Week 9 - Fetal Growth and Development Flashcards
State what tests can be done to monitor fetal growth and development.
- Ultrasound
- Doppler ultrasound
- Non-stress tests - monitors heart rate changes associated with fetal movements
- Biophysical profile - which includes 5 variables to be measured
- Vibroaccoustic stimulation - again monitoring fetal heart rate change
- Contraction stress test
- Fetal movements kick chart
What accounts for most of the weight gain in the later stages of the fetal period?
After week 28, most of the weight gain is due to fetal adipose tissue deposition in subcutaneous and abdominal stores
What is symmetrical growth restriction?
In which growth restriction is generalized and proportional
What is asymmetrical growth restriction?
In which abdominal growth lags, and there is relative sparing of head growth
When does asymmetrical growth restriction tend to occur?
In the last part of pregnancy when maternal, fetal or uteroplacental factors cause some deprivation of nutritional and oxygen supply to the fetus
List some factors that have an impact on fetal growth.
- Maternal nutrition and health
- Efficiency of placenta
- Adequate utero-placental blood flow
- Genetic factors
- Maternal parity - primaparous mothers have smaller babies than multiparous mothers
- Maternal habits - e.g. smoking, drug abuse, etc
- Also race, maternal height, maternal weight
How may uteroplacental or fetoplacental circulations be assessed?
Doppler ultrasound
What can compromise uteroplacental circulation?
- Hypertension
2. Blood clots
Why is 20 weeks a good time in pregnancy to have an ultrasound scan?
- At this stage of pregnancy, the organ systems are developed and can be visualised and anomalies can be identified
- If anomalies are seen, the pregnancy is still early enough for possible intervention or termination if appropriate
- The inherent error in these measurements increases with gestational age such that as a dating tool, ultrasound becomes less accurate as the pregnancy proceeds
State the errors of ultrasound in the first, second and third trimesters respectively.
1st trimester: +/- 1 week
2nd trimester: +/- 2 weeks
3rd trimester: +/- 3 weeks
State some uses of ultrasound in obstetrics.
- Determine the presence/absence of intrauterine pregnancy (or ectopic pregnancy)
- Determine gestational age and measure fetal growth when compared against standard tables
State some parameters that can be used to monitor fetal growth.
- Abdominal circumference
- Biparietal diameter
- Crown-rump length
- Femur length
- Head circumference
- Estimate fetal weight
- Identify multiple pregnancies
- Detect fetal anomalies (e.g. neural tube defects) or placental anomalies (e.g. placenta praevia)
- Measurement of amniotic fluid
- Identify maternal pelvic anomalies
- Guide for needle in amniocentesis
Why are folic acid supplements recommended for pregnant women?
Reduce the risk of neural tube defects
When are routine blood tests of alpha-fetoprotein done?
Between 15-19 weeks of gestation when levels are at their highest
What can raised alpha-fetoprotein levels indicate?
- Open neural tube defect
2. Multiple pregnancies
How early can the fetal heart beat be observed with transvaginal ultrasound?
As early as 5-6 weeks
When can you hear the fetal heart beat with a Doppler stethoscope?
10-12 weeks
When can you hear the fetal heart beat with a plain stethoscope?
18-20 weeks
What is the average fetal heart rate at term?
140-160 beats per minute
At what stage are fetal respiratory movements evident by sonography?
From about 12 weeks, fetal respiratory movements seen by sonographic evaluation
At what gestational age does surfactant production begin?
Surfactant production begins at 20 weeks, but increases dramatically after 30 weeks, reaching significant levels at about 34 weeks
What can be done antenatally to reduce risk of respiratory distress syndrome in premature infants?
Steroid therapy can be given to women ante-natally who are at risk of pre-term delivery: reduces the risk of RDS by 50% by promoting production of surfactant
What fetal landmark is used to assess fetal head position in the birth canal?
Fetal fontanelles
If an epidural is used for pain relief, what spinal segments are blocked?
T9-S4
Why is the patient with an epidural at risk of hypotension?
Lumbar sympathetic outflow blockade prevents vasoconstriction
Define post-partum haemorrhage.
Blood loss of greater than 500 ml after vaginal delivery
What physiological mechanism exists to prevent PPH?
Strong contractions after the 3rd stage of labour contract the uterus down, achieving closure of the “living ligature” - the unusual criss-cross arrangement of myometrial fibres, clamping the arterial supply to the placental bed in the endometrium
If the uterus is firm on palpation with continuous bleeding, what other cause should you consider?
- Laceration/trauma to the genital tract
2. Retained placenta
