Size at birth and neonatal and postneonatal mortality

Disproportionate fetal growth and the risk for congenital cerebral palsy in singleton births

OBJECTIVE

To investigate the association between proportionality of fetal and placental growth measured at birth and the risk for congenital cerebral palsy (CP).

STUDY DESIGN

We identified all live-born singletons born in Denmark between 1995 and 2003 and followed them from 1 year of age until December 31st, 2008. Information on four indices of fetal growth: ponderal index, head circumference/ abdominal circumference ratio, cephalization index and birth weight/ placenta weight ratio was collected. Cox proportional hazards regression models were used to estimate adjusted hazard ratios (aHR) and 95% confidence intervals (CI). All measurements were evaluated as gestational age and sex specific z-scores and in z-score percentile groups, adjusted for potential confounders, and stratified on gestational age groups (<32, 32-36, 37-38, 39, 40, ≥ 41 weeks).

RESULTS

We identified 503,784 singleton births, of which 983 were confirmed cases of CP. Head/ abdominal circumference ratio (aHR:1.12; 95%CI:1.07-1.16) and cephalization index (aHR:1.14; 95%CI:1.11-1.16) were associated with the risk of CP irrespective of gestational age. Birth weight-placental weight ratio was also associated with CP in the entire cohort (aHR:0.90; 95%CI:0.83-0.97). Ponderal index had a u-shaped association with CP, where both children with low and high ponderal index were at higher risk of CP.

CONCLUSIONS

CP is associated with disproportions between birth weight, birth length, placental weight and head circumference suggesting pre and perinatal conditions contribute to fetal growth restriction in children with CP.

The value of predicting restriction of fetal growth and compromise of its wellbeing: Systematic quantitative overviews (meta-analysis) of test accuracy literature

BACKGROUND

Restriction of fetal growth and compromise of fetal wellbeing remain significant causes of perinatal death and childhood disability. At present, there is a lack of scientific consensus about the best strategies for predicting these conditions before birth. Therefore, there is uncertainty about the best management of pregnant women who might have a growth restricted baby. This is likely to be due to a dearth of clear collated information from individual research studies drawn from different sources on this subject.

METHODS/DESIGN

A series of systematic reviews and meta-analyses will be undertaken to determine, among pregnant women, the accuracy of various tests to predict and/or diagnose fetal growth restriction and compromise of fetal wellbeing. We will search Medline, Embase, Cochrane Library, MEDION, citation lists of review articles and eligible primary articles and will contact experts in the field. Independent reviewers will select studies, extract data and assess study quality according to established criteria. Language restrictions will not be applied. Data synthesis will involve meta-analysis (where appropriate), exploration of heterogeneity and publication bias.

DISCUSSION

The project will collate and synthesise the available evidence regarding the value of the tests for predicting restriction of fetal growth and compromise of fetal wellbeing. The systematic overviews will assess the quality of the available evidence, estimate the magnitude of potential benefits, identify those tests with good predictive value and help formulate practice recommendations.

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

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

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

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

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

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