Metabolic Bone Disease of Prematurity: Report of Four Cases

Osteopenia of prematurity has become a common problem recently because of improved survival rates of infants with very low birth weight (VLBW). The incidence of neonatal osteopenia is inversely correlated with gestational age and birth weight. Herein, we present four cases of preterm osteopenia that were referred to the pediatric endocrinology outpatient clinic with diverse clinical and laboratory findings and we discuss the clinical course of these infants with regard to bone disease after discharge from the neonatal intensive care unit (NICU). This report highlights the importance of enteral calcium, phosphorus and vitamin D support at adequate doses following discharge from NICU for preterm infants with VLBW who are at risk of metabolic bone disease.     

The Association Between HIV/AIDS During Pregnancy and Fetal Growth Parameters in Florida: A Population Based Study

In this population-based retrospective study, we sought to investigate the association between HIV/AIDS during pregnancy and adverse birth outcomes, including low birth weight (LBW), very low birth weight (VLBW), preterm birth (PTB), very preterm birth (VPTB), and small for gestational age (SGA), among women in Florida by sociodemographic variables. Using data from Florida's maternally linked birth cohort files, we examined singleton live births in the state during 1998 to 2007 (N = 1,698,107). The study population was categorized based on the maternal HIV/AIDS status. Poisson regression models were used to generate adjusted rate ratios (ARR) to estimate the association between HIV/AIDS status and fetal growth parameters. The main outcome measures were fetal growth parameters, including LBW, VLBW, PTB, VPTB, and SGA. As compared to HIV/AIDS-negative women, mothers with HIV/AIDS had elevated risks for LBW (ARR = 1.40; 95% CI = 1.30-1.50), VLBW (ARR = 1.25; 95% CI = 1.04-1.51), SGA (ARR = 1.26; 95% CI = 1.17-1.35), PTB (ARR = 1.23; 95% CI = 1.03-1.47), and VPTB (ARR = 1.27; 95% CI = 1.20-1.36). Risk estimates for LBW and SGA were highest among Hispanics mothers with HIV/AIDS, while white mothers with HIV/AIDS had the highest risk levels for VLBW and PTB, compared to their HIV/AIDS negative counterparts. Our findings show that women with HIV/AIDS have elevated risks for inhibited fetal growth and shortened gestation with important racial/ethnic variation. This is the first known population-based study that reveals racial/ethnic differences in HIV/AIDS-related fetal growth morbidity outcomes.     

Bacillus Calmette-Guerin vaccination in preterm infants.

OBJECTIVE: To evaluate the tuberculin response after bacille Calmette-Guérin (BCG) vaccination in preterm infants. METHODS: Thirty-five infants born at <35 weeks gestation were included in the study. An intradermal injection of 0.05 ml BCG vaccine was given to each infant at postnatal months 2-3. Tuberculin skin tests (TSTs) were done 8-12 weeks after vaccination using 0.1 ml of 5 TU purified protein derivative (PPD). The diameter of induration was measured 72 h later and > or =5 mm induration was taken as a positive response. RESULTS: The babies had a mean birth weight (SD) of 1650 (424) g, and a gestational age of 32.4 (2.1) weeks. The TST was positive in 20 (57%) of the infants. The mean body weight of the tuberculin-positive babies was significantly higher than the others at both vaccination and TST. No difference was found between groups concerning sex, birth weight, gestational age, intrauterine growth and postnatal age at BCG vaccination and TST. CONCLUSION: BCG vaccination in preterm infants at months 2-3 of postnatal life results in a high percentage of BCG scarring and 57% TST conversion. A positive tuberculin response was significantly related to the postnatal weight gain of the preterm infants.     

Outcome of Preterm Infants With Postnatal Cytomegalovirus Infection via Breast Milk: A Two-Year Prospective Follow-Up Study

Approximately 15% of preterm infants may develop postnatal cytomegalovirus (CMV) infection from seropositive mothers via breast milk and are at risk for neurological sequelae in childhood. The aims of this study were to assess the effects and outcomes on growth, neurodevelopmental status, and hearing in very low birth weight (VLBW) premature infants with postnatal CMV infection via breast milk at the corrected age of 12 and 24 months.The prospective follow-up study population comprised all living preterm children (n = 55) with a birth weight ≤1500 g and gestational age of ≤35 weeks, who had been participated in our “postnatal CMV infection via breast milk” studies in 2000 and 2009, respectively. The cohort of children was assessed at 12 and 24 months. Clinical outcomes were documented during hospitalization and after discharge. Long-term outcomes included anthropometry, audiologic tests, gross motor quotient, Infant International Battery, and neurodevelopmental outcomes; all were assessed at postcorrected age in 12 and 24 months during follow-up visits.Of the 55 infants enrolled in the study (4 noninfected infants were excluded because their parents did not join this follow-up program later), 14 infants postnatally acquired CMV infection through breast-feeding (infected group) and were compared with 41 infants without CMV infection (control group). No significant differences were observed between the groups with regard to baseline characteristics, clinical outcomes, anthropometry, or psychomotor and mental development on the Bayley scale of infant development. None of the infants had CMV-related death or permanent sensorineural hearing loss.Transmission of CMV from seropositive mother via breast milk to preterm infants does not appear at this time to have major adverse effects on clinical outcomes, growth, neurodevelopmental status, and hearing function at 12 and 24 months corrected age.     

Association of the growth hormone receptor d3-variant and catch-up growth of preterm infants with birth weight of less than 1500 grams

BACKGROUND: Preterm infants with very low birth weight frequently exhibit impaired longitudinal growth during the first years of life. Recently, the d3-isoform (genomic deletion of exon 3) of the GH receptor (GHR) has been linked to an increased responsiveness to GH. OBJECTIVE: Our objective was to test whether the GHRd3 isoform is associated with postnatal catch-up growth in very low birth weight preterm infants. DESIGN AND PATIENTS: We compared the postnatal growth pattern of 77 otherwise healthy preterm infants (mean gestational age, 28.5 wk; range, 23-35 wk) with a birth weight below 1500 g (mean birth weight, 941 g) to their GHR exon 3 genotype, which was analyzed by multiplex PCR. On examination, mean age of the children was 6.0 yr (range, 4.2-8.0 yr). RESULTS: Children homozygous or heterozygous for the GHRd3 allele showed a significantly higher rate of postnatal catch-up, compared with those homozygous for the full-length allele. CONCLUSIONS: Our results define the GHR exon 3 genotype as a predictor for the postnatal growth pattern of very low birth weight preterm infants. Those who carry at least one GHRd3 allele are more likely to catch-up.     

Determinants of insulin sensitivity and secretion in very-low-birth-weight children

In prepubertal children, low birth weight is related to reduced insulin sensitivity, particularly if a history of rapid postnatal weight gain is present. We sought to determine whether these associations were also evident in premature, very-low-birth-weight (VLBW) children. We studied 60 VLBW prepubertal children aged 5-7 yr (mean age 5.7 +/- 0.7 yr). Birth weights ranged from 690 to 1500 g (mean 1195 +/- 31 g), with gestational ages between 25 and 34 wk (median 29 wk). A short iv glucose tolerance test was carried out to assess fasting insulin sensitivity and glucose-stimulated insulin secretion. The effects of current body mass index, birth weight (SD scores), postnatal growth rates, and indicators of postnatal morbidity were evaluated by analysis of covariance. Twenty children were born small for gestational age, and 40 were appropriate for gestational age. Ninety-eight percent of them had attained a height within target range. Children who were small for gestational age had lower insulin sensitivity than children who were appropriate for gestational age (homeostasis model assessment insulin resistance index 1.24 +/- 0.17 vs. 0.94 +/- 0.08, P < 0.05). Moreover, birth weight SD scores correlated significantly with homeostasis model assessment insulin resistance index (r = -0.326, P = 0.01). This effect persisted after adjustment for current body mass index, gestational age, and perinatal morbidity. In addition, fasting and postload insulin secretion during the short iv glucose tolerance test correlated significantly with early postnatal growth rates, independently of birth weight SD scores. Our findings in a cohort of VLBW prepubertal children indicate that growth in utero as well as postnatal growth rates are independent determinants of subsequent insulin sensitivity and secretion.     

Thymulin deficiency and low 3,5,3'-triiodothyronine syndrome in infants with low birth weight syndromes

Experimental and clinical evidence indicates that thymic endocrine function is under neuroendocrine control. Recently, a positive correlation was found between plasma thymulin (a major endocrine product of thymus) and serum thyroid hormone concentrations. Low serum thyroid hormone concentrations are frequently found in premature newborn infants. In this study we measured plasma thymulin by bioassay and serum T3 and T4 in a series of healthy fullterm newborns and in premature infants with various disorders. The study subjects were 26 healthy fullterm infants, 23 fullterm small for gestational age infants, 30 preterm appropriate for gestational age (AGA) infants, 22 preterm small for gestational age infants and 30 infants with respiratory distress syndrome, of whom 15 were fullterm and 15 were preterm AGA. Blood samples were obtained 3, 5, 10, 20, and 40 days after delivery. In the healthy fullterm infants plasma thymulin concentrations were low during the first days of life and subsequently increased, reaching normal values for children aged 1-12 months by the 10th day after birth. Persistently low plasma thymulin and serum T3 levels were found in the majority of infants with pathological conditions; the lowest values for both hormones were found in infants with respiratory distress syndrome. A highly significant positive correlation was present in all groups between mean plasma thymulin and serum T3, but not T4. Short term T3 administration in 6 additional preterm AGA infants caused a significant increase in plasma thymulin titers compared to those in 6 untreated infants. We conclude that plasma thymulin is decreased in premature newborns with the low T3 syndrome and that this abnormality may be reversed by administration of T3. These findings indicate that thymic endocrine activity is modulated by thyroid function in early postnatal life.     

Pulse oximetry: what's normal in the newborn nursery?

The objective of this study was to establish normal values for pulse oximetry saturation (POS) in healthy newborn infants in the nursery. POS values were obtained from the right (R) hand and R foot at admission, 24 hr, and at discharge. The following information was recorded: postnatal age, activity state, gender, gestational age (GA), birth weight (BW), mode of delivery (MOD), and Apgar scores. Charts were reviewed and follow-up information was obtained for newborns with measurements < or =92%. The study group consisted of a convenience sample of newborn infants, excluding those on supplemental oxygen. Seven hundred eighteen patients were studied: 51% males, 28% cesarean sections, gestational age 39.3+/-1.6 weeks (mean +/- SD), birth weight 3370+/-550 g, and median Apgar scores 8 and 9. The mean POS was 97.2 +/-1.6%, and the median value was 97%. Only postnatal age and activity state affected POS significantly. POS increased 0.17% per 24 hr in the nursery (P = 0. 0001). POS values obtained while the infants were fussy and crying were lower compared to measurements obtained while sleeping [mean decreases: 0.44% while fussy (P = 0.001), 0.98% while crying (P = 0.0001)]. We conclude that newborns in the nursery have an overall mean POS of 97.2% (+/-2 SD: 94-100%). Mean POS values increase to a small degree with increasing postnatal age. Fussy and crying newborns have lower POS values compared to quiet and sleeping newborns. These reference data can be used in the evaluation of POS measurements in symptomatic newborn infants.     

Maternal hepatitis B and hepatitis C carrier status and perinatal outcomes

Background and aims: To examine the association between maternal hepatitis B and C mono‐ and co‐infections with singleton pregnancy outcomes in the state of Florida. Methods: We analysed all Florida births from 1998 to 2007 using birth certificate records linked to hospital discharge data. The main outcomes of interest were selected pregnancy outcomes including preterm birth, low birth weight (LBW), small for gestational age (SGA), fetal distress, neonatal jaundice and congenital anomaly. Results: The study sample consisted of 1 670 369 records. Human immunodeficiency virus co‐infection and all forms of substance abuse were more frequent in mothers with hepatitis B and C infection. After using multivariable modelling to adjust for important socio‐demographical variables and obstetric complications, women with hepatitis C infection were more likely to have infants born preterm [odds ratio (OR), 1.40; 95% confidence intervals (CI), 1.15–1.72], with LBW (OR, 1.39; 95% CI, 1.11–1.74) and congenital anomaly (OR, 1.55; 95% CI, 1.14–2.11). In addition, women with hepatitis B infection were less likely to have infants born SGA (OR, 0.79; 95% CI, 0.66–0.95). Conclusions: Our findings provide further understanding of the association between maternal hepatitis B or C carrier status and perinatal outcomes. Infants born to women with hepatitis C infection appear to be at risk for poor birth outcomes, including preterm birth, LBW and congenital anomaly.     

Severity of bronchopulmonary dysplasia and increased risk of feeding desaturation and growth delay in very low birth weight preterm infants

Oral feeding has been reported to compromise breathing among preterm infants with bronchopulmonary dysplasia (BPD) during hospitalization or shortly after discharge. However, limited information was available concerning whether preterm infants with BPD remain vulnerable to feeding and growth insufficiency after a longer term of follow‐up. The purpose of this study was therefore to examine the effect of severity of BPD on pulse oxygen saturation (SpO₂) during feeding and growth in very low birth weight (VLBW) preterm infants during infancy. Seventy‐two preterm infants with VLBW and 15 term infants were prospectively examined their growth and SpO₂ during feeding at 2, 4, and 6 months of corrected age. The severity of BPD was graded in VLBW infants according to the American National Institutes of Health consensus definition. In comparison to VLBW infants with mild BPD and term infants, VLBW infants with severe BPD showed significantly lower mean levels of SpO₂ during feeding at 2–6 months corrected age (P < 0.05). Those with severe BPD further exhibited higher rates of growth delay (weight < 10th percentile) throughout the study period. Among VLBW infants, severe BPD had an adverse relation with subsequent weight measures after adjustment for medical and demographic confounding variables (β = ?904 g, P = 0.03). The consensus BPD definition is useful to identify those preterm infants who are at greater risk of feeding desaturation and growth delay during infancy and close monitoring of SpO₂ during feeding should be advised. Pediatr Pulmonol. 2010; 45:165–173. © 2010 Wiley‐Liss, Inc.     

Low birth weight and cardiovascular risk factors at school age.

BACKGROUND: Many epidemiological studies show a strong association between nutritional status at birth and later chronic diseases, particularly cardiovascular diseases. These results seem to confirm fetal programming regarding risk factors and future diseases such as diabetes, hypertension, cardiovascular disease and kidney dysfunction. The aim of the present study is to evaluate, in a group of low-birth-weight (LBW) newborns, the influence of nutritional status at birth on blood pressure and lipid profile at school age. METHODS: A group of low birth weight newborns (n = 30) and a group with appropriate gestational age (AGA) (n = 26) were prospectively evaluated from birth up to 84 months of age. Nutritional status was evaluated at every observation and blood pressure and lipid profile were measured at 84 months according to international recommendations. RESULTS: A catch-up growth was observed in the LBW group during the first two years of life, stature at 84 months being similar in both groups (AGA = -0.3 +/- 0.8 Z-score; LBW = -0.4 +/- 1.1 Z-score). When results are grouped according to weight gain between birth and 84 months of life, and taking account of breast-feeding duration, the LBW children show higher values, with significant differences in diastolic blood pressure between groups in those with greater weight gain (AGA = 88.8 +/- 5.8% of 50th percentile; LBW = 101.2 +/- 5.8% of 50th percentile; p < or = 0.01). Regarding lipid profile, no differences were found except for apolipoprotein A, with lower values in the LBW group (LBW = 125.6 +/- 4.1 mg/dl; AGA = 143.4 +/- 24.6 mg/dl; p < or = 0.05). CONCLUSIONS: Low birth weight newborns are at higher risk of future cardiovascular disease as they show higher blood pressure values compared to those with appropriate nutritional status at birth. These results are more evident in those individuals with greater weight gain, irrespective of breastfeeding duration. All efforts should be directed towards environmental factors that can negatively influence the health and nutritional status of pregnant women in order to reduce the prevalence of LBW newborns.     

Placental transfer of maternal rubella antibodies to full-term and preterm infants

Summary Premature infants are vulnerable to infections, partly because of the low transplacental transfer of maternal antibodies. The present study investigated the placental transfer of maternal rubella-specific antibodies to full-term and preterm infants. The study group consisted of 133 healthy, native Israeli mothers and their 159 newborns. Of these, 69 were full-term infants (gestational age >37 weeks) of 69 mothers, and 90 were preterm infants (gestational age <35 weeks) of 64 mothers. Antibody titers against rubella were measured in maternal and umbilical cord blood samples by hemagglutination inhibition and microneutralization techniques. There was no significant difference in the level of protection and in geometrical mean titers by hemagglutination between the full-term and preterm groups. Conversely, significant differences in geometric mean titers of neutralizing antibodies were found between full-term and preterm infants, e.g., 65.9 and 39.8, respectively (P<0.001). Very low birth weight preterm infants are at greater risk of rubella infection during the first year of life, due to the diminished transfer of neutralizing maternal antibodies. Therefore, earlier vaccination of this group may be beneficial.     

IGF-I, IGF binding protein (IGFBP)-3, phosphoisoforms of IGFBP-1, and postnatal growth in very low birth weight infants

Impaired postnatal growth in very low birth weight (VLBW, <1500 g) infants is per se a major clinical challenge and may also serve as a model in studying the mechanisms of growth retardation in general. This study was undertaken to characterize the role of IGFs and their binding proteins (IGFBPs), key regulators of fetal and infant growth, during the postnatal period in VLBW infants. Forty-eight VLBW infants (gestational age 27.6 +/- 2.2 wk, birth weight 923 +/- 257 g) were studied. Blood samples were drawn at 1, 2, 4, and 8 wk of age for measurements of IGF-I, IGFBP-1 (lesser phosphorylated, lpIGFBP-1, and highly phosphorylated, hpIGFBP-1), IGFBP-3, and insulin, simultaneous growth velocities being assessed by a rigorous protocol of repeated, frequent lower leg length and body weight measurements. All regression analyses were adjusted for postnatal age and repeated measurements. Lower leg growth velocity showed a positive correlation with IGF-I (P = 0.01) and IGFBP-3 (P = 0.03), and weight growth velocity with IGFBP-3 (P = 0.057) and with lpIGFBP-1/hpIGFBP-1 ratio (P = 0.01). Moreover, concurrent glucocorticoid dose showed a negative correlation with both IGFBP-1 isoforms, observable, however, only in samples with high (>10 U/liter) insulin (lpIGFBP-1, P = 0.02; hpIGFBP-1, P = 0.007). In backward multiple regression analysis, the factor remaining significantly associated with lower leg growth velocity (R(2) = 0.63) was IGF-I, and factors associated with weight growth velocity (R(2) = 0.81) were IGFBP-3 and the lpIGFBP-1/hpIGFBP-1 ratio. In conclusion, circulating IGF-I and IGFBP-3, and the lpIGFBP-1/hpIGFBP-1 ratio, reflect short-term growth velocity in VLBW infants. lpIGFBP-1 isoforms, abundant in the circulation of these infants, may thus also have properties that are at least less inhibitory, if not promoting, on the growth-stimulating action of IGF-I. Finally, the regulation of IGFBP-1 by glucocorticoids may be divergent in situations with a high or low insulin concentration.     

Fetal growth and the function of the adrenal cortex in preterm infants

Small for gestational age preterm infants have a higher risk of neonatal morbidity compared to appropriate for gestational age preterm infants. A diminished adrenal response to stress may be involved in the higher postnatal morbidity. The adrenal cortex response in relation to fetal growth was studied by ACTH stimulation tests in 43 preterm infants (born < or = 32 wk). The cortisol and 17-hydroxyprogesterone (17-OHP) responses to 1 microg/kg ACTH were analyzed in relation to birth weight SD scores (BW-SDS) corrected for gestational age, gender, and parity. BW-SDS was significantly associated with the cortisol and 17-OHP response. Infants with the lowest BW-SDS had the lowest cortisol levels after stimulation. No effect of size at birth was found on the ratio between cortisol and 17-OHP. In addition, basal cortisone levels in a single blood sample were higher in infants with the lowest BW-SDS than in infants with higher BW-SDS, but the ratio between cortisol and cortisone was comparable in the two groups. We conclude that the response of cortisol and 17-OHP to ACTH stimulation in preterm infants is related to fetal growth. The lack of influence of fetal growth on the ratio between cortisol and 17-OHP after ACTH stimulation suggests that the activities of 21- and 11 beta-hydroxylase are not affected. The lower adrenal response to stimulation may be important in neonatal morbidity and possibly the development of disease in later life in growth-restricted preterm infants.     

Variation of serum ferritin in low birth weight infants with maternal ferritin, birth weight and gestational age.

Serum ferritin measured at birth in 69 low birth weight infants proved to vary with gestational age as well as with weight. The increase with gestational age was even more striking when the infants small for gestational age were excluded. The relation between maternal and infant serum ferritin concentration was investigated for 2 groups of infants and their mothers (*preterm and term infants, respectively). Neither in preterm nor in term infants was the serum ferritin found to vary with that in the respective mothers.     

Low birth weight infants born to HIV-seropositive mothers and HIV-seronegative mothers in Chiang Rai, Thailand

The low birth weight (LBW) infant has a much higher risk of mortality and morbidity in infancy and early childhood. This study examined the effects of maternal HIV infection and other risk factors for LBW (< 2,500 g). A retrospective study of mothers who delivered at Mae Chan Hospital from 1997 to 2002 was conducted. Logistic regression was used to adjust for confounding factors. There were 266 infants born to HIV-seropositive mothers and 5,872 infants born to HIV-negative mothers. Low birth weight was significantly associated with maternal HIV status, gestational age, antenatal care, maternal age less than 20 years, and > 35 years. Maternal HIV positive status, young maternal age and gestational age were significant factors after adjusting for potential confounders. No significant effect of hilltribe on LBW was found. The results underline the need for nutritional surveillance and dietary counseling. HIV-seropositive women must receive early and continuing antenatal care for good pregnancy outcomes.     

Immunoglobulin serum levels in very low birth weight infants treated with different intravenous preparations

Summary Parenteral human immunoglobulin (IVIG) administration is widely used in low birth weight (LBW) infants for prevention and therapy of neonatal infection. In previous studies, IVIG preparations containing IgG and low IgM concentrations were commonly used. In this study we compare immunoglobulin serum levels in two groups of healthy preterm infants receiving prophylactically standard IVIG (Sandoglobulin, 0.1 mg/kg IgM) or IgM-enriched IVIG (Pentaglobin, 30 mg/kg IgM). Immunoglobulin levels were assayed by rate nephelometry at birth and at 3, 5, 7, and 14 days after birth. The two groups of patients were matched for gestational age (31±2.3 weeks), birth weight (1320±340 g), and serum IgG (4.1±1.9 g/l) and IgM (0.22±0.18 g/l) levels at birth. Significantly higher IgM levels were observed at 3 and 5 days after IgM-enriched IVIG administration (p<0.01). Higher IgG levels were attained and persisted for 2 weeks after standard IVIG administration (p<0.01). These data indicate different IgG and IgM target levels in LBW infants treated with different immunoglobulin preparations.     

Longitudinal changes in insulin sensitivity and secretion from birth to age three years in small- and appropriate-for-gestational-age children

Aims/hypothesis Insulin resistance and type 2 diabetes risk in human subjects who were small-for-gestational-age (SGA) at birth may be a consequence of rapid early postnatal weight gain. Materials and methods We prospectively studied early changes in fasting insulin sensitivity and insulin secretion, assessed by a short intravenous glucose tolerance test that was conducted several times from birth to 3 years of age in 55 SGA (birthweight below fifth percentile) newborns and in 13 newborns with a birthweight appropriate for gestational age (AGA). Results Most SGA infants showed postnatal upward weight centile crossing and by 3 years were similar in size to AGA infants. SGA infants had lower pre-feed insulin levels at postnatal age 48 h than AGA infants (median 34.4 vs 59.7 pmol/l, p<0.05), but by the age of 3 years they had higher fasting insulin levels (median 38.9 vs 23.8 pmol/l, p<0.005), which were related to rate of weight gain between 0 and 3 years (r=0.47, p=0.0003). First-phase insulin secretion did not differ between SGA and AGA infants, but SGA infants had a lower glucose disposition index (beta cell compensation) (median 235 vs 501 min mmol⁻¹ l⁻¹, p=0.02), which persisted after allowing for postnatal weight gain (p=0.009). Conclusions/interpretation SGA infants showed a marked transition from lower pre-feed insulin and increased insulin sensitivity at birth to insulin resistance over the first 3 years of life. This transition was related to rapid postnatal weight gain, which could indicate a propensity to central fat deposition. The additional observation of reduced compensatory beta cell secretion underlines the need for long-term surveillance of glucose homeostasis in all SGA subjects, whether or not they show postnatal catch-up growth.     

Infant mortality by gestational age and birth weight in Canadian provinces and territories, 1990-1994 births

We compared gestational age-specific and birth weight-specific infant mortality in the Canadian provinces (excluding Ontario) and territories using the linked birth and death records for 1990-1994 births. Compared with Quebec, early neonatal mortality rates were higher in Saskatchewan, Alberta and Newfoundland among extremely small and preterm infants and among infants with no information on gestational age and birth weight on their records. Post- neonatal mortality rates were higher in Prince Edward Island, Manitoba, Saskatchewan, Alberta, British Columbia and the Northwest Territories among preterm (and low birth weight) and term (and normal birth weight) infants. We suggest that differences in registration practices probably explain the substantial interprovincial variations in early neonatal mortality rates among extremely small and preterm infants, whereas differences in demographic profile and the quality of obstetric, neonatal and infant care probably explain interprovincial variations in infant mortality rates among less extremely small and preterm infants.