Physiology of Pregnancy and Development Flashcards
What is the duration of human pregnancy?
The duration of human pregnancy lasts:
280 days (40 weeks) from last menstrual period
or
266 days (38 weeks) from fertilisation
If for some reason these moments in time cannot be recalled or identified; estimations of foetal age can be made by ultrasound measurements of the foetus
What are the physical signs of pregnancy?
Cessation on menstruation
Morning sickness
Increased frequency of urination
Increased size of breasts
Fatigue
Darkening of areolae around the nipple
What biochemical marker signifies pregnancy is occuring?
Human chorionic gonadotropin (hCG)
It is present in the mother’s blood and urine
Maternal blood vessels bathe chorionic villi that form a single umbilical vein (oxygenated) and two umbilical arteries (deoxygenated)
This means there is no continuous circulation between mother and child – protects foetus from maternal vasoconstriction (e.g exercise)
Trophectaderm cells invade maternal endoderm and break down maternal blood vessels to form blood lakes for the blood to bathe.
HbF has a much higher oxygen affinity than Hb + in higher concentration means oxygen is transferred from mother to foetus
Describe the endocrine functions of the placenta in pregnancy
During pregnancy, the placenta becomes an endocrine organ secreting a number of factors that regulate the pregnancy period:
Human Chorionic Gonadotropin (hCG)
- Rescue’s and maintains the corpus luteum in early stages of pregnancy
- Is the basis of pregnancy tests
Human placental lactogen (hPL)
- Breast development and metabolic effects
Estrogen and Pregesterone
- Maintenance of pregnancy and breast development
- Responsible for the majority of pregnancy adaptations
Others
- Causing specific pregnancy adaptations
What is the difference between monozygotic and dizygotic twins?
**Monozygotic **
Occurs when a single fertilised ovum splits and become two blastocysts
Both blastocysts implant together in the same placental sac
The twins are genetically identical and of the same sex
**Dizygotic **
2 oocytes are released in the one menstrual cycle and are fertilised by two seperate sperm
How is partuition/labour induced and regulated?
Rhythmic uterine contractions are initiated to commence labour
Once initiated; oxytocin sustains the contraction via positive feedback
This is accompanied by the softening and dilation of the cervix in the lead up to delivery
What happen to the placenta following delivery of the baby?
The placenta is ejected through the cervical canal - following the baby out and attached to the umbilical cord
What processes are involved in the development of mammary glands over the course of a women’s reproductive life?
Puberty
Estrogen stimulates growth of ducts and fat deposition
Pregnancy
Estrogen, growth hormone and cortisol stimulate further gland development
Late Pregnancy
Progesterone stimulates the conversion of ducts into secretory epithelium
What processes are involved in regulating lactation?
Prior to birth
Prolactin-inhibiting hormone (PIH) blocks prolactin and high sex steroid levels prevent suppress milk production
After birth
High prolactin and low estrogen levels results in lactation
Breast milk provides neonate with nutrients and immunity
Suckling
Suckling inhibits PIH and Prolactin stimulates milk production
Oxytocin stimulates milk ejection
Prolactin and oxytocin levels inhibit GnRH and ovarian cycle
What are three complications of human pregnancy?
(The three covered in MD1)
Preterm Labour
Pre-Eclampsia
Intrauterine Growth Restriction
Other complications include:
Bleeding, anaemia, coagulation, maternal diseases, heart and renal disease, diabetes, convulsions, breech, intrauterine foetal death
Characterise Preterm Labour
Pre-term labour is defined as labour beofre 37 weeks gestation
It occurs in 5-8% of all deliveries
It is associated with an 80% peri-mortality rate
It is unknown why pre-term labours occur…
but it is associated with infections, premature rupture of membranes, multiple pregnancies and polyhydromnios (excess amniotic fluid)
Characterise pre-eclampsia
Pre-eclampsia is a condition of high maternal blood pressure and is the most common serious disorder of pregnancy
It causes placental dysfunction and intrauterine growth restriction to the developing foetus.
In the mother, it manifests as proteinuria and generalised oedema
Mild pre-eclampsia = 2-10% of pregnancies ; Severe pre-eclampsia = 1-2% of pregnancies
15% maternal mortality / 10% perinatal mortality
Occurs as a result of unknown aetiology
Treatment is induced delivery irrespective of the stage of pregnancy ; maternal life preserved at the cost of the child
Characterise IUGR
** Low birth weight (<2500g)**
- 2% of term babies
Small-for-gestational age (IUGR)
- <2SD below population mean
- 10% of babies
- Placental insufficiency**
- Predisposition to adult diseases**
- Incidence and Mortality**
- 2-10% of babies
- 2-3 times normal perinatal mortality
Causes of IUGR:
- Uteroplacental insufficiency
- Western Society
- Maternal undernutrition
- Third World
- Dutch Famine 1944/45 - trimester specific effects
- Maternal disease
- Genetic
What factors contribute to regulating growth?
Genetics
- About 15% of size of birth is dependent on genotype - a further 2% depends on sex
Growth Hormones
- Growth of foetus is not particularly GH dependent (IGF, Thyroid + insulin) - although glucocorticoids inhibit
Environmental / Maternal factors
- everything you can think of relating to environmental of maternal environment affects the developing foetus
What are the critical periods of human development?
What are the observed outcomes of IUGR in the animal model
The rat uteroplacental insufficiency model demonstrated:
- Sex specific deficits and differences in F1 offspring
- Deficits could be rescued through trans-fostering (for weaning) and exercise
- Pregnancy in F1 female rats revelaed greater dysfunction - would have further consequences for the foetus as F2 generation
Illustrate a summary of the mechanism by which IUGR causes organ deficits
