Pregnancy Flashcards
(77 cards)
1st trimester length
Week 1- end of week 13
2nd trimester length
Week 14- end of week 26
3rd trimester length
Week 27 until birth
What is day 1 of pregnancy?
First day of menses (still counts as day 1 even though conception hasn’t taken place yet!)
Risk of harming the fetus at weeks 3 and 4
All or none effect; fetus may be fine or die via spontaneous abortion
Risk of harming the fetus at weeks 5-10
Major congenital anomalies likely
Risk of harming the fetus at weeks 11-birth
Functional defects and minor anomalies possible
What can harm the fetus? (Causes for birth defects and the like)
“Naturally occurring” congenital anomalies, other causes like genetics/chromosomal, environmental, unknown causes, medication-induced
Teratogens definition
Exposure to an agent that causes malformation of an embryo
Teratogenic medications during weeks 5-11 that can result in structural abnormalities
Methotrexate, cyclophosphamide, diethylstilbestrol, lithium, retinoids, thalidomide, anti-epileptic drugs (AEDs), Coumadin/warfarin
Teratogenic medications after 11 weeks that may result in growth retardation, CNS, or other abnormalities or death
NSAIDs, TTC ABX
3 mechanisms on how medications can harm the fetus
- Act directly on the fetus to cause damage, abnormal development, or death
- Alter the function of the placenta by causing blood vessels to construct and reduce the supply of oxygen and nutrients to the fetus
- Cause the muscle of the uterus to contract forcefully, indirectly injuring the fetus by reducing its blood supply or triggering preterm labor and delivery
When estimating risk for whether or not a medication can be used in a pregnant patient, what do you have to consider and take into effect?
Consider the quality of evidence; use safety data from randomized, controlled trials if possible
Principles for drug use during pregnancy
- selecting drugs that have been used safely for a long time
- prescribing doses at the lower end of the dosing range
- elimination nonessential medications and discouraging self-medication
4, avoiding medications known to be harmful (teratogens)
How do most drugs move from the maternal to fetal circulation?
Diffusion through the placenta
Functions of the placenta
Transfers oxygen and nutrients from mother to fetus and permits release for CO2 and waste from the fetus
Effect of lipophilicity on medication diffusion across the placenta
More lipophilic, will cross more readily
Effect of molecular weight on medication diffusion across the placenta
MW <5000Da readily crosses the placenta
Effect of protein binding on medication diffusion across the placenta
Unbound (low protein binding) drugs cross more easily but highly protein-bound drugs will cross more easily as pregnancy progresses
Effect of pH on medication diffusion across the placenta
Weak bases cross more easily
Maternal plasma volume, cardiac output, and GFR increase by ≥30-50% on medication use
Lowers concentration of renally cleared medications
Maternal increase in body fat on medication use
Increased Vd of fat-soluble medications
Maternal decrease in plasma albumin concentration on medication use
Increased Vd of highly protein-bound medications; unbound drugs cleared more rapidly by the liver and kidney so little effect on concentration
Maternal hepatic perfusion increase on medication use
Increased hepatic extraction of drugs
