Common pathologies in pregnancy

Question 1

Basic anatomy

Answer 1

Question 2

What lies above the fundus of the uterus?

Answer 2

The fundus of the uterus has a periotenal layer on its upper surface and above this is the bowel which moves out of the way as the baby starts to grow during pregnancy. The bowel can be displaced whilst the liver and stomach are not affected.

Question 3

2 main functions of the Myometrium

Answer 3

Squeezing out the baby - induces uterine contractions

Menstruation - contractions in a fundal-to-cervical direction.

Question 4

What are the main functions of the cervix?

Answer 4

• It facilitates the passage of sperm into the uterine cavity. This is achieved via dilation of the external and internal os.
• Maintains sterility of the upper female reproductive tract. The cervix, and all structures superior to it, are sterile. This ultimately protects the uterine cavity and the upper genital tract by preventing bacteria from entering. This environment is maintained by the frequent shedding of the endometrium, thick cervical mucus and a narrow external os.

Question 5

What is a normal weight for a baby at full term?

Answer 5

3.3 kg around 7.3 pounds

Question 6

Which hormone levels keep rising if a women becomes pregnant?

Answer 6

Progesterone and oestrogen

Question 7

What does progesterone do to the endometrial lining?

Answer 7

It thickens it by changing the cells within.

Question 8

What does progesterone convert endometrial cells into? and what happens as a result?

Answer 8

Decidual cells

• Increase vascularity
• Creates a modified mucosal lining of the uterus (that is, modified endometrium) in preparation for pregnancy.
• Decidual cells lie between glands and vessels. They are procoagulant and so they stop bleeding

Question 9

Which cells cover the outside of a fertilised egg?

Answer 9

Trophoblast cells - these only exist during pregnancy

Question 10

Which hormone do Trophoblasts produce?

Answer 10

Beta-hCG or or Beta-human Chorionic Gonadotrophin

Question 11

What does B-hCG act on?

Answer 11

• The corpus luteum in the ovary (a mass of cells that forms in an ovary - produces progestogen during early pregnancy).
• The trophoblasts stimulate the follicle in the ovary to become corpus luteum and to produce progestogen which stops decidua from shedding i.e stops the endometrium from shedding at the end of a cycle

Question 12

Which hormone is detected in pregnancy tests?

Answer 12

B-hCG

Question 13

Discuss what happens after the fertilised egg implants in the decidua?

Answer 13

• It burrows in between blood vessels.
• Trophoblast cells stream off the egg and invade the mother’s blood vessels and (eventually) link these vessels up with those of the foetus
• The decidual cells act as a spongy medium for the cells to invade through and they are procoagulant so they help stop bleeding when the trophoblast cells invade mother’s blood vessels
• Projections of chorion (chorionic villi), covered in trophoblast cells, start to move into the decidua (between the blood vessels)
• Eventually the chorionic villi, covered by trophoblast cells, are bathed in the mother’s blood, forming the forerunner of the placenta

Question 15

General causes of miscarriage (5)

Answer 15

• Unknown - very common
• Foetal problem e.g chromosomal abnormality
• Placenta/membranes/cord problem e.g infection
• Uterus/cervix problem e.g cervical incompetence
• Maternal health issues e.g drug taking, diabetes etc

Question 16

CASE STUDY

• 32 y/o F. Misses period. 8 weeks pregnant + has small amount of bleeding per vagina. B-hCG is raised.
• US scan: Thickened lining of the endometrial cavity. Expanded fallopian tube on 1 side.

What is the diagnosis?

Answer 16

Ectopic pregnancy

Clue = expanded fallopian tube on one side

Question 17

CASE STUDY

• 23 y/o F. Sudden severe abdominal pain. Collapses
• Admission to A&E with fast pulse and low BP - the most dangerous combination
• Blood given. Emergency laparotomy found several litres of blood in the abdomen.
• Blood flowing from fallopian tube area.

What has happened?

Answer 17

Ruptured ectopic pregnancy - fragmented fallopian tube

Question 18

CASE STUDY

• 32 y/o F. Positive pregnancy test. 7 weeks pregnant - minor bleed.
• US scan: uterine cavity shows some placental tissue but no foetus. Fallopian tubes normal.
• B-hCG raised in circulation and urine

What is the diagnosis?

Answer 18

Incomplete Miscarriage - tissue/placenta have not been expelled

Question 19

Why is there a lot of bleeding within the fallopian tube in an ectopic pregnancy?

Answer 19

There is no decidual cell layer in the fallopian tube to help stop bleeding

Question 20

What is a molar pregnancy?

Answer 20

• It is a form of pre-cancer of trophoblast cells - if it persists (rarely) it can give rise to a malignant tumour called choriocarcinoma. However, a molar pregnancy will not be able to survive.
• There’s a problem with the fertilised egg, which means a baby and a placenta do not develop the way they should after conception.
• Overgrowth of trophoblast cells and large chorionic villi.

Question 21

What causes a molar pregnancy?

Answer 21

• Normally the mother to be (pre-pregnancy) switches off certain genes in her ova by methylating them.
• The father to be also switches off different genes in his sperm by methylating them
• The mother’s changes promote early baby growth and the father’s promote early placental growth via trophoblast proliferaton
• Overall effect is balanced growth of baby and placenta
• When both of them do this it means that the sperm and the egg fertilise correctly (23 chromosomes each)

In a Molar pregnancy 2 sperm fertilise an empty egg (no chromosomes within). This results in an imbalance in methylated (switched off) genes and results in trophoblast overgrowth and so overgrowth of placenta. So the baby doesn’t grow well and often disappears or miscarries within 2-3 weeks

Question 22

How is molar pregnancy treated?

Answer 22

• If BhCG returns to normal – no further treatment.
• If BhCG stays high (persistent disease) = cure by methotrexate

Question 23

CASE STUDY

• 28 y/o F. Poorly controlled DM
• Pregnancy doing well until 36 weeks (40 weeks = full term)
• Baby stops kicking 36 weeks
• US scan: No foetal heart movement

What has happened?

Answer 23

Intrauterine death (IUD)

Baby is born but it is a stillbirth

Question 24

A mother with poorly controlled DM gives birth to a huge baby with broad shoulders ‘diabetic cherub’. What is the physiology behind this?

Answer 24

• Effects of too much glucose in mother.
• Glucose crosses the placenta and raises baby’s blood glucose
• As a result of the raised glucose, the baby produces insulin from its pancreas (it is not diabetic so it can do this)
• The baby cannot reduce its glucose however as the mother keeps sending more through the placenta into the baby
• So then the baby has raised glucose and insulin
• Longterm high insulin and high glucose => massive growth + more susceptible to IUD
• Normally towards the end of pregnancy a baby’s growth is meant to tail off but in this case it doesn’t

Question 25

What are the problems caused by poorly controlled diabetes in pregnancy?

Answer 25

• 1st trimester: Malformations
• 3rd trimester: Intrauterine death (probable sudden metabolic and hypoxic problems)
• Labour: Huge babies that obstruct labour - shoulder dystocia
• Neonatal period: hypoglycaemia

Question 26

What is acute chorioamnionitis?

Answer 26

• Acute inflammation = neutrophils present in membranes (chorioamnionitis), cord, and fetal plate of placenta
• Caused by ascending infection - bacteria are typically perineal or perianal flora (eg E.coli) which ascend vagina and get into the amniotic sac
• Mother may present ill with fever and raised neutrophil count or she may be well

Question 27

How does chorioamnionitis infection present in the baby?

Answer 27

• IUD
• Ill in first few days of life and put into neonatal unit
• Cerebral palsy later on in life

Question 28

Do opiates cross the placenta?

Answer 28

Yes

• Pregnancy often proceeds well if mother eating properly
• Immediate withdrawal from heroin when baby is born
• Later withdrawal from methadone

Question 29

What are opioids?

Answer 29

Opioids are a broad group of pain-relieving drugs that work by interacting with opioid receptors in your cells.

E.g morphine, fentanyl, heroin and methadone

Question 30

Why is methadone commonly prescribed to drug addicts?

Answer 30

Heroin has short half life – quickly get the high but then get dreadful low

The aim is for them to take methadone as a substitute as it has a long half life so it stays in their system for days/weeks. This would prevent the severe withdrawal symptoms you get from heroin.

Concerns = many just take methadone as a background drug and continue to take other drugs

Question 31

Overtwisted cord

Answer 31

Common cause of intrauterine death and neonatal illness

Probably caused by normal, active, baby moving and twisting round it’s own cord

Question 32

CASE STUDY

33 y/o F. Hypertension during pregnancy. Vaginal bleed at 35 weeks.

US scan: Separation of part of the placenta from uterus with collection of blood (a haematoma) behind placenta. Haematoma enlarging during ultrasound.

What has happened and what next?

Answer 32

• An abruption has happened meaning there is a separation of the placenta from the uterine wall.
• Often results in hypoxia in the baby - as O2 supply from mother is reduced.
• Emergency C-section is required
• Baby is unwell in neonatal unit for 5 days then much better.

Question 33

What are some causes of abruption? (separation of placenta and uterus)

Answer 33

• Hypertension
• Trauma
• Other i.e Cocaine