Risk of Fetal Loss in Pregnancies Undergoing Midtrimester Amniocentesis after Inconclusive Chorionic Villus Sampling

Is Amniocentesis after CVS Risky?

OBJECTIVE

Approximately, 2% of women who undergo chorionic villi sampling (CVS) will subsequently undergo amniocentesis due to placental mosaicism or sampling/laboratory issues. Our objective was to compare obstetric outcomes in women who underwent both procedures with those who had CVS alone.

STUDY DESIGN

Retrospective case-control study of patients with singleton pregnancies undergoing invasive testing from 2010 to 2020 was performed. All women who underwent CVS followed by amniocentesis were compared with a control group who underwent CVS alone matched (2:1) for age and year of pregnancy. Women with pregnancy loss at <16 weeks were excluded from the control group. Pregnancies terminated for genetic abnormalities were excluded. Obstetric outcomes were compared between cases and controls. Student t-test and Fisher's exact test were used for statistical comparison.

RESULTS

During the study period 2,539 women underwent CVS, and 66 (2.6%) subsequently underwent amniocentesis. The 66 cases were compared with 132 age-matched controls who underwent CVS alone. Mean maternal age was 36.8 ± 3.4 years, and 43% of women were nulliparous. Amniocentesis was performed due to sampling or laboratory issues in 33% of cases, placental mosaicism in 44%, and further diagnostic testing in 23%. There were no pregnancy losses or stillbirths in either group. Those who had two invasive procedures delivered at similar gestational ages and birthweights and did not have higher rates of adverse outcomes compared with those who underwent CVS alone.

CONCLUSION

Patients considering CVS who are concerned about the possibility that a second invasive procedure could be required should be reassured that this does not appear to be associated with higher rates of adverse outcomes. Due to study size, we cannot exclude the possibility of small differences in uncommon outcomes, such as pregnancy loss or stillbirth.

KEY POINTS

· Amniocentesis may be recommended after CVS due to mosaicism, sampling issues, or further testing.. · Amniocentesis after CVS is not associated with pregnancy loss or other adverse outcomes compared.. · Patients who have both CVS and amniocentesis deliver at similar gestational ages and birthweights..

Performance of conventional cytogenetic analysis on chorionic villi when only one cell layer, cytotrophoblast or mesenchyme alone, is analyzed

OBJECTIVE

To provide an estimation of the probability of error when chorionic villi (CV) cytogenetic analysis is limited to a single placental layer; either a direct preparation (Dir) or long-term culture (LTC).

METHODS

We retrospectively reviewed cytogenetic studies on 81,593 consecutive CV samples in which both Dir and LTC were analyzed. All mosaic cases received amniocentesis. The false omission and false discovery rates were calculated by assessing the results that would have been reported when analysis was limited to either Dir or LTC.

RESULTS

For all abnormalities combined, the proportion of normal Dir or LTC only reports that would have been inconsistent with a subsequent amniocentesis was 0.09% and 0.03%, respectively (false omissions). Among abnormal reports based on Dir or LTC alone, 8.01% and 3.17%, respectively, would be inconsistent with a subsequent amniocentesis result (false discoveries). Differences are present for individual abnormalities.

CONCLUSIONS

From the perspective of identifying all abnormalities of potential clinical significance, the analysis of both placental layers is optimal. LTC alone is the preferred approach if only one layer of placenta is to be analyzed. Although rare, it is important to acknowledge that one cell layer analysis alone can cause misdiagnosis due to undetected mosaicism.

Risk factors for failed chorionic villus sampling: results of a 4-year retrospective study

Objectives: Chorionic villus sampling (CVS) allows for earlier results for aneuploidy or genomic abnormalities compared to amniocentesis. Nevertheless, the inability to provide complete results has been described as being more frequent with CVS. This study was conducted in order to identify risk factors for such failures.Study design: A retrospective single-center study was performed from January 2014 to December 2018. Participants were divided into two groups depending on whether complete CVS results were issued ("successful CVS group") or not ("failed CVS group"). Failure affected preliminary short-term cultures, long-term cultures, or both.Results: During the study period, 214 CVS were performed, 73 (34%) of which were classified in the failed CVS group. We observed significant intergroup differences between the successful and failed CVS groups for four variables: BMI (respectively 23.9 [±5.88] and 25.9 [±6.13] kg/m²), term at sampling (12.9 [±1.35] and 12.6 [±1.09] weeks gestation), trophoblastic location (posterior in 49 [40%] and 37 [66%] cases), and sampling approach (transcervical in 54 [43%] and 36 [64%] cases) (p < .05). In a stepwise binary logistic regression analysis, higher BMI, posterior trophoblastic location, and transcervical sampling approach were the only variables negatively influencing CVS success, with respective aOR [95% CI] of 0.947 [0.898; 0.996], 0.322 [0.160; 0.634], and 0.466 [0.238; 0.900].Conclusions: In the presence of CVS failure risk factors, a discussion could be initiated regarding a deferred amniocentesis as a first option.

Prevalence of mosaicism in uncultured chorionic villus samples after chromosomal microarray and clinical outcome in pregnancies affected by confined placental mosaicism

OBJECTIVE

To evaluate the prevalence of mosaicism in chorionic villus sampling (CVS) samples after chromosomal microarray (CMA) and clinical outcome of pregnancies affected by confined placental mosaicism.

METHOD

We retrieved all results from CMA, array-based comparative genomic hybridization, on CVS samples from January 2011 to November 2017 from Central and North Denmark Regions. Mosaic results from uncultured chorionic villi, cytotrophoblasts and mesenchymal cells, after CVS and follow-up on amniocytes, fetal tissue, or postnatal blood were studied and matched with clinical data from The Danish Fetal Medicine Database.

RESULTS

Prevalence of mosaicism was 93 out of 2,288 (4.1%) CVS samples of which 17 (18.3%) concerned submicroscopic copy number variations (CNVs) <10 Mb. Follow-up analyses were performed in 62 cases. True fetal mosaicism (TFM) was confirmed in 18.4% (7/38) when mosaicism involved whole chromosome aneuploidy and in 25.0% (6/24), when involving a CNV (P = .59). Median birth weight z-score was higher in cases of confined placental mosaicism for a CNV (0.21) than cases involving whole chromosomes (-0.74) (P = .02).

CONCLUSION

Prevalence of mosaicism in CVS samples is higher after CMA on uncultured tissue than after conventional karyotyping on cultured tissue. The risk of TFM is equally high in cases of mosaicism for CNVs and whole chromosomes.