415
Maternal weight gain in pregnancy Serial measurements of maternal weight have been of antenatal care since its inception, and were included initially to assess nutritional status. Subsequently, detailed physiological studies led to a a feature
good understanding of the components of the added weight, at least in normal pregnancy.’ Average total weight gain in pregnancy is as low as 6 kg in rural parts of developing countries such as Tanzania,2 but ranges from 10 to 16 kg in developed countries.3-6 This variation in western
be a function of maternal technical differences, characteristics, or dietary advice. Within-centre variation has often been studied in relation to pregnancy complications. Below-average weight gain is consistently associated with low birthweight or smallness for gestational age, which may be due to impaired fetal growth with an enhanced risk of mortality and morbidity, whereas above-average weight gain is commoner in cases of pre-eclampsia. However, it is unclear to what extent weight gain variation determines these outcomes, or whether it is a consequence of them. Can these associations be used clinically? Total weight gain is of epidemiological interest but of little or no predictive value. Valid prediction would require that deviation from the normal pattern of weight gain should antedate clinical recognition of the pregnancy complication, and that it should occur early enough for further investigation or intervention (preventive or therapeutic) to be undertaken. Conversely, if it is too early, women who do not register at an antenatal clinic until late in pregnancy, and who may be at higher risk of complications, will not benefit. The optimum gestation period for measurement of weight gain has not yet been established. The interval between measurements should be long enough to allow real differences to be detected. Diurnal variation is considerable7 and weekly measurements are therefore unreliable. Nevertheless, very long intervals may conceal genuine changes-eg, low weight gain followed by high weight gain, or vice versa. Some of the issues have been addressed in a study of 1092 women who gave birth in Oxford.6gAverage centres may
total
weight gain was 10 7 kg with an average weekly rate of038 kg, but it was not linear, varying between 0.31 and 0 50 kg per week in the four-week periods arbitrarily selected. Confounding variables such as parity, maternal age, smoking, occupation, and body mass index were taken into account. The positive predictive value for smallness for gestational age of an average weekly gain of less than 0-2 kg, or of ever having a weight gain less than the 10th centile, was low-at less than 13%-and the ability to predict raised blood pressure was not much better. The researchers concluded that maternal weight should no longer be measured routinely in pregnancy, after the booking visit. This recommendation may be premature, because it is not clear whether the most appropriate intervals or clinical endpoints were used.
Studies should be conducted in larger samples of unselected women. Requirements for such include measurement of weight during investigations periods of maximum increase, definition of preto the internationally agreed criteria9 rather than from single isolated recordings of high blood pressure, and consideration of the whole range of birthweight.1O If the predictive value of maternal weight change is low, it seems unlikely that the existing practice of very frequent weighing of pregnant women (eg, in Britain a woman will be weighed up to fourteen times in the antenatal clinic) can be justified, even if it can be done cheaply and conveniently during routine visits. However, before we abandon all measurement of weight change, randomised controlled trials of different policies would be valuable. Rosendahl and Kivinen" reported from Finland that assessment of weight change together with other clinical risk factors can reduce the need for ultrasound scans to detect smallness for gestational age. This approach sounds promising with respect to rational use of resources; the next step is to show improvement in fetal or maternal
eclampsia according
outcome.
Hytten FE, Chamberlain GVP. Clinical physiology in obstetrics. Oxford: Blackwell Scientific Publications, 1980. 2. Moller B, Gebre-Medhin M, Lindmark G. Maternal weight, weight gain and birthweight at term in the rural Tanzanian village of Ilula. Br J Obstet Gynaecol 1989; 96: 158-66. 3. Thomson AM, Billewicz WZ. Clinical significance of weight trends during pregnancy. Br Med J 1957; i: 243-47. 4. Lawrence M, McKillop FM, Durnin JVGA. Women who gain more fat during pregnancy may not have bigger babies—implications for recommended weight gain during pregnancy. Br J Obstet Gynaecol 1.
1991; 98: 254-59.
S, Fisher CC, Truswell AS, Allen JR, Irwig L. Maternal weight gain, smoking and other factors m pregnancy as predictors of infant birthweight in Sydney women. Aust N Z J Obstet Gynaecol 1989; 29:
5. Ash
212-19. 6. Dawes MG, Grudzinkas JG. Patterns of maternal weight gain in pregnancy. Br J Obstet Gynaecol 1991; 98: 195-201. 7. Hytten FE. Weight gain in pregnancy—30 years of research. S Afr Med J 1981; 60: 15-19. 8. Dawes MG, Grudzinkas JG. Repeated measurement of maternal weight during pregnancy: is this a useful practice? Br J Obstet Gynaecol 1991; 98: 189-94. 9. Davey DA, MacGillivray I. The classification and definition of the hypertensive disorders of pregnancy. Am J Obstet Gynecol 1988; 158: 892-98. 10. Kiely JL. Some conceptual problems in multivariable analysis of perinatal mortality. Paediatr Perinat Epidemiol 1991; 5: 243-57. 11. Rosendahl H, Kivinen S. Detection of small for gestational age fetuses by the combination of clinical risk factors and ultrasonography. Eur J Obstet Gynaecol Reprod Biol 1991; 39: 7-11.
Aortocaval fistula There are many clinical presentations of aortocaval fistula; some allow rapid recognition of the condition
widely known and may be Preoperative diagnosis enables the to surgeon plan the procedure and introduce measures to reduce operative morbidity and mortality.1,2 Thus, Ingoldby and colleagues’1 lately described how transvenous balloon tamponade could be used to good
but others overlooked.
are
less
effect. One of the first accounts of an aortocaval fistula was by James Syme in 1831.3 He described a
Maternal weight gain in pregnancy Serial measurements of maternal weight have been of antenatal care since its inception, and were included initially to assess nutritional status. Subsequently, detailed physiological studies led to a a feature
good understanding of the components of the added weight, at least in normal pregnancy.’ Average total weight gain in pregnancy is as low as 6 kg in rural parts of developing countries such as Tanzania,2 but ranges from 10 to 16 kg in developed countries.3-6 This variation in western
be a function of maternal technical differences, characteristics, or dietary advice. Within-centre variation has often been studied in relation to pregnancy complications. Below-average weight gain is consistently associated with low birthweight or smallness for gestational age, which may be due to impaired fetal growth with an enhanced risk of mortality and morbidity, whereas above-average weight gain is commoner in cases of pre-eclampsia. However, it is unclear to what extent weight gain variation determines these outcomes, or whether it is a consequence of them. Can these associations be used clinically? Total weight gain is of epidemiological interest but of little or no predictive value. Valid prediction would require that deviation from the normal pattern of weight gain should antedate clinical recognition of the pregnancy complication, and that it should occur early enough for further investigation or intervention (preventive or therapeutic) to be undertaken. Conversely, if it is too early, women who do not register at an antenatal clinic until late in pregnancy, and who may be at higher risk of complications, will not benefit. The optimum gestation period for measurement of weight gain has not yet been established. The interval between measurements should be long enough to allow real differences to be detected. Diurnal variation is considerable7 and weekly measurements are therefore unreliable. Nevertheless, very long intervals may conceal genuine changes-eg, low weight gain followed by high weight gain, or vice versa. Some of the issues have been addressed in a study of 1092 women who gave birth in Oxford.6gAverage centres may
total
weight gain was 10 7 kg with an average weekly rate of038 kg, but it was not linear, varying between 0.31 and 0 50 kg per week in the four-week periods arbitrarily selected. Confounding variables such as parity, maternal age, smoking, occupation, and body mass index were taken into account. The positive predictive value for smallness for gestational age of an average weekly gain of less than 0-2 kg, or of ever having a weight gain less than the 10th centile, was low-at less than 13%-and the ability to predict raised blood pressure was not much better. The researchers concluded that maternal weight should no longer be measured routinely in pregnancy, after the booking visit. This recommendation may be premature, because it is not clear whether the most appropriate intervals or clinical endpoints were used.
Studies should be conducted in larger samples of unselected women. Requirements for such include measurement of weight during investigations periods of maximum increase, definition of preto the internationally agreed criteria9 rather than from single isolated recordings of high blood pressure, and consideration of the whole range of birthweight.1O If the predictive value of maternal weight change is low, it seems unlikely that the existing practice of very frequent weighing of pregnant women (eg, in Britain a woman will be weighed up to fourteen times in the antenatal clinic) can be justified, even if it can be done cheaply and conveniently during routine visits. However, before we abandon all measurement of weight change, randomised controlled trials of different policies would be valuable. Rosendahl and Kivinen" reported from Finland that assessment of weight change together with other clinical risk factors can reduce the need for ultrasound scans to detect smallness for gestational age. This approach sounds promising with respect to rational use of resources; the next step is to show improvement in fetal or maternal
eclampsia according
outcome.
Hytten FE, Chamberlain GVP. Clinical physiology in obstetrics. Oxford: Blackwell Scientific Publications, 1980. 2. Moller B, Gebre-Medhin M, Lindmark G. Maternal weight, weight gain and birthweight at term in the rural Tanzanian village of Ilula. Br J Obstet Gynaecol 1989; 96: 158-66. 3. Thomson AM, Billewicz WZ. Clinical significance of weight trends during pregnancy. Br Med J 1957; i: 243-47. 4. Lawrence M, McKillop FM, Durnin JVGA. Women who gain more fat during pregnancy may not have bigger babies—implications for recommended weight gain during pregnancy. Br J Obstet Gynaecol 1.
1991; 98: 254-59.
S, Fisher CC, Truswell AS, Allen JR, Irwig L. Maternal weight gain, smoking and other factors m pregnancy as predictors of infant birthweight in Sydney women. Aust N Z J Obstet Gynaecol 1989; 29:
5. Ash
212-19. 6. Dawes MG, Grudzinkas JG. Patterns of maternal weight gain in pregnancy. Br J Obstet Gynaecol 1991; 98: 195-201. 7. Hytten FE. Weight gain in pregnancy—30 years of research. S Afr Med J 1981; 60: 15-19. 8. Dawes MG, Grudzinkas JG. Repeated measurement of maternal weight during pregnancy: is this a useful practice? Br J Obstet Gynaecol 1991; 98: 189-94. 9. Davey DA, MacGillivray I. The classification and definition of the hypertensive disorders of pregnancy. Am J Obstet Gynecol 1988; 158: 892-98. 10. Kiely JL. Some conceptual problems in multivariable analysis of perinatal mortality. Paediatr Perinat Epidemiol 1991; 5: 243-57. 11. Rosendahl H, Kivinen S. Detection of small for gestational age fetuses by the combination of clinical risk factors and ultrasonography. Eur J Obstet Gynaecol Reprod Biol 1991; 39: 7-11.
Aortocaval fistula There are many clinical presentations of aortocaval fistula; some allow rapid recognition of the condition
widely known and may be Preoperative diagnosis enables the to surgeon plan the procedure and introduce measures to reduce operative morbidity and mortality.1,2 Thus, Ingoldby and colleagues’1 lately described how transvenous balloon tamponade could be used to good
but others overlooked.
are
less
effect. One of the first accounts of an aortocaval fistula was by James Syme in 1831.3 He described a
