Pregnancy-induced hypertension and infant mortality: Roles of birthweight centiles and gestational age

OBJECTIVE: To assess the effect of pregnancy-induced hypertension (PIH) on infant mortality in different birthweight centiles (small for gestational age [SGA], appropriate for gestational age [AGA], and large for gestational age [LGA]) and gestational ages (early preterm, late preterm, and full term). DESIGN: Retrospective cohort study. SETTING: Linked birth and infant death data set of USA between 1995 and 2000. POPULATION: A total of 17 464 560 eligible liveborn singleton births delivered after 20th gestational week. METHODS: Multivariate logistic regression models were applied to evaluate the association between PIH and infant mortality, with adjustment of potential confounders stratified by birthweight centiles and gestational age. MAIN OUTCOME MEASURE: Infant death (0-364 days) and its three components: early neonatal death (0-6 days), late neonatal death (7-27 days), and postneonatal death (28-364 days). RESULTS: PIH was associated with decreased risks of infant mortality, early neonatal mortality, and late neonatal mortality in both preterm and term SGA births, and PIH was associated with lower postneonatal mortality in preterm SGA births. PIH was associated with decreased risks of infant mortality, early neonatal mortality, late neonatal mortality and postneonatal mortality in preterm AGA births. Decreased risk of infant mortality and early neonatal mortality was associated with PIH in early preterm LGA births. CONCLUSIONS: The association between PIH and infant mortality varies depending on different birthweight centiles, gestational age, and age at death. PIH is associated with a decreased risk of infant mortality in SGA births, preterm AGA births, and early preterm LGA births.     

Trends in fetal growth among singleton gestations in the United States and Canada, 1985 through 1998

We examined trends in fetal growth among singleton live births in the United States and Canada. The data files (n = 48,637,680; 16.6% blacks) for US births, and the Canadian Birth Database of Statistics Canada (n = 3,167,702) for Canadian births were used. Trends were assessed between 1985-86 and 1997-98 with reference to mean birthweight, birthweight-for-gestational-age z-score, and proportions delivered low birthweight (< 2,500 g), small for gestational age (SGA: birthweight < 10th centile for gestational age) and large for gestational age (LGA: birthweight > 90th centile). The term "mean birth weight" increased in the US and Canada between 1985 and 1998, as have the mean z-score. Rates of term SGA births declined among US (11% among whites and 12% among blacks) and Canadian births (27%). Preterm SGA births increased by 3% and 17%, respectively, among US whites and blacks, but declined by 11% among Canadian births. Further, term LGA births increased in the US (5% among whites and 9% among blacks) and Canada (24%). Preterm LGA births declined by 13%, 25%, and 14% among US whites and blacks, and Canadian births, respectively. These findings suggest that US and Canadian babies are getting bigger. The role of preterm obstetrical induction and preterm cesarean delivery are likely to have influenced these trends.     

Gestational age-specific normal birth weight for Japanese twins. Risk of early neonatal death in small-for-gestational-age and large-for-gestational-age twins.

OBJECTIVE: To construct nomograms for birth weight in Japanese twins and to investigate the risk of early neonatal death (death within seven days of birth) in small-for-gestational-age (SGA) and large-for-gestational-age (LGA) twins as compared with appropriate-for-gestational-age (AGA) twins. STUDY DESIGN: Of 89,253 infants born at > or = 24 weeks of gestation to women with multifetal pregnancies (96% twins) between 1989 and 1993 in Japan, 1,804 were stillborn, and 891 died within seven days of birth (early neonatal death [END] group). The remaining 86,558 infants were defined as the normal group. We constructed growth curves for the normal and END groups and compared the incidence of early neonatal death among the SGA, AGA and LGA infants. RESULTS: Birth weights in the END group were similar to those in the normal group until 33 weeks of gestation, but was lower than the birth weights of the normal group after 33 weeks. Both SGA and LGA infants had an increased risk of death within 7 days of birth as compared with AGA infants throughout gestation. CONCLUSION: Both SGA and LGA twins were at increased risk of death as compared with AGA twins. We recommend the use of birth weight nomograms in the management of twin pregnancies.     

Predictive value of a single early fetal weight estimate in normal pregnancies

OBJECTIVES: To evaluate the accuracy of ultrasound-based fetal weight estimates made at 28-34 weeks of gestation in predicting small- and large-for-gestational-age infants (SGA, LGA) at term. METHODS: Two-hundred and fifty-nine patients with a healthy, singleton pregnancy in whom fetal biometry measurements were routinely performed between 28 and 34 weeks' gestation, were recruited at term delivery. The sonographic estimated fetal weight (EFW) and the birth weight were converted to percentiles on the basis of locally developed growth charts and compared. Multivariate linear stepwise regression analysis was used to predict the birth weight and birth weight percentile. The resulting equation (projectile formula) was used to determine the calculated birth weight, and that value was compared with the actual birth weight. The Bland and Altman plot and Passing and Bablok regression were used to compare between the calculated birth weight and the actual birth weight. RESULTS: Mean gestational age at ultrasound examination was 32+/-1.6 weeks (28-34), and mean age at delivery was 39+/-1.7 weeks (37-42). The multivariate correlation between the calculated birth weight and the birth weight (R2 = 0.524) was higher than the correlation between the sonographic EFW and the birth weight (R2 = 0.083). Both the sonographic EFW and the calculated birth weight are characterized by low positive predictive values in predicting SGA or LGA infants. The calculated birth weight was more accurate in excluding SGA and LGA infants (negative predictive values of 99.5% and 100%, respectively). On method comparison tests, the calculated birth weight was not significantly different than the actual birth weight. CONCLUSIONS: Fetal weight estimation at the early third trimester poorly predicts the birth weight centile at term. It remains uncertain, however, if it would be useful to use the calculated birth weight in pregnancies with clinically suspected SGA or LGA fetuses.     

Placental abnormalities differ between small for gestational age fetuses in dichorionic twin and singleton pregnancies

ObjectiveTwin fetuses grow slower during the third trimester compared with singletons. However, the extent to which the relative smallness of twins is the result of placenta-mediated factors similar to those associated with fetal growth restriction in singletons remains unclear. Our aim was to address this question by comparing placental findings between small for gestational age (SGA) twins and SGA singletons.MethodsRetrospective cohort study of all SGA non-anomalous newborns from singleton and dichorionic twin pregnancies in a single tertiary referral center between 2002 and 2015. SGA was defined as birth weight <10th percentile for gestational age according to sex-specific national reference charts. Placental findings were compared between SGA twins and SGA singletons and were classified into lesions associated with maternal vascular malperfusion, fetal vascular malperfusion, placental hemorrhage and chronic villitis.ResultsA total of 532 SGA twins and 954 SGA singletons met the inclusion criteria. SGA twins had a higher mean placental weight (371 ± 103 g vs. 319 ± 107, p < 0.001) and a lower fetal-placental ratio (6.0 ± 2.5 vs. 6.7 ± 3.2, p < 0.001) compared with SGA singletons. Compared with SGA singletons, SGA twins were less likely to have any placental pathology (aOR 0.37, 95%-CI 0.29–0.46), hypercoiled cord (aOR 0.45, 95%-CI 0.33–0.61), placental weight<10th% (aOR 0.13, 95%-CI 0.08–0.20), maternal vascular malperfusion pathology (aOR 0.24, 95%-CI 0.18–0.30) and fetal vascular malperfusion pathology (aOR 0.62, 95%-CI 0.48–0.82). By contrast, SGA twins had higher odds of a marginal or velamentous cord insertion compared with SGA singletons (aOR 13.82, 95%-CI 10.44–18.30). Similar significant associations were observed in subgroups of SGA fetuses with a birth weight below the 5th and 3rd percentile for gestational age.ConclusionsOur findings illustrate that the mechanisms underlying reduced fetal growth in dichorionic twins differ from those involved in singletons, and may provide support to the hypothesis that smallness in dichorionic twins may be more benign than in singletons.     

A propensity-matched study of the association between pre-pregnancy maternal underweight and perinatal outcomes of singletons conceived through assisted reproductive technology

Research questionIs pre-pregnancy maternal underweight associated with perinatal outcomes of singletons who were conceived through assisted reproductive technology (ART)?DesignA 10-year (2006–2015) Chinese sample of 6538 women and their singleton infants who were conceived through ART was used to examine the association between pre-pregnancy maternal underweight and perinatal outcomes. Propensity scores for underweight were calculated for each participant using multivariable logistic regression, which was used to match 740 (91.36% of 810) underweight women with 740 normal weight women; the effects of underweight on birth weight and gestational age were then assessed by generalized estimating equation model.ResultsAfter propensity score matching, the birth weight was lower (difference –136.83 g, 95% CI –184.11 to –89.55 g) in the underweight group than in the normal weight group. The risks of low birth weight (LBW) and small for gestational age (SGA) were increased in the underweight group compared with those in the normal weight group (LBW: RR 1.64, 95% CI 1.01 to 2.67; SGA: RR 1.46, 95% CI 1.06 to 2.02). The risks of fetal macrosomia and being large for gestational age (LGA) were decreased in the underweight group compared with those in the normal weight group (macrosomia: RR 0.39, 95% CI 0.26 to 0.61; LGA: RR 0.36, 95% CI 0.24 to 0.53). The associations between underweight, gestational age and preterm birth were not statistically significant.ConclusionsAmong women undergoing ART, pre-pregnancy maternal underweight was associated with lower birth weight, increased LBW and SGA risks, and decreased fetal macrosomia and LGA risks in singleton infants.     

The risks of spontaneous preterm delivery and perinatal mortality in relation to size at birth according to fetal versus neonatal growth standards

OBJECTIVE: The aim of this study was to test the null hypothesis that size at birth relative to fetal or neonatal growth standards is not a significant variable related to the risk of spontaneous preterm delivery. STUDY DESIGN: This was a hospital-based cohort study of consecutive births at a tertiary care perinatal center from January 1, 1985, to December 31, 1996. A total of 37,377 pregnancies met the following inclusion criteria: (1) singleton gestation, (2) 25 to 40 weeks' gestation, and (3) no anomalies. Neonates were divided into 5 birth weight categories according to either fetal (uncorrected for sex) or neonatal (corrected for sex) growth standards, as follows: (1) intrauterine growth restriction, birth weight <3rd percentile; (2) borderline intrauterine growth restriction, birth weight > or = 3rd percentile and <10th percentile; (3) appropriate for gestational age, birth weight from 10th percentile through 90th percentile; (4) borderline large for gestational age, birth weight >90th percentile but < or = 97th percentile, and (5) large for gestational age, birth weight >97th percentile. Logistic regression analysis was used to estimate the independent effect of birth weight category on the risk of preterm delivery after spontaneous onset of labor, with the appropriate-for-gestational-age group serving as a reference. RESULTS: When fetal growth standards were applied, there was a significant increase in the risk of spontaneous preterm delivery when birth weight was outside the appropriate-for-gestational-age range (odds ratios of 2.5, 1.4, 1.2, and 1.9 for intrauterine growth restriction, borderline intrauterine growth restriction, borderline large-for-gestational age, and large-for-gestational-age groups, respectively). In contrast, when neonatal growth standards were applied, the risks of spontaneous preterm delivery in intrauterine growth restriction, borderline intrauterine growth restriction, and large-for-gestational-age groups were significantly lower (odds ratios of 0.5, 0.7, and 0.7 for intrauterine growth restriction, borderline intrauterine growth restriction, and large-for-gestational-age groups, respectively) because of an underestimation in the number of fetuses with abnormal size at birth delivered prematurely. With both fetal and neonatal growth standards there was a 5-to 6-fold greater risk of perinatal death for both preterm and term fetuses with intrauterine growth restriction. CONCLUSION: Fetal growth standards are more appropriate in predicting the impact of birth weight category on the risk of spontaneous preterm delivery than are neonatal growth standards. When fetal standards are applied, the risks of preterm birth in both extreme abnormal birth weight categories (intrauterine growth restriction and large for gestational age) are 2- to 3-fold greater than the risk among appropriate-for-gestational-age infants.     

Neurodevelopmental outcomes of twins

In population-based studies, the prevalence of neurodevelopmental disability is consistently higher in twins than singletons. This is largely because birth weight and gestational age (GA) distributions of twin births are shifted to the left when compared with singleton births, and lower birth weight and lower GA are associated with increased risk of neurodevelopmental disability. From a pathophysiologic perspective, a question of interest is whether neurodevelopmental outcomes of twins differ from singletons after controlling for covariates. If significant differences in outcomes persist, this would suggest that the twining process itself or something intrinsic to shared life in the womb may be responsible for observed differences. From a clinical perspective, when counseling parents at risk for preterm delivery of twins, it is useful to understand how twin outcomes compare relative to singleton outcomes at the same birth weight or GA. The purpose of this review is to examine the long-term neurodevelopmental outcomes of twins compared with singletons with control for important covariates.     

Contribution of Gestational Age and Birth Weight to Perinatal Viability in Singletons Versus Twins

The objective of this study was to determine the effects of birth weight and gestational age on twin vs. singleton mortality. Population-based analysis of live births, fetal deaths, and infant deaths by plurality in the United States from 1983 to 1986 was conducted. Seven mortality rates and relative risks (RRs) of twin vs. singleton mortality were calculated by birth weight, gestational age, and combined birth weight and gestational age. The mortality rates included fetal, perinatal, early neonatal, late neonatal, neonatal, postneonatal, and infant. Twins had 3–4 times the RRs of mortality compared to singletons, ranging from a RR of 2.71 for postneonatal mortality to a RR of 3.73 for late neonatal mortality. Generally, for birth weights of 2,800 g or less and gestational ages of 38 weeks or less, twins had lower combined birth weight and gestational age mortality rates and lower RRs. Between 1,900 and 2,799 g, mortality rates decreased then increased with advancing gestation between 31 and 42 weeks both more severely and consistently for twins than for singletons. In conclusion, twins have lower birth weight and gestational age-specific mortality rates and RRs than singletons below 2,800 g and 39 weeks. The “U”-shaped pattern of mortality beyond 38 weeks gestation, particularly for twins with birth weights below 2,500 g, reflects the combined influence of growth retardation and advancing gestation on mortality. The lowest mortalityfor twins is achieved at birth weights of 2,500-2,799gat35-38 weeks gestation. Only 1 in 7 twins is born within this “ideal window.” Efforts at reducing twin mortality should be directed toward reducing intrauterine growth retardation and achieving optimal timing for delivery.     

New-onset hypertension in late pregnancy is associated with lower fetal and infant mortality in preterm twins.

OBJECTIVE: To assess the association between new-onset hypertension in late pregnancy (NOH) and fetal and infant mortality in early preterm, late preterm, and full-term twins. METHODS: We conducted a retrospective cohort study in 275, 316 twins in 1995-1997 based on multiple birth registration dataset of USA. Generalized estimating equations (GEEs) was used to evaluate the odds ratios (OR) of fetal and infant death (at individual level) associated with NOH, with adjustment of potential confounders at both twin set level and individual level. RESULTS: The risks for early neonatal death (OR = 0.52, 95% CI: 0.36, 0.76) and late neonatal death (OR = 0.57, 95% CI: 0.37, 0.87) were decreased in early preterm twins born to mothers with NOH compared with early preterm twins born to mothers with normal blood pressure. The decreased risks for fetal death (OR = 0.40, 95% CI: 0.30, 0.53; OR = 0.46, 95% CI: 0.53, 0.65) and infant death (OR = 0.35, 95% CI: 0.28, 0.44; OR = 0.68, 95% CI: 0.51, 0.91) were associated with NOH in both early and late preterm twins, whereas no association between NOH and fetal/infant mortality were observed in full-term twins. CONCLUSION: NOH is associated with lower risk of fetal death and infant death in preterm twins.     

New-Onset Hypertension in Late Pregnancy is Associated with Lower Fetal and Infant Mortality in Preterm Twins

Objective: To assess the association between new-onset hypertension in late pregnancy (NOH) and fetal and infant mortality in early preterm, late preterm, and full-term twins. Methods: We conducted a retrospective cohort study in 275, 316 twins in 1995–1997 based on multiple birth registration dataset of USA. Generalized estimating equations (GEEs) was used to evaluate the odds ratios (OR) of fetal and infant death (at individual level) associated with NOH, with adjustment of potential confounders at both twin set level and individual level. Results: The risks for early neonatal death (OR = 0.52, 95% CI: 0.36, 0.76) and late neonatal death (OR = 0.57, 95% CI: 0.37, 0.87) were decreased in early preterm twins born to mothers with NOH compared with early preterm twins born to mothers with normal blood pressure. The decreased risks for fetal death (OR = 0.40, 95% CI: 0.30, 0.53; OR = 0.46, 95% CI: 0.53, 0.65) and infant death (OR = 0.35, 95% CI: 0.28, 0.44; OR = 0.68, 95% CI: 0.51, 0.91) were associated with NOH in both early and late preterm twins, whereas no association between NOH and fetal/infant mortality were observed in full-term twins. Conclusion: NOH is associated with lower risk of fetal death and infant death in preterm twins.     

Contributions of ischaemic placental disease to preterm birth in twin gestations

Objective.?To evaluate the extent to which ischaemic placental disease (IPD) – defined as women or newborns diagnosed with pre-eclampsia, small for gestational age (SGA), or abruption, is associated with preterm birth in twin gestations.

Methods.?A population-based study of women who delivered twin live births and stillbirths at 20–44 weeks gestation from 1995–2004 in the US was performed (n?=?1,105,666). We compared the frequency of IPD in term and preterm (<37 weeks) twin births. SGA was defined as twins with birthweight <10th percentile for gestational age, and corrected for infant sex. The association between IPD and preterm birth was expressed as hazard ratio, derived from Cox proportional hazard regression models after adjusting for potential confounders.

Results.?The overall rate of twin preterm birth was 57%. IPD was present in 20% of twin preterm births in comparison to a rate of 16% at term. Both pre-eclampsia and abruption, but not SGA, were associated with increased preterm birth rates. Women with two or more of the IPD conditions were more likely to deliver at preterm than at term gestations.

Conclusion.?In comparison to twin births delivered at term, IPD is more common in preterm births. Efforts to understand the role of IPD in twin gestations based on preterm birth subtypes may reveal important insights.     

Stillbirths and neonatal deaths in appropriate, small and large birthweight for gestational age fetuses

AIMS: To compare the risk of stillbirth and neonatal death in small-for-gestational-age (SGA), appropriate-for-gestational-age (AGA) and large-for-gestational-age (LGA) fetuses and neonates. DESIGN: Retrospective analysis of 662 043 births and outcomes recorded in the Victorian Perinatal Data Collection Unit (1992-2002). INCLUSION CRITERIA: Births in Victoria in 1992-2002. EXCLUSION CRITERIA: Multiple pregnancy and congenital birth defects. MAIN OUTCOME MEASURES: Births, stillbirths and neonatal deaths at each week of gestation after 23 weeks were stratified by birthweight into appropriate, small and large for gestational age. Stillbirth risk per 1000 ongoing pregnancies and neonatal death rate per 1000 live births were calculated. RESULTS: For the AGA group, the overall stillbirth risk was 2.88 per 1000 and neonatal death rate was 1.35 per 1000. In the LGA group, these were 2.62 and 1.83 per 1000, respectively. The slight increase in neonatal death rate among LGA fetuses was confined to those delivered after 28 weeks gestation. In the SGA group, the stillbirth risk and neonatal death rate were 15.1 and 3.99 per 1000, respectively. CONCLUSION: The risk of stillbirth per week of gestational age and neonatal death rates do not differ significantly between AGA and LGA fetuses and neonates. The SGA fetus is at significantly greater risk of both stillbirth and neonatal death, particularly with advancing gestational age.     

Birth weight by gestational age in twin pregnancies: analysis of 661 pairs.

The mortality of twin infants is four to five times higher than that of singletons, and one-half to two-thirds of all twins weigh < 2,500 g at birth. The appropriate interpretation of fetal growth throughout pregnancy is dependent upon the availability of adequate standards. We reviewed 661 pairs of live twin infants born at Chang Gung Memorial Hospital from 1979 to 1990. The frequency of twin births was 1.17% (1:86), and the ratio of males to females was 1.03. The frequency of preterm births (< 37 weeks) was 36.9%, the frequency of low birth weight (< 2,500 g) was 47.9% and very low birth weight (< 1,500 g) was 6.7%. A fetus grows most rapidly from the 32nd to the 35th week of gestation (200 g per week). The growth was 145 g per week from the 28th to the 32nd week and from the 35th to the 38th week of gestation. After the 38th week, the mean birth weight increased by only 35 g per week. Compared with a singleton birth, the mean birth weight of twins was about 100 g lighter during the 28th to the 32nd week, then the difference increased gradually to about 500 g at term.     

Is there a correlation between birth weights and first-trimester crown-rump length growth velocity?

Objective: To test the hypothesis that small- or large-for-gestational-age (SGA or LGA) newborns have anomalous crown-rump length (CRL) growth rates in the first trimester. Methods: Prospective observational study. Women in the first trimester presenting to the Early Pregnancy Unit, between November 2006 and December 2010, underwent transvaginal scan. Women with viable singleton pregnancies in the first trimester who had at least two CRL measurements > 5 mm, recorded at least 2 weeks apart, and also had birth weight data available were included in the final analysis. Birth weight percentiles were calculated and adjusted for gestational age and gender. SGA was equivalent to < 10th centile and LGA was equivalent to > 90th centile. Correlation analysis was performed between birthweight percentiles and first-trimester CRL growth-rate coefficients. In addition, we estimated early fetal growth rates (EFGR) by calculating the Δ CRL/Δ time (mm/day) to see if these differed according to the birth-weight percentiles. Results: A total of 107 women had complete data. The mean maternal characteristics were age 27.5 ± 6 years, weight 87 ± 29 kg and height 163 ± 8 cm. The mean birth weight and gestational age at delivery were 3405 g (SD = 597) and 269 days (SD = 13), respectively. The proportions of SGA and LGA were 7.5% and 18.7%, respectively. There were no significant correlations between birth-weight percentiles and any of the CRL growth rates. There were also no significant differences in the mean CRL velocities when comparing the SGA and LGA newborns birth weights. EFGR for SGA and LGA newborns were 1.34 mm/day (SD = 0.17) and 1.32 mm/day (SD = 0.24), respectively (p > 0.05). Conclusions: Newborns who are found to be SGA or LGA at delivery do not appear to have anomalous CRL growth patterns in the first trimester. The EFGR also did not correlate with birth-weight percentiles.     

Pre-pregnancy body mass, gestational weight gain and birth weight

OBJECTIVE: This study was undertaken to determine the effect of pregravid body weight and weight gain during pregnancy on birth weight of term newborns. MATERIALS AND METHODS: The study population consisted of 1443 healthy women, who delivered of singleton, live infants at or beyond 38 weeks of gestation. Maternal pregravid weight was obtained by recall and categorized into quartiles: < or = 53, < or = 58, < or = 65, > 65 (kg). Women were further divided according to their gestational weight gain into quartiles: < or = 10.5; < or = 12.5; < or = 15.5; > 15.5 (kg). Birth weight was measured and recorded at delivery. Newborns were classified as hypotrophic (SGA; < 10th percentile for the study population) and hypertrophic (LGA; > 90th percentile). RESULTS: The mean birth weight in the study population was 3499 +/- 447 g, 8.5% infants met the criteria for SGA, and 9.4%--for LGA. Studies showed that a progressive increase in maternal pregravid weight as well as gestational weight gain effect independently on increase birthweight, although the effect of weight gain during pregnancy was lessened as weight before gestation increased. For example, increasing gestational weight gain from < or = 10.5 kg to > 15.5 kg increased mean birthweight by 385 g (12.1%) for pregravid weight of 53 kg or less, compared with 142 g (4.0%) for weight of more than 65 kg. They were also associated with decreased frequency of hypotrophic infants and increased frequency of hypertrophic neonates. CONCLUSIONS: Both maternal prepregnancy weight and weight gain during gestation are important factors affecting fetal growth and birth weight. Increasing maternal weight before pregnancy diminishes the influence of weight gain on birthweight. As pregravid weight and prenatal weight gain increase, the incidence of LGA also increase, whereas the frequency of SGA decreases.     

Growth restriction as a determinant of outcome in preterm discordant twins

OBJECTIVE: To estimate the influence of intrauterine growth restriction (IUGR) on the outcome of preterm discordant twins. METHODS: Medical records of preterm twins born at 24-34 weeks of gestation between 1995 and 2000 were reviewed. Significant discordancy was defined as more than 15% difference in birth weight. Small for gestational age (SGA) was defined as birth weight less than 10th percentile, according to a twin-adjusted gestational age nomogram. The smaller twins of 96 discordant twin pairs were evaluated. The SGA-discordant group included the smaller twin of a discordant pair who was also SGA (n = 46); the appropriate-for-gestational-age (AGA)-discordant group included the smaller twin of a discordant pair who was appropriate for gestational age (n = 50). RESULTS: Maternal age, incidence of maternal hypertension, antenatal steroids, and gestational age at delivery were similar between groups. Delivery for suspected fetal compromise complicated significantly more pregnancies in the SGA-discordant group than in the AGA-discordant group (45.6% versus 16%, P = .005), as did respiratory distress syndrome (RDS) (37% versus 8%, P < .05) and intraventricular hemorrhage (21.7% versus 6%, P = .024). Mortality or severe neonatal morbidity (defined as severe RDS, intraventricular hemorrhage grades 3-4, or necrotizing enterocolitis) were significantly higher among neonates in the SGA-discordant group than in the AGA-discordant group (19.5% versus 6%, P = .04). The risk for major morbidity was 7.7-fold greater in the SGA-discordant than in the AGA-discordant group, adjusted for gestational age. CONCLUSION: Growth restriction in preterm discordant twins is associated with a 7.7-fold increased risk for major neonatal morbidity. Therefore, discordant twins with IUGR require closer monitoring than discordant twins without IUGR.     

Modifiable risk factors for growth restriction in twin pregnancies

OBJECTIVE: This study was undertaken to evaluate modifiable risk factors for adverse fetal growth in twin pregnancies. STUDY DESIGN: A large cohort study from a database of women with twin gestations identified at risk for preterm labor was performed. Examining each infant's birth weight and gestational age at delivery, infants were classified as being average (AGA), large (LGA), or small (SGA) for gestational age, using the Alexander reference curve. Clinical and demographic factors were compared between patients delivering at least 1 SGA infant and AGA pairs using Pearson's chi2 Student t test statistics and logistic regression. RESULTS: There were 11,827 twin pregnancies evaluated. Risk factors associated with SGA deliveries included tobacco abuse, poor weight gain, lean prepregnancy body mass index, African American race, and nonmarried. The logistic regression identified tobacco abuse as the single greatest risk for poor fetal growth, (odds ratio [OR] 1.95; 95% CI [1.68, 2.27]). Weight gain of less than one-half lb/wk also increased SGA risk (OR 1.35; 95% CI [1.16, 1.68]), whereas weight gain greater than 1 lb/wk decreased SGA risk (OR 0.77; 95% CI [0.68, 0.86]). CONCLUSION: Tobacco abuse and weight gain are the modifiable risk factors, which require intervention during a twin pregnancy. Patients should be encouraged to stop tobacco abuse and gain a minimum of one-half lb/wk in the later half of pregnancy to minimize the risk for growth restriction.     

Teen twin pregnancies: differences in fetal growth outcomes among blacks and whites

We set out to determine the magnitude of black-white disparity in intrauterine fetal growth inhibition among twin births to teenagers (age 15 to 19) in the United States using a retrospective cohort study design. We compared the risk for low and very low birthweight, preterm and very preterm, and small for gestational age between black and white twins born to teen mothers during the period 1995 through 1998. The methodology of generalized estimating equations was used to adjust for the presence of intracluster correlation within twin pairs. A total of 29,307 individual twins were analyzed. For all fetal growth indices examined, infants born to black mothers remained disadvantaged except for preterm birth, for which the risk was comparable to that of whites (adjusted OR, 1.03; 95% confidence interval [CI] 0.95 to 1.11). The racial gap was most marked for low birthweight (OR, 1.27; 95% CI, 1.19, 1.37]) and very low birthweight (OR, 1.30; 95% CI, 1.19 to 1.42). Black twins had an equal level of elevated risk for very preterm and small for gestational age (OR, 1.17; 95% CI, 1.07 to 1.27 and OR, 1.17; 95% CI, 1.07 to 1.28, respectively). In conclusion, we found significant differences in fetal growth parameters between black and white twins born to teen gravidas. Our findings confirm similar black disadvantage reported for singletons. Current prevention strategies aimed at reducing adverse fetal outcomes among teenagers in the United States need to consider the heightened risk among neonates born to black mothers.     

Previous induced abortions and the risk of very preterm delivery: results of the EPIPAGE study

OBJECTIVES: To evaluate the risk of very preterm birth (22-32 weeks of gestation) associated with previous induced abortion according to the complications leading to very preterm delivery in singletons. DESIGN: Multicentre, case-control study (the French EPIPAGE study). SETTING: Regionally defined population of births in France. SAMPLE: The sample consisted of 1943 very preterm live-born singletons (< 33 weeks of gestation), 276 moderate preterm live-born singletons (33-34 weeks) and 618 unmatched full-term controls (39-40 weeks). METHODS: Data from the EPIPAGE study were analysed using polytomous logistic regression models to control for social and demographic characteristics, lifestyle habits during pregnancy and obstetric history. The main mechanisms of preterm delivery were classified as gestational hypertension, antepartum haemorrhage, fetal growth restriction, premature rupture of membranes, idiopathic preterm labor and other causes. MAIN OUTCOME MEASURES: Odds ratios for very preterm birth by gestational age and by pregnancy complications leading to preterm delivery associated with a history of induced abortion. RESULTS: Women with a history of induced abortion were at higher risk of very preterm delivery than those with no such history (OR + 1.5, 95% CI 1.1-2.0); the risk was even higher for extremely preterm deliveries (< 28 weeks). The association between previous induced abortion and very preterm delivery varied according to the main complications leading to very preterm delivery. A history of induced abortion was associated with an increased risk of premature rupture of the membranes, antepartum haemorrhage (not in association with hypertension) and idiopathic spontaneous preterm labour that occur at very small gestational ages (< 28 weeks). Conversely, no association was found between induced abortion and very preterm delivery due to hypertension. CONCLUSION: Previous induced abortion was associated with an increased risk of very preterm delivery. The strength of the association increased with decreasing gestational age.