Normal pregnancy, labour and delivery Flashcards
How can mean sac diameter be used to assess failure of intrauterine gestation?
MSD > 25mm with no foetal pole
How can CRL be used to diagnose failure of intrauterine gestation?
Crown-rump length > 7mm with no heartbeat
How is the mean sac diameter calculated?
(length + height + width)/3
How is crown rump length calculated?
Length of the embryo or foetus from the top of its head to bottom of torso
What measurement provides the most accurate estimation of gestational age in early pregnancy and why?
Crown-rump length
There is little biological variability which affects this measurement in early pregnancy
What is a foetal pole?
First direct imaging manifestation of the foetus
Thickening of the yolk sac
When can the foetal pole first be visualised on US?
Transabdominal: 6.5 weeks
Transvaginal: 6 weeks
What normally happens to hCG levels in early pregnancy?
Doubles every 48-72 hours, peaking between weeks 8 and 11
What is the discriminatory zone?
The BhCG level above which an imaging scan should reliably visualize a gestational sac within the uterus in a normal intrauterine pregnancy
1500-1800 mIU/mL
Why is B-hCG as opposed to hCG measured in pregnancy?
hCG has a beta and alpha subunit
The beta subunit is unique to trophoblastic tissue
The alpha subunit is identical to that found in LH, FSH and TSH
At what bHCG should a foetus be visualised on TVUS?
1500
What is a normal birth weight?
2.4-4.6kg
What are the stages of labour?
- Contractions and cervical dilation
- Delivery of the foetus
- Delivery of the placenta
* Normally 24 hours*
What are each of these foetal positions?
What is effacement?
Cervical length
What is a station?
The relationship of the denominator of the presenting part to the ischial spines
What is this?
Caput
Reflects scalp oedema which can be present in normal and prolonged labour
What are 2 drugs that inhibit uterine contractions?
- Nifedipine
- Salbutamol
What is the most common type of twin?
Mono/dichorionic - mono/diamnioitc?
Monochorionic-diamniotic (70%)
Twins share a placenta and have individual amniotic sacs
Dizygotic twins always share the placenta and amniotic sac in which way?
Dichorionic-diamniotic
Each has an individual amniotic sac and placenta
How is due date calculated from last menstrual period?
40 weeks (280 days) from LMP
How does nifepipine work to delay labour?
Blocks Ca chennels → decreased intracellular Ca → myometrial relaxation
What is the effect of indomethacin on labour?
Delays labour by decreasing prostaglandin synthesis
How do prostaglandin analogues induce labour?
Loosen and ripen the cervix
What are the 3 p’s of labour that can cause issues?
Pelvis - size and shape
Passenger - size and position of baby
Power - strength and frequency of contractions
How is a due date calculated with Naegele’s rule?
- First day of LMP
- Add a year
- Subtract 3 months
- Add 7 days
What is a Bishop Score?
Method of assessing the readiness for induction of labour
Measures dilation, effacement, station, consistency and position
What is quickening?
Foetal movement
What causes a linea nigra?
Placenta produces melanocyte stimulating hormone
Occurs around 22 weeks
What is the most accurate means of determining the due date of a foetus?
First trimester ultrasound
Typically, how long is the 3rd stage of labour?
Delivery of the placenta - within 30 minutes of delivery of the child
If this does not occur within 30 minutes it is called “retained placenta” and the woman is at a higher risk of PPH and infection
What are the active and latent phases of the first stage of labour?
Latent: irregular contractions, dilatation < 4-6cm
Active: regular contractions, dilatation of at least 4-6cm
What are the active and passive stages of the second stage of labour?
Passive: full cervical dilatation without the urge to push
Active: full cervical dilatation of baby visible with involuntary expulsive contractions
What are 3 ways by which the cervix can be ripened to induce labour
- Stretch and sweep
- Prostaglandins
- Balloon catheter
How is a stretch and sweep performed?
Move your index finger into the cervix and use a circular motion to try separate the membranes of the amniotic sac from the cervix
Releases prostaglandins which promote cervical ripening
Which drug is used to induce contractions?
Syntocinon
What are the signs of placental separation in the 3rd stage of labour?
- Gush of blood
- Lengthening of the umbilical cord
- Upwards movement of the uterine fundus
What are Alvarez waves?
Low intensity, high frequency physiological contractions in the second half of pregnancy
What are false labour contractions?
Uncoordinated uterine contractions 3-4 weeks before birth
Contractions do not increase in frequency, intensity or duration
Helps to position the foetus
What are prelabour contractions?
Irregular, high-intensity contractions which occur ever 5-10 minutes
Position the foetal head in the pelvis
Do not cause cervical dilation
What is cervical funnelling?
Dilation of the internal cervical os and reduction of the cervical length
Significant funnelling is associated with preterm delivery
Why is nitrous oxide (N2O) given during labour?
Mild anaesthetic and anxiolytic
What information is obtained from the second trimester ultrasound?
- Structural abnormalities
- Gender
What is the value of a third trimester ultrasound?
Not necessary
Used for assessing complicated pregnancies e.g. foetal size, twins, abnormal positions
What is being visualised here?
Foetal pole and yolk sac
Why is intubating pregnancy women more difficult?
Progesterone: dilates smooth muscle
BUT
Oestrogen: tissue oedema and hyperplasia of mucus glands
Why does ESR increase in pregnancy?
ESR rises with increased proteins
Pregnancy → increased gammaglobulins
Immunity becomes increasingly humoral rather than cell-mediated
Why does blood pH increase in pregnancy?
Increased respiration → respiratory alkalosis
- Low CO2 increases the foetal/maternal gradient* → easier for foetal CO2 to enter maternal circulation and be expired
- Bicarbonate excretion increases*
Why do pregnant women become constipated?
Increased progesterone → smooth muscle relaxation → poor colonic motility
What is puerperium?
The period of adjustment after childbirth during which the mother’s reproductive system returns to its normal prepregnant state. It generally lasts six to eight weeks and ends with the first ovulation and the return of normal menstruation.
What is meconium?
Thick, black-green material formed from bile salts, gastric secretions, mucous, vernix, lanugo, blood, pancreatic enzymes, free fatty acids and squamous cells
What is the significance of meconium-stained liquor?
May suggest foetal hypoxia (more likely to be significant in a preterm foetus)
20% of newborns have MSAF at term
What are 5 obstetric risks of maternal smoking?
- Spontaneous miscarriage
- Preterm birth
- Placenta previa
- Placenta abruption
- Stillbirth
- Ectopic pregnancy
- PPROM
What are 5 risks of maternal smoking to the grown child and adult?
- SIDS
- T2DM
- Obesity
- HTN
- Nicotine dependence
- Respiratory disease (asthma, LRTI)
- Decreased cognitive performance
- Behavioural (conduct disorder, ADHD, antisocial behaviour)
- Increased risk of mental illness
What haemoglobin concentration to do you aim to maintain in pregnancy?
0-20 weeks: 110 mg/dL
>20 weeks: 105 mg/dL
Minimum
What serum iron level do we want pregnancy women to have?
> 15
> 30 if not pregnant
When is pre-conceptional 5mg of folic acid daily recommended? (as opposed to 0.5mg)
Anticonvulsant use
Pre-existing DM
Family history of NTD or a child with NTD
What are the indications for an early GTT?
18 weeks
Normal: 26-28
Previous GDM
Maternal age > 40
Asian, Indian, ATSI, African ethnicity
BMI > 30
Previous macrosomia
PCOS
Corticosteroid or antipsychotic medication
First degree relative with diabetes
What is the normal frequency of antenatal clinic appointments?
0-28/40: every 4 weeks
28-36/40: every 2 weeks
36/40-delivery: weekly
When might bleeding from implantation occur?
10-14 days from fertilisation (at time of missed period)
In order of when they appear, what are the first features that can be visualised on US in a pregnancy?
Gestational sac → yolk sac → embryo
When is cardiac activity first visualised on US?
7 weeks
How long following implantation do hCG levels become detectable?
6-12 days
What is this dermatological condition?
Melasma
Common in pregnancy
What are the three factors (3 P’s) that determine the progress through labour?
Passages Passenger Power
What about the contractions during labour do we monitor?
Strength
Frequency
Duration
What are the side effects of an epidural when used to control pain in labour?
Transient hypotension
Risk of dural tap
Increased length of second stage because of reduced pelvic floor tone and loss of bearing down reflex
What is a physiological 3rd stage of labour?
They do not receive any oxytocic drugs, the attendant waits for the umbilical cord to stop pulsating before cutting it and delivery of the placenta occurs passively.
How can we treat cervical incompetence or insufficiency?
Cervical cerclage can be performed. This is the insertion of a suture into the cervix to reduce the prolapsed membrane.
How should preterm babies be delivered? Vaginal or caesarean?
There is no evidence to suggest that caesarian section is any safer than vaginal birth in preterm babies.
What is the principal issue with preterm prelabour rupture of the membrane?
Sepsis of both the mother and the fetus.
How long after preterm prelabour rupture of membrane will a women normally go into labour?
Within 72 hours
What are the potential side effects of NSAIDs such as indomethacin when used as tocolytics?
Mother: Heartburn, nausea
Fetus: premature closure of ductus arteriosus, reduced renal function causing oligohydramnios
How often should women with gestational diabetes be checking their blood sugars?
Daily fasting (best in the morning) 2 hours after every meal
What should the target blood glucose levels be in GDM?
Fasting: less than 5.6mmol/L
1 hour after meals: less than 7.8mmol/L
2 hours after meals: less than 6.4mmol/L
Are the following low or high in trisomy 21?
Alpha fetoprotein
Oestriol
hCG
PAPP-A
Alpha fetoprotein - low
Oestriol - low
hCG - high
PAPP-A - low
Which LFT may be physiologically elevated in pregnancy?
ALP
Released by the placenta
What do you need to know to calculate a Bishop score?
- Dilation
- Effacement
- Station
- Consistency
- Position of the cervix
What is the definition of a postdates delivery?
42+0
What is the false positive rate of the first-trimester combined screening test?
5%
What is the sensitivity and specificity of the NIPT test?
Close to 99% for both
Slightly lower for Edwards and Patau
Should not be used for final diagnosis as it is not 100% accurate
When is the gestatial sac first visible on TVUS?
5 weeks
Foetal pole at 6 weeks
Why are pregnancy women advised to avoid soft cheeses, deli meats and pates?
They may be sources of Listeria monocytogenes
Pregnant women are particularly susceptible
May cause foetal death, premature birth or newborn infections
What corticosteroids readily cross the placenta?
Betamethasone
Dexamethasone
What is involved in active management of the 3rd stage of labour?
Oxytocin 10U IM/IV with delivery of the anterior shoulder
What are the most common adverse effects of syntocinon?
Nausea and vomiting
On what day is the blastocyst formed?
Day 5
From when in pregnancy can be NIPT be used?
10 weeks
What is being visualised and how far along is this pregnancy?
Gestational sac
4 weeks
What is being visualised and how far along is this pregnancy?
Yolk sac
5 weeks
What is the function of the yolk sac?
Provides nutrition to the foetus until the placenta takes over
What is being visualised and how far along is this pregnancy?
Foetal pole
6 weeks
What is being visualised and how far along is this pregnancy?
Foetal limb buds
8 weeks
What is involved in active management of the third stage of labour?
- Oxytocin 10U IM/IV
- Controlled cord traction once the uterus is well contracted and the placenta separated
What are the risks and benefits of delayed cord clamping?
Preterm
- Reduced risk of transfusion, infection, NEC and IVH
Term
- Reduced iron deficiency (may be beneficial if low maternal iron)
- Risk of PCV and jaundice
What is the difference between ergometrine and syntocinon?
Syntocinon - wave contractions
Ergometrine - one big contraction
Grand multiparity is an indepedent risk factor for which obstetric complications?
Placental previa
Placental abruption
What is the definition of grand multiparity?
5 or more births (> 20 weeks)
What are Category A drugs in pregnancy?
Drugs which have been taken by a large number of pregnant women and women of childbearing age without any proven increase in the frequency of malformations or other direct or indirect harmful effects on the fetus having been observed
What are Category B1/2/3 drugs in pregnancy?
Drugs have only been taken my a limited number of pregnancy women
No evidence of malformation of harmful effects in the foetus
B1 - no evidence of damage in animal studies
B2 - limited studies in animals, but no evidence of damage
B3 - evidence of damage in animal studies with uncertain significance in humans
What are Category C drugs in pregnancy?
Have caused or are suspected of causing harmful effects without malformation
Effects may be reversible
What are Category D drugs in pregnancy?
Drugs have cause or are suspected to have caused foetal malformations or irreversible damage
May also have adverse pharmacological effects
Which conditions are associated with an increased nuchal translucency?
Down syndrome
Congenital heart defects
Abdominal wall defects
Which conditions are associated with hyperechogenic bowel?
Cystic fibrosis
Down syndrome
CMV infection
What is the definition of increased nuchal translucency? (mm)
> 3.5 mm
A PAPP-A below what level is a poor prognostic sign?
< 0.4 MoM
Suggests poor placentation - SGA, IUGR, foetal demise, preterm birth, pre-eclampsia
