OB-GYN Revision 8

Question 2

What defines a fetus as being SGA, VSGA and LBW? [3]
How do you measure this? [2]

Answer 2

Small for gestational age
- is defined as a fetus that measures below the 10th centile for their gestational age.

VSGA:
- < 3rd centile

LBW:
- < 2500g

Assessed using:
* Estimated fetal weight (EFW)
* Fetal abdominal circumference (AC)

Question 3

What are the two main causes of SGA? [2]

Answer 3

Constitutionally small, matching the mother and others in the family, and growing appropriately on the growth chart

Fetal growth restriction (FGR), also known as intrauterine growth restriction (IUGR)

Question 4

The causes of fetal growth restriction can be divided into two categories.

What are they? [2]

Answer 4

Placenta mediated growth restriction

Non-placenta mediated growth restriction, where the baby is small due to a genetic or structural abnormality

Question 5

What are 4 causes of non-placental mediated growth restriction? [4]

Answer 5

Non-placenta medicated growth restriction refers to pathology of the fetus, such as:
* Genetic abnormalities
* Structural abnormalities
* Fetal infection
* Errors of metabolism

Question 6

What are causes of placental mediated growth restriction? [+]

Answer 6

Placenta mediated growth restriction refers to conditions that affect the transfer of nutrients across the placenta:
* Idiopathic
* Pre-eclampsia
* Maternal smoking
* Maternal alcohol
* Anaemia
* Malnutrition
* Infection
* Maternal health conditions

Question 7

Short term complications of fetal growth restriction include: [4]

Answer 7

Fetal death or stillbirth
Birth asphyxia
Neonatal hypothermia
Neonatal hypoglycaemia

Question 8

How do you monitor for SGA? [2]

Answer 8

RCOG green-top guidelines on SGA (2013) lists major and minor risk factors. At the booking clinic, women are assessed for risk factors for SGA.

Low risk women:
- monitoring of the symphysis fundal height (SFH) at every appointment from 24 weeks. If < 10th centile - booked for serial growth scans with umbilical artery doppler

Question 9

Women are booked for serial growth scans with umbilical artery doppler if they have [3]

Answer 9

Three or more minor risk factors
One or more major risk factors
Issues with measuring the symphysis fundal height (e.g. large fibroids or BMI > 35)

Question 10

How do you monitor SGA for those who are deemed high risk? [3]

Answer 10

Estimated fetal weight (EFW) and abdominal circumference (AC) to determine the growth velocity

Umbilical arterial pulsatility index (UA-PI) to measure flow through the umbilical artery

Amniotic fluid volume

Question 11

Babies are defined as being large for gestational age (also known as macrosomia) when the weight of the newborn is more than [] kg at birth.

Answer 11

Babies are defined as being large for gestational age (also known as macrosomia) when the weight of the newborn is more than 4.5kg at birth.

Question 12

What are the risks to baby if they are LGA? [4]

Answer 12

The risks to the baby include:
* Birth injury (Erbs palsy, clavicular fracture, fetal distress and hypoxia)
* Neonatal hypoglycaemia
* Obesity in childhood and later life
* Type 2 diabetes in adulthood

Question 13

When a baby is LGA - why do you perform US? [1]

Answer 13

Ultrasound to exclude polyhydramnios and estimate the fetal weight

Question 14

Women are routinely screened for anaemia twice during pregnancy.

When are these screenings? [2]

Answer 14

Booking clinic
28 weeks gestation

Question 15

Label A-C [3]

Answer 15

A - > 110 g/l

B: > 105 g/l

C: > 100 g/l

Question 16

Women with a haemoglobinopathy will be managed jointly with a specialist haematologist.

They require high dose [drug, dose] close monitoring and transfusions when required.

Answer 16

Women with a haemoglobinopathy will be managed jointly with a specialist haematologist. They require high dose folic acid (5mg), close monitoring and transfusions when required.

Question 17

Name two risks of IDA post-partum [2]

Answer 17

↑ post-partum depression
↑ risk of PPH: 60% if Hb < 8 5

Question 18

Lecture:

How do determine if the baby is small because the placenta is not formed properly? [3]

Answer 18

Check history and consider all risk factors for placental dysfunction
+
measure serum PAPP-A at 11-14 weeks: if < 0.4 placenta may not have formed properly
+
Doppler studies

Question 19

Name 5 risk factors for baby being small because placenta hasn’t formed properly [5]

Answer 19

Question 20

Describe the different dopplers you can do to determine if baby is small

Answer 20

Fetal investigations:
- Umbilical artery Dopplers
(UAD)

Maternal investigations:
- Uterine artery dopplers

Risk of fetal demise:
- ductus venosus

Fetal oxygenation:
- MCA

Question 21

Describe the fetal response to hypoxia [3]

Answer 21

• Reduced PO 2
• Reduced glucose supply
• Reduced amino acid supply

Question 22

Describe the the process of hypoxia causing stillbirth [4]

Describe how this would be detected on dopplers [4]

Answer 22

Hypoxia –> acidemia –> CNS damage –> stillbirth:

• Placental dysfunction would be indicated by abnormal uterine artery dopplers (UtA)
• Leads to abnormal umbilical artery
• Leads to brain sparing effect - causing an abnormal MCA Doppler
• Leads to reduced cardiac compliance and abnormal venous doppler
• Leads to fetal movements reduced and abnormal cCTG.
• Leads to still birth

Question 23

Lecture

Difference between LGA and macrosomia? [1]

Answer 23

LGA= EFW>90th centile or EFW>4000g

Macrosomia= EFW>4.500g

Question 24

Lecture

Name a genetic syndrome which might cause LGA/macrosomia [1]
What is the triad seen with it? [3]

Answer 24

Beckwith Wiedemann – macroglossia, exomphalos, organomegaly

NB: comes up a couple of times in lecture

Question 25

Name two maternal factors that might cause LGA/macrosomia? [2]

Answer 25

GENETIC / SOCIAL
* Parental height
* Malnutrition
* High BMI
* Maternal
depression

Question 26

The typical presentation of placental abruption is with: [6]

Answer 26

• Sudden onset severe abdominal pain that is continuous
• Uterine contractions may cause additional pain
• Vaginal bleeding (antepartum haemorrhage) - DURING 2ND HALF OF PREGNANCY. Painful, dark-red, non-clotting and usually non recurrent vaginal bleeding
• Shock (hypotension and tachycardia)
• Abnormalities on the CTG indicating fetal distress
• Characteristic “woody” abdomen on palpation, suggesting a large haemorrhage

NB: The amount of vaginal bleeding can vary greatly, and doesn’t necessarily indicate how much of the placenta has separated from the uterus.

Question 27

Name some key risk factors for placental abruption [+]

Answer 27

• Previous abruption (8-10x) * Cocaine / amphetamines
• Cigarette smoking (2x)
• HTN (3x)/ PET(2x)
• Fetal growth restriction
• Bleeding in the first trimester (1.5x)
• Thrombophilia
• Advanced maternal age
• Multiparity
• Low BMI
• IVF
• Intrauterine infection * PPROM
• Multiple pregnancy
• Trauma
• Rapid uterine decompression

Question 28

Describe the difference between revealed and concealed placental abruptions

Answer 28

Question 29

Describe how you manage placental abruption

Answer 29

Placental abruption is an obstetric emergency:
* Urgent involvement of a senior obstetrician, midwife and anaesthetist
* 2 x grey cannula
* Bloods include FBC, UE, LFT and coagulation studies
* Crossmatch 4 units of blood
* Fluid and blood resuscitation as required
* CTG monitoring of the fetus
* Close monitoring of the mother
* Active management of stage 3 labour
* Corticosteroids for baby between 24th and 34th weeks of getation

NB: It is important to consider concealed haemorrhage, where the vaginal bleeding may be disproportionate to the uterine bleeding.

Question 30

How do you decide whether to deliver baby if has placental abruption? [4]

Answer 30

Women with antepartum haemorrhage and associated maternal and/or fetal compromise are required to be delivered immediately.

While RCOG does not recommend premature delivery of fetus in women with less than 37 weeks of gestation with no fetal and maternal compromise.

If gestational age is equal to or more than 37 weeks and the bleeding presents as spotting or mucus streaks of blood, active intervention is unlikely needed.

Minor or major antepartum bleeding, RCOG suggests inducing labour with the aim of achieving vaginal delivery to avoid serious complications related to placental abruption

Question 31

Abnormal vaginal bleeding during the second half of pregnancy is usually due to either [2].

It is important to differentiate these two conditions.

Answer 31

Placental abruption:
- placenta partially or completely detaches itself from the uterine wall before delivery.
- Haemorrhage may be visible or concealed
- abdominal pain are intense and acute
- Fetal hearts sounds are absent or may show distress

placenta praevia:
- the placenta is located over or near the cervix, in the lower part of the uterus
- haemorrhage external and visible with placenta praevia
- less abdominal pain
- fetal heart sounds normal

Question 32

Describe the pathophysiology of placenta praevia [+]

Answer 32

• abnormal trophoblastic invasion of the endometrium. Normally, implantation occurs within the upper uterine segment, where a rich blood supply supports fetal development.
• Instead, as gestation progresses and lower uterine segment elongates and thins during third trimester - leads to: vascular disruption can cause bleeding as maternal vessels are torn away from the anchoring points; ineffective haemostasis; cervical effacement and dilatation
• Anatomically, placenta praevia impedes normal labour progression by obstructing the birth canal

Question 33

What are the 4 classifications of placenta praevia [4]

Answer 33

Grade 1
- also known as a low lying placenta
- The placenta is in the lower uterine segment
- The lower edge of the placenta is 0.5-2cm from the internal cervical os

Grade 2
- also known as marginal praevia
- The lower edge of the placenta reaches the internal cervical os
- The placenta extents to the margin of the os but does not cover it

Grade 3
- also known as partial praevia
- The placenta partially covers the internal cervical os

Grade 4
- also known as complete praevia
- The placenta completely covers the internal cervical os

NB: The RCOG guidelines (2018) recommend against using this grading system, as it is considered outdated. The two descriptions used are low-lying placenta and placenta praevia.

Question 34

What are the clinical features of placenta praevia? [+]

Answer 34

Often identified before symptoms develop during a routine ultrasound appointment.

Main symptoms:
- Painless vaginal bleeding from 30+ weeks
- uterus is not typically painful, unless in labour

Question 35

What is the definitive dx of placenta praevia? [1]

Answer 35

ultrasonography at 20 week routine anamoly scan

Question 36

What is the difference in timelines with regards PV bleeding with placenta praevia c.f miscarriage? [1]

Answer 36

Miscarriage is more common in the 1st and 2nd trimesters - placenta praevia often causes symptoms in the 3rd trimester

Question 37

How do you manage placenta praevia?

Answer 37

Diagnosed early in pregnancy (e.g. at the 20-week anomaly scan):
- Repeat scan at 32. If still present..
- Repeat at 36 weeks gestation

Corticosteroids are given between 34 and 35 + 6 weeks gestation to mature the fetal lungs, given the risk of preterm delivery.

Planned delivery is considered between 36 and 37 weeks gestation. It is planned early to reduce the risk of spontaneous labour and bleeding
- Planned cesarean section is required with placenta praevia and low-lying placenta (< 20mm from the internal os).

Question 38

What advice do you give to patients who have placental praevia during the pregnancy [3]

Answer 38

Recommend pelvic rest:
* No penetrative intercourse
* No vaginal douching
* Avoid vaginal examination unless completely necessary

Question 39

Describe the differences between placental praevia and abruption between the following:

• Bleeding
• Painful
• Abdominal pain
• General conditions
• Height and feel of uterus
• DIC
• Fetal distress

Answer 39

Question 40

Define vasa praevia [1]

What are the two types? [2]

Answer 40

Fetal vessels coursing through the membranes over the internal cervical orifice and below the fetal presenting part, unprotected by placental tissue or the umbilical cord.
- The fetal vessels consist of the two umbilical arteries and single umbilical vein.

Type 1 (A): Velamentous cord insertion in single or bilobed placenta.

Type 2 (B): Fetal vessels running between accessory lobes.

NB: Vasa translates from Latin as vessel. Praevia translates from Latin as “going before”. Vasa praevia is where the vessels are placed over internal cervical os, before the fetus.

Question 41

Describe the pathophysiology of vasa praevia (describe normal vs abnormal formations)

Answer 41

Normally:
- umbilical cord containing the fetal vessels (umbilical arteries and vein) inserts directly into the central portion of the placenta.
- The fetal vessels are always protected, either by the umbilical cord or by the placenta.
- The umbilical cord contains Wharton’s jelly. Wharton’s jelly is a layer of soft connective tissue that surrounds the blood vessels in the umbilical cord, offering protection.

Vasa praevia:
- Eccentric or marginal insertion of the umbilical cord. Get either:
- Velamentous cord insertion: umbilical cord inserts into the chorioamniotic membranes rather than centrally into the placental mass. The blood vessels branch out from this point and travel within these membranes before reaching their connection with the placenta. OR
- Bilobed or succenturiate-lobed placentas: variations in placental morphology where there’s more than one lobe to a placenta. If a blood vessel connects two lobes across fetal membranes that traverse overlying cervical os, it can lead to vasa praevia.

Question 42

Further subclassification of vasa praevia can be made based on clinical presentation:

What are they? [2]

Answer 42

Ramified Vasa Praevia:
- Also known as branching vasa praevia, it involves multiple small-calibre vessels crossing over the internal os.

Funic Presentation Vasa Praevia:
- Characterised by a single large vessel running over or near the internal os, often associated with a funic presentation of umbilical cord.

Question 43

Describe the clinical features of vasa praevia [5]

Answer 43

Painless PV Bleeding:
- Most common
- Often sudden and can be heavy

Abnormal Fetal Heart Rate Patterns:
- Due to compromise in fetal blood supply
- Most commonly bradycardia

Rupture of membranes:
- The membrane rupture exposes the unprotected vessels causing them to tear and bleed.

Fetal Anemia
- In cases where there has been chronic slow leakage from the vasa praevia, fetal anemia may occur due to gradual loss of fetal blood.

Fetal Distress or Death:
- If not promptly diagnosed and managed, vasa praevia can lead to severe fetal distress due to hypoxemia and even intrauterine death.

Question 44

Describe the management of suspect vasa praevia [3] and emergency vasa praevia [2]

Answer 44

Suspected vasa praevia: hospital admission between 28-32w, antenatal steroids, elective CS between 35-37w

Undiagnosed vasa praevia: emergency cat 1 CS and aggressive fetal resuscitation

Question 45

How do you differentiate vasa praevia from premature rupture of membranes? [1]

Answer 45

While both conditions can lead to membrane rupture, vasa praevia is associated with blood-stained amniotic fluid and significant changes in fetal heart rate patterns following rupture.

In contrast, PROM typically presents with clear amniotic fluid and does not directly cause changes in fetal heart rate unless it leads to complications such as cord prolapse or chorioamnionitis.

Question 46

How would you differentiate the following with regards to their abdominal pain presentation and associate symptoms

• Labour
• Pre-eclampsia
• Uterine rupture
• Placental abruption

Answer 46

Labour:
- Contraction pain
- W SROM or mucous plug

Pre-eclampsia
- epigastric or RUQ pain
- W HTN, proteinuria, headaches, swelling, blurred vision

Uterine rupture:
- Constant pain; profound shock
- W fetal distress, PV bleeding

Placental abruption:
- Sudden onset severe pain; rock hard uterus
- W fetal distress

Question 47

How would you differentiate the following with regards to their abdominal pain presentation and associate symptoms

• PID
• Endometriosis
• Ectopic pregnancy
• Ovarian Cancer
• Fibroids

Answer 47

PID:
- Acute pelvic pain
- W heavy vaginal disease; bleeding

Endometriosis:
- Mild - severe - debilitating pain
- Pain ++ during menstruation
- W bloating, worsened during bladder / bowel movement & sex

Ectopic pregnancy
- One sided abdomen pain - impulsive and sharp stabbing
- W +ve pregnancy test; previous Hx of STIs

Ovarian Cancer:
- Abdominal pain / discomfort
- W WL; bloating; (sometimes SOB / haemoptysis)

Fibroids
- Constant, severe lower abdomen pain
- W menorrhagia and dysmennorrhea

Question 48

What are blood gas results like in normal pregnancy? [3]

Answer 48

Breathe deeper, but not faster during pregnancy

Blood gas results:
* blow off more CO2 - should be lower
* breathe in more O2 - should be higher

Creates a respiratory alkalosis - which becomes a compensated metabolic acidosis

Question 49

What questions can you ask to determine if a patient is suffering from physiological breathlessness? [1]

Answer 49

Ask if it’s worse when walking or talking
- If worse when talking then might indicate physiological breathlessness

Question 50

Describe what causes physiologically caused dysopnea and how often it occurs [2]

Answer 50

60-70% of pregnant women

Unsure mechanism
- likely related to progesterone induced hyperventilation

Question 51

A pregnant patient presents with breathlessness. What questions would you ask to help determine the cause?

Answer 51

New onset?
- Help to distinguish if previous pathology that is exascerbated or a new pathology
- New problem - think PE; peripartum cardiomyopathy
- Older problem - think asthma
- If observations normal and associated with no other symptoms - think physiological dyspnea of pregnancy

Question 52

A pregnant patient presents with breathlessness and a swollen leg. What are key differentials?

What are key differentials?

Answer 52

If not above knee and presents with no other symptoms / signs
- think physiological dyspnea of pregnancy

If unilateral leg swelling
- Think VTE

If bilateral & hypertension (w/ proteinuira)
- Think pre-eclampsia - also ask about headache and visual changes
-

Question 53

What is key to note about the dx of PE in pregnancy? [1]

Answer 53

D-dimer accuracy is poor so can’t send
- If CXR normal - do a V/Q
- If CXR abnormal - do a CTPA

Question 54

Describe the risk of radiation from a V/Q or CTPA for baby and mother

Answer 54

For baby, risk of radiation is below level or harm

For mother - pregnant breast is at increased sensitivty to radiation, so more concerned about future risk of breast cancer