Lecture 1: Pregnancy and Labour Flashcards
What care is Obstetrics involved in
Care during pregnancy concerning conception, fetal growth and development and management of maternal conditions exacerbated by pregnancy
Care during birth: timing and managing birth stress for neonate
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What are the time frames for the 3 stages of labour
1: From onset of regular contractions to the cervix being fully dilated
2: From fully dilated to delivery of the baby
3. From delivery of baby to delivery of the placenta
Describe the intrauterine factors that influence growth and development of the fetus
Adequate nutrition via the placental circulation,
Describe the structure of the placental circulation
Placental circulation is where oxygen and nutrients diffuse over and actively transported across from maternal blood that bathes mesh of fetal blood vessels intertwined with umbilical cord
In what cases is the fetus not recieving adequate nutrition to enable them to achieve their genetic potential
- Increased nutrition (diabetic mother= excess glucose)
- Reduced nutrition (utero-placental failure)
What factors affect how we determine genetic growth potential
Maternal age, parity, BMI, ethnicity and fetal sex.
Chromosomal abnormalities reduce fetal growth potential
In what cases is the fetus not receiving adequate nutrition to enable them to achieve their genetic potential
- Increased nutrition (diabetic mother= excess glucose)
- Reduced nutrition (utero-placental failure)
What factors affect how we determine genetic growth potential
Maternal age, parity=number of babies over 20 weeks, BMI, ethnicity and fetal sex.
Chromosomal abnormalities reduce fetal growth potential
What does Utero-placental failure cause?
Reduced placental perfusion means reduced nutrients and oxygen to fetus
so Fetus conserves energy by restricting growth (abdominal) but brain sparing
What are growth restricted fetuses at risk of
Preterm, still birth and neonatal death
What are growth restricted fetuses at risk of
Preterm, still birth and neonatal death
What are the main environmental causes of growth restriction in fetuses
- Drugs (smoking, alcohol and medications)
- Infections (toxoplasmosis, rubella etc)
Define IUGR, Small for gestational age (SGA) and large for gestational age (LGA)
IUGR: interuterine growth restriction - fetus unable to achieve their growth potential
SGA= (<10th percentile)
LGA= (>90th percentile)
Are birth weights related to gestation time? What is low, v low and extremely low birthweight compared to macrosomic birthweight. Why is this measure used
Birth weight is not related to gestation period and is used because these babies have bigger risk for neonatal complications. Lbw: <2500 g vlbw:<1500 g Elbw:<1000 g Macrosomic: >4kg
What are the challenges with determining if a baby has IUGR and what tool can be used to help this
Depending on the genetically determined growth potential a SGA baby may not have IUGR and a normal baby may have IUGR if it was determined to be a LGA baby. Using a customisable growth chart based on maternal characteristics, the placement of the percentiles can be more accurate for what is expected
What happens in the first stage of labour
The fundus of uterine muscle contracts, pushing the fetus down onto the cervix causing cervical change to dilate to 10 cm
What is the dangerous part of first stage of labour that requires monitoring of the fetal heartbeat. Which babies are more susceptible ?
During contraction placental blood flow reduces, for up to 90 secs- leading to relative hypoxia.
Growth restricted/ pre term babies are more susceptible to fetal distress & hypoxia.
What happens in the second stage of labour and what needs to watched out for
Baby can have passive descent with epidural but for majority its active pushing out.
Fetus needs to more closely monitored as oxygen requirements increase in the 2nd stage
What are alternatives to normal vaginal birth and in what circumstances are these
Assisted vaginal birth using forceps or ventouse (suction cap) that pulls guides the head out.
Only performed if concerns with fetal wellbeing or maternal exhaustion as can be associated with maternal and fetal trauma
What happens in the 3rd stage of labour and what is the risk associated at this stage
Uterus muscles contract to mechanically obstruct maternal placental vessels and the placenta separates. Risk is post partum haemorrhage where uterus doesn’t contract well and >500 ml of blood loss 24hrs after delivery. Can lead to postpartum anaemia - reduced breast milk production, poor bonding and post natal depression
What are the risks of caesarean section
Elective CS prediposes the newborn to respiratory complications (wet lungs) because the lung fluid isn’t being squeezed out by contractions and can lead to 6 week maternal recovery
What are the main changes in ‘Transition’ (fetus going to baby) for gas exchange, ventilation, etc
Gas exchange goes from placenta to pulmonary with ventilation gaseous instead of liquid.
Instead of relying on the sterile uterine environment it must regulate its own body temp, glucose homeostasis and nutrition.
Compare the changes in respiratory system that occur before and at birth
Before birth the lungs stop secreting lung fluid in late pregnancy and labour squeezes lung fluid out, increasing its absorption via lymphatics.
At birth the baby’s first cry changes pulmonary dynamics, breathing is stimulated through tactile and thermal stimulation and the umbilical cord is delayed clamped
What happens when the umbilical cord is clamped
The low resistance placental circulation is removed and there is an increase in systemic blood pressure
Why is the first breath/cry so important
- helps to establish Residual volume and therefore functional residual volume vital for maintaining lung expansion
Describe the path of oxygenated blood getting to the brain in the fetus
- oxygenated blood (80% sat) enters fetus from placenta via the umbilical vein
- This joins the fetal circulation via the Ductus Venosus into the inferior vena cava.
- mixed with partially deoxy blood, it enters the RAtrium where it is diverted by Crista dividens through the Foramen Ovale to the LAtrium
- And this sends the most oxygenated blood to the brain
Describe the path of deoxy blood returning from the upper body
- Deoxy blood from upper body returns to RAtrium via superior vena cava where it goes to the main pulmonary artery
- 87% of blood ejected from RV is diverted through the Ductus arteriosus to descending Aorta
- Blood returns to the placenta via two umbilical arteries which attach to the common illiac arteries
Which ventricle pumps the lower 2/3 of the body and upper 1/3 of body.
Right pumps lower. Left pumps higher
What is the difference before and after birth the output of RV to the lungs
Before birth only 13% because of high blood pressure in the lungs but after birth 100%
What is the difference at birth and after birth the blood pressure between of right and left side of heart
At birth blood pressure is similar in each ventricle so shouldn’t hear murmurs
After birth left ventricle higher pressure than right
What things close in fetal circulation after birth
Ductus arteriosus functionally and then structurally closes. Foremen ovale and ductus venosus closes too
What are the possible conditions for failure of transition for respiratory, cardiovascular, metabolic, thermoregulatory, GI and Renal.urinary systems- seem in pre term babies
pulmonary hypertension, patent ductus arteriosus: too much blood in the lungs , hypoglycaemia, hypothermia, failure to thrive and hyperkalaemia
More babies you have…
the bigger they get
