PRENATAL DIAGNOSIS AND SCREENING

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PRENATAL DIAGNOSIS AND SCREENING
M Huggins, 2008
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Learning Objectives

• Discuss current guidelines for Prenatal Screening
  and Diagnostic testing
• Review the biochemical markers used in each
  Prenatal screening method
• Understand the importance of accurate clinical
  information in prenatal screening
• Emphasize the underlying theme of informed
  decision making

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You are seeing a 42 Year old woman for first PN
visit at 10 weeks of gestation.

• What is her risk of Down syndrome?
• What options can you offer her?

Are your answers different if she is 32 years old?
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Canadian Guidelines for Prenatal
DiagnosisGENETIC INDICATIONS FOR PRENATAL
DIAGNOSIS(CCMG / SOGC, 2001)

• The traditional recommendation is that all women
  who will be 35 years of age or older on the
  estimated date of delivery should be offered
  invasive prenatal testing

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Prenatal Screening for Fetal AneuploidySOGC
Practice Guideline(CCMG / SOGC, 2007)

• Maternal age screening is a poor minimum standard
  for prenatal screening for aneuploidy and should
  be removed as an indication for invasive testing.
  
• Amniocentesis/chorionic villi sampling (CVS)
  should not be provided without multiple marker
  screening results except for women over the age
  of 40. Patients should be counselled accordingly.
  

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ACOG Practice BulletinScreening for Fetal
Chromosomal Abnormalities(Obstet Gynecol, 2007)

• Screening and invasive diagnostic testing for
  aneuploidy should be available to all women who
  present for prenatal care before 20 weeks of
  gestation regardless of maternal age.
• Women should be counseled regarding the
  differences between screening and invasive
  diagnostic testing.

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Prenatal Screening Options

• First Trimester Screening (FTS)
• Maternal Serum Screening (MSS)
• Integrated Prenatal Screening (IPS)

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IPS and MSS Screen for Which of the Following
Conditions?

• Down syndrome
• Trisomy 18
• Trisomy 13
• Neural tube defects
• All of the above

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IPS and MSS Screen for Which of the Following
Conditions?

• Down syndrome
• Trisomy 18
• Trisomy 13
• Neural tube defects
• All of the above

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Maternal Serum Markers Can you Name Them?

• First Trimester
• Second Trimester

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Maternal Serum Markers Can you Name Them?

• First Trimester Papp-A free beta hcG
• Second Trimester AFP
• uE3
• hcG
• Inhibin-A

Are they low or high in Down syndrome?
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Maternal Serum Markers in Down syndrome
pregnancies

• First Trimester Papp-A (0.4 x normal) hcG
  (2.0 x normal)
• Second Trimester AFP (0.75 x normal)
• uE3 (0.72 x normal)
• hcG (2.0 x normal)
• Inhibin-A (2.0 x normal)

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Prenatal Screening Options

• First Trimester Screening (FTS)
• Maternal Serum Screening (MSS)
• Integrated Prenatal Screening (IPS)

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First TrimesterCombined Screening (FTS)

• When maternal age, NT, CRL, PAPP-A
• and free beta are combined
• (week 11 to 14)
• Detection rate T21 83
• Detection rate T18 91
• False positive rate 5

Cut off for positive 1 in 350 DS
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Second Trimester Screening (MSS, Quad Screen)

• When AFP, uE3, hCG and inhibin-A are combined
  with maternal age
• (week 15 to 20)
• detection rate DS 81
• T18 65
• ONTD 85
• false positive rate 5

Cut off for positive 1 in 200 DS
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Maternal Serum Screening (MSS, triple screen)
(no longer in use)

• When maternal age, AFP, uE3 and hCG are combined
• (week 15 to 20)
• detection rate 70
• false positive rate 8
• screens for Down syndrome, trisomy 18 and NTD

Cut off for positive 1 in 385 DS
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Integrated Prenatal Screening (IPS)

• Part One 11-14 weeks
• NT ultrasound
• PAPP-A

• Part Two 15-18 weeks
• AFP
• uE3
• hCG

• Results reported only after Part Two
• Detection rate T21 88 T18 90
• Detection rate NTD 85
• False positive rate 3

Cut off for positive 1 in 200 DS
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The Process of Prenatal Screening

• The results take 2 to 4 days to be reported
  (after the second blood test for IPS).
• Positive (high risk) results are reported by
  telephone or fax, while negative (low risk)
  results are sent in the mail.
• If the screen is positive, genetic counselling is
  available to discuss the risks and benefits of
  diagnostic testing (either CVS or amniocentesis,
  depending on gestational age and availability of
  CVS).

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An Example of Prenatal Screening Introducing
April

• 38 year old Black woman
• 12 weeks pregnant
• Healthy 2 year old son, full term vaginal
  delivery
• Family history is non-contributory

What is her risk of Down syndrome? Any other
genetic issues?
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April Is 38 Years Old

• Risk of Down syndrome 1 / 175
• Total risk of aneuploidy 1 / 100
• 12 weeks pregnant
• Family history non-contributory
• Hemoglobinopathy screening negative

Prenatal Screening Options for April?
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Aprils Chooses IPS

• Nov 2nd first PN visit, requests IPS (12w1d)
  book an ultrasound for NT, prepare requisitions
  for part I and part II, decide when part II will
  be done
• Nov 9th ultrasound for NT, part I IPS (13w1d)
• Nov 21st part II IPS, bloodwork only (15w0d)
  reminder sent from screening lab if sample not
  received by 17w6d
• Nov 24th IPS positive, report sent to ordering
  physician or midwife by phone or fax from the
  reporting centre PND clinic on behalf of the CVH
  screening lab

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Aprils IPS Result

• Maternal Age at EDD 38.1 years
• Gestational Age 1st sample 13w1d
• Gestational Age 2nd sample 15w0d
• Nuchal 2.0 mm 1.08 MoM AFP 0.47 MoM
• PAPP-A 0.34 MoM uE3 0.67 MoM hCG 1.52
  MoM

Risk of Down syndrome 1 in 14 Risk of NTD 1 in
11000
Screen Positive for Down syndrome
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Aprils IPS Result

• What is the chance that Aprils baby has Down
  syndrome?

Risk of Down syndrome 1 in 14 Approximately 7
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Screen Positive for Down syndrome

• What happens next?

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The Prenatal Diagnosis Clinic

• Genetic Counsellors, Genetic Nurse
• Sarah Ruddle, Marlene Huggins, Gwen White
• Physicians
• Dr. Mohide, Dr. Winsor, Dr. Defrance, Dr.
  McDonald
• (Dr. Smith, Dr. Mueller, Dr. Brennan, Dr.
  Muggah)
• Business Clerks
• Lynn Watson, Dianne Maynard, Joanne Whittaker
• Clinical Manager
• Kathy Clark

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Who We Serve

• Hamilton, Central West and Central South Regions
• Population 2.2 million, 22000 births
• 7 counties
• 9 cities Hamilton, Burlington, Guelph,
  Cambridge, Kitchener-Waterloo, Brantford,Niagara
  Falls, St. Catharines, Welland
• 9 towns Fergus, Arthur, Paris, Simcoe,
  Dunnville, Fort Erie, Port Colborne, Grimsby,
  Niagara-on-the-Lake
• 10 hospitals with birthing units
• Multicultural complexity
• Hamilton has a high proportion of immigrants
• Mennonites in Kitchener area
• Brant Reserve

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Central West and Central South Regions
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Who we see

• Late maternal age (LMA)
• Positive prenatal screening
• (T21, NTD , T18)
• Abnormal community ultrasound
• Suspected anomalies
• Soft signs
• Past history / family history of congenital
  anomalies, abnormal chromosomes or genetic
  conditions
• Exposure to potentially harmful drugs, infections
  or toxins
• Pre-conception counselling

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Aprils Experience with Prenatal Diagnosis

• November 30th (16w2d)
• PND clinic consultation
• genetic counselling
• Option to do same day amniocentesis

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Counselling Patients About Abnormalities

• What do we know and what do we not know?
• What are the possibilities? (ie the difference
  between a screening result and a diagnosis)
• Options for further testing risks and benefits
  (either for delivery planning or for
  decision-making about TOP)
• Prognosis for survival prognosis for
  developmental outcome
• Availability of specialist consultations

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Aprils Amniocentesis Result
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Aprils Experience with Prenatal Diagnosis

• Nov 30th seen for genetic counselling, requests
  amniocentesis, done same day (16w2d)
• Dec 15th karyotype 47,XX,21
• Phone call to April to tell her the result
• Dec 19th seen for genetic counselling (18w5d)

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Counselling Patients About Abnormalities

• What do we know and what do we not know
• What are the possibilities (ie the difference
  between a screening result and a diagnosis)
• Options for further testing either for delivery
  planning or for decision-making
• Prognosis for survival prognosis for
  developmental outcome
• Availability of specialist consultations

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Genetic Counselling

• Guilt and blame
• Comprehension of complex medical information
• Personal supports
• Social context
• Grief and anger
• Decision-making

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Counselling patientscontd

• Who to tell, how to tell?
• Why did this happen, will it happen again?
  (possible need for further testing eg autopsy)
• What will we tell the other children?
• Induction of labour vs DE
• Possible need (or choice) for burial / cremation

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Aprils Experience with Prenatal Diagnosis

• Nov 30th seen for genetic counselling, requests
  amniocentesis, done same day (16w2d)
• Dec 15th karyotype 47,XX,21
• Phone call to April to tell her the result
• Dec 19th seen for genetic counselling (18w5d)

Undecided, requests ultrasound for more
information
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How Is April Doing?

• Dec 19th seen for genetic counselling (18w5d)
• Known trisomy 21
• Undecided, requests ultrasound for more
  information
• December 28th no major anomalies, NF8mm,
  echogenic intracardiac focus (soft markers for
  Down syndrome)
• Met with social worker, genetic counsellor,
  obstetrician.

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• April requested pregnancy termination,
• and was admitted for induction of labour on Jan
  5th at 21w5d of gestation

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Prenatal Screening in Ontario

• First Trimester Screening (FTS)
• Second Trimester Screening (MSS) (quad screen in
  Ontario)
• Integrated Prenatal Screening (IPS)
• Nuchal Translucency ultrasound (for twins, not
  recommended for singletons without biochemistry)
• Ultrasound (18 20 weeks) current standard of
  care for all patients

Patients option to decline
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PRENATAL SCREENINGClinical Information Needed

• Date of Birth for age related a priori risk
• Gestation by LMP or by ultrasound
• Multiple Gestation AFP increases with number of
  babies serum screening for DS not available for
  multiples
• Maternal Weight marker levels decrease with
  increasing maternal weight, most important for
  AFP

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PRENATAL SCREENINGClinical Information Needed

• Diabetic Status Why is it important for prenatal
  screening?

• Maternal IDDM increases the risk of ONTD
• MSAFP is lower in women with IDDM

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PRENATAL SCREENINGClinical Information Needed

• Race why is it important for prenatal screening?

Blacks have higher MSAFP and lower population
prevalence of ONTD
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Prenatal Screening

• Case Examples
• (Trouble-shooting)

• Gestational age
• Maternal Weight
• Maternal Race
• Abnormal NT
• part II IPS not done

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Screen Positive for Down Syndrome Gestational
Age?

• Maternal Age at EDD 20.1 years
• Gestational Age 20w1d by LMP
• AFP 0.53 MoM
• uE3 0.56 MoM
• hCG 2.91 MoM
• InhibinA 1.66 MoM

• Risk of Down syndrome 130

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Screen Positive for Down SyndromeGestational
Age?

• Gestational Age (20w1d) AFP 0.53 MoM
• uE3 0.56 MoM
• hCG 2.91 MoM
• InhibinA 1.66 MoM

• 16w5d by BPD
• AFP 0.94 MoM
• uE3 1.23 MoM
• hCG 2.05 MoM
• InhibinA 1.99 MoM

• Risk of Down syndrome 11400
• INTERPRETATION SCREEN NEGATIVE

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MSS Positive for Down SyndromeCorrect
gestational age?

• Maternal Age at EDD 37.4 years
• Gestational Age 19w6d by u/s
• AFP 0.59 MoM
• uE3 0.82 MoM
• hCG 1.54 MoM
• Inhibin-A 0.81 MoM

• Risk of Down syndrome 1180

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MSS Positive Down SyndromeTranscription Error
CRL vs BPD

• Maternal Age at EDD 37.4 years
• Ultrasound BPD 15 mm (10w6d)
• Gestational Age (19w6d)
• AFP 0.59 MoM
• uE3 0.82 MoM
• hCG 1.54 MoM
• Inhibin-A 0.81 MoM

CRL 15 mm (8w0d) 17w0d at MSS AFP 0.95
MoM uE3 1.58 MoM hCG 1.16 MoM Inhibin-A
0.94 MoM

• Risk of Down syndrome 1880
• INTERPRETATION SCREEN NEGATIVE

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Practical Tidbit

• Accurate dating (by ultrasound) is important for
  correct interpretation of prenatal screening
• Less critical for IPS since ultrasound is
  incorporated (CRL correlated with NT)
• Dont forget to check dates even if MSS is
  negative

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Prenatal Screening

• Case Examples
• (Trouble-shooting)

• Gestational age
• Maternal Weight
• Maternal Race
• Abnormal NT
• part II IPS not done

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IPS positive for Down syndromePatients Weight
not provided

• Maternal Age at EDD 36.8 years
• Gestational Age 1st sample 13w3d
• Gestational Age 2nd sample 16w3d
• Nuchal 2.0mm 0.40 MoM AFP 0.40 MoM
• PAPP-A 0.38 MoM uE3 0.65 MoM hCG 0.80
  MoM

Risk of Down syndrome 170 Risk of NTD 113000
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IPS positive Patients Weight included

• Maternal Age at EDD 36.8 years
• Weight not known
• Gestational Age 16w3d by U/S
• AFP 0.40 MoM
• uE3 0.65 MoM
• hCG 0.80 MoM
• PAPP-A 0.38 MoM

Weight 295 lbs AFP 0.70 MoM uE3 0.89
MoM hCG 1.37 MoM PAPP-A 1.52 MoM

• INTERPRETATION SCREEN NEGATIVE
• (Down syndrome 13100 NTD 114000)

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IPS positive forDown syndrome and T18 Correct
Information?

• Maternal Age at EDD 30.9 years
• Gestational Age 1st sample 12w3d
• Gestational Age 2nd sample 15w1d
• NT 1.3mm 0.88 MoM AFP 0.73 MoM
• PAPP-A 0.15 MoM uE3 0.55 MoM hCG 0.64
  MoM

Risk of Down syndrome 1180 Risk of trisomy 18
114
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Screen Positive Corrected Patients Weight

• Maternal Age 33 years
• Weight 117.5 lbs
• Gestational Age 16w2d
• AFP 0.73 MoM
• uE3 0.55 MoM
• hCG 0.64 MoM
• PAPP-A 0.15 MoM

Weight 117.5 kg AFP 1.34 MoM uE3 0.66
MoM hCG 1.09 MoM PAPP-A 0.28 MoM

• INTERPRETATION SCREEN NEGATIVE
• (Down syndrome 13200 T18 no number reported if
  negative)

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Prenatal Screening

• Case Examples
• (Trouble-shooting)

• Gestational age
• Maternal Weight
• Maternal Race
• Abnormal NT
• part II IPS not done

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Screen positive NTDCorrect Information?

• Maternal Age at EDD 33.0 years
• Gestational Age 16w2d by U/S
• AFP 2.27 MoM
• uE3 0.49 MoM
• hCG 1.78 MoM

Risk of Open Spina Bifida 1399
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Screen Positive NTDCorrected Patients Race

• Maternal Age at EDD 33 years
• Race Caucasian
• Gestational Age 16w2d by U/S
• AFP 2.27 MoM
• uE3 0.49 MoM
• hCG 1.78 MoM

Race Black AFP 2.06 MoM uE3 0.49 MoM hCG
1.78 MoM

• Risk of Spina Bifida 11300
• INTERPRETATION SCREEN NEGATIVE

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Prenatal Screening

• Case Examples
• (Trouble-shooting)

• Gestational age
• Maternal Weight
• Maternal Race
• Abnormal NT
• part II IPS not done

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Patient chose IPS, but NT is abnormal

• Maternal Age at EDD 37.8 years
• CRL 56.9mm 12w2d
• Nuchal Translucency 3.8 mm 3.01 MoM
• (ideally, reported by phone or fax from the
  ultrasound unit)

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Abnormal NTOption to change IPS to FTS

• Maternal Age at EDD 37.8 years
• CRL 56.9mm 12w2d
• Nuchal Translucency 3.8 mm 3.01 MoM
• (discuss with patient, call or fax the screening
  lab)
• PAPP-A 0.43 MoM
• free beta hCG 1.73 MoM

Risk of Down syndrome 2 in 3
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FTS positive DS 2 in 3

• Ultrasound, blood drawn Feb 9th (12w2d)
• FTS report Feb 15th
• Seen in PND clinic Mar 3rd (15w3d).
• Amniocentesis same day.
• (could have been CVS if referred sooner)

Karyotype 47, XY, 21 Mar 17th (17w3d)
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Practical Tidbit

• Abnormal nuchal translucency should be treated as
  any other abnormal ultrasound finding
• Discuss options with patient, refer for genetic
  counselling and / or further testing as needed
• BUT normal NT is not a stand alone test for
  aneuploidy screening

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Prenatal Screening

• Case Examples
• (Trouble-shooting)

• Gestational age
• Maternal Weight
• Maternal Race
• Abnormal NT
• part II IPS not done

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IPS Requires Both Part I and Part II

• Maternal Age at EDD 34.8 years
• CRL 63.3 mm 12w4d
• Nuchal Translucency 1.5 mm 1.10 MoM

No result, waiting for part II serum
screening. Notification from lab at 17w6d when
part II not recd Report issued at 20w6d when
part II still not recd.
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IPS Requires Both Part I and Part II

• Maternal Age at EDD 34.8 years
• CRL 63.3 mm 12w4d
• Nuchal Translucency 1.5 mm 1.10 MoM

PAPP-A 0.53 MoM free beta hCG 4.43 MoM
Risk of Down syndrome 1 in 180 (reported at 21
weeks of gestation) Counselling Issues?
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Practical Tidbit

• Timing for IPS is determined by CRL
• (range for part I from 45 to 84 mm, or BPD less
  than 26.2 mm)
• If you dont complete IPS II before 17 6/7 weeks
  (according to the CRL for IPS I), they will send
  a reminder.
• If IPS II not received by 20 6/7, they will
  report FTS.

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Prenatal Screening

• A Few More Case Examples

• Dont be too pessimistic
• Ride the PND roller coaster
• Screening for other conditions

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IPS positive Down syndrome

• Maternal Age at EDD 35.8 years
• Gestational Age 1st sample 13w2d
• Gestational Age 2nd sample 17w1d
• Nuchal 2.8 mm 3.01 MoM AFP 0.84 MoM
• PAPP-A 0.43 MoM uE3 0.75 MoM hCG 1.73
  MoM

Risk of Down syndrome 9 in 10 Risk of NTD 1
in 16000
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Screen positive DS 9 in 10

• Seen in PND clinic (19w2d).
• G3, 2 healthy children at home.
• Family history of a paternal aunt with Down
  syndrome, another relative possible DS.
• Maternal karyotyping recommended (normal result).
• Amniocentesis same day.
• PI FISH Normal final karyotype Normal
• Ultrasound Normal (21w2d)

Whats the diagnosis?
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Prenatal Screening

• A Few More Case Examples

• Dont be too pessimistic
• Ride the PND roller coaster
• Screening for other conditions

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Case ExampleRide the PND roller coaster

• 26 year old,, first pregnancy
• routine prenatal screening

Gestational Age 20w0d AFP 5.54 MoM uE3
0.82 MoM hCG 0.85 MoM Inhibin-A 0.56 MoM
Risk of Neural Tube Defect 15 Screen
positive Risk of Down syndrome 120000 Screen
negative
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Screen positive NTD

• Referred for detailed ultrasound
• No evidence of NTD
• Abdominal wall defect, most likely an omphalocele
  (vs gastroschisis)
• Patient is completely blindsided
• Well prepared to hear about spina bifida,
  prepared to make decisions if severe anomalies
• Never heard of omphalocele

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Fetal omphalocele

• Abdominal wall defect, frequently associated with
  elevated maternal serum AFP
• Most are isolated, some have multiple anomalies,
  potential for syndromic associations
• Surgery in newborn period, potential
  complications
• 30 risk of chromosomal abnormalities (mostly
  T21, T18 or T13)

Counselling implications unexpected findings
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Abdominal Wall Defect Omphalocele
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Fetal omphalocele

• Most are isolated, some have multiple anomalies,
  potential for syndromic associations
• Surgery in newborn period, potential
  complications
• 30 risk of chromosomal abnormalities (mostly
  T21, T18 or T13)

• Amniocentesis, 21 weeks of gestation
• PI FISH is normal
• Apparently isolated omphalocele, transfer to MFM
  for ongoing care

Karyotype mosaic trisomy 14 (23 weeks)
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Prenatal Screening

• A Few More Case Examples

• Dont be too pessimistic
• Ride the PND roller coaster
• Screening for other conditions

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MSS positive T18
Maternal Age at EDD 32 years Gestational Age
17w3d by u/s AFP 2.21 MoM uE3 MoM hCG 0.28 MoM

• Screen Positive Risk of T18 18

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• Seen in PND 19w 6d. Ultrasound normal.
• 32 yo G1.
• Family history sisters son dry skin, needs
  moisturizer daily.
• No other family history

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Low uE3

• Associated with Smith Lemli Opitz syndrome (SLOS)
• Associated with X-linked ichthyosis steroid
  sulfatase (STS) deficiency
• Associated with normal outcome

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Amniocentesis

• Normal male karyotype
• FISH for STS probe microdeletion
• 46,XY.ish del(X)(p22.3p22.3)(STS-)

Diagnosis Steroid sulfatase deficiency, X-linked
ichthyosis
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Prenatal Screening Options

• First Trimester Screening (FTS)
• Maternal Serum Screening (MSS)
• Integrated Prenatal Screening (IPS)

81
PRENATAL SCREENINGClinical Information Needed

• Date of Birth for age related a priori risk
• Gestation by LMP or by ultrasound
• Maternal Weight marker levels decrease with
  increasing maternal weight, most important for
  AFP
• Diabetic Status maternal IDDM increases risk of
  ONTD, MSAFP is lower in women with IDDM
• Race Blacks have higher MSAFP and lower
  population prevalence of ONTD
• Multiple Gestation AFP increases with number of
  babies serum screening for DS not available for
  multiples

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PRENATAL SCREENINGGeneral Principles

• Should be offered to all women
• Originally designed for women for any age
• Offers women options for further testing if
  positive
• Reassurance if results negative does not
  guarantee healthy baby
• All positives reported by phone or fax
• Check dates if negative (MSS)

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Canadian Guidelines for Prenatal
DiagnosisGenetic Indications for Prenatal
Diagnosis(CCMG / SOGC, 2001)

• Screening for chromosomal anomalies based on
  biochemical markers should only be considered
  within a comprehensive screening and prenatal
  diagnosis program
• including interpretation, education, and
  follow-up counselling.

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Prenatal Screening for Fetal AneuploidySOGC
Practice Guideline(CCMG / SOGC, 2007)

• Screening programs should show respect for the
  needs and quality of life of persons with
  disabilities.
• Counselling should be nondirective and should
  respect a womans choice to accept or to refuse
  any or all of the testing or options offered at
  any point in the process.

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Things to think about in deciding about testing

• Understand that conditions such as Down syndrome
  or spina bifida are generally unrelated to family
  history all pregnancies have some risk.
• Pregnant women can choose whether to learn if
  their own pregnancy is at increased risk compared
  to background.

86
Womens Perceptions

• Does any woman believe herself to be at risk?
• Family lore mothers and grandmothers had
  healthy babies in their 40s and they didnt have
  testing or screening options.
• Prenatal screening as just one more blood test
  without really understanding that its about the
  health of the baby, and could lead to decisions
  about further testing.

87
Points to Consider..

• What would it mean for you if your baby has Down
  syndrome? Would you rather know that before the
  baby is born?
• What would it mean for you to find out during the
  pregnancy that the baby has a serious health
  problem? How would that be different if you find
  out after the baby is born?
• If you choose to do testing, you accept the added
  risk of miscarriage with the procedure. How
  would you handle a miscarriage?

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Reasons to Perform Prenatal Screening

• In most cases, the news will be good and may
  reassure the patient.
• Some patients may decide to terminate the
  pregnancy when faced with a significant
  abnormality.

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Reasons to Perform Prenatal Screening

• Anomaly detection may allow specialized antenatal
  or perinatal treatment in case of a lethal
  anomaly it might be reasonable to avoid a
  cesarean delivery for fetal distress.
• The parents have time to prepare emotionally and
  financially. They can educate themselves and
  their family members about the anomaly other
  children may be prepared before the birth.

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