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RANZCOG Guidelines > Obstetrics > Flashcards

Obstetrics Flashcards

1
Q

Pre-Pregnancy Counselling

A
  • Assess past medical, obstetric, and genetic/family history to stabilise pre-pregnancy medical conditions, implement measures to reduce recurrence risk of obstetric conditions and consider pre-implantation genetic diagnosis vs prenatal diagnosis
  • Examination including BP, weight, heart sounds, +/- breast exam and Pap smear
  • Review current medications Re appropriateness and teratogenic risk
  • Vaccination Hx for MMR, DTP and varicella, if incomplete immunity for rubella and varicella consider pre-pregnancy immunisation
  • Encourage healthy weight, nutrition, and moderate intensity exercise
  • Folic acid 1 month prior to conception and first 3 months of at least 0.4mg daily to prevent NTD (5mg daily if high risk incl anti-convulsant medication, pre-pregnancy DM, previous child or family Hx NTD)
  • Iodine supplementation 150mcg daily prior to planned pregnancy
  • Smoking, alcohol and illicit drug cessation
  • Assess environmental exposures to toxins or radiation
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2
Q

Cervical Length for Prediction of Preterm Birth

Measurement Technique

A
  • Most accurately measured by transvaginal examination
  • Empty bladder, probe in the anterior fornix (minimises pressure on the cervix which increases length)
  • Length of the endocervical canal measured from the internal to external os
  • Three measurements should be made over a five minute period and the shortest measurement reported for clinical use
  • Transabdominal assessment with a partially full bladder is a potential first line screening test
  • TA cervical length > 35mm precludes a TV cervical length < 25mm with over 95% sensitivity
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3
Q

Cervical Length for Prediction of Preterm Birth

Interpretation

A
  • Median cervical length at 20 weeks is 42mm
  • The 1st centile is 23mm
  • Using a cut-off of either 20 or 25mm TV to define “high risk” cohort appears to be appropriate
  • Other sonographic features of the cervix known to be associated with preterm delivery include funnelling, shortening in response to uterine activity or fundal pressure, and intra-amniotic “sludge”
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4
Q

Cervical Length for Prediction of Preterm Birth

Treatment of short cervix in otherwise low risk women

A
  • Routine mid-pregnancy cervical length assessment in low risk women can be a cost-effective method of preterm birth reduction but implementation of such a policy is highly dependent upon local factors
  • Treatment of women with a short cervix with vaginal progesterone reduces the risk of preterm delivery before 34 weeks or fetal death by 34% and significantly reduces neonatal morbidity
  • Approximately 11 women need to be treated to prevent one preterm delivery before 34 weeks
  • In low risk women with a short cervix, progesterone is generally the preferred treatment (over cerclage) due to the lower risk of surgical complications
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5
Q

Cervical Length for Prediction of Preterm Birth

Women with risk factors for PTB

A

Previous PTB
- may benefit from vaginal progesterone or cervical cerclage
- some evidence to support cervical length surveillance with recourse to cervical cerclage in only those women who develop a short cervix
Multiple pregnancy
- evidence regarding therapeutic intervention for those with a short cervix is conflicting
Previous cervical excisional procedures
- a midtrimester cervical length less than 25 or 30mm confers a greater risk of preterm birth compared to a longer cervix

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6
Q

Mid-Trimester Fetal Morphology Ultrasound Screening

A
  • provides information about fetal anomaly and growth, multiple gestation, placental position, and cervical dimensions
  • useful in detecting congenital anatomical and other anomalies - over half of major malformations and anomalies were detected before 24 weeks with this approach
  • principle objective is to provide diagnostic information that is accurate as possible with a view to optimising antenatal care and providing the best outcomes of pregnancy
  • practitioners involved with the provision of mid-trimester fetal morphology screening must undergo appropriate specific training in this critical and specialised area of practice
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7
Q

Maternal GBS Screening and Management

Clinical risk factors for EOGBS

A
  • spontaneous onset of labour at = 37 weeks gestation
  • rupture of membranes >/= 18 hours
  • maternal fever >/= 38 deg
  • previous infant with EOGBS
  • GBS bacturia during the current pregnancy
  • Known carriage of GBS in current pregnancy
  • Clinical diagnosis of chorioamnionitis
  • Other twin with current EOGBS
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8
Q

Maternal GBS Screening and Management

Early Onset Neonatal Sepsis

A
  • GBS leading cause in developed countries
  • 15 to 25% of pregnant women are asymptomatic carriers of GBS
  • <1/3 of neonates delivered vaginally are colonised
  • between 1:200 and 1:400 neonates develop baceraemia and EOGBS
  • fatality rate for EOGBS is 14%
  • risk of EOGBS can be reduced by 80% with the use of intrapartum antibiotics
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9
Q

Maternal GBS Screening and Management

Universal Culture-Based Screening

A
  • A large, prospective study showed universal culture-based screening and intrapartum antibiotic prophylaxis (IAP) led to an 84% decline in the incidence of EOGBS (Jeffery, Moses, 1998)
  • 1.4/1000 vs 0.2/1000 live births (NNT 224)
  • a systematic review of 9 studies showed the odds of EOGBS were lower with routine culture-based screening compared with risk factor based screening OR 0.45 (Kurtz, Davis. 2015)
  • combined low vaginal and anorectal swab with culture on selective enriched media (as detecting colonisation, not infection)
  • rectovaginal culture at 36 weeks: sensitivity 91% specificity 88.9% for intrapartum maternal vaginal colonisation
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10
Q

Maternal GBS Screening and Management

IAP Regime for GBS Colonised Women

A
  • IV penicillin G or ampicillin, optimally given at least 4 hours prior to delivery
  • if known penicillin allergy, sensitivities should be performed at the time of GBS culture
  • alternatives include cefazolin, clindamycin, and vancomycin
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11
Q

Obesity in Pregnancy

Antenatal Risks

A
  • miscarriage
  • gestational diabetes
  • fetal congenital abnormalities (i.e. neural tube defects)
  • antenatal stillbirth
  • pre-eclampsia
  • thromboembolism
  • abnormalities in fetal growth
  • obstructive sleep apnoea
  • preterm birth, mostly associated with comorbidities
  • maternal death
  • gestational HTN: 2% (normal BMI) 5% (obese class 1) 10% (obese class 3)
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12
Q

Obesity in Pregnancy

Intrapartum Risks

A
  • induction of labour, prolonged labour, and failure to progress
  • rate of instrumental delivery
  • failed instrumental delivery
  • shoulder dystocia
  • caesarean section
  • difficulties with fetal heart rate monitoring
  • postpartum haemorrhage
  • peripartum death
  • caesarean: 33% (normal BMI) 52% (obese class 3)
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13
Q

Obesity in Pregnancy

Postpartum Risks

A
  • delayed wound healing and infection
  • thromboembolic disease
  • support with breastfeeding establishment and continuation
  • postnatal depression
  • longterm neonatal consequences: neonatal body composition, infant weight gain, obesity
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14
Q

Obesity in Pregnancy

Anaesthetic Risks

A
  • difficulties with labour analgesia
  • use of general anaesthesia
  • difficulty maintaining an adequate airway, failed intubation
  • increased risk of need for ICU care postoperatively
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15
Q

Obesity in Pregnancy

BMI Categories

A
  • BMI is calculated at the first visit with kg/m2
  • underweight <18.5
  • healthy 18.5 to 24.9
  • overweight 25 to 29.9
  • obese (class 1) 30 to 34.9
  • obese (class 2) 35 to 39.9
  • obese (class 3) 40 or more
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16
Q

Obesity in Pregnancy

Pre-pregnancy

A
  • dietary modification and exercise
  • medications for weight management pre-conception or during pregnancy are not recommended: safety concerns and adverse effects
  • bariatric surgery reduces maternal risks but increases risk of FGR and stillbirth
  • previous bariatric surgery: lifelong vitamin supplementation (particularly malabsorptive surgery), avoid pregnancy immediately post surgery and during initial weight loss phase
  • high dose folate (5mg) and iodine 150mcg for obese women
  • consider psychological support
17
Q

Obesity in Pregnancy

Antenatal Care

A
  • measure BMI at first visit
  • healthcare facilities, multidisciplinary team, location and referral for care
  • folic acid 5mg, iodine 150mcg, increased risk for iron and vitamin D deficiency
  • influenza vaccination strongly recommended
  • early GTT with repeat at 28 weeks
  • anaesthetic assessment
  • monitor for PET
  • third trimester fetal growth ultrasound
  • start or continue exercise programs
  • decreased success for VBAC, increased operative and anaesthetic risks for emergency CS
  • timing for birth: ? by 40 weeks
18
Q

Obesity in Pregnancy

Intrapartum and Postpartum

A
  • BMI > 40 should have IV access
  • confirm presentation on US if uncertain
  • anticipate shoulder dystocia and PPH
  • equipment considerations (esp >120kg)
  • thromboembolism prophylaxis
  • if large FMH, consider IV rather than IM Rh(D) Ig
  • breastfeeding support
  • weight management postpartum
19
Q

Obesity in Pregnancy

Gestational Weight Gain Recommendations

A 
BMI < 18.5 --- 12.5 to 18 kg
BMI 18.5 to 24.9 --- 11.5 to 16 kg
BMI 25 to 29.9 --- 6.8 to 11.3 kg
BMI 30 or > --- 5 to 9.1 kg
(IOM 2009)
Assumes a 0.5 to 2kg weight gain in 1st trimester
20
Q

Prenatal Assessment of Fetal Structural Conditions

A
  • Fetal structural anomalies (FSA) affect 2-3.5% of all pregnancies
  • detection rates are about 60%
  • offer ultrasound assessment for FSA in the midtrimester (18-22 weeks): screen for number of fetuses, FSA, placental location, and cervical length using systematic approach
  • identifies anomalies and allows parents to obtain further information about the aetiology, associations, and implications for the pregnancy, newborn period and infancy
  • management involves timely review, multidisciplinary input, diagnostic evaluation (further imaging, bloods, invasive testing), detailed counselling, and plans for ongoing care
  • families can make an informed choice whether to continue the pregnancy or terminate
  • 25% of fetal conditions only manifest in the 2nd or 3rd trimester and therefore cannot be identified at 11-14 weeks
  • 1 to 3% of fetuses with a structural anomaly will have an abnormality on microarray that would not have been picked up on conventional karyotype
  • consider recurrence risk and implications for future pregnancies
  • US can produce bioeffects (heating of tissue and cavitation) - potential for subtle, delayed, low incidence, and as yet unrecognised effects
  • pulsed Doppler ultrasound should not be used in the 1st trimester
  • ‘ALARA’ principle: as low as reasonably achievable for US exposure duration
21
Q

Prenatal Screening and Diagnosis of Chromosomal and Genetic Conditions
Combined First Trimester Screening

A
  • performed 11+0 to 13+6 weeks
  • maternal age + NT + PAPP-A + BhCG
  • sensitivity 85% (T21)
  • specificity 95%
  • PPV 7 to 10%
  • risk score for T21, T18, T13
  • enhanced when including presence of nasal bone, ductus venosus waveform, and tricuspid valve flow
  • recommended screening modality in twin pregnancies
22
Q

Prenatal Screening and Diagnosis of Chromosomal and Genetic Conditions
Quadruple Test

A
  • performed 15 to 20 weeks
  • maternal age, AFP, BhCG, oestriol (UE3), inhibin
  • sensitivity 75% (T21)
  • specificity 95%
  • PPV 2 to 3%
23
Q

Prenatal Screening and Diagnosis of Chromosomal and Genetic Conditions
Cell-Free DNA

A
  • ie non-invasive prenatal testing (NIPT)
  • measures cfDNA in maternal plasma
  • accurate dating, confirm viability, and number of embryos prior to cfDNA screening
  • perform >10+ weeks
  • sensitivity 99% (T21)
  • specificity 99%
  • PPV 45%
  • offers fetal sex, sex aneuploidy screening, T21, T18, and T13
24
Q

Prenatal Screening and Diagnosis of Chromosomal and Genetic Conditions
Diagnostic Procedures

A
  • chorionic villus sampling (CVS) performed from 11 weeks (if prior, associated with transverse limb reduction defects)
  • amniocentesis performed from 15 weeks (if prior, increased risk adverse outcome such as talipes)
  • fetal loss rates quoted 0.5 to 1%, operator and experience dependent, equal between procedures and as low as 1 in 900 for experienced operators
25
Q

Prenatal Screening and Diagnosis of Chromosomal and Genetic Conditions
Assessment of Fetal Chromosomes

A
  • conventional G-banded karyotyping: stained metaphase chromosomes for microscopic inspection, identifies changes in chromosome number and subchromosomal rearrangements
  • rapid aneuploidy tests ie FISH (fluorescent in situ hybridisation): adjunct to full karyotyping for rapid assessment of common autosomal trisomies and sex chromosomes, diagnosis of specific microdeletion syndromes
  • chromosomal microarray analysis: genome-wide oligonucleotide array identifies both large and submicroscopic DNA variations across all chromosomes, assesses the fetal genome at higher resolution than a conventional karyotype, cannot identify balanced chromosome rearrangements or mutations causing single gene disorders
26
Q

Progesterone Support in the First Trimester

A
  • no evidence of benefit of progestin for prevention of miscarriage for unselected women
  • preliminary evidence of a reduction in the rate of spontaneous miscarriage with progestin use for threatened miscarriage
  • exogenous progesterone is associated with a significantly higher pregnancy rate when used as luteal support for ART
  • synthetic progesterone has better results than micronised progesterone
27
Q

Progesterone for the Prevention of Preterm Birth

A
  • 2/3 of PTB are spontaneous, 1/3 ‘indicated PTB’
  • vaginal progesterone therapy recommended for asymptomatic women with a shortened cervix <25mm on TV US in the midtrimester
  • (updated meta-analysis Romero et al 2016, including OPPTIMUM, showed progesterone reduced PTB <34 weeks if shortened Cx from 27.5% to 18.1%)
  • should be considered for women with a singleton pregnancy with a history of PTB (systematic review shows benefit, however doesn’t include OPPTIMUM trial- no benefit, updated meta-analysis awaited)
  • further research needed to determine optimal timing, dose and administration of progesterone
28
Q

Routine Antenatal Assessment

First Visit

A
  • confirm Pregnancy, establish EDD
  • full medical history, psycho-social assessment, and clinical examination
  • height and weight, calculate BMI (kgs/m2)
  • FBC: Hb, MCV, Plts
  • blood group and Ab screen
  • rubella Abs
  • syphillis serology: specific treponema pallidum assay (TPHA or TPPA), non-specific assays (RPR or VDRL) less likely to pick up latent infection
  • midstream urine MCS: asymptomatic bacturia
  • chlamydia: selective testing for at risk
  • HIV
  • Hep B: (HBsAg) if chronic carrier HBV DNA, HBe antigen, LFTs
  • Hep C: if pos Hep C RNA PCR and LFTs
  • varicella: consider if no history of natural infection
  • cervical screening
  • aneuploidy screening
  • consider screening for haemoglobinopathies, vit D, and TSH for high risk groups
  • do not screen for CMV and toxoplasmosis
29
Q

Routine Antenatal Assessment

General Pregnancy Advice

A
  • potential teratogens (medications, alcohol, X-rays etc)
  • lifestyle advice: dietary precautions, optimal gestational weight gain, exercise, smoking and illicit drug cessation, work and travel precautions
  • influenza and pertussis vaccination recommendations
  • vitamin and mineral supplementation
  • model of care, expected visit frequency
  • antenatal education options
30
Q

Routine Pregnancy Assessment

Subsequent Visits

A
  • measurement of symphysio-fundal height
  • BP, routine palpation
  • obstetric US at 18-20 weeks
  • screening for GDM as per ADIPS 2014
  • consider GBS screening
  • blood group Ab testing at 28 weeks for Rh neg, consider for Rh pos
  • FBC at 28 weeks
  • consider re-screening high- risk groups for Hep B, C, HIV and syphillis at 28 weeks
  • influenza vaccination
  • dTpa vaccination at 28-32 weeks
31
Q

Screening in Early Pregnancy

Pre-eclampsia

A
  • PET complicates 3-5% of pregnancies
  • risk factors: personal or family Hx, medical conditions such as DM, renal disease, HTN, multiple pregnancy
  • screen for pre-eclampsia risk factors to identify women at increased risk to offer aspirin, calcium (if diet deficient), and increased surveillance
  • the place of combination ultrasound and serum markers as predictors of PET awaits further clarification
  • some studies suggest this performs well as a predictor of severe early onset PET, which is rare
  • does not perform well to predict (more common) late onset disease
32
Q

Screening in Early Pregnancy

Fetal Growth Restriction

A
  • FGR is failure of a fetus to reach its growth potential
  • SGA is EFW or AC < 10th centile
  • perinatal mortality increases with decreasing birth weight centile
  • symphysis fundal height is unreliable in detecting SGA fetuses
  • major risk factors: previous SGA, previous stillbirth, current PET, significant APH, DM with vascular disease, renal impairment, APS, SLE, smoking > 11 cigarettes/day, daily vigorous exercise, maternal age > 40
  • minor risk factors: prev PET, mat age 35 or >, BMI <20 or >35
  • the evaluation of a combination of certain biomarkers, Doppler US, and maternal risk factors in the first trimester has the best results
  • uterine artery Doppler: high resistance, notching and abnormal flow after the first trimester
  • biomarkers include PAPPA, placental growth factor (PlGF), sFlt-1, and placental protein 13 (PP13)
33
Q

Screening in Early Pregnancy

PAPP-A and FGR

A
  • low PAPP-A <5th centile (0.4 MoM) associated with an increased risk of SGA
  • OR 2.7 for SGA and 3.7 for severe SGA <3rd centile
  • detection rate 12% and 16% respectively (Spencer et al 2008)
  • most accurate predictor PAPP-A <1st centile (0.3 MoM)
34
Q

Testing for Hypothyroidism

TSH Reference Ranges in Pregnancy

A
  • First trimester 0.1 to 2.5 mlU/L
  • Second trimester 0.2 to 3.0
  • Third trimester 0.3 to 3.0
35
Q

Testing for Hypothyroidism

Physiology in Pregnancy

A
  • hCG structurally similar to TSH
  • transient small increase in FT4 with suppression of TSH in first trimester
    Increased T4 production and requirement in Pregnancy:
  • increased iodine uptake and thyroid hormone hormone synthesis by the thyroid gland
  • increased hepatic production of thyroxine binding globulin (TBG) reducing the amount of biologically active T4
  • increased volume of distribution of T4 due to plasma volume expansion
  • transplacental passage of T4 to the fetus
    Fetal thyroid starts to become functional from 18 weeks
    Increased iodine clearance during pregnancy, so increased need for dietary iodine
    Fetus entirely dependent on maternal iodine intake for thyroid hormone synthesis
36
Q

Testing for Hypothyroidism

Overt Hypothyroidism

A
  • prevalence is 0.3 to 0.5%
  • main causes are iodine deficiency and Hashimotos
  • associated with increased risks of miscarriage, PIH, PET, placental abruption, anaemia, PPH, prematurity, low birth weight, perinatal mortality, cognitive impairment, and developmental delay (cretinism)
  • pregnant women on thyroxine for pre-existing disease often require a 30-50% increase in thyroxine dose in early T1
  • check TSH at least once per trimester
  • overt hypothyroidism should be treated in pregnancy (high TSH, low T4 or if TSH>10)
  • targeted screening is recommended
37
Q

Testing for Hypothyroidism

Subclinical Hypothyroidism

A
  • prevalence 2-3%
  • TSH increased, normal FT4
  • thyroid autoantibodies present in 50-60%
  • there is insufficient evidence to support universal TSH screening and treatment of SCH in pregnancy
  • Controlled Antenatal Thyroid Screening Study, 2012: no benefit in cognitive function in the children of treated women
38
Q

Vitamin and Mineral Supplementation in Pregnancy

A
  • folic acid at least 0.4mg daily to help prevent NTD
  • if increased risk of NTD or malabsorption, 5mg daily (DM, BMI >30, anticonvulsant medication, prev child or family Hx NTD)
  • vegetarians and vegans should have B12 supplements in pregnancy and lactation (RDI 2.6mcg/day in preg, 2.8mcg/day lac)
  • vitamin D deficiency in the neonate is associated with impaired skeletal development and an increased incidence of hypocalcaemic seizures
  • vitamin D level 30-49nmol/L, commence 1000iu per day
  • vitamin D level <30, commence 2000iu per day (repeat vit D level at 28 weeks)
  • vitamin D >50, take 400iu as part of a multivitamin
  • vitamin K should be administered to women with cholestasis in late pregnancy due to decreased vit K absorption
  • women with Fe deficiency anaemia require Fe supplements with at least 60mg iron daily
  • calcium RDI for pregnant women 1300mg (14-18yo) 1000mg (19-50yo)
  • women breastfeeding, pregnant or considering pregnancy should take iodine 150mcg/day

RANZCOG Guidelines (3 decks)

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