Some Common Pathologies of Pregnancy

Question 1

discuss how the decidua changes during a normal cycle

Answer 1

Oestrogen and progesterone are the hormones produced by the ovary. If fertilisation occurs progesterone continues to rise. Progesterone causes thickening of the endometrial lining turning it into decidua. Compared to the endometrium, decidua has increased vascularity and between the glands and vessels the stromal cells enlarge and become procoagulant. This stops bleeding.

Question 2

discuss the role of bHCG in preventing the decidua shedding

Answer 2

The egg is called a chorion. Trophoblast cells can be found on the outside of the fertilised egg. Trophoblasts produce B-hCG (beta human chorionic gonadotrophin). The target of B-hCG is the corpus luteum to stimulate production of progesterone which stops the decidua from shedding. This hormone forms the basis of pregnancy tests. Throughout pregnancy b-hCG stimulates the ovary to produce progesterone therefore preventing the decidua from shedding.

Question 3

discuss the early development of the placenta

Answer 3

Fertilised eggs burrow into the decidua. Trophoblast cells stream off to invade mother’s blood vessels and eventually link these vessels up with those of the foetus. Decidual stromal cells are found between the vessels. Projections of chorion (chorionic villi), covered in trophoblast cells, start to move into the decidua. The decidual cells are procoagulant and help stop bleeding when the trophoblast cells invade the mother’s blood vessels. Eventually the chorionic villi, covered in trophoblast cells, are bathed in the mother’s blood, forming the forerunner of the placenta.

Question 4

discuss the process and the effect of methylating genes in ova and testis

Answer 4

In a normal ovary certain genes in the ova are switched off by methylating them. In a normal testes different genes in the sperm are switched off by methylating them. Mum’s changes promote early baby growth whilst dad’s promote early placental growth via trophoblast proliferation. The overall effect is balanced growth of the baby and placenta.

Question 5

discuss the formation of a molar pregnancy

Answer 5

There are various causes of molar pregnancy but the most common results from 2 sperm fertilising an ova with no chromosomes. Whilst there is the correct total number of chromosomes there is no genes promoting early baby growth. This results in trophoblast overgrowth. No foetal growth occurs. A molar pregnancy is a form of precancer of trophoblast cells. If it persists it can (rarely) give rise to a malignant tumour known as choriocarcinoma. If B-hCG returns to normal there is no need for further treatment. If, however, it stays high (persistent disease) cure by using methotrexate.

Question 6

how does diabetes in pregnancy result in large babies?

Answer 6

Glucose from the mother passes the placenta and raises the babies blood glucose. As a result, insulin goes up in the baby. Baby cannot reduce its glucose as mum keeps sending more across the placenta. Insulin does not cross. Long-term high insulin and high glucose leads to massive growth. Diabetics are susceptible to intrauterine death. Normally at around 33 weeks the baby stops growing to prepare for the hypoxic insult that will occur at birth.

Question 7

what can diabetes in pregnancy cause?

Answer 7

1. Malformations – mermaid babies are almost always born to diabetic mothers
2. Huge babies that obstruct labour
3. Intrauterine death (probable sudden metabolic and hypoxic problems)
4. Neonatal hypoglycaemia

Question 8

why is cocaine extremely dangerous in pregnancy?

Answer 8

one dose can cause placental abruption, miscarriage and malformation
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