Administration of low‐dose aspirin to mothers with small for gestational age fetuses and abnormal umbilical Doppler studies to increase birthweight: a randomised double‐blind controlled trial

2000

BJOG

Self Cite

Sir,The report by McCowan and colleagues that low-dose aspirin did not increase birthweight when used to treat a small fetus with an abnormal umbilical Doppler is noted with interest. This finding would appear to contradict the first study of this type by myself' and a recent meta-analysis2. I write to highlight some important limitations of this present study.The authors chose to study fetuses with an abnormal umbilical Doppler and a small size on ultrasound. The authors cite a similar study3 to support their findings. These studies were made on a very different group to that reported in our study. We selected pregnancies in which the umbilical Doppler was abnormal without a requirement for an already established fetal effects (growth restriction) prior to treatment. We did not report 75% as having growth restriction at the commencement of therapy. It was the finding of our aspirin trial that the "early" use of aspirin benefited fetal growth. Indeed in our trial we reported that the most extremely affected fetuses did not benefit from treatment.The question of umbilical Doppler and established fetal effect (growth restriction -small abdominal circumference) confounding the results of clinical trials can be examined in another context to highlight the importance of the difference in patient selection. The clinical utility of umbilical Doppler in high risk pregnancy is supported by meta-analysis which suggests an impressive 32% reduction in perinatal mortality4. Of the many randomised trials carried out there is one which reports contradictory findings. In that study by Newnham et al.' women were enrolled if the fetal abdominal circumference was small (i.e. already established growth restriction). Umbilical Doppler was of no added value. In our first trial evaluating umbilical Doppler in clinical practice6 we suggested that the value of umbilical Doppler study was early identification of a fetus at risk so that clinical attention could be focused on a group of fetuses with risk recognised early. Using a fetal abdominal circumference measurement means that the fetal risk had already been identified and a fetal effect of the placental vascular disease has occurred.The dosage of aspirin may be important. I have always been impressed by the fact that the largest benefit in terms of fetal weight increase was associated with the use of the largest dose of 150 mg of aspirin. The study by Beaufils et d.' used that dosage and influenced the design of our trial. The CLASP" study used only 60 mg of aspirin. Since the umbilical Doppler study signals a problem in the fetal umbilical placental circulation we have suggested that the larger dose is important to ensure activity in the fetal circulation. We have shown fetal platelet consumption is increased in these cases9 with an abnormal umbilical Doppler and speculated that the aspirin needs to exert an effect in the fetal circulation. Maternal thromboxane concentration after aspirin therapy does not correlate with maternal or fetal benefit". There is not a similar study of fet...

supporting

confidence: 47%

supporting

confidence: 47%

Author's Reply

2000

BJOG

Self Cite

“…The study population were participants in a series of antenatal 8,9 and postnatal studies. 10,11 These studies were approved by the Auckland ethics committee.…”

Section: Methodsmentioning

confidence: 99%

Customised birthweight centiles predict SGA pregnancies with perinatal morbidity

Stewart

2005

BJOG

195

Objectives To determine the following: (1) the proportion of babies reclassified as small or appropriately grown using customised and population centiles; and (2) the relative risks of perinatal morbidity, including abnormal umbilical Doppler studies, in babies classified as small for gestational age (SGA) and appropriate for gestational age (non‐SGA) using the two centile calculations. Design Cohort study in SGA and general hospital populations. Setting National Women's Hospital, Auckland, NZ. Population A cohort of SGA pregnancies (n= 374) and a general obstetric population (n= 12,879). Methods Pregnancy outcomes were compared between ‘non‐SGA both’ (≥10th% by population and customised centiles) and those who were ‘SGA both’ (<10th% by population and customised centiles), ‘SGA customised only’ (SGA by customised but non‐SGA by population centiles) and ‘SGA population only’ (SGA by population but non‐SGA by customised centiles). Main outcome measures Maternal and newborn morbidity and perinatal death. Results In the SGA cohort 271 (72%) babies were ‘SGA both’, 27 (7%) were ‘SGA customised only’, 32 (9%) were ‘population SGA only’ and 44 (12%) were ‘non‐SGA both’. In the general obstetric population 863 (6.7%) babies were ‘SGA both’, 445 (3.5%) were ‘customised SGA only’, 285 (2.2%) were ‘population SGA only’ and 11,286 (88%) were ‘non‐SGA both’. Perinatal death and newborn morbidity including nursery admission and long hospital stay were increased and comparable between ‘SGA both’ and ‘customised SGA only’ in both study populations. Newborn morbidity was low and comparable between ‘population SGA only’ and ‘non‐SGA both’. No perinatal deaths occurred in ‘population SGA only’ babies. Abnormal Doppler studies were more common in ‘SGA both’ or ‘customised SGA only’ but not in ‘population SGA only’ groups compared with ‘non‐SGA both’. Conclusions Customised birthweight centiles identified small babies at risk of morbidity and mortality. Use of customised centiles is likely to detect more babies at risk of perinatal morbidity and mortality than would be detected by population centiles.

“…The participants in this study were the women and their babies who took part in one of two randomised controlled trials 12,13 in singleton small for gestational age pregnancies carried out at the National Women's Hospital, between 1993 and 1997. For the purposes of these studies small for gestational age was defined as abdominal circumference < 10th% on antenatal scan 14 .…”

Section: Methodsmentioning

confidence: 99%

Umbilical artery Doppler studies in small for gestational age babies reflect disease severity

Stewart

2000

BJOG

Self Cite

Objectives To determine: 1. whether abnormal umbilical artery Doppler studies were independently associated with newborn morbidity; and 2. whether small for gestational age babies with normal umbilical artery Doppler studies had small mothers and a low rate of newborn malnutrition and morbidity.Design Prospective observational study.Setting National Women's Hospital, a tertiary referral centre, Auckland, New Zealand.Population One hundred eighty-six women and their small for gestational age babies (birthweight < loth%) who had been participants in one of two randomised controlled trials of small for gestational age pregnancies between 1993 and 1997.Methods Newborn morbidity and morphometry were compared between small for gestational age babies with normal and abnormal umbilical artery Doppler studies (resistance index > 95th%).Maternal demographic characteristics and morbidity were also compared.Results Compared with small for gestational age babies with normal umbilical artery Doppler studies (n = 109), small for gestational age babies with abnormal umbilical artery Doppler studies (n = 77) were diagnosed earlier in pregnancy as being small for gestational age (30-3 vs 32.9 weeks, P < O.OOl), were smaller in all body proportions at birth (median Z score birthweight -1.82 vs -1.70, P = 0.004, Z score length -1.86 v s -1.36, P < 0.0001, Z score head circumference -1.31 vs -0.89, P < 0.0001) and were more likely to experience newborn morbidity. When birthweight and gestation were entered into a logistic regression model, an abnormal umbilical artery Doppler study was not an independent predictor of prolonged newborn nursery admission or hypoglycaemia. Of small for gestational age babies with normal umbilical artery Doppler studies, 53 (49%) had low ponderal indices, 26/98 (26%) were hypoglycaemic and 38 (35%) required admission to the newborn nursery. There was no difference in maternal height, weight and ethnicity between the abnormal and normal umbilical artery Doppler groups.Conclusions Abnormal umbilical artery Doppler studies reflect earlier onset and more severe growth restriction and are not independently associated with newborn morbidity. Small for gestational age babies with normal Doppler studies have a high rate of newborn nursery admission and malnutrition at birth and are not all just normal small babies.