O5. The Human Genome: Application to Obstetrics and Gynecology

I. Basic Genome Logic

• Human genome: complete genetic information in DNA.
• Somatic cells: 46 chromosomes. Gametes: 23 chromosomes.
• Genetic abnormality can be chromosomal, single-gene or multifactorial.
• Mechanisms relevant in OB-GYN: nondisjunction, balanced translocation, mosaicism, pathogenic familial mutation.

II. Obstetric Applications

• Risk assessment: maternal age, family history, previous affected fetus/child, recurrent miscarriage, consanguinity.
• Preconception application: identify carrier couples, optimize high-risk maternal disease, plan reproductive options.
• Pregnancy application: fetal anomaly or high-risk screen → choose appropriate genetic test.
• Result guides: prognosis, fetal surveillance, delivery place, neonatal care and parental decision-making.
• IVF application: preimplantation genetic testing when monogenic disease or structural rearrangement is known.
• Detailed genetic counseling and invasive prenatal diagnosis: see O41.

III. Gynecologic Applications

• Primary amenorrhea / DSD: karyotype or targeted testing can identify Turner syndrome, androgen insensitivity, gonadal dysgenesis or Y-chromosome material.
• Infertility / recurrent pregnancy loss: parental karyotype or selected genetic testing when history suggests chromosomal or monogenic cause.
• Premature ovarian insufficiency: consider genetic cause when young or family history is suspicious.
• Hereditary cancer: BRCA1/2 and Lynch syndrome affect surveillance, prophylactic surgery, systemic therapy and family testing.
• Tumor genetics: markers such as BRCA/HRD, MSI/MMR or HER2 may guide gynecologic cancer therapy.

IV. Practical Test Selection

• Karyotype: chromosome number and large structural rearrangements.
• Rapid aneuploidy tests: quick answer for common chromosomes, e.g. 13, 18, 21, X, Y.
• Microarray: fetal structural anomaly or suspected copy-number variant.
• Targeted molecular test: known familial mutation or strongly suspected syndrome.
• Sequencing: selected complex cases after specialist counseling.