Efecto de la presión en la conductividad de los gases puros

Apragmatic scheme of management for the small for gestational age infant is shown in Figure 1, using a primary screen of assessment of fetal size, liquor volume and umbilical artery Doppler as a starting point. All should have had a full repeat anatomical survey, and considered to be normal. If liquor volume is increased, these fetuses should be managed as fetuses with a probable abnormality.

GROUP A

Small for gestational age and all indices normal:

• In the absence of risk factors and where EFW 3rd to 10th centile, re-scan in 4 weeks to check growth velocity.

• If risk factors and EFW 3rd to 10th centile, re-scan in 3 weeks.

• If EFW less than 3rd centile perform detailed scan, consider karyotype and congenital infection screen; re-scan in 3 weeks.

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Recent Advances in Obstetrics and Gynaecology 22

At the next scan:

• If growth velocity and other indices are normal, no further follow-up is required.

• If indices are normal but growth velocity is reduced, again consider karyotype and infection screen.

• Use Z score or abdominal circumference 10 mm per week rule to determine velocity.

• If growth velocity is reduced and Dopplers or liquor volume are reduced, transfer to groups B, C or D.

GROUP B

Small for gestational age with normal Doppler but reduced liquor volume: • If more than 37 weeks’ gestation, consider delivery.

• If less than 37 weeks’ gestation, repeat scan in 3 weeks and manage as for group A following the next scan.

GROUP C

Small for gestational age with reduced EDF: • Repeat growth scan in 2 weeks.

• Repeat Doppler weekly.

• Taking gestational age and other risk factors into account, consider CTG or BPP monitoring. Monitoring should be no more frequent than twice weekly unless EFW/abdominal circumference less than 3rd centile.

Normal

Normal Reduced

Group A Group B Group C Group D

Raised Absent/reversed

Abdominal circumference and/or

estimated fetal weight below the 10th centile

Umbilical artery Doppler

Liquor volume

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Investigation and management of the small fetuschp title

• Consider delivery if greater than 36 weeks with evidence of poor growth velocity or further deterioration in the uterine artery Doppler.

• Give antenatal steroids if delivery less than 36 weeks’ gestation. GROUP D

Small for gestational age and absent or reversed EDF: • Admit and monitor as in-patient.

• Give antenatal steroids.

• Deliver if more than 32 weeks’ gestation.

• Monitor with daily or twice daily CTG, consider delivery if short-term variability is less than 3.5 or there are two successive non-reactive traces. • Monitor with weekly multivessel Doppler, consider delivery if there are

umbilical vein pulsations or reversed ductus venosus pulsations. • Consider therapy with 40% humidified oxygen.

Key points for clinical practice

• The diagnosis of small for gestational age is usually based on an abdominal circumference or estimated fetal weight below the 10th centile.

Small for gestational age fetuses are at increased risk of perinatal mortality and morbidity, in addition to possible long-term health consequences.

Fetal abnormality should be excluded in some small for gestational age fetuses.

Umbilical artery Doppler is the single most important test for determining the at-risk small fetus. Randomised controlled trials have shown improved outcome without increasing intervention. Monitoring growth velocity is important in the small fetus. Proper

velocity measures should be used.

Further monitoring of the at-risk fetus may include assessment of liquor volume, cardiotocography, biophysical profile and multivessel Doppler waveform analysis.

The use of venous Doppler waveforms shows promise in assessment of the preterm fetus with abnormal umbilical artery Dopplers, but its value has yet to be evaluated in randomised controlled trials.

The timing of delivery remains controversial, but delivery before 32 weeks’ gestation should only be considered where there is evidence of deterioration in fetal condition.

Maternal oxygen therapy shows promise as a treatment for early severe-growth restriction.

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Recent Advances in Obstetrics and Gynaecology 22

References

1. The GRIT Study Group. When do obstetricians recommend delivery for a high-risk preterm fetus? Eur J Obstet Gynecol Reprod Biol1996; 67: 121–126.

2. Cnattingius S, Haglund B, Kramer MS. Differences in late fetal death rates in association with different determinants of small for gestational age fetuses: population based cohort study. BMJ1998; 316: 1483–1487.

3. McIntyre DD, Bloom SL, Casey BM, Leveno KJ. Birth weight in relation to morbidity and mortality among newborn infants. N Engl J Med1999; 340: 1234–1238.

4. Strauss RS. Adult functional outcome of those born small for gestational age. Twenty–six-year follow-up of the 1970 British Birth Cohort. JAMA2000; 283: 625–632. 5. Morley R, Dwyer T. Fetal origins of adult disease? Clin Exp Pharmacol Physiol2001; 28:

962–966.

6. Neilson JP. Symphysis-fundal height measurement in pregnancy (Cochrane Review). Oxford: The Cochrane Library, Issue 2, 2002.

7. Chang TC, Robson SC, Boys RJ, Spencer JA. Prediction of the small for gestational age infant: which ultrasonic measurement is best? Obstet Gynecol1992; 80: 1030–1038. 8. Mongelli M, Gardosi J. Reduction of false-positive diagnosis of fetal growth restriction

by application of customized fetal growth standards. Obstet Gynecol1996; 88: 844–848. 9. Chien PFW, Arnott N, Gordon A, Owen P, Khan KS. How useful is uterine artery

Doppler flow velocimetry in the prediction of pre-eclampsia, intrauterine growth retardation and perinatal death? An overview. Br J Obstet Gynaecol2000; 107: 196–208. 10. Macara L, Kingdom JC, Kohnen G, Bowman AW, Greer IA, Kaufmann P. Elaboration of

stem villous vessels in growth restricted pregnancies with abnormal umbilical artery Doppler waveforms. Br J Obstet Gynaecol1995; 102: 807–812.

11. Maulik D, Yarlagadda P, Youngblood JP, Ciston P. Comparative efficacy of umbilical arterial Doppler indices for predicting adverse perinatal outcome. Am J Obstet Gynecol 1991; 164: 1434–1438.

12. Karsdorp VH, van Vugt JM, van Geijn HPet al. Clinical significance of absent or reversed end diastolic velocity waveforms in umbilical artery. Lancet1994: 344: 1664–1668.

13. Trudinger BJ, Cook CM, Giles WB et al. Fetal umbilical artery velocity waveforms and subsequent neonatal outcome. Br J Obstet Gynaecol1991; 98: 378–384.

14. Ozcan T, Sbracia R, d’Ancona RL, Copel JA, Mari G. Arterial and venous Doppler velocimetry in the severely growth-restricted fetus and associations with adverse perinatal outcome.Ultrasound Obstet Gynecol1998; 39: 39–44.

15. Baschat AA, Gembruch U, Harman CR. The sequence of changes in Doppler and biophysical parameters as severe fetal growth restriction worsens. Ultrasound Obstet

Gynecol2001; 18: 571–577.

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17. Sickler GK, Nyberg DA, Sohaey R, Luthy DA. Polyhydramnios and fetal intrauterine growth restriction: ominous combination. J Ultrasound Med1997; 16: 609–614. 18. Magann EF, Sanderson M, Martin JN, Chauhan S. The amniotic fluid index, single

deepest pocket, and two-diameter pocket in normal human pregnancy. Am J Obstet

Gynecol2000; 182: 1581–1588.

19. Owen P, Mires GJ, Christie AD. Impaired fetal growth velocity in the presence of notched uterine artery velocity waveforms. Br J Obstet Gynaecol1996; 103: 1247–1249. 20. Alfirevic Z, Neilson JP. Doppler ultrasonography in high-risk pregnancies: systematic

review with meta-analysis. Am J Obstet Gynecol1995; 172: 1379–1387.

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25.Gugmundsson S, Tulzer G, Huhta JC, Marsal K. Venous Doppler in the fetus with absent end-diastolic flow in the umbilical artery.Ultrasound Obstet Gynecol1996; 7: 262–267. 26. Sicco A. Neurodevelopmental outcome at 3 years of age after fetal ‘brain sparing’. Early

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Liver dysfunction complicates as many as 3% of pregnancies.1_{Liver disease in}

pregnancy can effect both maternal and fetal health. Hypertensive disease of pregnancy, which encompasses the spectrum of pre-eclampsia and HELLP syndrome, accounted for 16 maternal deaths in the UK between 1997–1999. Two deaths were from hepatic rupture as a complication of severe pre- eclampsia – five deaths were associated with HELLP syndrome.2 _Likewise,

acute fatty liver of pregnancy (AFLP) continues to cause small numbers of maternal deaths.2 _{Intrahepatic cholestasis of pregnancy causes maternal}

morbidity and is responsible for significant fetal mortality and morbidity.3

PHYSIOLOGICAL CHANGES

Anatomically, the liver does not change in size during pregnancy but is more difficult to palpate due to rotation to a more superior and posterior position.4

During pregnancy, blood flow through the liver remains unaltered.5 _The

increased circulating volume in pregnancy is redistributed through the portal veins and vena cava resulting in the appearance of engorgement of the oesophageal veins at endoscopy in 50% of normal pregnancies.6

Pregnancy-induced physiological changes in liver metabolism are shown in Table 1. A study in 1997 of measured aspartate transaminase (AST), alanine aminotransferase (ALT), bilirubin and γ-glutamyltransferase (γ-GT) in 430 apparently normal pregnant women reported these indices to be approxi- mately 20% lower in pregnant women compared to laboratory reference ranges.7_{Total serum protein concentration also decreases, mainly due to a 25%}

57

Mark D. Kilby MD MRCOG, Professor of Maternal and Fetal Medicine, Department of Fetal Medicine,

Division of Reproduction and Child Health, Birmingham Women’s Hospital, University of Birmingham, Edgbaston, Birmingham B15 2TG, UK (for correspondence)

Katherine J. BarberMB ChB MRCOG, Wellcome Research Fellow, Department of Reproduction and

Child Health, University of Birmingham, Edgbaston, Birmingham B15 2TG, UK

Mark D. Kilby Katherine J. Barber

5

Management of abnormal