FETAL SURVEILLANCE

BY

Dr. A. E. EDUGBE (MBBS, FMCOG, FWACS)

OUTLINE

• Introduction
• Aetiology of fetal deaths
• Aims of fetal surveillance
• Indications for fetal surveillance
• Antepartum fetal surveillance
• Intra-partum fetal surveillance
• Conclusion

​

INTRODUCTION

Fetal surveillance are the various methods or techniques employed to assess the risk of adverse perinatal outcome of a fetus at risk for antepartum and/or intra-partum fetal loss

​

Placenta is the only fetal supply line for nutrition and gas exchange, hence, the fetus is vulnerable to any strain in the utero-placental unit

Any utero-placental disorder becomes more critical as the fetus gets bigger

Currently, there are no treatment modalities for reversion of utero-placental insufficiency

​

INTRODUCTION CONT;

• Fetal monitoring (FS) is crucial for detection of fetuses at risk of jeopardy – early or late stages of hypoxia

Timely delivery is effected when findings suggest fetal compromise

​

• The aim of FS is to deliver the most mature fetus in the best possible condition with minimal risk to the mother
• Reduce the risk of fetal death in utero
• Delay the need for inappropriate interventions
• Prolong the gestation in pregnancies at risk for preterm delivery

​

• Most authorities begin at 32 weeks, and the interval of testing is generally weekly to twice weekly
• FS may done antepartum or intra-partum

DEFINITION OF TERMS

• Hypoxia: Decreased PO2 in tissues
• Acidosis: Decreased PH in tissues
• Asphyxia: Hypoxia with metabolic acidosis
• Utero-placental insufficiency;
• Inadequate delivery of nutrients or oxygen to appropriate fetal tissues
• Inadequate exchange within the placenta could be due to decreased blood flow, decreased surface area or increased membrane thickness
• Theoretical scheme of fetal deterioration: nutritional compromise → growth restriction → fetal hypoxia → acidosis → asphyxia → death

​

​

​

Aetiology of fetal loss

Fetal deaths

Antepartum 70-90%

Intrapartum 10-30%

• Chronic asphyxia
• Anomalies
• Pregnancy complications
• Unexplained IUDs

• Chronic asphyxia
• Anomalies
• Pregnancy complications
• Unexplained IUDs

Asphyxia 30%

Maternal compl 30%

Malformations 15%

Infection 5%

Unexplained 20%

Asphyxia 30%

Maternal compl 30%

Malformations 15%

Infection 5%

Unexplained 20%

AIMS OF FETAL SURVEILLANCE

1. To ensure satisfactory growth and well being of the fetus throughout pregnancy

​

2. To screen out high risk factors that affect the growth of the fetus

​

3. To determine when the risk of IUFD outweighs the risk of premature delivery

​

4. To determine optimum timing of delivery

​

5. To avoid unnecessary obstetric interventions

​

​

INDICATIONS FOR FETAL SURVEILLANCE

• Prolonged pregnancy
• Diabetes mellitus
• Hypertensive disorders in pregnancy
• Previous Stillbirth
• Suspected intra-uterine growth restriction
• Rhesus isoimmunization
• Decrease fetal movements
• Amniotic fluid disorders – oligo/polyhydramnios
• PPROM, Antepartum haemorrhage
• Multiple pregnancy
• Maternal medical disorders e.g renal, heart etc

​

ANTEPARTUM FETAL SURVEILLANCE

• Most fetal deaths occur in the antepartum period

​

• Antepartum fetal deaths – causes;

- Asphyxia (IUGR, post dates) – 30%

- Maternal complications(PE, abruption, DM) – 30%

- Congenital malformations/chromosomal abnormalities – 15%

- Infection – 5%

​

• About 20 percent of stillbirths have no obvious cause

​

METHODS OF ANTENATAL FETAL SURVEILLANCE

This can be subclassified under:

​

• Clinical

​

• Biophysical

​

• Biochemical – Prenatal diagnosis lecture e.g AFP

​

​

CLINICAL METHODS OF ANTENATAL FS

• Use mainly for fetal growth assessment
• Useful as screening test for further investigation

1. Maternal weight gain

• In second half of pregnancy, average weight gain is 0.5 Kg/week
• Excess weight gain may be due to excess fluid retention – May be first sign of pre-eclampsia
• Weight gain that is less than normal, stationary or even falling may points to IUGR

2. SFH

• Correspond to GA in second half of pregnancy up to 36 weeks with error margin of 1-2 cm
• Aim is to compare SFH with GA calculated from LMP (certain date) or early USS
• SFH > GA – causes include Wrong date (LMP), multiple pregnancy, polyhydramnios, pelvic tumours etc
• SFH < GA – causes include wrong LMP, IUGR, oligohydramnios etc

3. Auscultation of fetal heart

• Assessment of rate & rhythm using;

- Pinard stethoscope or doppler (Sonicaid)

BIOPHYSICAL METHODS OF ANTENATAL FS

• Principle - Biophysical profile is a screening test for utero-placental insufficiency
• Fetal biophysical activities are initiated, modulated and regulated through fetal nervous system
• The fetal CNS is very sensitive to diminished oxygenation
• Hypoxia → metabolic acidosis → CNS depression → changes in fetal biophysical activity

��

1. Fetal movement count

Decreased placental perfusion and fetal hypoxia are associated with decreased fetal movements

• Cardiff count to 10 –
• The patient counts fetal movements starting from a specific time e.g 9 am
• The counting comes to an end as soon as 10 movements are perceived
• She is instructed to report if;

(i) less than 10 movements occur during 12 hours on 2 successive days

(ii) no movement is perceived even after 12 hours in a single day

​

Biophysical methods of antenatal FS

• Daily fetal movement count (DFMC):
• Three counts each of one hour duration (morning, noon and evening) are recommended
• Total counts multiplied by four gives daily (12 hour) fetal movement count (DFMC)
• If there is diminution of the number of ‘kicks’ to less than 10 in 12 hours (or less than 3 in each hour), it indicates fetal compromise
• Loss of fetal movements is commonly followed by disappearance of FHR within next 24 hours
• Ominous fetal kick count is an indication for NST

NOTE;

• Maternal hypoglycemia is associated with increased fetal movements
• Maternal perception of fetal movements may be reduced with;

- Fetal sleep (quiet)

- Fetal anomalies (CNS)

- anterior placenta

- Polyhydramnios

- Obesity

- Drugs (narcotics)

- Chronic smoking

- Hypoxia

FETAL KICK CHART IN BHUTH

BIOPHYSICAL METHODS OF ANTENATAL FS

2. Ultrasound;

• late USS helps in detecting:

i) Fetal growth abnormalities – IUGR, fetal macrosomia

ii) Abnormalities in amniotic fluid volume

iii) Problems with placenta – calicifications etc

iv) Abnormalities of fetal position

v) Fetal wellbeing

• IUGR can be diagnosed accurately with serial measurement of BPD, AC, HC, FL and amniotic fluid volume
• AC is the single measurement which best reflects fetal nutrition

​

• Mean increase of BPD after 34 weeks is 1.7 mm/week
• When HC/AC ratio is elevated (> 1.0) after 34 weeks, IUGR should be suspected

Amniotic fluid volume assessment;

• A vertical pocket of amniotic fluid 2-8 cm is considered normal, <2 cm, > 8cm – oligo/polyhydramnios resp
• AFI ranges;

- <5 cm, 5-7 cm, 7-10 cm denote severe, moderate and mild oligohydramnios respectively

- 10-25 cm – Normal

- >25 cm – Polyhydramnios

• Oligohydramnios – Assoc fetal morbidity/mortality

​

3. Fetal cardiotocography (NST);

​

​

​

​

• NST involves continuous electronic monitoring of the fetal heart rate along with recording of fetal movements
• There is association of FHR acceleration with fetal movements
• When present, indicates a healthy fetus
• Tracing is done over 20-30 minutes usually in third trimester
• Reactive (Reassuring) CTG consist of;

- Base line HR of 110–160 beats/minute

- Base line variability 5–25 bpm

- No deceleration

- Two or more accelerations of > 15 bpm above baseline, lasting at least 15 seconds or more

​

​

• Non reactive (Non reassuring ) CTG – absence of fetal reactivity

Normal CTG tracing

​

FETAL SURVEILLANCE

23

04/10/2019

BIOPHYSICAL METHODS OF ANTENATAL FS

4. Fetal biophysical profile

• It combines NST with four USS features of fetal behaviour and physiological characteristics
• USS PROCEDURE: It is performed over 30 minutes and assesses fetal behaviour by observing
• Fetal breathing movements
• Body movement
• Fetal muscle tone
• Amniotic fluid volume

​

NDUKA EMMANUELLA

25

10/4/2019

BPP INTERPRETATION

• 8-10 (8/8 if NST is not done)

- Interpretation: No fetal asphyxia

- Management: Repeat testing at weekly interval or more

- Interventions should be from obstetric or maternal factors

• 4-6

- Interpretation: Equivocal test; suspect chronic asphyxia

- Management: if >34 weeks, deliver

If <34 weeks repeat test in 24 hours, if result is same, mature lungs and deliver within 48 hours

​

​

​

• 0-2

- Interpretation: Strongly suspect chronic fetal asphyxia

- Management: Evaluate patient for immediate CS delivery.

If 34 weeks, mature lungs and deliver

• N.B Oligohydramnios alone is an indication for delivery

* Modified Biophysical Profile consists of NST and amniotic fluid index in USS

Interpretation - Considered abnormal (non reassuring) when the NST is non-reactive and/or the AFI is < 5

​

BIOPHYSICAL METHODS OF ANTENATAL FS

5. Contraction stress test;

• Evaluates response of the FHR to induced contractions
• CST is NST done in the presence of at least 3 contractions in a 10 minute period
• Designed to unmask poor placental function
• Principle - contractions transiently decrease fetal oxygenation → decreased FHR in a marginally compromised fetus with limited placental function
• Can be done with naturally occurring contractions or with induced nipple stimulation or IV oxytocin

​

BIOPHYSICAL METHODS OF ANTENATAL FS

• Advantage of CST - most closely approximates intra-partum surveillance of fetal risk even during the antepartum period
• CST is rarely done

Interpretation;

* Negative result - No late or significant variable decelerations

* Positive result - Late decelerations (occurs after 50% contractions)

​

BIOPHYSICAL METHODS OF ANTENATAL FS

6. Doppler velocimetry

• Doppler USS uses sound waves to study blood circulation in the Uterus, placenta and fetus
• Normal blood in tissues occur without resistance in diastole

Uterine artery Doppler

• Resistance within the placenta can be measured from the maternal side, usually as a screening test at 23 weeks
• High resistance in the uterine artery indicates; - Increased risk of development of early onset pre-eclampsia

- Risk of a fetus with IUGR

​

BIOPHYSICAL METHODS OF ANTENATAL FS

Umbilical artery Doppler

• Increasing resistance in the umbilical artery is an indicator of placental failure
• Using this in high risk pregnancies reduces the risk of fetal death

Middle Cerebral artery (MCA) Doppler

• The artery shows increasing diastolic flow as hypoxia increases due to redistribution of blood to the brain
• Peak systolic velocity in MCA Doppler increases with fetal anemia as seen in Rhesus iso-immunization

​

NORMAL DOPPLER WAVEFORM

ABNORMAL DOPPLER WAVEFORMS

• Reduced end diastolic flow

​

• Reversed end diastolic flow

​

​

INTRA-PARTUM FETAL SURVEILLANCE

• Simply means watching fetal behavior during labour
• AIM - To detect hypoxia during labour and to initiate management depending n the severity of the hypoxia
• In labour, 3 major factors occurs - uterine contractions, cord accident & prolonged head compression

​

​

UTERINE CONTRACTIONS

METHODS OF INTRA-PARTUM FETAL MONITORING

• 1. Intermittent auscultation – using pinard or hand held doppler (sonicaid)
• Aim – To detect fetal bradycardia and tachycardia

​

​

​

​

• 2. Liquor assessment – Clear liquor (Normal), meconium stain [fresh (green) or stale (brown)], blood stain

3. CTG – continuous fetal heart monitoring

4. Fetal pulse oximetry

​

​

​

5. Fetal scalp sampling 🢡 PH determination

​

PH INTERPRETATIONS

CONCLUSION

• Perinatal morbidity and mortality can be reduced with utilisation of robust antenatal and intra-partum monitoring approach

​

• Training and Practice is the way forward

​

• There is no one best test and none of the testing modalities has been shown to reduce perinatal morbidity nor increase long term fetal neurologic outcome

​

FETAL SURVEILLANCE

39

04/10/2019

​

​

​

​

• THANK YOU