42. Genetic counseling – Teratology

Question 1

what abnormalities can be caused my teratogens?

Answer 1

fetal loss and IUGR, malformations due to abnormal growth and morphogenesis, fetal and placental endocrine disruption, and abnormal central nervous system performance

Question 2

what are the three broad categories of teratogens?

Answer 2

1) drugs and chemical agents
2) infectious agents
3)radiation.

Question 3

principles of teratology

Answer 3

1. Fetal susceptibility- The efficacy of a particular teratogen is, in part, dependent on the genetic makeup of both mother and fetus, and maternal-fetal environment.
2. Dose A given teratogen can have a dose-dependent or a dose-independent effect.
3. Timing- Three stages of teratogenic susceptibility may be identified based on gestational age

Before implantation (1-week post-ovulation in humans) → there is no demonstrable teratogenic insult. 4-10 weeks gestation → the most vulnerable stage (period of organogenesis); the timing determines

which organ system or systems are affected.

From about the 4th month of pregnancy to the end of gestation → with the exception of brain and gonads, teratogenic exposure causes decreased growth without malformation (during this period embryonic development consists primarily of increasing organ size).

Question 4

what occurs in a dose-dependent effect causing teratology?

Answer 4

Depending on the particular teratogen, there may be:
1) no apparent effect at a low dose; 2) an organ-specific malformation at an intermediate dose; 3) a spontaneous abortion at a high dose.

Smaller doses administered over several days may produce different effects from a single large dose.

Question 5

why is timing an important principle in teratology?

Answer 5

the timing determines which organ system or systems are affected.
the most vulnerable stage (period of organogenesis) is 4-10 weeks of gestation
Before implantation → there is no demonstrable teratogenic insult

Question 6

what does teratogenic exposure cause from the 4th month of pregnancy to the end of gestation?

Answer 6

decreased growth without malformation (during this period embryonic development consists primarily of increasing organ size).
**with the exception of brain and gonads

Question 7

what are PLLR guidelines (pregnancy and lactation labeling rule)?

Answer 7

the new system to label drugs for pregnancy and lactation (2015)
composed of 3 subsections:
1. pregnancy- information for a pregnancy exposure registry for the drug when one is available.
2. lactation-information about using the drug while breastfeeding.
3. The Females and Males of Reproductive Potential subsection- information about the need for pregnancy testing, contraception recommendations, and information about infertility as it relates to the drug.

Question 8

Indications for genetic counseling and prenatal diagnosis

Answer 8

-Maternal age ≥ 35 y’
-A previous child with or a family history of birth defects, chromosomal abnormalities, or known genetic disorder
-A fetus with suspected abnormal US findings
-Other conditions predisposing the fetus to congenital abnormalities (consanguinity, maternal diabetes)

Question 9

What are the 4 questions used to guide genetic counseling?

Answer 9

1. What is the disease of interest?
2. How severe is the disease?
3. How is the disease inherited?
4. how can the disease be prevented?

Question 10

Indications for termination of pregnancy (maternal)

Answer 10

• Free-will (up to 12th week)
• Medical condition (CV disease, renal disease,
  neurologic disease, neoplastic disease)

Question 11

Indications for termination of pregnancy (fetal)

Answer 11

• Known major fetal anomaly (anencephaly, severe cardiac defect, renal agenesis)
• Chromosomal anomalies
• Inherited metabolic disease
• Fetal exposure to known teratogen or radiation

Question 12

Indications for termination of pregnancy (maternal-fetal)

Answer 12

• Intrauterine infection
• ROM before fetal viability
• Severe preeclampsia or eclampsia
• Polyhydramnios