O&G Flashcards

1
Q

Cancer screening:
- cervical
- breast
-bowel
-targeted lung

A

Cervical: every 3 years (25-49yo), every 5years (50-64yo)

Breast: every 3 years(50-70yo)

Bowel: one off flexisig 55yo, home kit (FIT test) every 2 years (60-74yo in England).

Targeted lung: low dose CT scan offered to 55-74yo at high risk of cancer & reinvited every 2 years

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How do you test if someone has ovarian failure as a cause of secondary amenorrhoea?

A

FSH>=20IU/l

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Emergency contraception ?options
(UPSI - unprotected sexual intercourse)

A

FIRST LINE - Copper IUD: use 5days post UPSI or within 5days of expected ovulation. Directly toxic to sperm, reduce sperm numbers that reach uterus, damage embryo before implant, interfere with implantation.

Levonorgestrel: progesterone only pill. Used within 3days of UPSI. Inhibit ovulation.

Ullipristal acetate: selective progesterone receptor modulator. Use 5days UPSI. Inhibit/delay ovulation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Causes of post coital bleeding

A

Cervical ectropion (most common)
Vaginits
Vaginal cancer
cervical cancer (most malignant cause)
Cervicitis
Cervical polyps
Trauma

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Types of miscarriage: threatened, complete, incomplete, missed, inevitable

A

Threatened: minimal pain, less bleeding compared to menstruation, closed cervix, fetal heart visualised

Complete: no pain, less bleeding compared to menstruation, closing cervix, empty uss

Incomplete: pain +/-, a lot more bleeding compared to menstruation, open cervix, retained products/no fetal heart

Missed: no pain, minimal bleeding, closed cervix, small uterine size, no fetal heart

Inevitable: pain +, more bleeding compared to menstruation, open cervix, fetal heart may/may not be visualised

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Normal physiological changes of blood test when comparing pregnancy and pre-pregnancy state

A

Hb drops
Haematocrit drops
WBC increase
Platelet count drops
Urea and creat drops
GFR increases
Albumin, ALT, AST drops - dilutional effect
ALP rise due to placental production

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Cause of chancroid

A

Haemophilia ducreyi
-painful genital ulcer
- tender inguinal lymphadenopathy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Cause of chancre

A

Treponema pallidum (syphilis)
- small painless ulcer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Cause of strawberry cervix

A

Trichomonas vaginalis
- frothy greenish discharge with fishy odour
- tx: metronidazole

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Cause of lymphogranuloma venereum

A

Chlamydia trachomatis
- painless genital ulcer
- painful lymphadenopathy ‘buboes’ or abscess

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Risk factor for endometrial cancer

A

Obesity
Nulliparity
Late menopause
Fhx
Tamoxifen
HRT
Pelvic irradiation
Diabetes
Pcos

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Red degeneration of fibroid

A

Degeneration of myoma
Uss shows mixed echodense or echolucent appearance
Tx: supportive - analgesia, rehydration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How to check cervical ripeness?

A

PEDSS
Position
Effacement
Dilation
Softness/consistency
Station of foetus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Risk factor of hyperemesis gravidarum

A

Nulliparity
Fhx
Personal history
Multiple pregnancy
Female foetus
Age<30yo
Trophoblastic disease
Maternal obesity
Non smoker

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Smoking in pregnancy - what are the features?

A

Miscarriage 2x risk
Preterm labour
Lighter for date babies
Reduced reading ability up to 11yo
Reduced ovulation
Abnormal sperm production

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Definition of preterm, term and postterm delivery

A

<37 week
37-42 week
>42 week

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Asthenozoospermia
Oligospermia
Azoospermia
Hypospermia
Teratospermia

A

Asthenozoospermia: reduced sperm motility
Oligospermia: low sperm count
Azoospermia: no sperm in ejaculate
Hypospermia: reduced semen volume
Teratospermia: poor sperm morphology

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Iron supplement - what are the indication during pregnancy

A

Hb<100
MCV<84

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What and when to check that one is ovulating?

A

Progesterone
Mid-luteal phase (ie one week before period - IE day 21 out of 28day cycle or day 28 out of 35day cycle)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Tx of menorrhagia

A

Mirena 1st line
Trenaxamic acid
Nsaids - only take during menstruation
Cocp
Norethisterone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Mechanism of action of:
COCP
MIRENA
POP (emergency)

A

Cocp- prevent ovulation via HPO axis

POP (except desogestrel)- increase volume and viscosity of cervical mucus, endometrial changes, reduction in cilia activity

POP (desogestrel): suppress ovulation, also thickens cervical mucus

Mirena- changes to cervical mucus, endometrial changes (atrophy)

Copper coil - toxic to ovum and sperm, anti-implantation effect

Pop (emergency)- delays ovulation, prevent follicular rupture and causes luteal dysfunctuon

Ullipristal (emergency) - delays ovulation for at least 5 days

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Difference between lentigo and malasma

A

Lentigo - flat brown lesions which do not darken in sun exposure

Malasma aka chloasma - macules and larger patches that is brought on by pregnancy or sun exposure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Test for downs

A

Combined testing - mum’s age, nuchal translucency, HCG, Papp

If greater than 1:200, offered either chorionic villus sampling (<13 weeks) or amniocentesis (>15 weeks gestation)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

When & whom do you give anti -d

A

Rhesus negative mothers
28 & 34 weeks

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Definition of:
Dysmenorrhagia - primary Vs secondary
Menorrhagia - metrorrhagia, menometrorrhagia, dub

A

Primary dys - cramping pain due to menstruation (NO pelvic pathology)
Secondary dys - menstrual related pain due to another medical or physical condition such as endometriosis/fibroids

Metrorrhagia - breakthrough bleeding either between periods or not related to periods

Menometrorrhagia - heavy and prolonged bleeding that occurs in irregular intervals

Dub - excessive bleeding due to hormonal problems usually lack of ovulation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Placental abruption
Placenta praevia
Vasa praevia

A

Premature separation of placenta from uterus.

Praevia - implantation of placenta over the internal cervical os.

Vasa - foetal vessels running close to internal cervical os.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Cocp and cancer

HRT and cancer

A

COCP: Protective for endometrial, ovarian and colorectal cancer. Can increase risk of breast and cervical cancer.

HRT: Increase risk for breast and endometrial cancer.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Tx options of endometriosis

A

COCP (for those who wanted contraception) or NSAIDs (for those who didn’t want contraception)

Danazol (once tried COCP/POP/NSAIDs but no response)

Oral or depot medroxyprogesterone acetate

Levonorgestrel IUS

GnRH analogues (before surgical procedure)

Laparoscopic ablation (most effective method)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Fibroadenoma Vs lipoma Vs breast cancer in signs

A

Fibroadenoma - small, smooth, rubbery, firm, mobile. breast mice. Found in 20-30yo

Lipoma - small, mobile, palpable, painless. Found in 40-60yo.

Cancer- dimpling

Fat necrosis - similar to cancer. Only a biopsy can differentiate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Catamenial epilepsy

A

Seizures linked with menstrual period

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Which hormone (sexual) have effect on seizure (specifically the catamenial)?

A

Oestrogen lowers seizure threshold
Progesterone increases seizure threshold

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

what is the Amstel criteria?

A
  • clue cells on saline smear
  • pH >4.5
  • thin, grey and homogenous discharge
  • positive whiff test

if 3 or more present, patient has bacterial vaginosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

treatment of maternal hyperthyroidism when pregnant

A

carbimazole or propylthiouracil
(as these can cross the placenta and cause fetal hypothyroidism)

BUT carbimazole can be teratogenic -> therefore, avoid in 1st trimester & can be started in 2nd trimester.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

when would you do block and replace for maternal hyperthyroidism?

A

when maternal TSH antibody is affecting the fetus (in a mum who had ablative therapy for Grave’s disease) and causes fetal hyperthyroidism.

so give anti-thyroid drug (for the fetus) and levothyroxine (for the mum)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

side effect when used during pregnancy

A

tetracycline -> teeth discolouration- (if taken in 2nd/3rd trimester)
ACEi -> impaired fetal renal function, oligohydramnios, skull abnormalities
Streptomycin -> auditory and vestibular nerve damage
beta-blockers -> intrauterine growth retardation, bradycardia, neonatal hypoglycaemia
NSAIDs -> closure of ductus arteriosus, persistent pulmonary hypertension of newbown, delay labour, impair placenta blood flow

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

blood-stained discharge from nipple and small lumpy mass
?diagnosis

A

duct papilloma
local areas of epithelial proliferation in large mammary ducts.
hyperplastic lesions rather than malignant or premalignant

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

fibroadenosis - what is it?

A

fibrocystic disease OR benign mammary dysplasia
- seen in middle aged women
- painful, lumpy breast that flare during menstruation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

which one is associated with male infertility?
- sodium valproate
- varicocele
- epididymal cyst
- hydrocele

A

varicocele
(the most correct answer from the list)

39
Q

painless penile sore with weight loss
?diagnosis

A

squamous cell carcinoma

syphillis chancre does NOT cause weight loss

40
Q

PCOS - which is higher - LH or FSH

A

LH is higher than FSH

41
Q

triad of abdo pain, uterine rigidity, vaginal bleeding ?diagnosis

A

placental abruption

42
Q

USS at these weeks - what for?
- 11-14 weeks
- 18 weeks

A

11-14 weeks: dating scan
18 weeks: anomaly scan

43
Q

how to detect neural tube defects during pregnancy?

A

ultrasound for at risk ladies
amniocentesis if uncertain USS images -> measure alpha-fetoprotein and neuronal acetylcholinesterase

44
Q

how to screen for Down’s in pregnancy?

A

combined test at 11-13 weeks - include nuchal transclucency, free b-hcg, pregnancy associated plasma protein and the woman’s age

if >1:200, then offered chorionic villus sampling (<13 weeks gestation) or amniocentesis (>15 weeks gestation)

45
Q

what antibodies would be raised in maternal hyperthyroidism during pregnancy?

A

thyroid peroxidase auto-antibodies
(if this is positive, then 50% chance of postpartum thyroiditis)

46
Q

Adenomyosis - what is it? treatment?

A

ectopic endometrial tissue and stroma within the tissue myometrium

risk factors: increase parity, early menarche, short menstrual cycles, increase BMI, OCP, tamoxifen, prior to uterine surgery

tx: check if they want to be pregnant or not (definitive tx: hysterectomy)
- NSAIDs
- OCP
- levonogestrel intrauterine system
- danazol
- aromatase inhibitors (eg anastrozole)
- endometrial ablation
- adenomyomectomy
-

47
Q

Painful ulcer with tender inguinal lymphadenopathy

A

haemophilus ducreyi
- causes chancroid

48
Q

painless ulcer with painful lymphadenopathy ‘buboes’ or abscess

A

chlamydia trachomatis - causes lymphogranuloma venereum

49
Q

small painless ulcer - chancre
?diagnosis

A

syphilis caused by treponema pallidum

50
Q

post-coital bleeding. no cervical motion tenderness, friable cervix when scraped with a swab. mucopurulent discharge from cervical os. cervix can be moved from side to side

post-coital bleeding and offensive discharge. ulcerated lesion on cervix.

?diagnosis

A

urogenital chlamydia causing cervicitis

cervical cancer

51
Q

how to write gravida and para?

A

gravida- total nubmber of times pregnant including the current one

para- X + Y
(X= no of pregnancies beyond 24 weeks)
(Y= no. of losses before 24 weeks)

52
Q

Fetal alcohol syndrome

A

microcephaly
thin upper lip
indistinct philtrum
flat midface
low nasal bridge
micrognathia
small palpebral fissures

53
Q

investigation for endometrial cancer

A

USS may be suggestive BUT definitive diagnosis is made on endometrial sampling or currettage

54
Q

UKMEC - what is it?

A

UKMEC 1: a condition for which there is no restriction for the use of the contraceptive method
UKMEC 2: advantages generally outweigh the disadvantages
UKMEC 3: disadvantages generally outweigh the advantages
UKMEC 4: represents an unacceptable health risk

Examples of UKMEC 3 conditions include
more than 35 years old and smoking less than 15 cigarettes/day
BMI > 35 kg/m^2*
family history of thromboembolic disease in first degree relatives < 45 years
controlled hypertension
immobility e.g. wheel chair use
carrier of known gene mutations associated with breast cancer (e.g. BRCA1/BRCA2)
current gallbladder disease

Examples of UKMEC 4 conditions include
more than 35 years old and smoking more than 15 cigarettes/day
migraine with aura
history of thromboembolic disease or thrombogenic mutation
history of stroke or ischaemic heart disease
breast feeding < 6 weeks post-partum
uncontrolled hypertension
current breast cancer
major surgery with prolonged immobilisation
positive antiphospholipid antibodies (e.g. in SLE)

Diabetes mellitus diagnosed > 20 years ago is classified as UKMEC 3 or 4 depending on severity

Changes in 2016
breast feeding 6 weeks - 6 months postpartum was changed from UKMEC 3 → 2

55
Q

In miscarriage situation - which rhesus negative mums should STILL be given anti-D injection?

A

surgical or medical terminations of pregnancy
spontaneous miscarruage followed by medical or surgical evacuation
spontaneous complete miscarriage >12 weeks gestation
significant transplacental haemorrhage (due to procedures or trauma)
ectopic pregnancy
threatened miscarriage >12 weeks

56
Q

breast lump - small, hard, tethered to skin and skin puckering
?diagnosis

A

breast cancer

57
Q

what are the normal ECG changes in pregnancy?

A

LAD
small Q waves & inverted T wave in lead III
ST depression & inversion or flattening of T wave in inferior & lateral leads
atrial and ventricular ectopics

58
Q

bleeding, tender tense uterus and fetal distress
?diagnosis

A

placental abruption

59
Q

painless vaginal bleeding with non-tender abdomen and no fetal distress
?diagnosis

A

placental praevia

60
Q

continuous vaginal bleeding during induction of labour and fetal distress
?diagnosis

A

vasa praevia

61
Q

Up to how many weeks can you request for abortion?

A

24 weeks gestation

62
Q

what is the age for:
- NEVER able to consent for sex
- consent for sex

A

13
16

63
Q

what is the UKMEC for progesterone only pill?

A

UKMEC 3: IHD & stroke, past breast cancer, severe decompensated cirrhosis, liver tumours (benign adenoma and malignant)

UKMEC 4: current breast cancer

64
Q

Leiomyoma VS leiomyosarcoma VS adenomyosis

A

Leiomyoma - fibroids (benign tumours in the myometrium)

Leiomyosarcoma: rare malignancies that are difficult to distinguish from fibroids

Adenomyosis: extension of endometrial tissue and stroma into uterine myometrium

65
Q

20 weeks gestation - lower abdominal discomfort following a minor fall. pain increased over time and tender in the lower abdomen. USS shows fluid in the lower pelvis below the fallopian tubes and the ovaries.

?diagnosis

A

ruptured ovarian cyst

66
Q

alternatives to hormone replacement therapy to control/reduce hot flushes in menopause?

A

citalopram/anti-depressants!
clonidine
gabapentin

other lifestyle changes: increase exercise, lighter clothing, sleeping in cooler room, reduce spicy food, caffeine, smoking, alcohol

67
Q

Goserelin - what is it used for and what are the side effects?

A

LHRH agonists/GnRH agonist
used for prostate cancer, breast cancer, endometriosis, for endometrial thinning prior to endometrial ablation or resection, before surgery to remove fibroids

SE: osteoporosis

68
Q

types of POP - give examples and what happens if missed one pill?

A

traditional- levonogestrel (LNG), norethisterone (NET)
newer- desogestrel (DSG), drospirenone (DRSP)

what constitutes a missed pill:
LNG/NET: 3 hours late
DSG: 12 hours late
DRSP: 24 hours late

take the missed pill and take extra precautions for 48hrs

69
Q

what is the normal results for pregnancy?
- WCC
- FBC
- platelet
- U&E (sodium, potassium, urea, creat, eGFR)
- albumin
- bilirubin
- ALT
- AST
- ALP
- TFT (T3, T4, TSH)
- total calcium
- magnesium

  • cardiac output
  • tidal volume
  • urinary frequency
A

WCC increased
FBC decreased (but if Hb is <110 at booking or <105 at 28 weeks with normal/low MCV, need to start iron supplementation)
platelet decreased
U&E decreased (but GFR increased)
albumin decreased
bilirubin decreased
ALT, AST unchanged/slightly decreased
ALP increased
TSH decreased in 1st trimester, normal in 2nd and increased in 3rd
T3/T4 unchanged
Total calcium decreased
Magnesium unchanged

CO increases
Tidal volume increases
Urinary frequency increases

70
Q

how long can you detect HCG in pregnancy?

A

as early as 8/9 days and in 98% patients, by day 11
level peak at 10-12 weeks gestation
and until 20 weeks of gestation

will be positive 5days post miscarriage
also positive in trophoblastic disease

71
Q

treatment of these antenatal infections:
- listeria
- syphilis
- toxoplasmosis

A

listeria: amoxicillin & gentamicin
syphilis: benzathine benzylpenicillin
toxoplasmosis: spiramycin (for tetus: pyrimethamine & sulfadiazine)

72
Q

treatment of UTI in pregnancy

A

nitrofurantoin (but avoid this at term due to risk of neonatal haemolysis)

trimethoprim

73
Q

risk factors for cervical cancer

A

HPV 16 & 18 & 33
smoking
HIV
young age of first coitus
high number of sexual partners
young age of first pregnancy
high parity
low socioeconomic class
a sexual partner with multiple sexual partners

74
Q

what drugs cause these:
- Ebstein’s anomaly
- placental abruption
- jitteriness,fits, irritability

A
  • benzodiazepines/lithium
  • coccaine use
  • heroin
75
Q

24yo, deep dyspanerunia and dysmenorrhoea and not secual active until 2 months ago

?diagnosis

A

endometriosis

76
Q

24 yo dysmenorrhoea, irregular periods and recurrent episodes of yellow-green vaginal discharge

?diagnosis

A

chronic pelvic inflammatory disease

77
Q

Tx of fibroids

A

transcervical resection of fibroid- for submucous fibroid & helps retain fertility

myomectomy - for large intramural fibroid

78
Q

Foetal hydrops

  • caused by what viral infection during pregnancy?
  • how do we investigate?
A
  • parvovirus b19
  • USS first and then cordocentesis
79
Q

how would the baby turn out if these occur in pregnancy?
- maternal diabetes
- trisomy 18
- valproate ingestion

A
  • sacral agenesis, fetal cardiomyopathy, cardiac defects, cleft palate
  • Edward’s syndrome!
  • cleft palate and learning difficulties
80
Q

treatment of primary dysmenorrhagia

A

NSAIDs - mefenamic acid, ibuprofen
COCP

81
Q

treatment of primary postpartum haemorrhage

A

apply pressure to uterus
IV oxytocin/ergometrine
IM/intrauterine carboprost (unless asthmatic)
rectal/SL misoprostol
surgical - balloon tamponade, ligation of uterine arteries, B-lynch suture OR hysterectomy

82
Q

risk factors for pre-eclampsia

A

age >40
nulliparity
pregnancy interval >10years
FHx
previous medical history
BMI>30
HTN/other pre-existing vascular disease
pre-existing renal disease
multiple pregnancy

83
Q

what type of vaccines are these:
- gardasil
- ceravix
- gardasil 9

A

gardasil : HPV 6,11,16,18
ceravix : HPV 16 &18
gardasil 9 : 9 variants (6,11,16,18, 31,33, 45, 52, 58)

84
Q

what is acute fatty liver of pregnancy?

A

rare life threatening complication of pregnancy
- ALT and AST raised (<500U/L)
- due to disordered metabolism of fatty acid - deficiency of LCHAD.
- Abdo USS -> fat deposition of liver & microvascular steatosis
- liver biopsy is rarely needed
Tx: delivery of foetus

85
Q

which HRT to start for the lady?

A

No uterus: oestrogen-only (Elleste-Solo)

Uterus present:
- if no period for >1year: continuous progesterone (Elleste-Duet Combi)
- if still having periods/finishing: cyclical progesterone given monthly or 3 monthly (Elleste-Duet)

86
Q

once the lady enters menopause, do they still need contraception?

A

Yes
- still need contraception for 1 year after the last period if >50yo or 2 years if <50yo.

87
Q

contraceptive - when would they be effective? (these are not on 1st day period)
- IUD
- POP
- COCP

A

IUD: instantly
POP: 2 days (*if they have taken this in the first 5 days of cycle - no need to wait)
COCP: 7 days

Injection, implant, IUS: 7 days

88
Q

which emergency contraceptive pill cannot be use for asthmatics?

A

ullipristal

89
Q

how long post-partum can you have unprotected sex & not needing contraception for?

and what type of contraception is allowed after?

A

21 days post-partum

POP: can start anytime post-partum. but if taken post-21 days, then need alternative protection for 2 days.

COCP: start 6weeks-6months post-partum & breastfeeding(UKMEC 2) and alternative protection for 7 days

IUD/IUS: inserted 48hours post-partum or after 4 weeks.

90
Q

what type of contraception do you need if >40yo?

A

DON’T PRESCRIBE implantable contraceptive device (eg Depo-Provera) as it can cause lost of bone mineral density.

If using COCP (<50yo) -> switch to non-hormonal or progesterone-only-pill (>50yo)

If using depo-provera (<50yo) -> Switch to either a non-hormonal method and stop after 2 years of amenorrhoea OR switch to a progestogen-only method and follow advice below

If using implant, POP, IUS (<50yo) ->
- Continue
- If amenorrhoeic check FSH and stop after 1 year if FSH >= 30u/l or stop at 55 years
- If not amenorrhoeic consider investigating abnormal bleeding pattern

91
Q

what type of CYP450 effect does st john’s wart do?

A

CYP450 inducer!

92
Q

intrauterine system VS intrauterine device

A

IUD: copper IUD

IUS: contain levonogestrel

93
Q

which contraceptive option causes weight gain?

A

implantable device - ie Depo Provera

94
Q
A