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Determinants of fetal growth and body proportionality
M S Kramer1, M Olivier, F H McLean
1Department of Pediatrics, McGill University Faculty of Medicine, Montreal, Quebec, Canada.
Insights
Accurate fetal growth assessment requires validated gestational age and birth weight standardization. Maternal factors significantly influence fetal growth, but only a few, like hypertension and maternal height, affect body proportionality.
Area of Science:
- Obstetrics and Gynecology
- Perinatology
- Fetal Development Research
Background:
- Previous fetal growth studies relied on inaccurate gestational age estimates and inconsistent birth weight comparisons.
- Accurate assessment of fetal growth and body proportionality is crucial for understanding developmental trajectories.
Purpose of the Study:
- To identify maternal and fetal determinants of fetal growth and body proportionality using validated gestational age and standardized birth weight.
- To re-evaluate previous findings on fetal growth retardation and its relationship with proportionality.
Main Methods:
- Analysis of a cohort of 8719 infants with gestational ages validated by early ultrasonography.
- Standardization of body proportionality indexes for birth weight to assess determinants of fetal growth and proportionality.
Main Results:
- Maternal factors like history of low birth weight, hypertension, diabetes, prepregnancy weight, weight gain, smoking, height, parity, and fetal sex were associated with fetal growth.
- Fetal growth ratio, pregnancy-related hypertension, fetal sex, and maternal height significantly determined proportionality.
- Growth-retarded infants, those with taller mothers, severe maternal hypertension, and males tended to be longer and thinner with larger heads relative to weight.
Conclusions:
- Maternal characteristics significantly impact fetal growth, while fetal proportionality is influenced by a smaller set of factors including hypertension and maternal height.
- Gestational age was not independently associated with proportionality in growth-retarded infants, challenging theories on growth retardation onset and proportionality.
- Findings question previous studies on proportionality, particularly those suggesting a nutritional cause for proportional intrauterine growth retardation.
Abstract:
Previous studies of fetal growth and body proportionality have been based on error-prone gestational age estimates and on inappropriate comparisons of infants with dissimilar birth weights. Based on a cohort of 8719 infants with validated (by early ultrasonography) gestational ages and indexes of body proportionality standardized for birth weight, potential maternal and fetal determinants of fetal growth and proportionality were assessed. Maternal history of previous low birth weight infants, pregnancy-related hypertension (particularly if severe), diabetes, prepregnancy weight, net gestational weight gain, cigarette smoking, height, parity, and fetal sex were all significantly associated with fetal growth in the expected directions. Consistent with previous reports, maternal age, marital status, and onset or total amount of prenatal care had no significant independent effects. Fetal growth ratio (relative weight for gestational age), pregnancy-related hypertension, fetal sex, and maternal height were the only significant determinants of proportionality. Infants who were growth-retarded, those with taller mothers, those whose mothers had severe pregnancy-related hypertension, and males tended to be longer and thinner and had larger heads for their weight, although these variables explained only a small fraction of the variance in the proportionality measures. Among infants with intrauterine growth retardation, gestational age was not independently associated with proportionality (in particular, late term and post-term infants did not tend to be more disproportional), a finding that does not support the hypothesis that earlier onset of growth retardation leads to more proportional growth retardation. The results raise serious questions about previous studies of proportionality, particularly those suggesting a nutritional etiology for proportional intrauterine growth retardation.(ABSTRACT TRUNCATED AT 250 WORDS)