Foetal Growth

Question 1

What are the three phases of foetal growth and development?

Answer 1

First = 4-20 weeks, increases in foetal weight, protein content and DNA content (cellular hyperplasia)
Second = 20-28 weeks, increased in protein and weight and lesser increases in foetal DNA content (hyperplasia and concomitant hypertrophy)
Third = 28 weeks - term, continued increases in foetal protein and weight but no increase in DNA (hypertrophy)

Question 2

Define IUGR

Answer 2

Intrauterine growth restriction

- failure of the foetus to achieve his or her growth potential

Question 3

Define small for gestational age (SGA)

Answer 3

Brith weight <10th centile for gestational age

• centimes are based on local populations
• can be adjusted for sex, parity, race, maternal weight and height

Question 4

Define large gestational age (LGA)

Answer 4

birth weight >90th percentile

Question 5

Define low birth weight

Answer 5

birth weight less than a certain threshold e.g. 2500g

Question 6

What other neonatal indices can be measured to find out about foetal growth?

Answer 6

• ponderal index, skin fold thickness, MAC/HC ratio (mid arm circumference, head circumference)

Question 7

What are the consequences of foetal growth restriction?

Answer 7

LBW infants are more likely to:
- die within first year of life
- suffer from neonatal problems (birth asphyxia, hypoglycaemia, hypothermia)
Foetal origin of adult disease?

Question 8

What is foetal programming/Barker hypothesis?

Answer 8

• most show catch p with n childhood though may have smaller size in adulthood
• however, IUGR can have lifelong impact
  Increased risk of:
• diabetes, obesity, BP, stoke, CVD
  “Thrifty phenotype” programming: evolved to offer advatage in ‘famine environment’ but proves in industrialised society

Question 9

-

Answer 9

• have SGA babies

- have increase perinatal mortality

Question 10

What are the 2 proposed mechanisms of transgererational effects of SGA?

Answer 10

Epigenetics
- heritable changes in gene expression by mechanisms other than underlying DNA sequences
- DNA methylation, histone modification, micro RNA
Maternal Mitochondria
- food restriction can alter number and function
- these are directly passed onto offspring through ova

Question 11

What are the defining for large for gestational age (LGA)?

Answer 11

• birth weight >90th gentile

- macrosomia - birth weight >4500g

Question 12

What are the causes of LGA?

Answer 12

• gestational age, increased incidence of pregnancies over 40 weeks
• foetal sex, male infants tend to weight more
• excessive maternal weight gain and obesity
• multiparty
• erythroblastosis fettles - hydrops details
• genetic disorders of overgrowth e.g. Beckwith-Wiedemann syndrome, Sotos syndrome
• maternal diabetes (prepexisignt of gestational)

Question 13

What is the pathophysiology of LGA and diabetes?

Answer 13

• increased maternal glucose concentration
• increased foetal insulin concentrations
• increased foetal growth factors

Question 14

How does LGA fit into the foetal programming/Barker hypothesis?

Answer 14

• evidence suggests that curve may actually be u-shaped
• babies born to GDM mothers in adulthood are at increased risk of IGT, diabetes and obesity
• early exposure to insulin levels leads to metabolic and epigenetic differences

Question 15

What is placental and foetal growth regulated by?

Answer 15

by combination of substrate availability and endocrine or paracrine signalling
- IGF 1 and IGF 2 major stimulus

Question 16

What maternal factors affect growth?

Answer 16

• ethnicity
• maternal stature/BMI
• drugs: cigarettes, alcohol, drugs of abuse
• nutrition
• material hypoxia: cyanotic heart disease, chronic respiratory disease, altitide

Question 17

Describe the link between IUGR and perinatal mortality/morbidity in the developing world

Answer 17

• maternal undernutrition

- synergistic with low age, maternal anaemia, chronic disease, HIV, placental malaria

Question 18

What foetal factors affect growth?

Answer 18

Genome
- chromosomal disorders
- trisomy 13, 18, 21 
Growth factors 
- insulin like growth factors, thyroxine 
Congenital infections
- CMV, toxoplasmosis, rubella

Question 19

What placental factors affect growth?

Answer 19

Primary placental problems 
- abnormality of placenta structure/function
Secondary placental problems 
- hypertension
- chronic renal disease
- vasculitis 
- pro-thrombotic disorders 
Multiple gestation 
- growth discordance

Question 20

Describe the process of malplacentation in IUGR

Answer 20

• majority of blood flow to uterus is suppled by uterine arteries (supplying arcuate and spiral arteries)
• shape of uterine artery waveform in unique and changes with gestation: early –> high vascular impedance and low flow, mid –> high flow, low resistance
• poor trophoblast invasion of maternal spiral arteries
• increased impedance to flow and decreased placental perfusion
• change in Dopper indices, raaiend RI, diastolic notch etc.

Question 21

Describe the difference sweeten asymmetrical and symmetrical patterns of IUGR
This can help you determine the cause

Answer 21

Asymmetrical
- uteroplacental insufficiency
- decreased glycogen shoes, so decreased abdominal circumference
Symmetrical
- early growth insult, chromosomal, viral infection - disrupted
- regulation of growth processes or disruption at cell hyperplasia stage

Question 22

IUGR is a combination of…

Answer 22

• reducing growth velocity and placental insufficiency

Question 23

How can IUGR be identified on uterine doppler?

Answer 23

different uterine waveforms

abnormal - high resistance to flow, notch seen

Question 24

How do we asses foetal growth clinically?

Answer 24

Measure symphysiofundal height at each antenatal visit from 24 weeks
Ultrasound can calculate foetal weight using head, femur, abdominal measurements

Question 25

How can we assess foetal wellbeing in the long and short term?

Answer 25

Short term = cardiotocography, septal heart rate and contractions
Long term = umbilical artery doppler, middle cerebral artery doppler, ductus venous doppler, liquor volume

Question 26

What is gestational diabetes?

Answer 26

• defined as any degree of glucose intolerance with its onset (or first recognition( during pregnancy
• affect 5% of pregnancies

Question 27

How does gestational diabetes come about?
Pre-existing risk..
Pregnancy risk…

Answer 27

Pre-existing risk
- pancreatic B cell dysfunction on background chronic insulin resistance present before pregnancy
Pregnancy
- is a state of insulin resistance - hormonal, inflammatory, cytokines, adipokines changes,
- resistance increases with advancing gestation

Question 28

How and when is gestational diabetes screened for?

Answer 28

Screen from early pregancy 16-18 weeks if - PMH of GDm or glucose intolerance
Screen from 24-26 weeks if: family history, BMI>30, ethnicity, previous macrosomia, previous unexplained stillbirth, on steroids
Screen urgently if arises in current pregnancy: significant glyosuria, polyhydraminons and macrosomia
Screen via: OGTT (overnight fast then 75g glucose load, test at 2 hrs), random blood glucose profile >36 weeks

Question 29

What are the maternal complications of GDM?

Answer 29

• pre-eclampsia
• pre-term labour
• instrumental delivery/caesarean section
• diabetes later in life

Question 30

What are the foetal complications of GDM?

Answer 30

• macrosomia
• shoulder dystocia
• polyhydraminos
• perinatal mortality and morbidity: neonatal hypogylcaemia, jaundice, polycythaemia, and hypocalcaemia
• foetal programming and increased risk of adult disease

Question 31

How is GDM managed?

Answer 31

MDT: obstetrician, diavetologist, diabetic nurse, dietician
Regular monitoring and strict control - blood sugars up to 7 times per day
Medical management: diet, oral agents e.g. metformin, insulin

Question 32

What is obstetric management of GDM?

Answer 32

• regular growth scans
• regular BM (blood glucose measurement) monitoring
• deliver around 38 weeks
• offer GTT at 6 weeks postnatal