Fetal Growth and Development (and RFM) Flashcards
On what day of the menstrual cycle does fertilisation usually occur?
What happens then?
How are these days counted?
- Fertilization happens day 14 (around the day of ovulation)
- The zygote then divides into more cells (cleavage)
- When there are 16 cells its called a MORULA
- Continues to divide> BLASTOCYST
- The blastocyst will then implant (after further 9 days)-day 23 of menstual cycle
days from last menstrual period (LMP)
Where does the blastocyst implant and what changes occur then?
- Blastocyst implants 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 do levels of B-hCG change in the first weeks of pregnancy?
When can you test for B-hcg levels?
- B-hcg is produced when the blastocyst implants in the decidua
- levels rise for the first 10 weeks of pregnancy and then plateau
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?
INTRINSIC FACTORS (genetic) Maternal -Maternal weight and height -Parity (more babies = bigger) -Ethnic group Fetal -Fetal sex (M slightly bigger) -Fetal genes -Multiple pregnancy
What are some extrinsic factors that affect fetal growth?
EXTRINSIC FACTORS Maternal -Nutrition -Drugs, smoking and alcohol -Social class -Altitude -Pregnancy related disease -Pre-existing disease (cardiovascular, renal, resp, vascular) -TORCH infections (toxoplasmosis, rubella, cytomegalovirus, herpes, HIV) -Others: toxoplasma, listeria, syphilis
Maternal: poor trophoblast infiltration, pre-eclampsia
How do we assess a woman for proper fetal growth and development?
HISTORY
- PMH: any medical conditions?
- POH: small babies before?
- SH: smoking? alcohol?
EXAMINATION
- General assessment
- Symphysis-Fundal height (no. of cm should be approx the same at weeks of gestation +/-2cm)
INVESTIGATIONS
Additional scans
1. How are they growing? look for: HC, AC, FL, BPD and liquor volume
- How are they coping? Biophysical profile (BPP) look for:
- fetal breathing
- fetal movements (mum record, should start feeling 18-20 weeks)
- fetal tone
- amniotic fluid volume (good idea of how placenta and baby is - remember amniotic fluid is baby urine) - How are they being fed? look at placenta.
- doppler studies to asses placental artery blood flow
- Particularly useful in IUGR
When are we able to palpate the uterus and how quickly does it grow? (when does it reach umbilicus and xiphisternum)
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
What do dopplers tell us?
Explain a normal doppler of umbilical artery (2)
-Dopplers tell us resistance index and pulsatility index
Normal umbilical artery doppler
-forward blood flow during systole and diastole
-End diastolic flow should 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)
What happens within the first 12 weeks?
What happens after 12 weeks?
Before 12 weeks ○ Organs develop ○ Placenta assumes major role - gas exchange, nutrient, waste transfer, steroidogenesis ○ Highest risk of miscarriage After 12 weeks ○Growth and maturation
When do women start feeling foetal movements and how will they change over the pregnancy?
At 18-20 weeks (?earlier if multip) will increase up to around 32 weeks and then plateau
What can influence a woman’s ability to interpret fetal movements?
Women who are busy and on their feet will often not notice them and then will become concerned
Anterior placentas can affect a woman’s ability to feel fetal movements before 28 weeks
What drugs can lead to reduced fetal movements?
Alcohol, BZDs and opioids
What could some causes of RFM be?
Fetal death
Drugs and alcohol
IUGR (extreme starvation, poor oxygen supply, placental hypertrophy, cardiac disease)
Poor trophoblastic infiltration
SGA
Placental insufficiency e.g. pre-eclampsia, smoking
