Fetal growth problems Flashcards
Development vs Growth. what is the difference ?
- In the very early stages of pregnancy is where the development is happening. where all the different organs are forming.
- Later in the pregnancy, everything is fully formed and the baby is just growing, putting on weight.
First 12 weeks fetal development occurs – organs formed. This is where teratogenous drugs can affect the baby.
Then the baby needs to get bigger – fetal growth. if they take a teratogenous drug at this stage, it will not cause fetal anomaly because all their organs have developed.
Why do We Monitor Fetal Growth?
Growth restriction is associated with;
•Stillbirth
• Neonatal death
• Perinatal morbidity
Confidential enquiries have demonstrated that most stillbirths due to IUGR ( Intra uterine Growth restriction) are due to;
•Associated with suboptimal care
• and are Potentially avoidable
The Small-for-Gestational-Age Fetus (SGA)
Why do babies not grow to expected potential?
•SGA (Small-for-Gestational-Age Fetus) : Estimated fetal weight (EFW) or abdominal circumference (AC) of < 10th centile on the fetal growth scan
•SGA is not synonymous with fetal growth restriction (FGR) – (also referred to as IUGR)
-not all SGA babies are growth restricted, they are just small!
- constitutionally small baby
- normal baby that is showing reduced growth.
- its important to look at the size of the parent , if they are tiny, then its normal for their baby to be less than < 10th centile
- the importance of picking up an SGA baby is to differentiate an SGA baby that is fine and coping well and an SGA baby that is growth restricted.
•Ultrasound measurements for growth (growth scan)
- we check Abdominal circumference (AC)
- we check Head circumference (HC)
- we check Femur length (FL)
- we check Liquor volume (LV) - volume of fluid around baby
- we can also do an ultrasound Dopplers test for the baby
we then do a calculation to try and measure the estimated weight.
Causes of Small Babies
3 main groups of SGA fetuses:
1.“Normal” baby ie. constitutionally small
Based on maternal size & ethnicity
2.Non-placenta mediated growth restriction
eg. structural or chromosomal problem, fetal infection, inborn errors of metabolism
3.Placenta mediated growth restriction
eg. PET, hypertension, autoimmune disease (lupus), thrombophilias, renal disease, diabetes (Type 1 AND 2)
Growth restricted babies can be
1. Symmetrically Growth restricted
In a symmetrical growth restriction, all the measurements that you have taken will all be small. all in proportion to each other.
- Groups 1 and 2
- HC (head) , AC (abdomen), FL (femur) all reduced
2. Asymmetrically Growth Restricted
The head and the femur will measure normal but the abdominal circumference will be very small.
- Group 3
- AC reduced
Trophoblast invasion
Risk factors for IUGR
- Maternal age > 40yrs. you are more likely to make placenta properly, harder to make the trophoblast invasion properly).
- Nulliparity (first baby)
- Very Low or Very high maternal BMI
- Diabetes / Renal disease / APLS (Antiphospholipid syndrome) - sometimes known as Hughes syndrome, is a disorder of the immune system that causes an increased risk of blood clots.
- Smoking
- Maternal SGA (if mum is small for gestational age)
- IVF
- Previous SGA (small for gestational age) infant
- Previous stillbirth
- PAPP-A < 0.4 MoM at combined screening
Pregnancy-associated plasma protein A. Low levels of PAPP-A (when it is less than 0.4 MoM in pregnancy) may be associated with: A lower birth weight baby as your placenta may not work as well. An increased chance of having an early birth. Miscarriage in the second half of pregnancy. An increased chance of developing pre-eclampsia.
•Hypertension/PET/recurrent APH this pregnancy
What happens in Fetal growth restriction
The placenta invasion doesn’t happen properly, the blood space that is allowing all the nutrient isn’t working properly so the baby isn’t getting enough of things like O2 and nutrients.
The more severe the event, the worst.
The list of what is going on is ;
- Deficient placental invasion
- Reduced placental reserve
- Fetal need exceeds supply
- IUGR
- Hypoxia
- Fetal vascular redistribution
- Oliguria (low Urine output)
- Abnormal CTG (Cardiotocography)
- Fetal death
Diagnosis of Fetal growth restriction
Clinical suspicion – abdomen “looks smaller”
Clinical measurement of uterine size: Symphysis - fundal height (SFH)
-The SFH measure should be roughly the same as the amount of weeks that a woman is pregnant.
-If a woman is 28 weeks pregnant, it should be around 28 cms. can change a little but it’s all about pattern.
-if someone has been measuring a couple of centimetres above their date for the whole pregnancy and then suddenly it drops, then that is important.
-if we understand a probable with that measurement, the the next step is an ultrasound scan
Fetal growth restriction
Asymmetrical Growth Restriction: just abdominal growth affected
Abdominal circumference reflects the size of the fetal liver
Causes:
Placental insufficiency – no excess glycogen being deposited within the liver
Consequences of hypoxia in the fetus
•Blood flow (oxygen and nutrients) redirected to areas of greater importance like the Brain
- Blood flow (oxygen and nutrients) redirected away from areas of lesser importance
- Gut (doesn’t eat!)
- Kidneys (placenta clears waste products)
- Lungs (placenta brings O2)
Ultrasound findings in IUGR
- Small Abdominal circumference ( due to small liver)
- Decreased amniotic fluid ( this is produced by the kidneys). the kidneys are not working properly because the fetus is diverting blood to the brain where the blood is most needed.
- Increased blood flow to the brain (look at Middle Cerebral arteries in the brain – using the doppler effect scan
Clinical features of IUGR
- Symphysial fundal height (SFH) smaller than expected
- Baby’s movements lessen to conserve energy. because the baby is hypoxic, it does not have the energy to run around.
- Fetal heart rate changes as hypoxia develops (as seen on CTG)
- if it goes undiagnosed, it leads Fetal death
Management / Monitoring of a baby that we think is growth restricted
•Serial ultrasound evaluation of - fetal growth, liquor volume and fetal doppler.
•we then need to decide when to deliver the baby. Timing delivery will depend on a combination of factors including.
- Gestational age
- Doppler studies
- Other risk factors
•The goal is to maximize fetal maturity and growth but minimize the risks of perinatal mortality and morbidity.
-you want the baby to stay in the womb for as long as possible to maximise its growth and to minimise the risk of still birth.
Normal vs Abnormal pregnancy
middle cerebral artery
in a doppler, we are measuring the pressure during systole and the pressure during diastole. that is the spike you can see on the screen.
normally in the brain there is a big difference in the middle cerebral artery between systole and diastole. when the baby is struggling and all the blood vessels dilate massively, you get much less difference between the pressure is systole and diastole.
Wait or deliver in IUGR?
its all about judgement in deciding whether the baby will be better in the mum or out.
