Pathologies of Pregnancy Flashcards
Describe the levels of oestrogen and progesterone in a normal menstual cycle
Oestrogen:
Rises up until day 14 of the cycle, which neg. feedbacks to FSH so that only one follicle survives. Decreases to Day 28 (other than another surge)
Progesterone:
Puts negative feedback on the HPG axis. This, together with inhibin (inhibits FSH) stalls the cycle in anticipation of fertilisation.
Without fertilisation, corpus luteum regresses and hormone levels fall, releasing neg feedback on HPG axis
What has happens to the hormonal cycle to allow fertilisation?
Progesterone keeps rising
What does progesterone do to the endometrium?
Progesterone turns endometrium into decidua
- Increases vascularity
- Between glands and vessels the stromal cells enlarge and become procoagulant ⇒ stops bleeding
What do the trophoblast cells (found on the outer edge of a chorion) produce?
B-hCG or Beta-human Chorionic Gonadotrophin
What is the action of Beta-human Chorionic Gonadotrophin (B-hCG)?
Targets the corpus luteum in the ovary
Function is to stimulate corpus luteum to produce progestogen, which stops decidua from shedding to maintain the pregnancy
How is B-hCG used clinically?
Pregnancy tests
What is the fate of the trophoblasts of the chorion and how does it occur?
Helps to form the placenta
- Fertilised egg burrows in to decidua
- Trophoblast cells stream off to invade mother’s blood vessels and (eventually) link these vessels up with those of the fetus
- Projections of chorion (chorionic villi), covered in trophoblast cells, start to move into the decidua
- Eventually the chorionic villi, covered by trophoblast cells, are bathed in the mother’s blood, forming the forerunner of the placenta
What are decidual stromal cells?
The decidual cells are procoagulant and help stop bleeding when the trophoblast cells invade mother’s blood vessels
Case 1:
- Woman, 26 yrs
- Misses period
- Pregnancy test positive
- Vaginal bleeding 7 weeks after missed period
- What has probably happened?
- US scan: No fetuspresent but membranes and decidua lining uterus still there = miscarriage
- Removal of remaining tissue by obstetrician
Follow up:
- No problems afterwards
- B-hCGreturns to normal (ie zero)
What are causes miscarriages?
Causes include: chromosomal abnormality, infection, and maternal issues (such as ill-health, trauma, hormonal problems)
Case 2:
- Woman, 32 years old
- Misses period.
- 8 weeks pregnant ⇒ Small amount of bleeding per vagina
Findings:
- BhCG raised
- Ultrasound: Thickened lining of endometrial cavity. Expanded fallopian tube on 1 side.
Diagnosis?
- Diagnosis = ectopic pregnancy
- Considered using methotrexate – but opted foroperative removal of fallopian tube àtissue sent to pathology
Follow up:
- •Woman well 1 week after operation
- •B-hCG returned to zero
Case 3:
- Woman 23 years
- Sudden severe abdominal pain. Collapses.
- Admission to A&E àPulse fast. BP low.
Findings:
- Blood given
- Emergency laparotomy
- At operation - several litres of blood in abdomen
- Blood flowing from fallopian tube area - clamped, removed and sent to pathology
- Microscopy = blood, fragments of fallopian tube and occasional chorionic villi (part of what will become the placenta and therefore tissue which confirms pregnancy)
Diagnosis?
Ruptured ectopic pregnancy
Follow up:
- B-hCGraised after operation, but returns to normal
- Woman is well 3 weeks later.
What is an ectopic pregnancy?
- Pregnancy in the wrong anatomical site
- Most common in fallopian tube
- Lack of proper decidual layer (stops trophoblast cells from causing bleeding when they invade mother’s BV) and small size of tube predispose to haemorrhage and rupture
- If it presents early woman may not even know she is pregnant
Case 4:
- 32 year old woman
- +ve pregnancy test
- 7 weeks pregnant – minor bleed
- Ultrasound: uterine cavity shows some placental tissue but no fetus. Fallopian tubes normal.
- B-hCG raised
Diagnosis?
Miscarriage
- Endometrial tissue removed by obstetrician and sent to pathology
- Microscopy = enlarged abnormal chorionic villi with abundant trophoblast
⇒ Molar pregnancy
What is a Molar pregnancy?
In normal conception, the fetus is formed from 23 maternal chromosomes and 23 paternal chromosomes. A molar pregnancy arises from an abnormality in chromosomal number during fertilisation.
- They have large choronic villi and overgrowth of trophoblast cells
- A form of precancerof trophoblast cells
How does normal fertilisation occur (to understand how molar pregnancies happen)?
In normal gonads of adults:
- Mum switched off certain gene in ova by methylating them (adding methyl groups) ⇒ promotes early baby growth
- Dad switched of different genes in sperm by methylating them ⇒ promotes early placenta growth via trophoblast proliferation
Overall effect is balanced growth of baby and placenta
How does molar pregnancies occur?
Various cases but often caused by two sperm fertilising one egg with no chromosomes
This results in imbalance in methylated (switched off) genes ⇒ too many of dad’s methylated genes causes the trophoblast cell proliferation
A problem because in the testis dad has inactivated several genes by adding methyl groups to stretches of DNA ⇒ massive overgrowth of trophoblast cells and therefore overgrowth of placenta ⇒ no or all but non-existent fetalgrowth
What can molar pregnancies potentially give rise to?
Can rarely give rise to a malignant tumour called choriocarcinoma, as it’s a form of precancer of trophoblast cells
What is the treatment for molar pregnancies?
- If BhCGreturns to normal – no further treatment.
- If BhCGstays high (persistent disease) ⇒ cure by methotrexate
