Notes — Pregnancy: Teratogens, Genetics, and Safety

High-mercury fish (e.g., tuna, swordfish, some mackerel) can accumulate mercury that affects fetal brain development; the fetus cannot eliminate it as efficiently as the mother.
For the mother, mercury exposure is a concern, especially with continual intake; limit high-mercury fish and choose lower-mercury options.

Most exercise can continue with modifications; avoid starting new high-intensity activities.
If you were a runner, you can usually continue until mid-pregnancy, then taper to walking due to balance and fall risk.

Some antibiotics are safer than others; avoid drugs with known fetal risks (e.g., fluoroquinolones like Cipro can cause limb deformities).
Any prescription should account for fetal safety; doctors should be informed you are pregnant.
Antibiotics that require long courses (e.g., three times daily for ten days) are often avoided if possible in favor of shorter or safer regimens.

Not all OTCs are safe for the baby; some antihistamines can cause problems.
Ibuprofen: avoid in late pregnancy due to risk of hemorrhage at delivery; early pregnancy use is more nuanced.
Acetaminophen (Tylenol): previously considered safe, now advised to limit use to extreme situations due to potential liver effects on mother and fetus with heavy use.
Antidepressants: certain older findings linked birth defects; many have been reconsidered, but discuss risks with a clinician.
Herbal teas/supplements: not always safe; some herbal regimens used to induce labor can cause miscarriage if used early.

Vaccines: some vaccines are safe in early pregnancy and help protect the baby.
Measles exposure: early pregnancy exposure may cause miscarriage; late exposure can affect eye/ear development.
Early infections (viruses/bacteria) have varying effects on pregnancy.

Cats and litter boxes: toxoplasmosis risk from cat feces; have someone else clean litter or use precautions and inform providers of pregnancy.

If needed, dental X-rays or injuries should be discussed with a provider to minimize fetal exposure; disclose pregnancy status prior to imaging or procedures.

Fetal alcohol syndrome: alcohol use during pregnancy can cause physical defects and intellectual disabilities.
Smoking and other drug use increase risks; newborns may require monitoring for developmental issues.
Neonatal drug exposure (e.g., opiates) may involve child protective services and safety considerations for home care.

Timing matters: certain exposures cause miscarriage early on; others affect development later in pregnancy.
If a pregnancy is unplanned, unhealthy exposures may occur before awareness; planning and early prenatal care help minimize risks.

Half from each parent: $frac{1}{2}$ from mom and dad for the offspring's DNA.
Genetic variation: alleles are variant forms of a gene.
Population genetics: in a small, isolated gene pool, disease protection can be reduced, leading to higher expression of certain conditions.
Example: historical European royal families showed how limited diversity increased certain disorders (e.g., hemophilia).
Laws against close-relatives marriages exist to reduce homozygosity and congenital issues.
Genotype vs. phenotype:
- Genotype: the DNA sequence (what’s in the genes).
- Phenotype: observable traits (appearance, traits).
Dominant vs recessive:
- Dominant alleles primarily determine phenotype when present.
- Recessive alleles can be carried without shown effects unless paired with another recessive from the other parent.
Carriers can pass recessive alleles to offspring; expression depends on the other parent’s genes.
Sex determination:
- The sex of the baby is influenced by whether the sperm contributes an X or a Y chromosome.l
Twin concepts:
- Fraternal (dizygotic) twins: two separate eggs fertilized by two separate sperm (two zygotes); not more genetically similar than typical siblings; incidence about twice that of identical twins.

Minimize known teratogens (high-mercury seafood, tobacco, heavy alcohol use, certain medications).
Discuss all medications and supplements with a healthcare provider when planning pregnancy or during pregnancy.
Understand basic genetics: genotype vs phenotype, alleles, carriers, dominance, and how these relate to inheritance in offspring.
Recognize that timing of exposure matters for fetal risk; early pregnancy is a particularly sensitive window for many teratogens.