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INTRAUTERINE GROWTH RESTRICTION |
Br J Obstet Gynaecol. 1998 May;105(5):524-30.
Analysis of birthweight and gestational age in antepartum stillbirths.
Gardosi J, Mul T, Mongelli M, Fagan D.
Department of Obstetrics and Gynaecology, Queen's Medical Centre,
Nottingham, UK.
Objectives:
To study the characteristics of birthweight and gestational age
of third trimester fetal deaths which occurred before the onset of labour.
Design:
Review of computerised confidential perinatal mortality records.
Data originated from the 1992 Trent Region Perinatal Mortality Survey.
Sample:
One hundred and forty-nine antepartum stillbirths of at least 24
weeks of gestation confirmed by early ultrasound scan. Congenital
abnormalities and multiple pregnancies were excluded.
Main Outcome Measures:
Reported causes of stillbirth; weight-for-gestational age centiles based on
a standard derived from normal pregnancies; pregnancy characteristics
compared with the local maternity population.
Results:
Of 149 stillbirths,
83 (56%) were preterm and 66 were at term, and the majority (126; 85%)
occurred from 31 weeks. Most of the deaths (97; 65%) were reported as
'unexplained' even though post-mortems had been carried out in 60% of all
cases. Using a gestational age-specific fetal weight standard derived from
normal, term live births, 41% of all cases of stillborn infants were
small-for-gestational age (< 10th centile; OR 6.2; 95% CI 3.3-11.5); 39% of
which had been classified as unexplained were small for gestational age (OR
5.6; 2.6-12.0). This excess of small stillbirths was most pronounced between
31 and 33 weeks, where the weights of 63% of all stillbirths and 72% of
unexplained fetal deaths were < 10th centile. Overall, a higher proportion
of preterm (< 37 weeks) than term stillbirths were small for gestational
age: 53% vs 26% (OR 3.3; 1.6-6.5). However, at term there were also more
subtle differences in weight deficit, with more fetuses with a weight
between the 10th and 50th centiles than between 50th and 90th (36 vs 11; OR
3.3; 1.4-7.8). Mothers of pregnancies ending in stillbirth were similar in
age, size, parity and ethnic group to mothers of live born babies, but were
more likely to be smokers (37 vs 27%, OR 1.6; 1.2-2.3).
Conclusions:
Many
stillborn babies are small for gestational age. In the absence of
significant differences in physiological pregnancy characteristics, this is
unlikely to be a constitutional smallness, but represents a preponderance of
intrauterine growth restriction. For a full appreciation of the strength of
this association, appropriate weight standards and classifications need to
be applied in perinatal mortality surveys. Many antepartum stillbirths which
are currently designated as unexplained may be avoidable if slow fetal
growth could be recognised as a warning sign.
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