Fetal growth and assessment of fetal wellbeing in late pregnancy

done by :-

SABA AL-THUWAINY

The period of fetal growth during pregnancy divided into two phases, 1st below 20 weeks of gestation which characterized by hyperplasia, cell division and organogenesis.

2nd above 20 weeks of gestation which characterized by hypertrophy, increase in size of cells, organs, and increase in fetal wt.(usually in the last 8 weeks) e.g. fetal wt. at 28 wk. equal to approximately 1/3 of average, at 32wk.__1/2 the average.

The average wt. at term approx.3250- 3500 gm .

Factors that affect fetal growth:-

These can be divided into:-

• Physiological:

–Parity

–Age

– Sex

–Maternal wt.+ht. and paternal ht.

These physiological factors could result in what called Small for GA.

• Pathological:

– This also can be divided into:

• Fetal causes: congenital infections e.g.TORCH, congenital anomalies, chromosomal abnormalities; these also called Interinsic causes , these factors result in( Symmetrical IUGR) and usually presented below 24 wk.

• maternal causes (extrinsic)..

– Placental insufficiency and its causes i.e. hypertension , PE, diabetes, smoking, severe anemia, hypoxic conditions kike asthma and high altitude….and these usually result in asymmetrical IUGR and usually presented above 24 wk.

Abnormalities of fetal growth

• Defined as failure of fetus to get its growth potential and is so called when it is below 10th centile of growth chart.

However even the fetal wt. below 10th centile, it will divided into

1. Small for GA:-this occur usually due to physiological and constitutional factors and the fetus healthy and with normal catch up of wt. within 2 wk of monitoring.

2. IUGR:-also below 10th centile and is due to pathological causes and the fetus has abnormal catch up of wt. within 2wk. Of monitoring and this IUGR subdivided into:-– Symmetrical IUGR

– Asymmetrical IUGR

MANAGEMENT• The most important point is to differentiate

between normal SGA and IUGR, this done by:

–Proper history..

• Age, parity, obstetrical hx, any previous delivery of SGA, any chronic medical disease, F. hx of chronic disease, genetic disease, previous chromosomal abnormalities, smoking, hx of this pregnancy e.g. any 1st trimisterinfections, any ULS abnormality.

• Examination:-– General ex. e.g. BMI, blood pressure, any sign of

chronic disease.

– Abdominal ex. After ensuring the GA by dating scan, we can use what called symphysio-fundal height…

• Investigation:-– Ultrasound:- it is usually used to diagnose and

differentiate between SGA and IUGR, this done by measure the fetal wt. in the 1st visit, then repeat it after 2 wk.and not less( the 2 wk. enough to measure catch up of wt. for the fetus),

• If it was within normal standard growth----SGA---healthy

• If it was less than normal standard growth----IUGR---If symmetrical ---- so manage acc. To the cause

------if asymmetrical which is due to placental insufficiency we should continue to assess fetal wellbeing and decide whether the delivery is appropriate at the presenting GA, and this done by:-

1. Try to treat the underlying e.g. hypertension, DM.

2. Fetal kick count:-ask the mother about fetal movements (normally at least 12 movement per 24hr.), it is less sensitive method affected by maternal perception, fetal sleeping cycle.

3. 2 weekly ultrasound to check the fetal growth.

4. Weekly ultrasound and biophysical profile:-it is scoring system used to assess fetal wellbeing, it consist of 5 parameters and maximum score of 10.

parameters Normal(score 2) Abnormal(score0)

Fetal breathing movements >1 episode in 30 min. Absent in 30 min.

Gross body movements >3body movements in 30 min. <3

Fetal tone >1 episode Absent or slow

Reactive fetal HR >2accelerations with fetal movement in 30min.

<2 accelerations

Qualitative amniotic fluid >1pool of fluid(1cm*1cm) <1cm*1cm

• Abnormal score of <6, however now the new modified biophysical profile using only reactive fetal heart rate with movement and amniotic fluid amount.

5. CTG and NST:-It is external method to monitor the fetal heart rate by using uls transducer put on the abdomen of the pregnant whose comfortable in the left lateral or semi-recumbent position and a tocodynameter for recording uterine contractions.

***normal fetal cardiac physiology that recorded by CTG:-

a. Fetal heart rate—110-150b/min.

b. Fetal heart rate variability:-oscillation of fetal HR around the baseline. It indicate normal autonomic system function and normally occurring between 2-6 times/min.

c. Fetal HR accelerations:-increase in the baseline fetal HR of at least 15bpm, lasting for at least 15 sec.

*the presence of two or more

accelerations in 20-30 min.CTG defines a reactive trace, and if the accelerations occur with fetal movement it called reactive non stress test.

d. Absence of decelerations:-these are transient reductions in the fetal HR of 15bpm or more than 15 sec. in relation to uterine contractions.

***suspicious+ abnormal CTG:-

1. Baseline fetal HR <or equal to 110bpm( bradycardia),>or equal to 150bpm( tacchycardia)

2. Reduction or absence of variability.

3. Absence of accelerations.

4. Presence of decelerations.

6. Doppler investigation:- by using doppler ulsfor measuring waves formed by these vessels providing information on feto-placental blood flow and should be performed on high risk mothers e.g. hypertension, IUGR; and this done by measuring resistance index and end-diastolic blood supply in umbilical artery, umbilical vein, middle cerebral artery and ductus venosus in sequence if one abnormal so shift to another( normally the resistance index low to allow blood supply during diastole to the fetus)..

Absent or reversed end diastolic flow in the umbilical artery reflect fetal distress and IUD.

****New developments:-MRI :-

Advantages:-It is superior to uls in tissue characterization.It provide sectional images in any plane.

Disadvantages:-Expensive.More likely to be affected by

movement artefacts,

so sedation may be used.It is sub-optimal in

maternal obesity.

Three dimensional uls:-

– The beam is swept in two orthogonal planes to capture a block or volume of echoes that are digitally stored.

– Time required is 5-15 sec , depending on the volume required for diagnosis.

• Advantages:-

– Shortening of time.

– Volumes can be stored for later analysis.

– There is evidence that it improves diagnosis of certain fetal abnormalities like cleft lip and palate.

• So these factors and investigations collected together to make the decision about the pregnancy with IUGR, either continue with full monitoring or termination of the pregnancy and councelling the risk of preterm delivery with the patient, however, even there is fixed rule to manage the case of IUGR and it managed case by case..

• There is advice to deliver the fetus at 32 wk. of gestation,

• If there is reversed end diastolic blood supply and to deliver the fetus at 34wk.,If there is absent end diastolic blood supply and as usual we depend on obstetrical history and progress in this pregnancy.