Midtrimester genetic amniocentesis in eastern Ontario: a review from 1970 to 1985

Comparative analysis of the application with the combination of CMA and karyotype in routine and late amniocentesis

PURPOSE

This is a retrospective comparative study. We aimed to analyze the results of karyotype and chromosomal microarray analysis (CMA) of amniotic fluid across different gestational weeks and evaluate the clinical value in prenatal diagnosis, particularly in the late pregnancies.

METHODS

Samples from 580 pregnant women of 18-23 weeks of gestation (mid-gestation group) and 196 pregnant women of 24-32 weeks of gestation (late group) were performed both standard G-band karyotype analysis and CMA.

RESULTS

Among the 580 pregnant women in the routine group, the most common indications were positive Down's screening (213/580, 36.7%), followed by advanced maternal age (196/580, 33.8%); while fetal structural anomalies on ultrasonography were the top reason for amniocentesis in the late group (56/196, 28.6%). In the routine group, the total detection rate was 12.1% (70/580), of which 4.1% (24/580) were identified by karyotype analysis and 11.2% (65/580) by CMA. The total detection rate was 15.3% (30/196) in the late group, of which 5.1% (10/196) were detected by karyotype analysis, and 14.3% (28/196) by CMA.

CONCLUSION

Karyotype analysis and CMA are complementary in detecting chromosomal abnormalities. Amniotic cavity puncture in the karyotype analysis in 18-23 weeks of gestation and 24-32 weeks of gestation is safe and effective, more obvious effect on the latter.

Amniocentesis in pregnancies at or beyond 24 weeks: an international multicenter study

BACKGROUND

Amniocentesis for genetic diagnosis is most commonly done between 15 and 22 weeks of gestation but can be performed at later gestational ages. The safety and genetic diagnostic accuracy of amniocentesis have been well-established through numerous large-scale multicenter studies for procedures before 24 weeks, but comprehensive data on late amniocentesis remain sparse.

OBJECTIVE

To evaluate the indications, diagnostic yield, safety, and maternal and fetal outcomes associated with amniocentesis performed at or beyond 24 weeks of gestation.

STUDY DESIGN

We conducted an international multicenter retrospective cohort study examining pregnant individuals who underwent amniocentesis for prenatal diagnostic testing at gestational ages between 24w0d and 36w6d. The study, spanning from 2011 to 2022, involved 9 referral centers. We included singleton or twin pregnancies with documented outcomes, excluding cases where other invasive procedures were performed during pregnancy or if amniocentesis was conducted for obstetric indications. We analyzed indications for late amniocentesis, types of genetic tests performed, their results, and the diagnostic yield, along with pregnancy outcomes and postprocedure complications.

RESULTS

Of the 752 pregnant individuals included in our study, late amniocentesis was primarily performed for the prenatal diagnosis of structural anomalies (91.6%), followed by suspected fetal infection (2.3%) and high-risk findings from cell-free DNA screening (1.9%). The median gestational age at the time of the procedure was 28w5d, and 98.3% of pregnant individuals received results of genetic testing before birth or pregnancy termination. The diagnostic yield was 22.9%, and a diagnosis was made 2.4 times more often for fetuses with anomalies in multiple organ systems (36.4%) compared to those with anomalies in a single organ system (15.3%). Additionally, the diagnostic yield varied depending on the specific organ system involved, with the highest yield for musculoskeletal anomalies (36.7%) and hydrops fetalis (36.4%) when a single organ system or entity was affected. The most prevalent genetic diagnoses were aneuploidies (46.8%), followed by copy number variants (26.3%) and monogenic disorders (22.2%). The median gestational age at delivery was 38w3d, with an average of 59 days between the procedure and delivery date. The overall complication rate within 2 weeks postprocedure was 1.2%. We found no significant difference in the rate of preterm delivery between pregnant individuals undergoing amniocentesis between 24 and 28 weeks and those between 28 and 32 weeks, reinforcing the procedure's safety across these gestational periods.

CONCLUSION

Late amniocentesis, at or after 24 weeks of gestation, especially for pregnancies complicated by multiple congenital anomalies, has a high diagnostic yield and a low complication rate, underscoring its clinical utility. It provides pregnant individuals and their providers with a comprehensive diagnostic evaluation and results before delivery, enabling informed counseling and optimized perinatal and neonatal care planning.

Role of late amniocentesis in the era of modern genomic technologies

OBJECTIVE

Traditionally, amniocentesis is performed between 17 and 23 weeks of gestation. This enables decisions regarding the course of pregnancy to be made before viability. Less frequently, amniocentesis is performed in the third trimester. Advanced genomic technologies such as chromosomal microarray analysis (CMA) provide more detailed information about the fetus compared with traditional G-banded chromosomal analysis. The aim of this study was to assess the indications for and safety of late amniocentesis, genetic-test results (especially in the context of CMA technology) and outcome of pregnancies that underwent the procedure after 24 weeks.

METHODS

Medical records were analyzed retrospectively of all women in whom amniocentesis was performed at a gestational age of 24 + 0 to 38 + 6 weeks, at Hadassah Medical Center, between June 2013 and March 2017. Parameters investigated included indications for late amniocentesis, complications, CMA results and pregnancy outcome.

RESULTS

During the study period, 291 women (303 fetuses, 277 singleton and 14 twin pregnancies; in two twin pairs, one fetus was terminated before amniocentesis) underwent late amniocentesis. CMA was performed in all instances of amniocentesis. The most frequent indication was abnormal sonographic finding(s) (204/303 fetuses, 67%). Preterm delivery occurred in 1.7% and 5.1% of pregnancies within the first week and within 1 month following the procedure, respectively. Aneuploidy was detected in nine (3%) fetuses and nine (3%) others had a pathogenic/likely pathogenic copy number variant, suggesting that CMA doubled the diagnostic yield of traditional karyotyping. Maximal diagnostic yield (17.5%) was achieved for the subgroup of fetuses referred with abnormal sonographic findings in two or more fetal anatomical systems. Variants of uncertain significance or susceptibility loci were found in another nine (3%) fetuses.

CONCLUSIONS

In pregnancies undergoing late amniocentesis, CMA increased detection rates of fetal abnormalities and had a shorter turnaround time compared with traditional chromosomal analysis; therefore, late amniocentesis may serve as a helpful tool for detecting fetal abnormalities or reassuring parents following late-appearing abnormal sonographic findings. However, CMA may expose findings of uncertain significance, about which the couple should be precounseled. The procedure appears to be safe. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.

Development and Evaluation of a Decision Aid About Prenatal Testing for Women of Advanced Maternal Age

OBJECTIVE

To develop and evaluate a decision aid designed to prepare patients of advanced maternal age for counseling about prenatal diagnostic testing.

SETTING

A regional genetics center.

DESIGN

A before/after study.

INTERVENTIONS

Participants used an audioguided workbook to learn about options and outcomes and to clarify personal risks, values, questions, and predispositions.

SUBJECTS

21 women of advanced maternal age and 17 spouses.

MAIN OUTCOME MEASURES

Knowledge of prenatal testing alternatives, decisional conflict, level of anxiety, and acceptability of the decision aid.

RESULTS

After using the decision aid, participants had significantly reduced decisional conflict (uncertainty) and a significant increase in knowledge. There was no effect on state or trait anxiety. More than three-quarters of participants were satisfied with the length, clarity, balance, and acceptability of the decision aid.

CONCLUSIONS

The decision aid shows promise as a useful aid for preparing couples for counseling.

Frequencies of chromosomal abnormalities at amniocentesis: over 20 years of cytogenetic analyses in one laboratory

Prenatal diagnosis of chromosomal disorders has been performed for more than 20 years, mainly for advanced maternal age. Chromosomal abnormality rates derived from second trimester amniocentesis have mainly come from a collection of small-scale studies from North America and Western Europe. Accurate risk estimates for chromosomal abnormalities are important tools for the physician or obstetrician who would need to make referrals to a prenatal genetic center. This paper presents amniocentesis rates of clinically significant cytogenetic abnormalities for various indications, including advanced maternal age, previous chromosomal abnormality, parental structural rearrangement and a family history of aneuploidy as defined in the text. These data come from a Canadian prenatal diagnosis laboratory with more than 20 years experience in second trimester cytogenetic analysis. They show that the overall frequency of chromosomal abnormalities for advanced maternal age (> or = 35 years) is 1.79%. In this group, 21% of all abnormalities are structural rearrangements (including markers) and less than half of all abnormalities are trisomy 21. The advanced maternal age specific risk of aneuploidies at second trimester is 1.24%. Recurrence risk for aneuploidy after a previous one is 1.29%. However, it is much higher (4.84%) for women of > or = 35 years. When a parent's brother, sister, nephew or niece is affected, the risk of occurrence of aneuploidies (0.24%) is not elevated. When there is a balanced translocation in one of the parents, the overall risk is 10.2% for unbalanced translocations and 37.3% for balanced translocations.

A retrospective survey of community based utilization of Tay Sachs screening in Eight New Jersey counties

The purpose of this study was to determine the rate of utilization of Tay Sachs disease screening by the Ashkenazi Jewish population. Pregnant women who were referred to one of three genetic centers in New Jersey for amniocentesis unrelated to Tay Sachs screening were the study population. 4490 charts were reviewed retrospectively to determine the at risk population for Tay Sachs disease (Ashkenazi Jews) and whether or not patients and their spouses had elected Tay Sachs screening prior to referral. A group of 25 patients who did not elect screening were questioned as to their specific reason for declining Tay Sachs screening. Overall community utilization was 90%. Of the couples who did not elect screening, 64% felt that their risk to have an affected child was too small, 16% could not recall Tay Sachs screening being offered to them, 8% felt that screening was inconvenient. Tay Sachs screening as a voluntary preventive health care program has a high utilization rate in our study group.

Prenatal diagnosis of fetal anomalies during the second trimester of pregnancy: their characterization and delineation of defects in pregnancies at risk

During a follow-up study of 19,790 pregnancies at risk for a genetic disease, from 1968 to 1989, 1083 fetuses were found to have an anomaly during the second trimester, leading to 977 terminations of pregnancy. Neural tube defects (31.4 per cent), chromosomal disorders (27.1 per cent), and Mendelian or multifactorial diseases (10.6 per cent) were the main causes of fetal anomaly. More than half (52.9 per cent) of the fetal anomalies were detected by routine ultrasound examination. Forty-two per cent of cystic hygromas were secondary to a chromosomal defect. We stress the importance of a comprehensive fetal and newborn examination to ensure an accurate diagnosis so that subsequently accurate counselling can be provided.

Prenatal diagnosis in multiple gestation: 20 years' experience with amniocentesis

Three hundred and thirty-nine cases of multiple gestation underwent prenatal diagnosis by amniocentesis. The spontaneous abortion rate (to 28 weeks) in this group was 3.57 per cent compared with our singleton abortion rate of 0.60 per cent. The perinatal mortality rate (PMR) and prematurity rate were not different from the singletons, and compared favourably with the PMR reported in the literature for multiple gestations which did not undergo any intervention during pregnancy. This increased abortion rate following amniocentesis may only represent the increased natural loss rate in multiple gestations, and not indicate any increased risk added by the procedure.

Perceived risk not actual risk predicts uptake of amniocentesis

A consecutive cohort of 71 women eligible for amniocentesis because they were over 38 years of age completed questionnaires during the first trimester of pregnancy. Sixty-one women underwent amniocentesis, an uptake rate of 86%. Uptake was associated with a less negative attitude towards termination of an affected baby and a higher perceived risk of the fetus being abnormal. It was not associated with actual age-related risks. There was no significant relation between actual risk and perceived risk. The results of this study suggests that it is important for doctors to understand the basis of women's decisions to have amniocentesis, and the difference between actual and perceived risk if they are to communicate effectively with women about the test and their options.

Amniocentesis or chorionic villus sampling for prenatal genetic testing: a decision analysis

We used decision analysis to examine the strategies of amniocentesis, chorionic villus sampling, and no prenatal testing for a pregnant woman who would be 35 years of age at the expected date of delivery. Probabilities were obtained from the obstetric and genetic literature, and utilities from previously published standard reference gambles and from responses of obstetric residents and students recorded on a linear rating scale. The expected utility of amniocentesis exceeded that of chorionic villus sampling by 0.1 utility units, and of no prenatal testing by 0.12 utility units. The decision was insensitive to clinically plausible values for the probabilities of spontaneous abortion after amniocentesis and chorionic villus sampling, the probabilities of abnormal and indeterminate chorionic villus sampling results, the probability of an abnormal amniocentesis result after an indeterminate chorionic villus sampling, the sensitivities and specificities of amniocentesis and chorionic villus sampling, and the probabilities of significant maternal morbidity after first- and second-trimester therapeutic abortion. Chorionic villus sampling was preferred to amniocentesis when the utility of a first-trimester therapeutic abortion exceeded that of a second-trimester abortion by 23.2 utility units, or when the anxiety "cost" of awaiting second-trimester amniocentesis results exceeded 0.1 utility unit. We conclude that over a range of assumptions concerning the probabilities involved in the prenatal testing decision, amniocentesis was preferred to chorionic villus sampling. However, for a decision maker for whom a second-trimester therapeutic abortion would be significantly less acceptable than a first-trimester procedure, or for whom the anxiety of awaiting second-trimester chromosomal diagnosis might be an important consideration, chorionic villus sampling could become the procedure of choice.

Maternal sex chromosome mosaicism diagnosed by amniocentesis and percutaneous umbilical cord sampling

We present a remarkable chain of events in which percutaneous umbilical cord sampling was performed in an attempt to clarify a situation of possible fetal sex chromosome mosaicism in an amniotic fluid culture and led to the discovery that the mother herself had a 45,X/46,XX/47,XXX chromosome constitution. This may have simply represented the chance concurrence of pseudo-mosaicism in the amniotic fluid culture of a woman with an abnormal sex chromosome constitution, but it is also possible that the 45,X colony was maternal in origin. Although clearly a most unusual circumstance, the possibility should be kept in mind when termination of a pregnancy is being considered because of apparent mosaicism in a prenatal diagnostic study.

Invasive prenatal testing

Invasive prenatal diagnosis is a major diagnostic tool which is used in modern obstetrical care. A synopsis of these techniques is provided to assist the family practitioner in providing this information to his patients.