Foetal size and body proportion at 17–19 weeks of gestation and neonatal size, proportion, and outcome
Introduction
Foetal growth restriction has been associated with foetal and perinatal morbidity and mortality [1] in the current [2], [3] and subsequent pregnancies [4], [5], and with diseases in adult life [6]. Therefore, considerable effort has been spent to identify predictors of low birth weight [7].
It has been assumed that foetuses suffering a suboptimal environment, such as nutrient limitation or placental dysfunction within the second trimester tend to be proportionately small in weight and length at birth (symmetric growth restriction) while growth restriction beginning later in pregnancy results in thin small infants (asymmetric growth restriction) [8], [9]. More recent evidence suggest that both disproportionate and proportionate foetal growth restriction may start in the second trimester [10], [11], [12]. However, in these studies early foetal body proportion was not determined [10], [12] or the conclusions were based on neonatal morphometrics [10]. Thus, direct evidence is lacking whether second trimester foetal smallness and thinness predict disproportionate and proportionate small for gestational age (SGA) newborns.
Several studies indicate that asymmetrically grown foetuses have worse perinatal outcome than symmetric grown [13], [14], [15], [16], [17], [18]. Most of these studies were based on foetal morphometrics within 1 [13] to 4 [18] weeks of delivery, or on neonatal morphometrics [14], [16], [17] and thus did not include foetal size and body proportion in early pregnancy.
In the present study, we wanted to determine whether proportionate or disproportionate foetal smallness at 17–19 weeks in low-risk pregnancies was associated with size, body constitution, and adverse outcome at birth.
Section snippets
Material and methods
In Norway, most women are scheduled for ultrasound examination, which includes term prediction and structural evaluation of the foetus between 17 and 19 weeks of gestation. From June 15, 1993 to June 30, 1998, data from the second trimester ultrasound scan in a non-selected population were entered into a database at our department. Biparietal diameter (BPD) and mean abdominal diameter (MAD) were determined as the average of three repeat measurements. The examination was performed by specially
Results
Asymmetric as well as symmetric small foetuses, were generally lighter, shorter, thinner, and had lower head circumference at birth than larger foetuses (Table 1). In particular, odds ratios for SGA significantly decreased with increasing MAD percentile (p < 0.0001). The risk of foetuses which were both thin and extremely small (MAD below the 2.5th percentile), of being SGA (below the 10th weight percentile) at birth was 27.9% (Table 1), which may be considered as the positive predictive value of
Discussion
The present study showed that asymmetric as well as symmetric foetal smallness may start early in pregnancy, and thus does not support the concept that asymmetrical growth deviation is a late phenomenon. Symmetric and particularly asymmetric small foetuses at 17–19 weeks of gestation were generally lighter, shorter, thinner, had lower head circumference at birth, and had worse perinatal outcome than larger foetuses.
A strength of this study is its large size. Due to the prospective design and
Acknowledgements
The authors would like to thank the midwives who performed the ultrasound examinations.
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