Appropriate For Gestational Age Babies Research Articles

Progression of waist–hip circumference ratio in full-term symmetric and asymmetric small for gestational age infants

Background: Children born as small for gestational age (SGA) tend to develop central adiposity and may have chances of developing metabolic syndrome. Waist–hip circumference ratio (WHR) is considered as a good indicator of central/truncal obesity. The complete absence of information on growth dynamics of WHR among Indian symmetric and asymmetric SGA infants has prompted us to undertake this study. Aim: The aim was to study the pattern of growth of waist circumference, hip circumference, and WHR of symmetric and asymmetric SGA infants. Materials and Methods: Waist and hip circumference of full-term 100 symmetric SGA, 100 asymmetric SGA, and 100 appropriate for gestational age (AGA) infants was measured at 1, 3, 6, 9, and 12 months in Growth Laboratory/Clinic of the Department. Student's unpaired t-test was used to assess intragroup (symmetric vs. asymmetric), intergroup (SGA vs. AGA), and gender differences. Results: A consistent increase in the mean waist and hip circumference was noticed among symmetric and asymmetric SGA and AGA infants of two sexes. Male infants of both SGA groups possessed similar waist and hip circumference at 1 month. Whereafter, asymmetric SGA males had a larger waist and lesser hip circumference than symmetric infants. Asymmetric SGA females possessed larger waist circumference throughout infancy, while hip circumference measured larger only till 3 months as compared to symmetric females. Conclusion: SGA infants of two types and gender exhibited compromised auxological attainments for waist and hip circumference compared to normal babies. Higher WHR recorded in asymmetric SGA than symmetric SGA and AGA babies appear to suggest that asymmetric infants may have greater tendency to develop central obesity, subsequently.

Critical Evaluation of various Sonologic Parameters of Early Foetal Growth Discrepancies in Predicting Adverse Pregnancy Outcomes

Introduction: It is well established that adverse perinatal outcomes such as Small for Gestational Age (SGA), preterm delivery, and pre-eclampsia are associated with higher incidence of neonatal complications and death. Evidence suggests that these adverse outcomes may have their origins dating back to early pregnancy growth discrepancies. Aim: To establish an association between early fetal growth discrepancies and occurrence of adverse obstetric outcomes such as pre- clampsia and SGA. Materials and Methods: This is a prospective observational study done in the Department of Obstetrics and Gynaecology, Kasturba Medical College, Manipal Academy of Higher Education, Manipal, Karnataka, India, between Jan 2015 to May 2016 involving 314 pregnant women, using Crown Rump Length (CRL) measurements at the time of early anomaly (11-14 week scan). Pregnancies with congenital and chromosomal defects, multifetal gestation and non viable foetuses were excluded from the study. The biometric parameters mainly Biparietal Diameter (BPD), Head Circumference (HC), Abdominal Circumference (AC), Femur Length (FL), and Estimated Foetal Weight (EFW) at the time of targeted organ scan (between 18 to 20 weeks) were recorded and reverse calculations were done to convert these parameters to corresponding GA based on published regression formulae. The GA at the time of targeted scan was also calculated based upon the first trimester CRL values. The growth discrepancy was calculated by deducting CRL based GA from biometrically estimated GA for each individual growth parameters. Fisher’s-exact test was used to compare the means of biometric lags in SGA vs. Appropriate for Gestational Age (AGA) fetuses and also in Pre-eclampsia vs. normotensive groups. For each biometric parameter, the best cut-off for discrepancy value was determined using Receiver Operator Characteristic (ROC) analysis along with their diagnostic ability to predict occurrence of SGA in terms of sensitivity, specificity, positive and negative likelihood ratio with their 95% confidence intervals. The Area Under Curve (AUC) and z-test statistics were taken into account to decide the best parameter to predict adverse outcome. A p-value of <0.05 was considered statistically significant.Results: Out of 314 women studied, 62 (19.7%) delivered an SGA neonate, and 30 (9.5%) had pre-eclampsia. All biometric parameters of SGA babies showed growth lag compared to AGA babies which was statistically significant (BPD p<0.001, HC p<0.001, AC p<0.001, FL p<0.01, and EFW p<0.001). However, we could not establish similar associations between early growth discrepancies and onset of pre-eclampsia.Conclusion: Models of second trimester growth discrepancies can be used to predict SGA babies. Earlier anticipation of adverse perinatal outcome may add to quality of antenatal care and timely delivery to prevent late stillbirths associated with SGA.

Comparative Study of Cord Lipid Profile in Small for Gestational Age and Appropriate for Gestational Age Newborn

Background: This study was conducted to compare the cord blood lipid profile in term small for gestation (SGA) and appropriate for gestational age (AGA) babies as determination of cord blood lipid profile is useful screening tool for early detection of babies at higher risk as atherosclerosis has its genesis in childhood. Methods: Study Design: Hospital based cross sectional study. Setting: neonatal unit of tertiary care hospital. Subjects: 200 full term babies born at SGRDIMSR during study period out of which 100 were AGA and 100 were SGA babies. Mean cord cholesterol, triglyceride, HDL, LDL, VLDL was measured in both the groups. Results: Mean cord blood cholesterol was 72.29± 21.13 mg/dL, triglycerides 67.18± 20.36 mg/dL, HDL 28.51± 5.68 mg/dL, LDL 34.94± 16.45 mg/dL, VLDL 13.43± 04.10 mg/dl in 100 AGA babies. In 100 SGA babies, mean total cholesterol was 100.85± 26.82 mg/dl, triglycerides 82±22.58 mg/dL, HDL 27.70± 7.79 mg/dL, LDL 44.93± 7.663 mg/dL, VLDL 16.40± 4.479 mg/dL. Conclusion: Lipid profile values except HDL were significantly higher in SGA compared to AGA neonates (p <0.001 for all parameters).

Association of intrapartum maternal mean platelet volume with neonatal birth weight

Purpose: To investigate the relationship between neonatal birth weight (NBW) and intrapartum maternal mean platelet volume (MPV). Materials and Methods: A total of 650 women who had a live birth at the Etlik Zubeyde Hanım Women's Health Education and Research Hospital in Ankara were divided into three groups according to the babies'birth weight adjusted for gestational week: 145 delivered small for gestational age (SGA) (th percentile), 363 delivered appropriate for gestational age (AGA) (10-90th percentile), and 142 delivered large for gestational age (LGA) babies (> 90th percentile). Maternal MPV value of the women were taken into account together with demographic values, body mass index (BMI), and gestational age at delivery and birth weight. Results: MPV was found to be significantly higher in the mothers of LGA babies (9.69 ± 1.11) in comparison to SGA (9.38 ± 1.03) and AGA (9.36 ± 1.09) babies in the statistical analysis (p = 0.009). More than 9.65 fL value of intrapartum maternal MPV was associated with LGA. Conclusion: MPV was increased in the intrapartum period in women who delivered LGA babies.

Small-for-gestation birth exerts a minor additional effect on functional impairment of the auditory brainstem in high-risk babies born at late preterm

To address if small-for-gestational-age (SGA) significantly affects the developing auditory brainstem in late preterm babies with perinatal problems (i.e. high-risk), providing valuable information for management of such babies. SGA and appropriate-for-gestational age (AGA) babies born at 33-36weeks of gestation were studied at term using maximum length sequence brainstem auditory evoked response in response to 91-910/s clicks. Compared with AGA late preterm babies without perinatal problems (i.e. low-risk), the high-risk SGA babies manifested a significant increase in wave V latency and I-V interval at all 91-910/s clicks, and III-V interval at 455 and 910/s. The amplitude was smaller for wave I at 227 and 910/s, wave III at 910/s and wave V at 227 and 910/s. Compared with low-risk SGA babies, the high-risk SGA babies showed similarly abnormalities. Compared with high-risk AGA babies, the high-risk SGA babies manifested slightly different abnormalities. Brainstem auditory response was abnormal in high-risk SGA late preterm babies. The abnormalities, suggesting brainstem auditory impairment, were slightly different from high-risk AGA late preterm babies. SGA birth exerts a minor additional effect on the impaired auditory brainstem in high-risk babies born at late preterm. For these babies, neuroprotective measures should mainly target at associated perinatal problems, although the relatively minor adverse SGA effect cannot be ignored.

Born Large for Gestational Age: Bigger Is Not Always Better

Born Large for Gestational Age: Bigger Is Not Always Better

Brainstem auditory evoked responses in small-for-gestational age babies born at 30 and less weeks of gestation.

Brainstem auditory function is deviant from the normal in SGA babies born at 30 and less weeks of gestation. There is delayed brainstem neural maturation, which is associated with a small head size, and slightly precocial maturation in the more peripheral brainstem auditory regions. Intrauterine growth retardation has a subtle degree of adverse effect on central brainstem auditory pathway in preterm babies born at 31-36 weeks of gestation. Brainstem neural maturation is delayed, with slightly precocial maturation in the more peripheral brainstem auditory regions, in SGA babies born at 30 and less weeks of gestation.

A new serum cystatin C formula for estimating glomerular filtration rate in newborns.

The levels of serum cystatin C (CysC) and creatinine (Cr) were determined in small-for-gestational-age (SGA) babies and compared with those for normal term newborns appropriate for gestational age (AGA), at birth and 3 days later. We then compared a number of cysC-based, Cr-based and combined formulas for estimation of glomerular filtration rate (GFR) with the neonatal reference GFR. Fifty full-term SGA and 50 AGA newborns were enrolled in the study. Kidney volume measurements were performed by ultrasound for each newborn. At birth, the mean level of CysC in SGA babies was 1.48 ± 0.30 mg/l in cord blood and 1.38 ± 0.18 mg/l in day 3 blood samples, and the mean Cr level, determined simultaneously, was 67.08 ± 17.62 and 55.62 ± 14.91 μmol/l, respectively. These levels did not differ significantly from those determined in AGA babies. A 10 % reduction in kidney volume was associated with an increase in CysC value of 9.3 % in cord blood. The Cr-based and Schwartz-combined equations underestimated GFR relative to CysC-based and Zappitelli-based equations at birth and 3 days later. A newly constructed Cys-C based formula which includes kidney volume and body surface area in the calculations for GFR is a reliable marker of GFR compared with neonatal reference clearance values.

Biparietal diameter (BPD) growth rate between the first and second trimester as a predictor of poor obstetric and neonatal outcome among the Indian population

Background: The Objective of this study was to evaluate the association of BPD at 11-14 weeks and pregnancy outcome and to determine the role of incremental BPD growth from 11-14 weeks and 17-20 weeks in pregnancy outcome. Methods: Women (n=910) with singleton pregnancies were included in this prospective observational study after an early anomaly scan (11 to 14 weeks). Outcomes noted were the incidence of adverse events and the neonatal birth weight. Results: Irrespective of their original BPD at 11 to 14 weeks, fetuses had acquired optimum BPD growth rate on a follow up scan at 17-20 weeks, i.e., a majority of them fell in the 10 th to 90 th percentile group (P value &lt;0.001). Fetuses with BPD below the 10 th percentile were small for gestational age (SGA) at birth despite an optimal growth rate. Also, a significant majority of the fetuses with BPD in the 10 th to 90 th percentile were Appropriate for Gestational Age (AGA) at birth. Conclusion: The BPD at 11 to 14 weeks scan predicts the incidence of SGA and AGA babies, independent of BPD growth rates between first and second trimester. The BPD growth rates were neither significantly different nor predictive of the birth weight or adverse pregnancy outcomes.

Fetal growth in relation to maternal and fetal IGF‐axes: a systematic review and meta‐analysis

Insulin-like growth factors (IGFs) and their binding proteins (IGFBPs) are key regulators of fetal growth. However, the literature is inconsistent. Our objective was to systematically and objectively evaluate the available literature and to develop a balanced opinion on the relation between maternal and fetal IGF-axes and birthweight. A systematic review and a meta-analysis were conducted according to the published Moose (Meta-analysis of Observational Studies in Epidemiology) guidelines. A robust recognized systematic methodology was used in the literature search and analysis to avoid bias. Weighted mean difference and 95% confidence intervals of cord/maternal IGFs and IGFBP-1 and -3 were calculated. Eleven observational studies were included. Cord IGF-I (p < 0.0001) and IGFBP-3 (p = 0.003) were significantly higher in large-for-gestational age (LGA) than appropriate-for-gestational age (AGA) babies. Cord IGFBP-1 was significantly higher in small-for-gestational age (SGA) than AGA babies (p < 0.0001). LGA and AGA babies had similar IGF-II levels, whereas SGA and AGA babies had comparable IGF-I levels. IGF-I was significantly higher in mothers of AGA than SGA babies (p < 0.0001). The assay methods and background population marginally affect the overall homogeneity and the direction of the primary analysis. Fetal IGFs and their binding proteins play different roles in fetal growth at either end of the growth spectrum. Fetal IGF-I and IGFBP-3 may be influential in LGA. However, fetal IGFBP-1 has a more prominent role in SGA.

Neurodevelopmental delay in small babies at term: a systematic review

Being small for gestational age (SGA) or having fetal growth restriction (FGR) may be associated with poorer neurodevelopmental outcomes compared to being appropriate for gestational age (AGA). The aim of this paper was to evaluate the existence and magnitude of decrease in neurodevelopmental scores in SGA and FGR infants born at term from a systematic review of the existing literature. Studies of neurodevelopment in SGA/FGR babies were identified from a search of the internet scientific databases. Studies that included preterm births and those that did not define absolute indices of standardized cognitive outcome were excluded. SGA was defined as birth weight below the 10(th) centile for gestation and FGR as the same birth-weight standard with abnormal umbilical artery Doppler ultrasound or evidence of abnormal placentation on pathology specimen studies. Effect size was calculated as the standardized mean difference between neurodevelopment scores of controls and SGA/FGR children. There were 28 studies of SGA, with a total of 7861 SGA and 91 619 control AGA babies, and three studies of FGR, with a total of 119 FGR and 49 control AGA babies. Data synthesis showed that standardized neurodevelopmental scores in SGA babies were 0.32 SD (95% CI, 0.25-0.38) below those for normal controls, though with heterogeneity between studies (I(2) = 68.3%). Insufficient data were available for FGR babies. The findings of the study demonstrate that among babies born at term, being SGA is associated with lower scores on neurodevelopmental outcomes compared to AGA controls. A trial designed to evaluate the effects of intervention in small fetuses born at term in order to improve the neurodevelopmental outcome is urgently needed.

Postnatal percentile growth charts for Indian appropriate for gestational age (AGA) very low birth weight babies

To develop postnatal percentile growth charts for Indian very low birth weight (VLBW) appropriate for gestational age (AGA) babies till 37 weeks post conceptional age (PCA). Prospective, mixed longitudinal study in 105 VLBW AGA (male 73 and female 32) babies weighing <1500 g and <34 weeks gestation born over 1 year. All were weighed daily until discharge and then weekly till 37 weeks of PCA. The percentile weight curves were computed in four categories : ≤28 weeks, 29-30, 31-32 and 33 weeks, and a total of seven percentile distributions (3rd, 10th, 25th, 50th, 75th, 90th& 97th) were generated. Entire data were subjected to Tanner's 1951 method to compute mean and standard deviation for body weight. The arithmetic mean served the 50(th) percentile. All babies at birth were <50th centile as per Lubchenco's intrauterine growth chart. This pattern was more evident in higher gestation (31-32 and 33 weeks) than lower gestation (≤28 and 29-30 weeks). At 37 weeks PCA, all were <10th centile and the lowest was in ≤28 weeks gestation. Our babies are born smaller, and growth rate is slower than their western counterparts. Babies at lowest gestation had slowest postnatal growth. Hence, we need a separate growth chart for our babies.

The influence of intrauterine growth retardation on cardiac function, left ventricular mass and superior vena cava return in newborns

Background Low birth weight (LBW) in neonates is a problem leading to high morbidity and mortality. Barker hypothesized that fetal cardiac remodeling during hypoxic conditions or maternal under􀁏nutrition is a risk factor for coronary heart disease in theyoung. Early vascular changes may influence cardiac function and newborns' cerebral blood flow.Objective The aim of this study was to detennine the effects of being small for gestational age (SGA) on newborns' cardiac function, left ventricular (LV) mass and superior vena cava (SYC) return.Methods This cross􀁏sectional study was conducted in Cipto Mangunkusumo Hospital from February to June 2008. LBW and nonnal newborns who fulfilled the inclusion criteria were recruited as subjects. Maternal history, infant physical examination, and echocardiography were obtained Mthin 48 hours oflife to exclude those with congenital heart disease, and assess cardiac function and SYC flow.Results Subjects were 21 preterm appropriate for gestational age (AGA), 19 SGA and 19 normal newborns. SGA newborns showed lower LV mass, stroke volume and cardiac output than normal newborns. However, these SGA parameters were not different from preterm AGA babies. In additio n, LV mass index was sig nificantly different but no difference ofSVC return between the three groups.Conclusion SGA newborns' LV function was lower than that of nonnal newborns, as low as pretenn AGA newborns. N onnal SVC return was observed in the three groups. This finding may be due to a brain􀁏sparing effect to maintain sufficient cerebral blood flowin the fetus.

Ghrelin Levels and Postnatal Growth in Healthy Infants 0-3 Months of Age

Objective: The effect of ghrelin on growth of the newborn has long been argued, but not fully clarified. In this study, we aimed to investigate the relationship between ghrelin levels and growth parameters in the first 3 months of life.Methods: The study included 60 babies (27 girls and 33 boys) born at gestational ages between 38-42 weeks. The newborns were divided into three groups according to the Lubchenco curves as: small for gestational age (SGA), appropriate for gestational age (AGA) and large for gestational age (LGA). The relationship between ghrelin levels and growth parameters in the third month was investigated. Results: Ghrelin concentrations were significantly higher in SGA (2.4±2.6 ng/dL) babies than in AGA (1.3±0.9 ng/dL) and LGA (1.0±0.8 ng/dL) babies. The lowest ghrelin levels were in the LGA group. In SGA infants, ghrelin concentrations were inversely correlated with change in weight (r=-0.577; p=0.001), change in length (r=-0.361; p=0.005), and change in head circumference (r=-0.387; p=0.002).Conclusion: The results show that at age 3 months, SGA infants had higher ghrelin levels than AGA and LGA infants. Our findings indicate that ghrelin may be involved in the process of catch-up growth in these infants.Conflict of interest:None declared.

Distinguishing pathological from constitutional small for gestational age births in population-based studies

Background Small for gestational age (SGA) can occur following a pathological process or may represent constitutionally small fetuses. However, distinguishing these processes is often difficult, especially in large studies, where the term SGA is often used as a proxy for restricted fetal growth. Since biologic variation in fetal size is largely a third trimester phenomenon, we hypothesized that the definition of SGA at term may include a sizeable proportion of constitutionally small fetuses. In contrast, since biologic variation in fetal size is not fully expressed in (early) preterm gestations, it is plausible that SGA in early preterm gestations would comprise a large proportion of growth restricted fetuses. Aim We compared mortality and morbidity rates between SGA and appropriate for gestational age (AGA) babies. Subjects A population-based study of over 19 million non-malformed, singleton births (1995–04) in the United States was performed. Gestational age (24–44 weeks) was based on a clinical estimate. SGA and AGA were defined as sex-specific birthweight < 10th and 25–74th centiles, respectively, for gestational age. All analyses were adjusted for a variety of confounding factors. Outcome measures Excess mortality risk in SGA and AGA babies. Results On an additive scale, stillbirth and neonatal mortality rates were higher at every preterm gestation among SGA than AGA births, and similar at term gestations. An inverse relationship between gestational age and excess deaths between SGA and AGA babies delivered at < 37 weeks was evident. Conclusions In early preterm gestations, the definition of SGA may well be justified as a proxy for IUGR. In contrast, SGA babies that are delivered at term are likely to be constitutionally small.

Urinary uric acid in preterm neonates

Study of uric acid level in spot urine of normal preterm AGA (appropriate for gestational age) babies in day one of their life. Spot urine samples were collected from 45 normal preterm neonates within 24 hours of their birth for estimation of uric acid. The mean uric acid level was 36.50 +/- 5.99 mg/dl in normal preterm neonates as compared to 18.40 +/- 0.45 mg/dl in normal term babies (documented in another study) (p < 0.001). Also a significant negative linear correlation between body weight and urinary uric acid level was found {r (correlation coefficient) = - 0.970, P (probability) < 0.001 }. Higher mean uric acid level was found in spot urine samples of preterm normal neonates than that of normal term babies on day one. Further, urinary uric acid levels were found inversely proportional to the body weight or to the gestational age (as they are AGA) of the babies.

Two hour blood glucose levels in at-risk babies: An audit of Canadian guidelines

The Canadian guidelines recommend blood glucose (BG) screening starting at 2 h of age in asymptomatic 'at-risk' babies (including small-for-gestational-age [SGA] and large-for-gestational-age [LGA] infants), with intervention cut-offs of 1.8 mmol/L and 2.6 mmol/L. The present study reviews and audits this practice in full-term newborn populations. A literature review meta-analyzed BG values in appropriate-for-gestational age (AGA) term newborns to establish normal 1 h, 2 h and 3 h values. A clinical review audited screening of 'at-risk' SGA and LGA term newborns, evaluating both clinical burden and validity. The review included six studies, although none clearly defined the plasma glucose standard. The pooled mean (plasma) BG level in AGA babies 2 h of age was 3.35 mmol/L (SD=0.77), significantly higher than 1 h levels (3.01 mmol/L, SD=0.96). In the audit, 78 SGA and 142 LGA babies each had an average of 6.0 and 4.7 BG tests, respectively. The mean 2 h BG levels for SGA (3.42 mmol/L, SD=1.02) and LGA (3.31 mmol/L, SD=0.66) babies did not differ significantly from the AGA pooled mean. Receiver operating characteristic curves showed that 2 h BG levels in LGA and SGA babies predicted later hypoglycemia (defined as a BG level lower than 2.6 mmol/L), but sensitivities and specificities were poor. Published 2 h BG levels for AGA babies are higher than 1 h values and are similar to audited 2 h levels in SGA and LGA babies. Clinically, 2 h levels are predictive of later hypoglycemia but may require repeat BG testing. Audit is an important tool to validate national guidelines, to minimize their burden and to maximize their utility.

The relationship between birth weight, oxidative stress and bone mineral status in newborn infants

It was shown that oxygen-derived free radicals, and particularly the superoxide anion, are intermediaries in the formation and activation of osteoclasts. Many antioxidant defence systems depend on micronutrients or are micronutrients themselves. Oxidative stress might be related to bone indices in newborn infants. To assess the relationship between oxidative status and bone indices in small-for-gestational-age (SGA), large-for-gestational-age (LGA) and appropriate-for-gestational-age (AGA) babies born to healthy mothers. Umbilical cord venous blood samples were obtained at the delivery from 100 term newborn infants to measure plasma malondialdhyde, superoxide dismutase (SOD) and myeloperoxidase concentrations. Forty of the newborn infants had birth weights AGA, 30 were SGA and 30 LGA. Data were acquired using the whole body dual-energy X-ray absorptiometry scanner in the first 24 h after birth. Plasma malondialdhyde and SOD concentrations of the mothers and their newborn infants were positively correlated; however, plasma myeloperoxidase concentrations were not. SOD concentrations of SGA infants were significantly higher than those of AGA and LGA infants. Whole body bone mineral density and content were lower in SGA but higher in LGA babies than in AGA babies. Oxidative stress status of both infants and their mothers was not related to the bone indices. Our study does not provide support for the hypothesis that oxidative status of the infants and mothers may play a major role in the regulation of bone metabolism in the developing skeleton.

Serum triglyceride level in IUGR babies and its comparison with preterm AGA and term normal babies

Intrauterine growth and birth weight are probably the most important factors that affect in survival and future quality of life. Intrauterine growth retardation causes program changes in body systems specially lipid metabolism that creates various problems of which coronary heart disease is important. Higher serum triglyceride (TG) level in IUGR babies relates to increase incidence of coronary heart disease. This cross sectional study was conducted in Bhangabandhu Sheikh Mujib Medical University (BSMMU), Dhaka, Bangladesh during July 2004 to June 2005. Serum TG levels were estimated among three groups: IUGR (n=30), preterm appropriate for gestational age (AGA) (n=30) and term normal (n=30) new born babies. Blood samples were collected from the study population in the neonatal unit and serum TG level were measured with all accuracy in a computerized automated biochemical analyzer in Biochemistry department of BSMMU. Statistical analysis were done by using student's 't' test. It was observed that serum TG level (54.4 +/- 11.2 mg/dl) in IUGR babies were significantly higher than that of term normal babies (38.7 +/- 5.8 mg/dl), p value < 0.05. This implicate future coronary heart disease in these babies as shown by others in long term prospective studies.

Impact of advanced maternal age on neonatal survival of twin small-for-gestational-age subtypes

We examined the impact of advanced maternal age (>40 years old) on the survival of twin small-for-gestational-age (SGA) infants, that is, infants who were smaller in size than was expected for the baby's sex, genetic heritage, and gestational age. The present study was a retrospective cohort study on twin live births in the USA from 1995 to 1998 inclusive. Two categories of SGA babies were defined: discordant (when only one of a twin pair was SGA) and concordant (when both were SGA). Otherwise, the twin pair was appropriate-for-gestational-age (AGA) concordant. 192,195 twin pairs were analyzed. The incidence of SGA discordance and concordance was 11.8% and 3.9%, respectively. The occurrence of both SGA subtypes tended to decrease with increasing maternal age. The unadjusted risk for neonatal mortality increased when both twins were affected (15.8: 22.8 and 56.6 per 1000 among AGA concordant, SGA discordant and SGA concordant twins; P-value for trend < 0.0001). Using maternal-age-specific AGA babies as reference, the adjusted risk for neonatal mortality climbed progressively with advancing maternal age in a dose-dependent pattern, being lowest among teenagers and highest in mothers aged > or =40 years. SGA discordance and concordance declined with advancing maternal age. In contrast, neonatal mortality of both SGA subtypes worsened with the increase in maternal age compared with that of the age-specific AGA infants. These findings are potentially useful to care providers in counseling older women, a group that is progressively increasing in size and is most susceptible to twining.