A Yolk Sac Larger Than 5 mm Suggests an Abnormal Fetal Karyotype, Whereas an Absent Embryo Indicates a Normal Fetal Karyotype

Comparative cytogenetics of anembryonic pregnancies and missed abortions in human

Miscarriage is an important problem in human reproduction, affecting 10-15 % of clinically recognized pregnancies. The cases of embryonic death can be divided into missed abortion (MA), for which the ultrasound sign of the embryo death is the absence of cardiac activity, and anembryonic pregnancy (AP) without an embryo in the gestational sac. The aim of this study was to compare the frequency of chromosomal abnormalities in extraembryonic tissues detected by conventional cytogenetic analysis of spontaneous abortions depending on the presence or absence of an embryo. This is a retrospective study of 1551 spontaneous abortions analyzed using GTG-banding from 1990 to 2022 (266 cases of AP and 1285 cases of MA). A comparative analysis of the frequency of chromosomal abnormalities and the distribution of karyotype frequencies depending on the presence of an embryo in the gestational sac was carried out. Statistical analysis was performed using a chi-square test with a p <0.05 significance level. The total frequency of chromosomal abnormalities in the study was 53.6 % (832/1551). The proportion of abnormal karyotypes in the AP and MA groups did not differ significantly and amounted to 57.1 % (152/266) and 52.9 % (680/1285) for AP and MA, respectively (p = 0.209). Sex chromosome aneuploidies and triploidies were significantly less common in the AP group than in the MA group (2.3 % (6/266) vs 6.8 % (88/1285), p = 0.005 and 4.9 % (13/266) vs 8.9 % (114/1285), p = 0.031, respectively). Tetraploidies were registered more frequently in AP compared to MA (12.4 % (33/266) vs. 8.2 % (106/1285), p = 0.031). The sex ratio among abortions with a normal karyotype was 0.54 and 0.74 for AP and MA, respectively. Thus, although the frequencies of some types of chromosomal pathology differ between AP and MA, the total frequency of chromosomal abnormalities in AP is not increased compared to MA, which indicates the need to search for the causes of AP at other levels of the genome organization, including microstructural chromosomal rearrangements, monogenic mutations, imprinting disorders, and epigenetic abnormalities.

Maternal selection of human embryos in early gestation: Insights from recurrent miscarriage

Compared to most mammals, human pregnancy is unusual in that it involves chromosomally diverse embryos, cyclical breakdown and regeneration of the uterine mucosa, and intimate integration of fetal and maternal cells at the uteroplacental interface. Not surprisingly, pregnancy often falters in early gestation. Whether these losses result in clinical miscarriages depends on the origins and impacts of chromosomal errors on fetal development and the ability of the decidualizing endometrium to engage in embryo biosensing and selection. Aneuploidy originating in oocytes during meiosis drives the age-related risk of miscarriage. By contrast, the frequency of endometrial cycles with an impaired decidual response may account for the stepwise increase in miscarriage rates with each pregnancy loss independently of maternal age. Additional physiological mechanisms operate in early gestation to ensure that most failing pregnancies are lost before vascular maternal-fetal connections are established by the end of the first trimester. Here, we summarise how investigations into the mechanisms that cause miscarriage led to new insights into the processes that govern maternal selection of human embryos in early gestation.

Study on the correlation between the ultrasound phenotype and copy number variation of abnormal embryo in spontaneous abortion

OBJECTIVE

This study aimed to explore the correlation between the ultrasound phenotype and copy number variation (CNV) of abnormal embryos in spontaneous abortion by investigating the abnormal chromosome copy number of embryos at different developmental stages in early spontaneous abortion.

METHODS

A total of 539 patients who had early spontaneous abortion in our hospital between 2015 and 2019 were divided into seven groups according to the phenotype of abnormal embryonic development during pregnancy, and the embryonic tissues of the patients were subjected by single nucleotide polymorphism (SNP) microarray.

RESULTS

Among 377 cases with abnormal CNV, 295 (78.25%) cases had chromosome trisomy, and 28 (7.43%) cases had a combination of more than two chromosomes. Triploidy, tetraploidy, chromosome microdeletion/duplication, uniparental disomy, and monosomy 45,X were found in 32 (8.48%), five (1.32%), 31 (8.22%), four (1.02%), and eight (2.12%) cases, respectively. Two (0.53%) cases had autosomal chromosome 21 monosomy. Normal karyotype had the highest proportion in the empty sac group; trisomy 16 accounted for the bulk of chromosomes in the normal yolk sac group, complex triploidy occupied the most part in the abnormal yolk sac group, and no remarkable difference in chromosomal abnormality proportion was found between the normal and abnormal yolk sac groups; the most frequent chromosomal anomaly in a group of germ without cardiac activity and germ<5 mm was trisomy 16; triploidy was the most common in the group with 5 mm ≤ germ ≤ 15 mm, whereas the main distribution of chromosome karyotype was normal, followed by trisomy 13 in a group with germ>15 mm.

CONCLUSION

Abnormal embryos with different ultrasound phenotypes in early spontaneous abortion have various CNV types and characteristic distribution. Thus, ultrasound combined with SNP array can provide a basis for the etiological analysis of embryos in spontaneous abortion.

Early pregnancy ultrasound measurements and prediction of first trimester pregnancy loss: A logistic model

Our objective was to prospectively validate the use of gestational sac (GS), yolk sac (YS) diameter, crown-rump length (CRL), and embryonal heart rate (HR) dimensions to identify early pregnancy loss. This was a prospective cohort study of first trimester pregnancies. GS and YS diameter, CRL, and HR measurements were serially obtained in singleton and twin pregnancies from 6 through 10 weeks' gestation. Non-parametric tests and logistic regression models were used for comparisons of distributions and testing of associations. A total of 252 patients were included, of which 199 were singleton pregnancies, 51 were twins, and 2 were triplets (304 total fetuses). Fifty-two patients had 61 losses. We built nomograms with the changes of the parameters evaluated in ongoing, as well as in pregnancy loss. In the pregnancies which failed, all the parameters showed significant changes, with different temporal onsets: GS and YS were the first to become abnormal, deviating from normality as early as 6 weeks' gestation (OR 0.01, 95% CI 0.0-0.09, and OR 3.36, 95% CI 1.53-7.34, respectively), followed by changes in HR, and CRL, which became evident at 7 and 8 weeks (OR 0.96, 95% CI 0.92-1.0, and OR 0.59, 95% CI 0.48-0.73, respectively). Our observations showed that, after 5 complete weeks' gestation, a small GS and a large YS reliably predicted pregnancy loss. The YS reliably identified the occurrence of a miscarriage at least 7 days prior its occurrence. CRL and HR became abnormal at a later time in pregnancy and closer to the event. These findings have important implications for patient counseling and care planning, as well as a potential bearing on cost effectiveness within early pregnancy care.

Pilot study establishing a nomogram of yolk sac growth during the first trimester of pregnancy

AIM

The yolk sac (YS) has been reported as a reliable predictor of adverse pregnancy outcomes, however, it has always been evaluated cross-sectionally with a single ultrasound per patient. We sought to validate the use of YS dimensions in serial ultrasounds throughout the first 10 weeks of singleton and multiple gestations.

METHODS

This was a prospective cohort study where YS diameters were serially obtained with 2D ultrasound in singleton and multiple gestations from 5 to 11 weeks. Nonparametric test were used for comparisons with P < 0.05 indicating significance.

RESULTS

One hundred ninety-three patients were included, 42 twins (3 monochorionic and 39 dichorionic), 2 triplets (monochorionic twins plus a singleton) and 148 singleton pregnancies (238 total fetuses). There was no difference in YS dimensions in singleton versus multiple pregnancies. Starting at 5 weeks' gestation, the YS increased 0.4 mm (95% CI 0.3-0.5 mm) per week until 10 weeks' gestation. Forty-five fetuses were lost in the first trimester. The risk of pregnancy loss was higher with a large YS until 8 weeks (P ≤ 0.001), while after 8 weeks it was higher with a small YS (P < 0.005).

CONCLUSION

We established a nomogram of YS development during the first 10 weeks of pregnancy. The YS reliably detected pregnancies that ended in loss as early as 6 weeks' gestation. The YS was either smaller or larger than in ongoing pregnancies. While all pregnancies with large YS were lost within 10 weeks, those with smaller YS were lost beyond the first 10 weeks.

Do specific ultrasonography features identified at the time of early pregnancy loss predict fetal chromosomal abnormality? - A systematic review and meta-analysis

To investigate the association of specific ultrasonography features identified during the diagnosis of early pregnancy loss (EPL) and abnormal karyotype. This was a systematic review and meta-analysis conducted in accordance with PRISMA criteria. We searched PubMed, Cochrane and Ovid MEDLINE from 1977 to Jan 2017 to identify the articles that described EPL with karyotype and ultrasonography features. Risk differences were pooled to estimate the chromosomal abnormality rates in ultrasonography features, including pre-embryonic, enlarged yolk sac (YS), short crown rump length (CRL), small gestational sac (GS), symmetrical arrested growth embryo, or gestational sac with only a YS. Quality assessment of included studies was performed using Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) checklists for Observational Studies (2007 version). Thirteen studies were included in the meta-analysis. Chromosomal abnormality was more likely to occur in embryonic EPL and enlarged YS. On the other hand, short CRL, small GS, symmetrical arrested growth embryo, or gestational sac with only a YS, were not associated with an increased risk of fetal chromosomal abnormality. Ultrasonography features at the time of diagnosis of EPL have limited predictive value of fetal chromosomal abnormality.