From the Guidelines
The risk of chromosomal abnormalities in pregnancies increases significantly with maternal age, and women of advanced maternal age (typically defined as 35 years or older) may benefit from more comprehensive prenatal screening and diagnostic options, such as fluorescence in situ hybridization (FISH), which can detect approximately 65-70% of all clinically significant cytogenetic abnormalities 1.
Key Points to Consider
- The study by Hook (1981) demonstrates the age-related increase in chromosomal abnormalities, particularly trisomies, which is crucial for genetic counseling and prenatal care.
- According to the technical and clinical assessment of FISH by the ACMG/ASHG position statement 1, the detection rate of FISH rises with increasing age, approaching 80% for women over 35 years old.
- FISH can detect abnormalities associated with advanced maternal age, including those related to nondisjunction, which is a major contributor to age-related risks.
- The identification of de novo balanced rearrangements and marker chromosomes is critical in determining those rearrangements carrying the greatest risk of leading to abnormal liveborns, as stated in the study 1.
- Decisions to act on laboratory test information should be supported by two of the three possible pieces of information, i.e., FISH results, routine chromosome analysis, and clinical information, as recommended by the ACMG/ASHG position statement 1.
Implications for Clinical Practice
- Women of advanced maternal age should be offered comprehensive prenatal screening and diagnostic options, including FISH, to assess age-related risks.
- Healthcare providers should consider the age-related increase in chromosomal abnormalities when counseling patients and making decisions about prenatal care.
- The use of FISH as an initial study may become more favorable with either significantly lower costs or technical enhancements to available probe sets, as noted in the study 1.
From the Research
Chromosome Abnormalities and Maternal Age
- The study by Hook (1981) investigated the rates of chromosome abnormalities at different maternal ages, but the provided evidence does not directly cite this study 2, 3, 4, 5, 6.
- However, it is well-established that the risk of chromosome abnormalities increases with maternal age, as reported in several studies 2, 3, 4.
Prenatal Testing and Diagnosis
- Prenatal detection of chromosome abnormalities has been available for over 40 years, with methods including amniocentesis and chorionic villus sampling (CVS) 2.
- Noninvasive prenatal testing (NIPT) has also been developed, using cell-free fetal DNA in maternal blood to detect chromosomal aneuploidies 2.
- Invasive prenatal diagnosis, such as CVS and amniocentesis, carries a small but finite risk of miscarriage and is not feasible for all low-risk mothers 2, 5, 6.
Advanced Maternal Age and Pregnancy Outcomes
- Pregnancies at advanced maternal age (over 35 years) are associated with increased risks of adverse maternal and perinatal outcomes, including chromosomal abnormalities, miscarriage, and stillbirth 3, 4.
- The management of pregnancy in women of advanced maternal age requires careful consideration of these risks and the use of appropriate prenatal testing and diagnosis 3, 4.