 years) compared to 20-29 year olds. Observed intervals are 31 (+/-24) months for mothers aged 20-29 years, 25 (+/-17) months for mothers aged 30-34 years, 21 (+/- 14) for 35-39 year olds, and 19 (+/-16) for 40-50 year olds (P < 0.0001). A significant trend for shorter intervals was noted as maternal age at first pregnancy increased (P < 0.0001). Factors associated with interpregnancy interval for women delaying initiation of childbearing included adverse outcome in preceding pregnancy, and low educational status. Mothers aged 35 and above at first pregnancy had increased odds for a second pregnancy following short IPI <6 months; (35-39 years OR = 1.26 95% CI 1.11-1.44; 40-50 OR = 1.91 95% CI 1.13-3.24). Mothers aged 30-34 years have lower odds for short IPI (OR = 0.93 95% CI 0.87-0.99). CONCLUSION: First time mothers aged 35 and above have higher odds of having a second pregnancy shortly after their first pregnancy. Given the increasing number of first time mothers aged 35 and above, these findings are of relevance for preconception counseling for this unique population of women.

Obesity and extreme obesity: new insights into the black-white disparity in neonatal mortality.

OBJECTIVE: To estimate whether the preponderance of obesity among black women could explain the black-white disparity in neonatal mortality. METHODS: This is a population-based study using longitudinally collected data among pregnant women from the state of Missouri spanning almost two decades (1978-1997). Obesity is defined in this study as body mass index (BMI) of at least 30 and further categorized into the typically reported three subclasses: class I (BMI 30.0-34.9), class II (BMI 35.0-39.9), and extreme/morbid obesity (BMI at least 40). The main outcome measures were neonatal mortality, early neonatal mortality, and late neonatal mortality. RESULTS: Overall, neonatal mortality and early neonatal mortality but not late neonatal mortality increased with higher obesity subclass, with the greatest risk registered among morbidly obese mothers (hazards ratio for neonatal mortality 1.3; 95% confidence interval [CI] 1.1-1.5; hazards ratio for early neonatal mortality 1.3; 95% CI 1.1-1.5). Among blacks, the risk for neonatal, early, and late neonatal mortality increased significantly with rising BMI (50-100% increments). However, offspring of obese white mothers had no elevated risks for any of the three indices of mortality regardless of maternal obesity subclass. CONCLUSION: Neonates of obese black mothers have an elevated risk of mortality throughout the neonatal period, whereas those of obese white mothers do not. Obesity among black mothers may contribute to the persistent black-white disparity in infant survival in the United States and could provide an avenue for narrowing the black-white gap in infant mortality. LEVEL OF EVIDENCE: II.

The increasing racial disparity in infant mortality rates: composition and contributors to recent US trends.

OBJECTIVES: We examined trends in birthweight-gestational age distributions and related infant mortality for African American and white women and calculated the estimated excess annual number of African American infant deaths. STUDY DESIGN: Live births to US-resident mothers with a maternal race of white or African American were selected from the National Center for Health Statistics' linked live birth-infant death cohort files (1985-1988 and 1995-2000). RESULTS: The racial disparity in infant mortality widened despite an increasing rate of white low-birthweight infants. White preterm infants had relatively greater gains in survival and the white advantage in survival at term increased. Annually, African American women experience approximately 3300 more infant deaths than would be expected. CONCLUSION: The increasing US racial disparity in infant mortality is largely influenced by changes in birthweight-gestational age-specific mortality, rather than the birthweight-gestational age distribution. Improvement in the survival of white preterm and low-birthweight infants, probably reflecting advances in and changing access to medical technology, contributed appreciably to this trend.

Pregnancy outcomes of American Indians: contrasts among regions and with other ethnic groups.

OBJECTIVES: The two-fold purpose of this analysis is first to contrast the maternal risk factors and birth outcomes of American Indians (AIs) with other race/ethnic groups and to compare the maternal risk factors and birth outcomes of AIs by region to assess whether there are geographic variations in the adverse outcomes that might suggest intervention strategies. STUDY DESIGN: This study used the National Center for Health Statistics live birth infant death cohort files from 1995-2001. Singleton live births to U.S. resident mothers were selected. The analyses were limited to non-Hispanic American Indians, including Aleuts and Eskimos (n = 239,494), Non-Hispanic White (n = 15,488,133), and Hispanic births (n = 5,284,978). RESULTS: This comparison of birth characteristics and outcomes by ethnic group revealed that AIs have more adverse maternal risk factors (e.g., unmarried and <18 years of age) than Whites and Hispanics. After adjustment for these factors, AIs have higher risks of low birth weight and preterm birth and elevated risks of postneonatal and infant mortality. Their cause-specific rates for perinatal, SIDS, injury and infection are also higher. The regional analysis indicated the South/Northeast have more low birth weight and preterm problems, but the Mid-West has the highest risks of infant mortality among LBW infants gestational age-specific mortality rates, and mortality from SIDS. CONCLUSIONS: These data show that AIs are not a homogenous group as evinced by distinct regional differences. SIDS is mainly a problem in the Mid-West, suggesting the involvement of environmental factors in that region. Further investigation is needed to examine the current AI perinatal health concerns.

Comparison of gestational age classifications: date of last menstrual period vs. clinical estimate.

PURPOSE: The purpose was to compare the two different measures of gestational age currently used on birth certificates (the duration of pregnancy based on the date of last menstrual period [LMP] and the clinical estimate [CE] as related to health status indicators. We contrasted these measures by race/ethnicity. METHODS: NCHS natality files for 2000-2002 were used, selecting cases of single live birth to U.S. resident mothers with both LMP and CE gestational age information. RESULTS: Approximately 75% of the records had valid LMP and CE values and for approximately one-half of these, the LMP and CE values did not exactly agree. Overall and for each race and ethnic group, the LMP measures resulted in higher proportions of very preterm, preterm, postterm and SGA births. CE value provided preterm rates of 7.9% and for LMP, 9.9%. The odds ratio of preterm birth for African-Americans using the CE measure was 1.78 [95% Cl 1.77-1.79]. The odds ratio using LMP was 1.93 [95% Cl 1.92-1.94]. Whites were the referent population. CONCLUSIONS: Different measures of gestational age result in different overall and race-specific rates of very preterm, preterm, postterm, and SGA births. These findings indicate that substituting or combining these measures may have consequences.

Extreme obesity and risk of stillbirth among black and white gravidas.

OBJECTIVE: To estimate the risk for stillbirth among three generally accepted obesity subtypes based on severity. METHODS: We used the Missouri maternally linked cohort data containing births from 1978 to 1997. Using prepregnancy weight and height, mothers were classified on the basis of calculated body mass index (BMI) above 30 into three subsets: class I (30-34.9), class II (35-39.9), and extreme obesity (greater than or equal to 40). Using normal-weight, white women (18.5-24.9) as a reference, we applied Cox proportional hazard regression models to estimate risks for stillbirth. RESULTS: The prevalence of obesity in pregnant women was 9.5% (12.8% among blacks and 8.9% among whites). Overall, obese mothers were about 40% more likely to experience stillbirth compared with nonobese gravidas (adjusted hazard ratio 1.4; 95% confidence interval [CI] 1.3-1.5). The risk for stillbirth increased in a dose-dependent fashion with increase in BMI: class I (adjusted hazard ratio 1.3; 95% CI 1.2-1.4); class II (adjusted hazard ratio 1.4; 95% CI 1.3-1.6) and extreme obesity (adjusted hazard ratio 1.9; 95% CI 1.6-2.1; P for trend <.01). Obese black mothers experienced more stillbirths than their white counterparts (adjusted hazard ratio 1.9; 95% CI 1.7-2.1 compared with adjusted hazard ratio 1.4; 95% CI 1.3-1.5). The black disadvantage in stillbirth widened with increase in BMI, with the greatest difference observed among extremely obese black mothers (adjusted hazard ratio 2.3; 95% CI 1.8-2.9). CONCLUSION: Obesity is a risk factor for stillbirth, particularly among extremely obese, black mothers. Strategies to reduce black-white disparities in birth outcomes should consider targeting obese, black women. LEVEL OF EVIDENCE: II.

Racial and ethnic differences in perinatal mortality: the role of fetal death.

PURPOSE: We investigate whether variations in infant mortality rates among racial/ethnic groups could be explained by variations in fetal mortality rates where relatively higher infant mortality rates may correspond to lower fetal mortality rates due to possible systematic differences in reporting of fetal death compared to live births. METHODS: Using US perinatal data from 1995 to 1999, we calculated crude mortality rates, birth weight-specific fetal and hebdomadal mortality rates, risks of perinatal death, and the risk of being classified as a fetal death versus other period death among infants born to Non-Hispanic White, Non-Hispanic Black, and Hispanic mothers. RESULTS: Two-fold disparities between Whites and Blacks persist for all mortality categories. Black low birth-weight deliveries, compared to Whites, have perinatal advantages in both fetal and hebdomadal periods. Hispanics were less likely than Whites to be reported as a fetal versus a hebdomadal death. CONCLUSIONS: While these data suggest some underreporting of Black fetal deaths, they provide little evidence that Black-White disparities in infant mortality are a function of variations in classifying a death occurring at delivery as either a fetal death or as a live birth-infant death. These data suggest that the lack of a White-Hispanic disparity in fetal mortality rates may be influenced by underreporting.

Preterm delivery and age of SIDS death.

PURPOSE: The aim of the study is to (i) reexamine risk factors for sudden infant death syndrome (SIDS) and (ii) describe the relationship between length of gestation and age at death from SIDS. METHODS: To evaluate risk factors for SIDS, we used multivariable logistic regression and included maternal demographic characteristics, maternal health and behavioral factors, and infant characteristics, including fetal growth, using US national linked birth and death files from 1996 to 1998. We used multivariable linear regression with mean postnatal age of death as the outcome of interest, controlling for the factors listed (referent length of gestation, 40 to 41 weeks). RESULTS: The crude SIDS rate was 0.7 deaths/1000 live births (8199 deaths). Length of gestation was a strong risk factor for SIDS, with the adjusted odds ratio (OR) greatest at shorter gestations: 28 to 32 weeks (OR, 2.9; 95% confidence interval, 2.6-3.2). Infants with gestations of 22 to 27 and 28 to 32 weeks died at mean ages of 20.9 (SD = 0.8) and 15.3 (SD = 0.5) weeks, respectively (p < or = 0.002). Term infants (40 to 41 weeks) died of SIDS at an adjusted mean age of 14.5 (SD = 0.4) weeks. CONCLUSIONS: Preterm birth continues to be a strong risk factor for SIDS after controlling for fetal growth. With increasing gestational age, mean age of SIDS death decreases considerably, with the postnatal age of death of very preterm infants 6 weeks later than that of term infants.

Fetal growth risk curves: defining levels of fetal growth restriction by neonatal death risk.

OBJECTIVE: We developed a fetal growth risk curve that delineates the birth weight values for gestational age that reflect a 2-, 2.5-, and 3-fold neonatal death risk relative to infants with normal fetal growth. STUDY DESIGN: We analyzed 18,085,052 single gestation infants (25-42 weeks) who were born to US resident mothers from 1996 to 2000. Multivariate models were used to predict the relationship between neonatal death and birth weight percentile. Fetal risk curves were derived on the basis of birth weight percentile-specific neonatal mortality rates that were relative to an average rate of neonatal death for a comparison group that was representative of typical growth (ie, infants between 45th-55th birth weight percentiles for gestational age). RESULTS: The 10th percentile of birth weight for gestational age is associated with an increased but variable risk of neonatal death relative to the comparison group across the spectrum of gestational ages. At 26 weeks of gestation, infants at the 10th percentile experienced a 3-fold risk of dying within the first 28 days of life (relative to the comparison group); whereas at 40 weeks, the risk was 1.13. CONCLUSION: Fetal growth risk curves facilitate the identification of populations of infants whose risk of death are deemed excessive compared with that of infants at the norm of fetal growth and may be useful for counseling pregnant women.

The healthy migrant theory: variations in pregnancy outcomes among US-born migrants.

Various studies have observed that infants born to foreign-born women have better birth outcomes (lower rates of preterm, low birth weight, and infant mortality) than those delivered to US-born women. While much attention has been given to the "healthy migrant effect" as an explanation for these positive outcomes, this theory has not been examined in an internally migrant population. The purpose of this study is to examine the relationship between maternal mobility history and birth outcomes among infants born to US resident mothers of Mexican origin. The study used 1995-1999 National Center for Health Statistics (NCHS) live birth/infant death cohort files of singleton infants delivered in the US to white women of Mexican origin (n = 2,446,253). Maternal mobility history (MMH), which refers to the relationship between the maternal place of birth and the state of residence at delivery, was categorized into the four following groups: (a) foreign-born-place of birth outside the US and delivery in the US; (b) outside-region-place of birth in one US region and delivery in another US region; (c) within-region-place of birth in one US region and delivery in a different state in the same US region; and (d) within-state-place of birth and delivery in the same US state. Consistently, there is evidence to support the healthy migrant effect in an internally migrant population. Unique to this study are the findings that infants born to mothers with outside-region MMH had a lower risk of low birth weight (LBW) and small-for-gestational age (SGA) compared to those who did not move. Overall, this study provides evidence that the healthy migrant effect and its relationship to birth outcomes can be applied to an internally migrant population.

First-time births among women 30 years and older in the United States: patterns and risk of adverse outcomes.

OBJECTIVE: To update the trends in initiation of childbirth by age of the mother, describing the characteristics of women having their first child at age 30 or above, and to determine the risk for adverse pregnancy outcomes for this group of women. STUDY DESIGN: This was a cross-sectional study using National Center for Health Statistics linked live birth and infant death cohort files from 1995 to 2000, and Natality file from 1980 to 2002. Analysis was limited to index pregnancies only. Logistic regression analysis was used to determine the risk of poor outcomes. RESULTS: There is a decreasing trend of first-time births to women 20-29 years old, while births to women 30 and older are showing a continued rise. As compared to 20-29-year-olds, women who start childbearing at age 30 or older are at increased risk of maternal complications in general. However, 30-34-year-olds have a reduced risk for pregnancy-induced hypertension and pre-existing hypertension. Infants born to women aged 30 and above are at increased risk for prematurity and low birth weight in addition to fetal and infant mortality. CONCLUSION: Because of the increasing trend of women starting childbearing in their 30s and the increased risk for poor outcomes in older women, health providers need to pay extra attention to this group of women as they plan and deliver services for them.

Secular trends in cesarean delivery rates among macrosomic deliveries in the United States, 1989 to 2002.

OBJECTIVES: We describe national trends in cesarean delivery rates among macrosomic infants during 1989 to 2000 and evaluate the maternal characteristics and risk factors for macrosomic infants delivered by cesarean section as compared to macrosomic infants delivered vaginally. STUDY DESIGN: We analyzed US 1989 to 2000 Natality files, selecting term (37 to 44 week) single live births to U.S. resident mothers. We compare macrosomic infants (4000 to 4499, 4500 to 4999 and 5000+ g infants) to a normosomic (3000 to 3999 g) control group. RESULTS: The proportion of cesarean deliveries among 5000+ g infants increased significantly over the time period. The adjusted odds ratio of cesarean delivery increased for all macrosomic categories over the 12-year period, as compared to normal birth weight infants. CONCLUSIONS: Rates of cesarean delivery among macrosomic infants continue to increase despite a lack of evidence of the benefits of cesarean delivery within this population. Further exploration of the rationale for this trend is warranted and should include the development of an optimal delivery strategy for such patients.

Fetal and neonatal mortality risks of multiple births.

The purpose of this article is to describe the perinatal mortality experience and mortality-related risk factors of recent US multiple births. First, we describe trends in fetal and neonatal mortality rates for singleton and multiple births to understand if the improvements in perinatal mortality in the United States are equally or differentially reflected among multiple births. Because the characteristics of women who have multiple deliveries differ from those of mothers of singletons, we describe the risk of fetal and neonatal mortality by maternal characteristics and plurality. Finally, we examine the distribution and fetal and neonatal mortality risk of singleton and multiple births by birth weight and gestational age to provide an updated assessment and contrast of their comparative survival chances within similar birth weight-gestational age categories of intrauterine development.

Influence of nativity on neonatal survival of Black twins in the United States.

OBJECTIVE: To determine the association between maternal nativity and neonatal survival of twins among Black mothers. METHODS: We conducted a retrospective cohort study of twin live births to Black mothers in the United States from 1995 through 1998. We compared levels of overall, early, and late neonatal mortality between twins of US-born and those of foreign-born Black mothers by using hazard ratios generated from a Cox Proportional Hazards Regression model. We adjusted for dependence of observations within twin clusters by means of the Robust Sandwich Estimator. RESULTS: A total of 70,884 individual twin live births to US-born (64,035) and foreign-born (6,849) mothers were analyzed. Twins of US-born mothers had a 23% higher likelihood of dying within the neonatal period compared to those of foreign-born mothers (hazard ratio [HR]=1.23; 95% confidence interval [CI]=1.04-1.46). The disparity in neonatal demise occurred exclusively in the early neonatal period (HR=1.29; 95% CI, 1.06-1.50), with mortality indices comparable in the late neonatal period (HR=0.96; 95% CI, 0.68-1.35). Low and very low birth weight (P<.0001), preterm and very preterm (P<.0001), and small-for-gestational-age neonates (P<.0001) were more prevalent among twins of US-born mothers. CONCLUSIONS: Compared to those of foreign-born, twins of US-born Black mothers experienced higher mortality in the neonatal period. The mortality disadvantage resulted mainly from lower gestational age at birth and the preponderance of small-for-gestational-age babies among US-born Black mothers.

Advanced maternal age and fetal growth inhibition in triplets.

OBJECTIVE: To determine whether advanced maternal age is associated withfetal growth inhibition in triplets. STUDY DESIGN: We conducted a retrospective cohort study on triplet live births in the United States from 1995 through 1998. The outcomes of fetal growth inhibition measured were low birth weight, very low birth weight, preterm birth, very preterm birth and smallnessfor gestational age. We generated adjusted ORs after taking into account intracluster correlations using the generalized estimating equation framework. RESULTS: As compared to women of younger maternal age (20-29), mature (30-39) and older women (> or =40 years) with triplet gestations tended to have a lower likelihood offetal growth inhibition. Mean birth weight and mean gestational age at delivery increased with increasing maternal age in a dose-dependent pattern (p for trend < 0.0001). As compared to triplets born to younger mothers, those of older women were less likely to have low birth weight (OR=0.51, 95% CI=0.37-0.69) or very low birth weight (OR = 0.58, 95% CI = 0.47-0.72) or to be preterm (OR = 0.39, 95% CI = 0.27-0.56) or very preterm (OR = 0.67, 95% CI = 0.55-0.80). The riskfor small-for-gestational-age infants was comparable. CONCLUSION: Older maternal age is associated with morefavorable triplet fetal growth parameters, although the exact mechanisms of this paradox remain poorly understood.

Survival of "pre-viable" infants in the United States.

OBJECTIVE: We investigated temporal trend in survival of pre-viable (200-499 g) fetuses over the previous decade, and estimated future survival rates based on previous and current survival thresholds. DESIGN, SETTING AND PARTICIPANTS: This was a retrospective cohort study on live-born pre-viable fetuses (200-499 g) in the United States comparing two period cohorts; 1985-1988 versus 1995-1999. We computed survival of pre-viable babies (who were still alive at 24 hours) during the two periods and based on these results, we estimated future survival rates for the coming decades. MAIN OUTCOMES: Survival beyond the neonatal period. RESULTS: About 35 million live births were analyzed for the two periods. In the first period (1985-1988), 927 live births among pre-viable fetuses were recorded while in the second period (1995-1999) 2585 were counted, equivalent to a birth rate of 60.6 and 131.9 per million live births respectively. This corresponds to an increase of more than 100% across the decade (p for trend < 0.0001). Survival improved by about 50% across the period, from 12.0% to 17.4% (p < 0.0001). Based on these results, the survival rate among pre-viable fetuses will be expected to rise to about 24.0% within the next 6 years (2010). CONCLUSIONS: Survival among pre-viable fetuses is increasing in the United States. This raises ethical, legal and medical issues concerning the defined viability status of these babies, which is currently described as "non-viable".

Racial disparity in stillbirth among singleton, twin, and triplet gestations in the United States.

OBJECTIVE: We investigated the relationship between maternal race and stillbirth among singletons, twins, and triplets. METHODS: We conducted a retrospective cohort study on 14,348,318 singletons, 387,419 twins, and 20,953 triplets delivered in the United States from 1995 through 1998. We compared the risk of stillbirth between pregnancies of black and those of white mothers using the generalized estimating equations framework to adjust for intracluster correlation in multiples. RESULTS: The proportion of black infants was 16%, 18%, and 8% among singletons, twins, and triplets, respectively. Crude stillbirth rate among singletons was 6.6 per 1,000 and 3.5 per 1,000 for black and white fetuses, respectively. Among twins, 796 stillbirths (11.6 per 1,000) were recorded for black mothers versus 3,209 stillbirths (10.1 per 1,000) among white mothers, whereas among triplets there were 233 stillbirths, of which 39 stillbirths were black fetuses (24.6 per 1,000) and 194 stillbirths were white fetuses (10.0 per 1,000). Black singletons, twins, and triplets weighed 278 g, 186 g, and 216 g less than white fetuses, respectively (P <.001). Risk of stillbirth was elevated in black fetuses compared with white fetuses among singletons (adjusted odds ratio [OR] 2.9, 95% confidence interval [CI] 2.8-3.0) and twins (OR 1.3. 95% CI 1.2-1.4) but comparable among triplets (OR 1.2, 95% CI 0.7-2.1). This decreasing trend was significant (P for trend <.001). CONCLUSION: The disparity of stillbirths between black and white fetuses still persists among singletons and twins. Among triplet gestations, however, the 2 racial groups have a comparable risk level. Our findings highlight the need for a rigorous research agenda to elucidate causes of stillbirth across racial/ethnic entities in the United States. LEVEL OF EVIDENCE: II-2

Potentially preventable excess mortality among higher-order multiples.

OBJECTIVE: To estimate the level of potentially preventable excess mortality achievable by avoiding the creation of higher-order multiple gestation with assisted reproductive technologies. METHODS: This was a retrospective cohort study of multiple pregnancies delivered in the United States between 1995 and 1997 involving 304,466 twins, 16,068 triplets, 1448 quadruplets, and 180 quintuplets. We used the generalized estimating equation framework to compute adjusted relative risks for combined perinatal and infant mortality (early mortality). We then calculated potentially preventable excess mortality among higher-order gestations, using twins and triplets sequentially as the referent category. RESULTS: Early mortality increased significantly with each additional fetus in a dose-dependent fashion (P <.001), corresponding to relative risks (95% confidence interval) of 2.4 (2.2, 2.6) for triplets, 3.3 (2.5, 4.4) for quadruplets, and 10.3 (5.0, 21.4) for quintuplets. The creation of twin rather than quadruplet pregnancies would be associated with a substantially higher level of preventable excess mortality (70%) than the creation of triplet pregnancies (28%). By contrast, limiting quintuplets to twins or triplets did not exhibit a similar level of difference (89% versus 75%, respectively). CONCLUSIONS: Our findings support the need for regulating the number of transferred embryos that result in quadruplet and quintuplet pregnancies.

Low maternal age and neonatal survival of extremely preterm twins (20-28 weeks of gestation).

OBJECTIVE: We investigated the relationship between low maternal age and neonatal survival among extremely preterm twins. METHODS: This was a retrospective cohort study on live births of extremely preterm twins delivered to teenaged mothers (aged 15-19 years) in the United States within the period 1995 through 1998. Overall neonatal and early and late neonatal mortality in this category was compared with that of a similar group of twins born to young adult mothers (aged 20-29 years). We used the generalized estimating equation framework in computing relative risks after adjusting for intracluster correlations. RESULTS: Analysis involved 2,290 extremely preterm liveborn twins of teenaged mothers and 8,709 born to young adult mothers. Overall, neonatal mortality was 29% higher among the extremely preterm twins born to teenaged mothers (adjusted odds ratio [OR] 1.29; 95% confidence interval [CI] 1.04%, 1.59%). The disparity in neonatal survival was chiefly in the early neonatal period (adjusted OR 1.34; 95% CI 1.07%, 1.67%), while late neonatal mortality was comparable (adjusted OR 0.91; 95% CI 0.58%, 1.42%). In addition, twins of teenaged mothers had significantly higher level of mortality, except for the birth weight category of 1,000-1,499 g. CONCLUSION: Low maternal age was found to be associated with elevated risk of neonatal death among extremely preterm twins. The preponderance of deaths among extremely preterm twins of teenaged mothers in the early neonatal period appeared to be responsible for the disparity in survival. This information may be useful for targeted interventions aimed at enhancing survival of extremely preterm twins born to teenagers, as well as for instituting optimal management options in the clinical setting. LEVEL OF EVIDENCE: II-2