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Biomedical subjects

Louis G Keith

Publications and source records attributed to Louis G Keith.

At least 19 recordsLinked to original sources
PubMed2006

The association between small-for-gestational age triplet pregnancies and neonatal mortality: a novel approach to growth assessment in multiple gestations.

It is customary to estimate the uteroplacental function in singletons by defining appropriateness of birth weight by gestational age. Such a measure, however, is not available for the entire multiple pregnancy set. We evaluate a new index, total triplet birth weight, expressed as multiples of the median (MOM) birth weight of singleton gestations. We categorized triplet sets as small-, appropriate-, and large-for-gestational age pregnancies (SGA, AGA, and LGA, respectively), defined as <1 SD, +/-1 SD, and >1 SD from the mean MOM birth weight of singleton gestations. We used the 1995-1998 US matched multiple dataset to evaluate this index and to explore the association between the three categories in terms of risk of neonatal mortality. The mean +/- SD MOM value was 2.3 +/- 0.4. There was an inverse correlation between mean MOM and gestational age. LGA pregnancy status was associated with multiparity, race (being white), and high social status (education). Maternal age did not influence MOM scores. Compared with the LGA pregnancy category, the risk for neonatal mortality was more than doubled in the AGA pregnancy group and more than 9-fold in the SGA pregnancy category. We propose that this new measure could be a useful proxy for the uteroplacental efficiency in a similar way that the SGA designation works for singleton infants.

Adult↗
PubMed2006

The Northwestern twin chorionicity study: testing the 'placental crowding' hypothesis.

OBJECTIVE: To evaluate the relation between placental proximity and frequency of birth weight discordance and small-for-gestational age (SGA) infants. STUDY DESIGN: Retrospective three-tier chorionicity analysis of 1155 twin placentas comparing birth weight characteristics of the twins in different placental types. RESULTS: Dichorionic-separate, but not dichorionic-fused twins, are heavier than monochorionic-diamniotic and monoamniotic twins (2376+/-721 vs. 2274+/-770, P < 0.006, and 2376+/-721 vs. 2166+/-782, P < 0.04). SGA twins are less frequent among dichorionic twins (OR 0.4; 95% CI 0.3, 0.6). Fewer sets with two SGA infants are present among dichorionic-separate compared to monochorionic-diamniotic pairs (OR 0.3; 95% CI 0.1, 0.8). The same trends are found when comparing all dichorionic to all monochorionic twins. Twins of all placental types have similar gestational ages and discordance values. CONCLUSIONS: Dichorionic-separate placentas are least likely to experience 'placental crowding' and thus are associated with heavier twins and fewer sets with one or two SGA infants.

Adult↗
PubMed2005

The decreased rates of triplet births: temporal trends and biologic speculations.

Recent data from the US and from England and Wales demonstrate decreasing rates of higher-order multiple births and represent, for the first time, a striking change in trend when compared with the previous steep 4-fold increase since the early 1980s. However, the incidence of other multiples--twins--continued to escalate. The most probable reasons for this change are new embryo transfer guidelines and availability of multi-fetal pregnancy reduction procedures. Because actual numbers of higher-order multiples are by far lower than the number of twins, and because twins are predictably associated with significant perinatal morbidity and mortality, the implications of the ever-increasing multiple birth rates are no less alarming. As long as the incidence of twins is not reduced, the decreasing incidence of higher-order multiples, per se, does not herald the end of the epidemic of multiple births.

Embryo Transfer↗
PubMed2005

The paradox of old maternal age in multiple pregnancies.

The study of multiple gestations in older mothers has been furthered by the analyses of large data sets published in recent years. These initial analyses are counterintuitive in that the obstetric and neonatal outcomes of the older mothers (>40 years) are better than those of their younger counterparts (aged 25-29). Currently, it is not clear if older mothers of multiples are advantaged or younger mothers of multiples are disadvantaged. It seems reasonable, however, to conclude that pregnancy after age 40 represents a new obstetric entity, one in which many women will have twins or triplets as a result of assisted reproductive technologies. Further study in this area is clearly warranted, preferably using databases that combine maternal and neonatal data.

Adult↗
PubMed2005

High parity and fetal morbidity outcomes.

OBJECTIVE: We investigated the association between high parity and fetal morbidity outcomes. METHODS: We analyzed 22,463,141 singleton deliveries at 20 weeks or more of gestation in the United States from 1989 through 2000. Adjusted odds ratios generated from logistic regression models were used to approximate relative risk for neonatal morbidity in women with 1-4 (moderate parity or type I; referent group), 5-9 (high parity or type II), 10-14 (very high parity or type III) and 15 or more (extremely high parity or type IV) prior live births. Main outcome measures included low and very low birth weight, preterm and very preterm birth, and small and large for gestational age delivery. RESULTS: The overall crude rates for low birth weight, very low birth weight, preterm birth, very preterm birth, and small and large for gestational age were 55, 11, 97, 19, 83, and 129 per 1,000 live births, respectively. The adjusted odds ratios for low birth weight, very low birth weight, preterm, and very preterm delivery increased consistently and in a dose-effect fashion with ascending parity (P for trend < .001). In the case of large for gestational age delivery, the adjusted odds ratio showed an inverted-U pattern, being highest among women in the type III parity cluster. The findings with respect to small for gestational age were inconclusive. CONCLUSION: High parity is a risk factor for adverse fetal outcomes. However, the impact of heightened parity is more manifest as shortened gestation rather than physical size restriction. These findings could prove beneficial for counseling women of high parity.

Adult↗
PubMed2005

Extreme parity and the risk of stillbirth.

OBJECTIVE: We examined the relationship between extreme parity and risk for stillbirth in the United States. METHODS: Singleton deliveries at 20 weeks of gestation or later in the United States from 1989 through 2000 were analyzed. Risk for stillbirth in women with 1-4 (moderate parity, category I), 5-9 (high parity, category II), 10-14 (very high parity, category III), and 15 or more (extremely high parity, category IV) prior live births were computed using logistic regression. RESULTS: Overall, 27,069,385 births, including 1,206 to extremely high parity mothers, were analyzed. Of the 81,386 stillbirths, 71,623 (2.8/1,000), 9,206 (5.0/1,000), 531 (14.4/1,000), and 26 (21.6/1,000) cases occurred among category I, category II, category III, and category IV gravidas, respectively. With category I as referent category, the odds ratio for stillbirth increased consistently with ascending parity after adjusting for potential confounders: category II (odds ratio [OR] 1.05, 95% confidence interval [CI] 1.02-1.07), category III (OR 1.97, 95% CI 1.81-2.15), and category IV (OR 2.31, 95% CI 1.56-3.42) (P for trend < .001). Among extremely high parity women (category IV), the odds ratio for stillbirth also increased with unit increment in the number of prior live births: 15 (OR 2.72, 95% CI 1.29-5.74), 16 (OR 3.14, 95% CI 1.17-8.41), 17 (OR 6.11, 95% CI 2.56-16.5), and 18 or more prior live births (OR 16.17, 95% CI 8.77-29.82) (P for trend < .001). CONCLUSIONS: The risk for stillbirth is substantially elevated among very high and extremely high parity women, and care providers may consider these groups for targeted periconceptional counseling. LEVEL OF EVIDENCE: II-2.

Adult↗
PubMed2005

Characteristics of mothers who delivered the heaviest, average-weight, and lightest triplet sets.

We analyzed a cohort of 2850 live-born triplet sets to compare age, parity, stature, pre-gravid body mass index (BMI), and weekly weight gain in mothers who delivered triplets with a total weight in the 10th, 5th, and 1st deciles corresponding to the heaviest, average-weight, and lightest triplet sets, respectively. Mothers who delivered the heaviest triplets were significantly older, multiparous, taller, heavily built, and gained more weight compared with mothers of average-weight triplets. In contrast, except for higher parity, mothers of average-weight sets were not significantly different compared with mothers who delivered the lightest triplet sets. We concluded that parity was the only significant factor for increased total triplet weight in the first five deciles. However, the presence of other factors in addition to parity is needed for a triplet pregnancy to be included in the 10th decile.

Adolescent↗
PubMed2005

Gestational age-specific distribution of twin birth weight discordance.

AIM: To examine the gestational age-specific distribution of twin birth weight discordance. METHODS: We analyzed all liveborn twin sets between 28 and 40 weeks' gestation from the United States 1995-1998 Multiple Matched Birth Data Set compiled by the National Center for Health Statistics. We calculated the 50th and 95th percentiles of birth weight discordance at each gestational age. Neonatal mortality rates were calculated for discordant twins at the 95th percentile of birth weight discordance for each gestational age. RESULTS: At older gestational ages, the 95th percentile of birth weight discordance resulted in an inter-twin birth weight difference of approximately 25%, a value often used to define twins as birth weight discordant. However, at earlier gestational ages, the 95th percentile of birth weight discordance was greater, reaching nearly 50% at 28 weeks. CONCLUSIONS: The inter-twin birth weight difference at the 95th percentile is greater at lower gestational ages, possibly illustrating the different nature or severity of twin birth weight discordance at an earlier gestational age.

Birth Weight↗
PubMed2005

Early adequate maternal weight gain is associated with fewer small for gestational age triplets.

OBJECTIVE: To examine whether the recommended weight gain during the first 24 weeks reduces the frequency of SGA triplets. STUDY DESIGN: We used data collected by the Women's Health Division of Matria Healthcare, Inc (Marietta, GA). We studied the frequency of SGA triplets (birth weight <10th percentile by triplet standards) by weight gain, parity, and pregravid BMI category. Adequate weight gain was defined as >16.2 kg at 24 weeks and BMI categories were defined as underweight (<19.8), normal (19.8-26), and obese (BMI>26). RESULTS: We studied 2890 triplet sets. Adequate weight gain reduces the frequency of SGA triplets, irrespective of pregravid BMI category and parity, except for obese nulliparous women. However, the reduced frequency of SGA infants was significant only in underweight nulli-paras (OR 0.3, 95% CI 0.1, 0.9). CONCLUSION: Higher pregravid BMI and parity seem to reduce the occurrence of SGA triplets. However, lean mothers, especially nulliparas, may be the most important target population for nutritional intervention in triplet pregnancies.

Adult↗
PubMed2005

Trends in birth across high-parity groups by race/ethnicity and maternal age.

BACKGROUND: The changing racial and ethnic diversity of the U.S. population along with delayed childbearing suggest that shifts in the demographic composition of gravidas are likely. It is unclear whether trends in the proportion of births to parous women in the United States have changed over the decades by race and ethnicity, reflecting parallel changes in population demographics. METHODS: Singleton deliveries > or = 20 weeks of gestation in the United States from 1989 through 2000 were analyzed using data from the "Natality data files" assembled by the National Center for Health Statistics (NCHS). We classified maternal age into three categories; younger mothers (aged < 30 years), mature mothers (30-39 years) and older mothers (> or = 40 years) and maternal race/ethnicity into three groups: blacks (non-Hispanic), Hispanics and whites (non-Hispanic). We computed birth rates by period of delivery across the entire population and repeated the analysis stratified by age and maternal race. Chi-squared statistics for linear trend were utilized to assess linear trend across three four-year phases: 1989-1992, 1993-1996 and 1997-2000. In estimating the association between race/ethnicity and parity status, the direct method of standardization was employed to adjust for maternal age. RESULTS: Over the study period, the total number of births to blacks and whites diminished consistently (p for trend < 0.001), whereas among Hispanics a progressive increase in the total number of deliveries was evident (p for trend < 0.001). Black and white women experienced a reduction in total deliveries equivalent to 10% and 9.3%, respectively, while Hispanic women showed a substantial increment in total births (25%). Regardless of race or ethnicity, birth rate was associated with increase in maternal age in a dose-effect fashion among the high (5-9 previous live births), very high (10-14 previous live births) and extremely high (> or = 15 previous live births) parity groups (p for trend < 0.001). After maternal age standardization, black and Hispanic women were more likely to have higher parity as compared to whites. CONCLUSIONS: Our findings demonstrate substantial variation in parity patterns among the main racial and ethnic populations in the United States. These results may help in formulating strategies that will serve as templates for optimizing resource allocation across the different racial/ethnic subpopulations in the United States.

Adult↗
PubMed2004

Neonatal mortality rates among growth-discordant twins, classified according to the birth weight of the smaller twin.

OBJECTIVE: The purpose of this study was to evaluate neonatal mortality rates among discordant twins, classified according to the birth weight of the smaller twin. STUDY DESIGN: We compared neonatal mortality rates among three groups of discordant twins (>25%), distinguished by the birth weight of the smaller twin being <10th, 10th to 50th, or >50th percentile. RESULTS: Among the 10,683 pairs of twins who were studied, the respective proportions of the three groups were 62.4%, 32.9%, and 4.7%. The neonatal mortality rate was significantly higher among pairs in which the smaller twin weighed <10th birth weight percentile (29. vs 11.1 and 11 per 1000; odds ratio, 2.7; 95% CI, 1.3, 5.7). This difference results from the higher mortality rates among the smaller but not among the larger twins. CONCLUSION: Severely discordant twin pairs in whom the smaller twin is also small for gestational age are at an increased risk of neonatal death. Identification of this group is an imperative step in the management of birth weight discordance in twin gestations.

Birth Weight↗
PubMed2004

The likelihood of adverse outcomes in triplet pregnancies estimated by pregravid maternal characteristics.

OBJECTIVE: To estimate the likelihood of adverse outcomes in triplet pregnancies by a score comprising pregravid maternal characteristics. DESIGN: A cross-sectional study. SETTING: Triplets database collected by Matria Healthcare, Inc. PATIENT(S): A scoring system was constructed, assigning 1 point for the presence of a risk factor (nulliparity, stature <165 cm, and age <35 years) and 0 for the absence of a risk factor. Data related to 2,887 triplet sets were analyzed. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Total triplet birth weight <4,500 and delivery at 27-32 weeks. RESULT(S): We identified 18% of triplets' mothers (score 3) in whom the likelihood for adverse results is 50%-90% higher and the likelihood for optimal results is 40% to 70% lower than background rates. CONCLUSION(S): A pregravid maternal profile could estimate the likelihood of adverse outcomes and be used for consulting patients at risk of having or carrying a triplet pregnancy.

Birth Weight↗
PubMed2004

The ponderal index in triplets: I. Relationship to small for gestational age neonates.

The aim of the study was to examine the ponderal index in small for gestational age (SGA) triplets. Prospectively collected data from a cohort of triplets born at 28 to 37 weeks were analyzed. A low neonatal ponderal index (birth weight/[length]3) was defined as less than 1 SD below the mean (2.0), and SGA was considered as birth weight below the 10th percentile by triplet standards. We studied 2181 sets of triplets. Triplets delivered at < or = 33 weeks have a lower mean ponderal index compared with those delivered at > 33 weeks. About 70% of SGA triplets do not have a low ponderal index, whereas 79.2% of infants with a low ponderal index are not SGA by triplet standards. Both the frequency of a low ponderal index and the frequency of infants with a low ponderal index who are not SGA decrease with increasing gestational age. We conclude that the majority of triplets with a low ponderal index might not be considered growth restricted, supporting the concept that reduced fetal weight of triplets is more likely a physiological rather than a pathological phenomenon.

Anthropometry↗
PubMed2004

The ponderal index in triplets: II. Gestational age-related patterns of neonatal weights and lengths.

In order to evaluate the determinants of high and low ponderal indices in triplets, we analyzed prospectively collected data from a cohort of 2181 triplet births. Low and high neonatal ponderal indices (birth weight/[length]3) were defined as below or above 1 SD from the mean. The mean ponderal index was of 2.4 +/- 0.4. At 30-31 weeks, there were significantly more infants with a low ponderal index; after 33 weeks, more infants were born with a high index. Birth weights of infants with a high index were significantly higher throughout the entire range of gestational ages, whereas their lengths were significantly smaller. Both birth weights and infant length had significant correlations with gestational ages for infants with a low (R2=0.97 and R2=0.94, respectively) as well as with high ponderal indices (R2=0.95 and R2=0.94, respectively). The regression analyses suggest, however, different patterns for infants with low or high ponderal indices.

Anthropometry↗
PubMed2004

The ponderal index in triplets: III. Association with birth weight discordance.

Our objective was to determine the association of the ponderal index with birth weight discordance in triplets. We analyzed data from triplets delivered at 28-37 weeks for birth weight discordance (>25% difference between the heaviest and lightest triplet). Three categories of discordance (low skew, symmetrical, and high skew) were classified according to the relative position of the middle triplet. Birth weights and the ponderal index (birth weight/[length]3) of all concordant and discordant triplet groups were compared. Of 752 triplet sets included, 184 (24.5%) were discordant. Total triplet birth weight was higher in the concordant compared to all discordant categories. As opposed to birth weight, where only the middle triplet differed according to discordance pattern, the ponderal index for the largest triplet was significantly higher in the low skew discordant group compared to the concordant and other discordant triplet groups. In contrast, the ponderal index for the smallest and middle triplets were similar among the discordant groups. We concluded that discordance in triplet pregnancies exhibits different patterns of mass (birth weight) versus size (ponderal index). Our findings suggest that it may be the size of largest triplet that determines the presence or absence or discordance in triplet gestations.

Adult↗
PubMed2004

The ponderal index in triplets: IV. Relationship with maternal height.

The purpose of the study was to further evaluate the relationship between maternal height and neonatal ponderal index and length. A total of 774 triplet sets with matched maternal stature was available for analyses. We found a significant correlation between maternal height and infant length for both nulliparas (R2=0.70, p=0.04) and multiparas (R2=0.99, p=0.00005). The slopes of the regressions were different than zero, but the difference between the respective regressions was not significant (p=0.83). The analysis revealed a significant correlation between infant ponderal index and maternal stature for nulliparas (R2=0.68, p=0.04) but not for the multiparas (R2=0.08, p=0.6). The slope of the regression for nulliparas was different than zero, but that for the nulliparas was not. The difference between the respective regressions was significant (p=0.03). We conclude that taller mothers deliver longer infants, irrespective of parity, whereas the effect of maternal height on the ponderal index is parity-dependent.

Anthropometry↗