Fetal Growth and Development Flashcards
On what day of the menstrual cycle does fertilisation usually occur?
How many days after this does it take a fertilised ovum to implant? What stage is the ovum at now?
Day 14 (around the day of ovulation)
Takes a further 9 days for the egg to implant by which time it is at the BLASTOCYST stage (4-16 cells)
Where does the blastocyst implant and what changes occur then?
In the decidua layer of the endometrium. Maternal blood vessels in the endometrium start growing towards it to establish links
When it implants it begins releasing hCG which stimulates ovary to produce progesterone which keeps the corpus luteum alive
After 10-12 weeks the placenta will take over production of progesterone
How to levels of B-hCG change in the first weeks of pregnancy?
Produced when the blastocyst implants in the decidua they rise for the first 10 weeks of pregnancy and then plateau
Before 3-4 weeks levels aren’t high enough to be detected and so no point doing test before then
What is the role of progesterone?
This is the MAIN HORMONE in the beginning of pregnancy. It starts causing changes in the mother:
- CARDIOVASCULAR: increase circulating volume and and increases CO (Increased SV and HR). BP drops as SVR goes down
- RESP RATE: increases as increased IAP causes diaphragmatic splinting
- UTERINE QUIESCENCE - progesterone prevents the normal uterine contractions that cause shedding of endometrial layer every month during menstruation
- IMMUNE SYSTEM - progesterone dampens immune system to tolerate fetus. There is a relative lymphopenia and the T cell count drops
- GI - bowel motility is decreased
What are some intrinsic factors that influence fetal growth?
Maternal weight and height Parity (more babies = bigger) Ethnic group Fetal sex (M slightly bigger) Fetal genes Multiple pregnancy
What are some extrinsic factors that affect fetal growth?
Nutrition
Drugs, smoking and alcohol
Social class
Pre-existing disease (cardiovascular, renal, resp)
TORCH infections (toxoplasmosis, rubella, cytomegalovirus, herpes, HIV)
PLACENTAL: poor trophoblast infiltration, pre-eclampsia
How do we assess a woman for proper fetal growth and development?
Full history and examination (has she got any factors such as chronic diseases or social factors that might be influencing fetal growth and development)
Symphysis-Fundal height (no. of cm should be approx the same at weeks of gestation +/-2cm)
FETAL MOVEMENTS - really important - should start feeling at 18-20 weeks and should increase up to 32 weeks
SCANS (as well as dating and anomaly scan can offer extras) look for: HC, AC, FL, BPD and liquor volume
When are we able to palpate the uterus and how quickly does it grow?
We should be able to palpate uterus by 12 weeks and it should have reached the umbilicus by 20-24 weeks.
Reaches the xiphisternum by approaching 36 week
If the baby is small what are the two options for the cause?
IUGR babies (concerning - not reaching their growth potential)
Constitutionally small babies (not concerning, reaching milestones but just small)
SEE SMALL FOR DATES PACK FOR MORE
If we are worried the baby isn’t growing properly what extra measurements can we make to assess risk?
Fetal breathing movements (towards term babies will start expanding their chests to work the muscles needed for breathing)
Fetal movements - ask mother to record
Fetal tone - if the baby looks flaccid on the scan it might be very low on energy
Amniotic fluid volume - good idea of how placenta and baby is - remember amniotic fluid is baby urine
What other specific measurement can we make to assess how well the placenta is perfusing the baby?
Umbilical artery doppler
EDFis particularly important - should always be positive. If it is approaching 0 or is negative then this is very bad sign that baby is not receiving enough placental blood - delivery might be needed
Pulsatility index gives idea of flow and resistance index of resistance
