Assessing fetal wellbeing

Published on 09/03/2015 by admin

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Last modified 09/03/2015

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Chapter 28 Assessing fetal wellbeing

The method used in the assessment of fetal wellbeing depends on:

• level of risk to the fetus

• low-risk pregnancy

• high-risk pregnancy

• antenatal or intrapartum monitoring

In a fetus with low-risk status, screening only fetal movements has been shown to identify the fetus at risk of intrauterine death.

Tests available for assessing fetal wellbeing

• fetal movement, including kick charts

• cardiotocography (CTG)

• biophysical assessment

• amniotic fluid volume assessment

• Doppler flow studies

• fetal scalp pH or lactate

Fetal movement

Antepartum stillbirths account for 50% of the perinatal mortality rate. In late antepartum intrauterine fetal death, 60% occur at less than 37 weeks gestation and 2% at gestation over 42 weeks.

Fetal movement in late pregnancy

• Activity of individual fetuses varies, with only 1% of quiet phases lasting over 45 minutes.

• The perception of fetal movement varies between different women. There is reduced activity in fetuses with malformations.

• There appears to be no advantage to formal counting compared with informal inquiry at antenatal clinic.

• Fetal movement assessment should be used as a screening test to prompt other investigations.

High-risk pregnancies, including hypertensive disorders, vascular diseases, thyroid disease, diabetes, isoimmunisation, multiple pregnancies, as well as reduced fetal movements, vaginal bleeding and prolonged pregnancy, should have regular assessment, including umbilical artery Doppler recordings, fetal growth measurement, amniotic fluid volume, as well as CTG and biophysical profile score.

Cardiotocography (CTG)

A CTG is considered normal when the fetal baseline heart rate is between 120 and 160 beats/minute, the variability of heart rate is between 5 and 25 beats/minute, there are two or more accelerations in a 10-minute period and there are no baseline decelerations. An acceleration of fetal heart rate is a rise in heart rate of ≥15 beats/minute and lasting for 15 seconds or more.

Non-stress test (NST) is a reactive CTG where there are two accelerations exceeding 15 beats/minute amplitude and 15-second duration in 20 minutes.

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