Preconception Counselling (PreTest Notes) Flashcards
(48 cards)
How does an initial spontaneous abortion affect the risk of recurrence in future pregnancy?
The risk remains the same. An initial spontaneous abortion regardless or karyotype or gender of the child does not change the risk of recurrence in future pregnancy
What proportion of spontaneous abortions in the first trimester are found to have chromosomal abnormalities?
50%
What is the most common group of chromosomal abnormalities causing first trimester loss?
Autosomal trisomies
What is the most common single anomaly found in first trimester miscarriage?
45X (Turner syndrome)
What screening should be done for patients with recurrent miscarriage?
- Parental karyotype
- Thyroid function
- DM
- Collagen vascular disorders
- Lupus anticoagulant
Why should a hysterosalpingogram be ordered in second trimester pregnancy loss?
Rule out uterine structural abnormalities e.g.:
- bicornuate uterus
- septate uterus
- unicornuate uterus
When does paternal age contribute to aneuploidy?
Father age ~55+
The risk of what genetic conditions are most increased with increased paternal age?
Point mutations
When is the optimal time for NT measurement?
12-13 weeks
What are the sequelae of alcohol consumption during pregnancy?
- IUGR
- craniofacial abnormalities
- mental retardation
- cardiac anomalies
- joint defects
What effect do tetracyclines have on the foetus in utero?
Interfere with bone development and may produce stained teeth
How should patients who have inadvertently become pregnant on birth control pills be counselled?
- Incidence of birth defects is no higher for them than the general population.
- Progesterone implicate in multiple birth defects but studies failed to demonstrate significant association with increased risk.
What is the assumed threshold for increased foetal risk from radiation?
10 rads
Achondroplasia pattern of inheritance?
Autosomal dominant
What accounts for 90% of achondroplasia?
New mutations
What are the special considerations in managing a pregnant patient with achondroplasia?
- C section due to distorted maternal pelvis
- C section to protect foetus neck if also has achondroplasia
- Spinal stenosis may make spinal / epidural anaesthesia more challenging
What is the likelihood of a child of a 46XY father and mother who carries a balanced 13;13 translocation having chromosomal abnormality? Why?
100%: carriers of a balanced translocation of the same chromosome are phenotypically normal BUT in the process of gamete formation the translocated chr cannot divide and therefore meiosis products end up with either 2 or 0 copies of the chr.
Which monosomies can be live births?
Everything lethal except monosomy X (Turner)
What is an encephalocele?
Version of a NTD involving outpouching of neural tissue through a defect in the skull
What is a cystic hygroma?
Emerges from base of neck with an intact skull present; easily confused with encephalocele
What is the MSAFP used to screen for?
Offered 15-21 weeks gestation to screen for NTDs
MSAFP cutoff?
2.5 MoM (multiples of median)
What should be conducted if elevated MSAFP?
Genetic amniocentesis: elevated AFP and acetylcholinesterase in amniotic fluid. If both elevated, identifies 100% cases of anencephaly and open NTDs.
What is the incidence of NTDs?
1.4-2.0 / 1000
