Human Life Cycle Flashcards
What is the definition of foetal growth?
Increase in mass that occurs between the end of embryonic period and birth
What 2 components does foetal growth depend on?
1) Genetic potential
- derived from both parents
- mediated through growth factors e.g. insulin like growth factors
2) Substrate supply
- essential to achieve genetic potential
- derived from placenta which is dependent upon both uterine and placental vascularity
What 3 phases in normal foetal growth characterised by?
1) Cellular hyperplasia
2) Hyperplasia and hypertrophy
3) Hypertrophy alone
What is the foetal growth velocity between 14-15 weeks?
5g/day
What is the foetal growth velocity at 20 weeks?
10g/day
What is the foetal growth velocity at 32-35 weeks?
30-35g/day
How does the foetal growth velocity change at >34 weeks?
Growth rate decreases
What is symphysis fundal height?
Distance over the abdominal wall from the symphysis to the top of the uterus
Where is the fundal height landmark at 12 weeks?
Symphysis pubic
Where is the fundal height landmark at 20 weeks?
Umbilicus
Where is the fundal height landmark at 20-34 weeks?
Gestational age +/- 2 cm
Where is the fundal height landmark at 36-38 weeks?
Gestational age +/- 3 cm
Where is the fundal height landmark at >38 weeks?
Gestational age +/- 4 cm
For what reasons could a baby be measuring as having a small fundal height?
- Wrong dates
- Small for gestational age
- Oligohydramnios
- Transverse lie
For what reasons could a baby be measuring as having a larger fundal height?
- Wrong dates
- Molar pregnancy
- Multiple gestation
- Large for gestational age
- Polyhydramnios
- Maternal obesity
- Fibroids
What are the pros and cons of symphysis fundal height?
Pros: - Simple - Inexpensive Cons: - Low detection rate: 50-86% - Great inter-operator variability - Influenced by a number of factors (BMI, foetal lie, amniotic fluid, fibroids)
Why is dating by last menstrual period inaccurate?
- Irregular periods
- Abnormal bleeding
- Oral contraceptives
- Breastfeeding
Why is correct dating important?
- Small for gestational age or large for gestational age confusion
- Inappropriate inductions
- Steroids in preterm deliver
How should all pregnancies be dated?
Crown Rump Length
- EXCEPT IVF pregnancies
When is head circumference dating used?
If the first scan is done after 14 weeks (CRL>84mm)
Which 4 biometrical parameters assess foetal growth when using an ultrasound?
1) Biparietal diameter
2) Head circumference
3) Abdominal circumference
4) Femur length
Combination = Estimated foetal weight
How are normaltive growth curves constructed from ultrasound measurements expressed?
Centiles
- Used clinically to identify a normal intrauterine growth and detect risk of obstetric and neonatal complications
What maternal factors influence foetal growth?
- Poverty
- Age
- Drug use
- Weight
- Disease (hypertensiom, diabetes, coagulopathy)
- Smoking and nicotine
- Alcohol
- Diet
- Prenatal depression
- Environmental toxins
What foeto-placental factors affect foetal growth?
- Genotype (genetic potential)
- Gender (B>G)
- Hormones
- Previous pregnancy
What are the foetal hormones and from where are they secreted?
Pituitary - Somatrophin - Prolactin - FSH/LH Pancreas- Insulin Adrenals - Androgens Gonads- Androgens Thyroid- Iodothryonines
By which principles does the customised growth charge define individual foetal growth potential?
1) Adjusted to reflect maternal constitutional variation. Maternal height, weight, ethnicity, parity
2) Optimised by presenting a standard free from pathological factors such as diabetes and smoking
3) Based on foetal weight curved derived from normal pregnancies
What is covered in obstetric ultrasound examination?
- Assessment of foetal ‘wellness’ not just size
- Looking at trends in growth
- Predicting foetal metabolic compromise
- Anticipating the need to deliver prematurely
- Liaising with neonatal services
When is a foetus considered small for gestational age (SGA)?
Birth weight
What is the definition of foetal growth restriction (FGR)?
Failure of the foetus to achieve its predetermined growth potential for various reasons
What is a severe SGA ( small for gestational age)
EFW or AC
What is considered a low birthweight?
less than 2500 g
What is considered a very low birthweight?
less than 1500 g
What do epidemiological studied use?
- Use birth weight alone, not gestastional age
What is the increase in perinatal mortality in FGR babies?
3-10 fold increase
When choosing centiles, which is the most sensitive and which is the most specific?
Sensitive= 10th Specific= 3rd
Why will you get a number of false positives with the tenth centile?
It captures all babies with FGR but will also include those babies that are just small for gestational age
Why will you get a number of false negatives with the third centile?
All babies recorded using the third centile will have FGR, but some FGR babies may be missed
What are the short term problems of LBW/FGR/ Prematurity?
- Respiratory distress
- Intraventricular haemorrhage (cannot fight infection)
- Sepsis (cant fight infaction)
- Hypoglycaemia
- Necrotising enterocolitis
- Jaundice
- Electrolyte imbalance
What are the medium term problems of LBW/FGR/Prematurity?
- Respiratory problems
- Developmental delay ( brain damage)
- Special needs schooling
How will premature babies with electrolyte imbalance appear?
Have thin porous skin, not fat
approx 34 weeks
Why would premature babies be jaundice?
Immature liver pathways
What is the long term problem with LBW/FGR/Prematurity?
Foetal programming
IHD, CHD, diabetes are more common due to compensatory pathways initiated due to poor growth
What are the differential diagnoses of smallness?
- Not small at all
- Normal small
- Abnormal small
- Starved small
What is the type of growth seen in abnormal small fetuses?
Symmetrical or asymmetrical
What is preeclampsia?
- Normal pregnancy: spiral arteries that reside in the endometrium open to form a funnel which allows trophoblasts to invade the maternal vascular system
- In preeclampsia, this doesn’t happen. The placenta is not perfused properly therefore the mother compensates by throwing blood down the arteries at higher and higher pressure. The mother therefore becomes increasingly ill whilst their is no growth in the foetus
What maternal medical factors are associated with FGR and SGA foetus?
- Chronic hypertension
- Connective tissue disease
- Severe chronic infection
- Diabetes mellitus
- Anaemia
- Uterine abnormalities
- Maternal malignancy
- Pre-ecamplsia
- Thrombophilic defects
What foetal factors are associated with FGR and SGA foetus?
- Multiple pregnancy
- Structural abnormality
- Chromosomal abnormalities
- Intrauterine (congenital) infection
- Inborn errors of metabolism
What maternal behavioural factors are associated with FGR and SGA foetus
- Smoking
- Low booking weight (35 years at delivery
- Alcohol
- Drugs
- High altitude
- Social deprivation
What placental factors are associated with FGR and the SGA foetus?
- Impaired trophoblast invasion
- Partial abruption or infarction
- Chorioamnionitis
- Placental cysts
- Placenta praevia
When is the period of placentation?
10-12 weeks
What are the functions of the placenta?
- Maintains immunological distance between mother and the foetus
- Special endocrine organ: produces protein-peptides and steroid hormones and functions as a ‘transient hypothalamo-pituitary-gonadal axis’
- Responsible for exchange of nutrients, gases and metabolic waste products between maternal and foetal circulation
What does preeclampsia result from?
A combination of impaired trophoblast differentiation and invasion during the first trimester.
Results in the failure of trophoblast cells to destroy the muscularis layer or the spiral arterioles which causes the development of a poorly perfused placenta
Where do spiral arteries sit in non-pregnant women?
Within the endometrium
What is seen in pre-eclampsia?
- Hypertension
- Oedema
- Proteinuria
What is the definition of pre-eclampsia?
Gestational hypertension of at least 140/90 mmHg on two separate occasions > 4 hours apart
- Significant proteinuria of at least 300 mg in a 24- hour collection of urine, arising de novo after the 20th week of gestation in a previously normotensive woman and resolving completely by the 6th postpartum week
What foetuses need growth monitoring?
Those with bad obstetric history
- Previous maternal hypertension
- Previous FGR
- Stillbirth
- Placental abruption
Those with concerns in index pregnancy as they arise
- Abnormal serum biochemistry
- Reduced symphysis fundal height
- Maternal systemic disease e.g. hypertension, renal, coagulation
Antepartum haemorrhage
Multiple pregnancy e.g. monochorionic twins
Why may foetal movement counting be of value?
A reduction in foetal movements may precede foetal death by a day or more
What is the most used method for foetal movement counting?
Cardiff kick method
What is needed for women who report a reduction or absence of foetal movements?
Cardiotocography
and/or ultrasounds assessment of the foetus to reassure the mother and ensure foetal wellbeing
What is the use of the Doppler ultrasound?
To determine the pattern of waveforms on the umbilical artery
Where is the ductus venosus?
- Longitudinal through upper abdomen
- Parallel, anterior to the right of the aorta
What is the purpose of the ductus venosus?
- Receives 40% of umbilical venous flow
- Direct oxygenated blood to the left ventricle
Which maternal risk factors may contribute to a foetus becoming growth restricted?
- Poor obstetric history
- Primips
- Obese
- Afro-Carribean/ African
- Strong family history
- Essential hypertension
- Diabetes/impaired glucose tolerance
- Systemic vascular disease
- Renal disease
- Thrombophilias
What should be administered at gestations
Corticosteroids
What does the mode of delivery depend upon?
- Gestation of the pregnancy
- Condition of the pregnancy
- State of the cervix
- Presentation of the foetus
- Other factors: oligohydramnios (labour may be poorly tolerated due to cord compression)
What stage is a blastocyte?
9 days
Approx 0.1cm
What stage is an embro?
5-6 weeks
Approx 1 cm
What stage is a foetus?
3 months
Approx 7cm
What is the concentration of oxygen in the first trimester?
3%
What occurs in the 3rd week of the first trimester?
- Formation of the trilaminar disc (mesoderm)
- CNS and somites
- Blood vessel initiation
- Initiated of placental villi (3mm)
What occurs in the 4th week of the first trimester?
- Closure of the neural tube
- Heart, face and arm initiated
- Umbilical cord
- Elaboration of placental villi (4mm)
What occurs in the 5th week of the first trimester?
- Face and limbs continue
5-8mm
What forms in the 6th week of the first trimester?
Face, ears, hands, feet, liver, bladder, gut, pancreas
10-14mm
What forms in the 7th week of the first trimester?
Face, ears, hands, fingers, toes
17-22mm
What forms in the 8th week of the first trimester?
Lungs, liver, kidneys
28-30mm
- Placental elaboration continues, development of villi
- Placental endocrinology becomes dominant