DE LAS FACULTADES DE LA ADMINISTRACIÓN TRIBUTARIA

Specific risk

These are relatively uncommon and include:

• maternal drugs for fetal cardiac arrhythmias

• intrauterine blood transfusion for fetuses with severe Rhesus isoimmunization

• laser ablation of placental vascular communications in twin–to–twin transfusion syndrome.

CONCLUSIONS

CONCLUSIONS

• Most, though not all, fetuses with structural or chromosomal abnormality are identified during pregnancy with current screening programmes. similar to those described in labour (seeChapter 11)

with the difference that uterine activity is minimal and more emphasis is therefore placed on the interpretation of baseline heart rate. An example of a normal antenatal CTG is shown inFigure 10.13. This shows a baseline variability of more than 5 beats/ min with accelerations and no decelerations.Figure 10.14 shows a normal baseline rate but reduced baseline variability.

• Fetal movements: there should be at least 3 separate/ discreet movements in 40 minutes of fetal observation with US.

• Fetal tone: at least one of these fetal movements should demonstrate a full 90° flexion–extension– flexion cycle.

• Fetal breathing: there should be a sustained 30 second period of regular fetal breathing movements during the 40 minute observation period.

• AFV: there should be at least one vertical pool measuring between 2 and 8 cm.

Fig. 10.13

Fig. 10.13 Normal antenatal cardiotocograph. The recording shows a baseline variability of>5 beats/min and episodes of accelerations.

Fig. 10.14

Fig. 10.14 Antenatal cardiotocograph showing a normal heart rate but reduced baseline variability.

Essential obstetrics | 22 |

Section

• In normally formed fetuses that are apparently at no risk the current method of routine surveillance during pregnancy (maternal perception of fetal movements, fundal height measurement and auscultation of the fetal heart) is limited and does not identify all fetuses that are genuinely at risk.

• In normally formed fetuses, once risk is identified, both specific and non-specific, the current methods of surveillance coupled with the judicious use of maternal steroid administration and elective delivery are effective in the sense that most fetuses identified to be ‘at risk’ will not diein utero_.

Essential information Essential information

Congenital Abnormalities Congenital Abnormalities

• Fetal abnormality is found in: – over 50% of conceptions – about 70% of miscarriages

– 15% of deaths between 20 weeks and 1 year postnatal

– 1–2% of births, including major and minor anomalies

– 8% of special needs register/disabled children • The overall UK incidence has fallen over the past 30y

due to

– Introduction of screening programmes in pregnancy – Greater success at diagnosis during pregnancy, and – Parents choosing pregnancy termination • The commonest four groups of defects are – Neural tube defects (3–7/1000 births) – Congenital cardiac defects (6/1000 births) – Down’s syndrome (1.5/1000 births) – Cleft lip/palate (1.5/1000 births)

• Screening for fetal abnormality can be undertaken – Clinically in early pregnancy (including maternal age,

certain drugs, previous abnormal baby, diabetes) – Clinically in late pregnancy (including abnormal

uterine size, abnormal fetal movements, abnormal fetal lie)

– Using ultrasound (including measurement of nuchal translucency at the end of the first trimester and an anatomical survey at 20 weeks)

– Biochemically (measurement of biochemical markers which in combination with nuchal translucency measurement estimate chromosomal abnormality risk)

– Balance pre-test counselling is important with ultrasound and biochemical screening • Options following non-directive counselling with an

abnormal/positive screening test include

– Further assessment (such as repeat ultrasound scan after an interval, amniocentesis or CVS to establish the felt karyotype, other imaging including MRI) – Specific interventions (such as anti-arrhythmic drugs,

drainage of fetal fluid collections) – Termination of pregnancy

– Continuation of pregnancy with ongoing surveillance and specific plans for timing, mode and place of delivery

Assessing the health of a normally Assessing the health of a normally formed fetus

formed fetus

• Surveillance of fetal health in a low-risk pregnancy comprises

– Maternal vigilance for fetal activity in the latter half of pregnancy

– Fundal height measurement and charting – Auscultation of the fetal heart

• Surveillance of fetal health in a high-risk pregnancy comprises

– Tests used will depend on the presumed underlying pathophysiology (such as Doppler recordings of middle cerebral artery blood flow if fetal anaemia is a risk)

– The majority of fetuses including those where there is uncertainty about the pathophysiology will have combined serial measurements of

■ Umbilical artery blood flow using Doppler ultrasound

■ Fetal growth (especially head and abdominal circumferences)

■ Amniotic fluid volume

■ Biophysical parameters (fetal heart rate, movements, tone and breathing) • Interventions

– Non-specific or unknown pathophysiology ■ Elective delivery – the timing depending on the

degree of fetal risk

■ Maternal administration of steroids if a preterm delivery is planned

– Specific or known pathophysiology (rare) ■ Maternal anti-arrhythmic drugs for fetal cardiac

arrhythmias

■ Fetal blood transfusion(s) for severe fetal anaemia

■ Laser ablation of placental vascular anastamoses with twin-twin transfusion syndrome

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11

11

Chapter

Management of labour

Labour or parturition is the process whereby the products of conception are expelled from the uterine cavity after the 24th week of gestation. About 93–94% deliver at term, i.e. between 37 to 42 weeks, while about 7–8% develop preterm labour and deliver preterm from 24 to 37 weeks. Preterm labour is defined as labour occurring before the commencement of the 37th week of gestation. Prior to 24 weeks this process results in a previable fetus and is termed miscarriage. Prolonged labour is defined as labour lasting in excess of 24 hours in a primigravida and 16 hours in a multigravida. Prolonged labour is asso- ciated with increased fetal and maternal morbidity and mortality.