Placenta and inter-uterine growth restriction

Question 1

What is growth restriction associated with?

Answer 1

Stillbirth, perinatal morbidity, neonatal death

Question 2

What measurements are taken to determine if a baby is SGA (small for gestational age)?

Answer 2

Estimated fetal weight (EFW) or abdominal circumference (AC) of < 10th centile on the fetal growth scan

Question 3

What are the ultrasound measurements for growth?

Answer 3

Abdominal circumference (AC), head circumference (HC),
femur length (FL), liquor volume (LV), dopplers

Question 4

What are the 3 main groups of SGA foetuses and which groups result in symmetrical and asymmetrical IUGR?

Answer 4

1. “Normal” baby ie. constitutionally small - based on maternal size and ethnicity.
2. Non-placenta mediated growth restriction - e.g. structural or chromosomal problem, fetal infection, inborn errors of metabolism.
3. Placenta mediated growth restriction - eg. PET, hypertension, autoimmune disease, thrombophilias, renal disease, diabetes.
   Symmetrical IUGR - groups 1 and 2, HC, AC, FL all reduced
   Asymmetrical IUGR - group 3, AC reduced.

Question 5

What are some of the risk factors for IUGR?

Answer 5

Maternal age > 40yrs, nulliparity, low or high maternal BMI,
diabetes / renal disease, smoking, IVF, previous stillbirth,
low PAPP-A, hypertension/PET/recurrent APH.

Question 6

How is uterine size clinically measured?

Answer 6

Symphysis to fundal height (SFH)

Question 7

What occurs in symmetrical fetal growth restriction?

Answer 7

HC, BPD (biparietal diameter of head) and AC are all reduced

Question 8

What occurs in asymmetrical fetal growth restriction?

Answer 8

Only abdominal growth is reduced - reflects size of foetal liver

Question 9

What are the causes of foetal growth restriction?

Answer 9

Placental insufficiency – no excess glycogen being deposited within the liver

Question 10

What are the clinical features of IUGR?

Answer 10

SFH smaller than expected
Baby’s movements lessen to conserve energy
Fetal heart rate changes as hypoxia develops (as seen on CTG)
Fetal death

Question 11

How is an FGR baby monitored and managed?

Answer 11

Serial ultrasound evaluation of fetal growth, liquor volume and fetal doppler.
Timing delivery will depends on: gestational age, doppler studies, other risk factors.
Goal is to maximise fetal maturity and growth but minimise risks of perinatal mortality and morbidity.

Question 12

What are the effects of betamethasone / dexamethasone on the foetus?

Answer 12

When given to mother it will cross the placenta and stimulate alveoli cells to produce surfactant gene.
Surfactant stops collapse of alveoli cells.
Helps prevent respiratory distress syndrome which leads to neonatal death in premature babies.

Question 13

How is the placenta formed?

Answer 13

Syncytiotrophoblast invades endometrium.
Cytotrophoblast cells erodes maternal spiral arteries and veins.
Spaces (lacunae) between fill up with maternal blood.
Mesoderm develops into fetal vessels that aids transfer of nutrients and O2 across a simple cellular barrier.

Question 14

What goes wrong in pre-eclampsia?

Answer 14

Syncytiotrophoblasts unable to invade uterus

Question 15

What are the features of cytotrophoblast cells?

Answer 15

Undifferentiated stem cells
Invade maternal blood vessels and destroy epithelium
Gives rise to syncytiotrophoblast cells
Reduce in number as pregnancy advances

Question 16

What are the features of syncytiotrophoblast cells?

Answer 16

Fully differentiated cells
Direct contact with maternal blood
Produce placental hormones

Question 17

Which substances can get transferred across the placenta?

Answer 17

Oxygen and carbon dioxide by simple diffusion, water and electrolytes, steroid hormones, proteins poor – only by pinocytosis, transfer of maternal antibodies IgG starts later so lack of protection for premature infants

Question 18

Name parts of the decidua?

Answer 18

capsularis – overlying embryo and chorionic cavity
parietalis – side uterus not occupied by embryo
basalis – between uterine wall and chorionic villae

Question 19

What are the features of placenta praevia?

Answer 19

Massive bleeding in pregnancy, painless bleeding.

Fetal death, maternal death.

Question 20

What can failure of trophoblastic invasion into maternal circulation at 12 and 18 weeks lead to?

Answer 20

Poor maternal fetal mixing of blood
Lack of oxygen and nutrients to the fetus
Fetal growth restriction
Pre-eclampsia (raised blood pressure)

Question 21

What is placenta accreta and how is it treated?

Answer 21

Placenta unable to separate at birth – uterus can not contract down causing massive bleeding.
Hysterectomy.

Question 22

What is placental abruption and what can it lead to?

Answer 22

Massive bleeding in pregnancy (often concealed)
Extremely painful
Fetal death, maternal death