Prognostic significance of the human yolk sac assessed by ultrasonography

Predictive value of ultrasound-related scoring system on embryo development in early pregnancy after IVF/ICSI: An observation of embryonic quality

OBJECTIVE

This study aims to evaluate the value of the ultrasound-related scoring system on pregnant patients receiving assisted reproductive technology (IVF/ICSI) and early pregnancy outcome.

MATERIALS AND METHODS

This prospective study included 208 pregnant women receiving assisted reproductive technology (IVF/ICSI). The following ultrasound parameters were measured: gestational sac size, the proportion of the embryo and gestational sac (embryo/gestational sac), yolk sac size, and fetal cardiac activity. The above data were assigned according to the ongoing pregnancy rate (up to 14 weeks), and the score increased parallel to the pregnancy rate. All patients were grouped according to their scores.

RESULTS

Patients with a score of 4-5 had a low ongoing pregnancy rate of 14.29%, while patients with a score of 6-7 had an ongoing pregnancy rate of 55.56%. Surprisingly, patients with a score of 8-9 had an ongoing pregnancy rate of 97.22%. In addition, it was found that the ongoing pregnancy rate was 100% (36/36) in patients with a score of 9. Conversely, there was no ongoing pregnancy in patients with a score of 4.

CONCLUSION

First, this scoring system is strongly associated with an ongoing pregnancy of over 14 weeks. Second, some reassurance can be given to patients with favorable ultrasound parameters, regardless of maternal age or previous pregnancy loss. Third, it would be meaningless to continue the pregnancy in patients with a score of 4, according to the scoring system. Fourth, patients without cardiac activity and embryos at days 33-35 after embryo transfer should discontinue the pregnancy, while patients with embryos should proceed with the pregnancy.

A logistic model to predict early pregnancy loss following in vitro fertilization based on 2601 infertility patients

BACKGROUND

According to previous studies, even after embryonic cardiac activity is detected, the pregnancy loss rate remains 3-4 %. The objectives of this study were to investigate the differences in ultrasound parameters between a miscarriage group and an ongoing pregnancy group during the 1(st) trimester and to build a logistic model to predict early pregnancy loss (EPL) after the appearance of embryonic cardiac activity in patients who have undergone in vitro fertilization embryo transfer (IVF-ET) treatment.

METHOD

A total of 2601 patients with early singleton pregnancies with embryonic cardiac activity were retrospectively analyzed after IVF from January 2010 to June 2011. Transvaginal sonography (TVS) was performed at 6 to 10 weeks of gestational age (GA). The mean gestational sac diameter (MSD), crown-rump length (CRL), fetal heart rate (FHR), and yolk sac diameter (YSD) were measured by TVS.

RESULTS

A total of 2400 patients had an ongoing pregnancy and an additional 201 (7.7 %) patients miscarried during the first trimester after fetal cardiac activity had been established. The maternal age (MA) and infertility duration were much greater, and the MSD, CRL, and FHR were much lower in the miscarriage group than in the ongoing pregnancy group after IVF (P < 0.05). The prediction model utilized the following equation: the possibility of EPL = exp(z)/(1 + exp(z)), where z = -21.456 + (0.114 × MA) + (4.305 × × GA) - (0.043 × MSD) - (0.359 × CRL) - (0.091 × FHR) + 2.243 (fluid collection present around the gestational sac (GS)) + 2.519 (when YSD < 3) or - 0.347 (when YSD > 5.5).

CONCLUSION

The MA, MSD, CRL, YSD, FHR, infertility duration, and fluid collection around the GS were each correlated with EPL after IVF in infertile patients. A logistic model is a useful tool for predicting EPL after the appearance of embryonic cardiac activity (area under the curve [AUC] = 0.909).

Prediction of abortion using three-dimensional ultrasound volumetry of the gestational sac and the amniotic sac in threatened abortion

PURPOSE

To determine whether gestational sac volume (GSV) or amniotic sac volume (ASV) and/or the difference between them can predict abortion in women with first-trimester threatened abortion.

METHODS

Ninety patients between 6 and 12 weeks of gestation presenting with vaginal bleeding were studied. Seventy-six delivered after 24 weeks of gestation (group A) and 14 aborted before 20 weeks of gestation (group B). All patients had a singleton viable pregnancy demonstrated by transvaginal ultrasound. Gestational sac and amniotic sac volumes were measured in all the patients using three-dimensional transvaginal ultrasound with Virtual Organ Computer-aided Analysis software, and the gestational sac volume - amniotic sac volume (GSV - ASV) was calculated.

RESULTS

The groups did not differ in terms of age, parity, number of previous abortions, or term deliveries. The GSV (group A: mean 32.0 ± 27.7 cm(3) ; group B: 26.7 ± 29.1 cm(3) ) and the ASV (group A: 21.1 ± 25.5 cm(3) ; group B: 20.6 ± 26.0 cm(3) ) were not statistically different, while the GSV - ASV was significantly smaller in group B (aborting before week 20) (group A: 10.9 ± 10.9 cm(3) ; group B: 6.1 ± 8.6 cm(3) ; p < 0.05). Using receiver operator curves, the area under the curve for predicting normal pregnancy outcome of the GSV - ASV measurement was 0.654. When the GSV - ASV was 1.8 cm(3) or less, abortion was predicted with 84% sensitivity and 43% specificity.

CONCLUSIONS

The measurement of the GSV and the ASV are not good predictors of abortion in patients with first-trimester vaginal bleeding, whereas the use of the GSV - ASV may be helpful in predicting the outcome of pregnancy.

Triple ultrasound markers including fetal cardiac activity are related to miscarriage risk

OBJECTIVE

To identify early ultrasound markers in pregnant patients that predict a favorable pregnancy outcome.

DESIGN

Retrospective case-control study.

SETTING

Infertility patients in fertility clinic.

PATIENT(S)

1051 women with early pregnancies conceived after fertility treatment.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Ongoing pregnancy >20 weeks' gestation.

RESULT(S)

Ongoing pregnancy rate was 90.5% for those pregnancies having early fetal cardiac activity (odds ratio [OR] = 66.5). Gestational sac diameter ≥12 mm was associated with ongoing pregnancy rate of 91.9%. Small gestational sac diameter, <8 mm, was associated with high miscarriage rate, 85.3%. Ongoing pregnancy rates for yolk sac diameter <2 mm, 2-6 mm, and >6 mm were 20%, 89.2%, and 20%, respectively (OR = 33.1, 2-6 vs <2 mm; OR = 33.1, 2-6 vs >6 mm). Ongoing pregnancy rate was 94% when all three markers were present.

CONCLUSION(S)

On postconception days 33-36, gestational sac diameter ≥12 mm, yolk sac diameter 2-6 mm, and the presence of fetal cardiac activity were favorable markers.

Sonographic markers of aneuploidies at 6-10 weeks of gestation

OBJECTIVES

To determine if sonographic features of live embryos at 6-10 weeks' gestation are altered in aneuploidies.

METHODS

Embryonic crown rump length (CRL), embryonic heart rate, gestational sac diameter (GSD) and yolk sac diameter (YSD) were measured by transvaginal sonography in 5603 live embryos from singleton pregnancies at 6-10 weeks' gestation. The measurements were expressed as differences from the expected normal mean for CRL (delta values) and median delta values in the aneuploid cases were compared to the euploid group.

RESULTS

5393 pregnancies resulted in the live birth of phenotypically normal neonates and these cases constituted the euploid group. In 55 cases there was subsequent prenatal diagnosis of aneuploidies (trisomy 21, n=28; trisomy 18, n=10; trisomy 13, n=10; triploidy, n=4; Turner syndrome, n=3). The median and interquartile range (IQR) of delta embryonic heart rate in trisomy 18 was -19.44 (-23.77 to -7.20)bpm and in trisomy 13 it was 11.12 (7.25 to 20.39)bpm, which were significantly lower and higher, respectively, than in euploid embryos (median -0.05, IQR -6.18 to 6.21bpm). The median delta YSD in trisomy 21 was higher than in euploid fetuses (median 0.56, IQR 0.23 to 0.79 and median -0.17, IQR -3.11 to 2.82 mm). There were no other significant differences in measurements between the groups.

CONCLUSION

At 6-10 weeks' gestation there are sonographically detectable differences between euploid and trisomic embryos.

Ultrasonographic prediction of early miscarriage

BACKGROUND

The aim of this retrospective study was to assess the value of maternal history and ultrasound scan findings at 6-10 weeks for predicting early miscarriage.

METHODS

Embryonic crown-rump length (CRL), heart rate (HR), gestational sac diameter (GSD) and yolk sac diameter (YSD) were compared in two groups of women with singleton pregnancies attending an early pregnancy unit. In the first group the initial scan demonstrated a live embryo but in a subsequent visit the scan showed a dead embryo, complete or incomplete miscarriage. In the second group with a live embryo there was subsequent live birth of a normal neonate.

RESULTS

There were 729 pregnancies with miscarriage and 4698 with normal outcome. Logistic regression analysis demonstrated that in the prediction of miscarriage the risk was higher in women of African racial origin [odds ratio (OR) 1.62], cigarette smokers (OR 1.91) and those with vaginal bleeding (OR 2.03) and increased with maternal age (OR 1.05) and YSD (OR 1.88) and was inversely related to CRL (OR 0.79), HR (OR 0.96) and GSD (OR 0.84). At false-positive rate of 30%, the detection rate of miscarriage in screening by vaginal bleeding was 45%, 53% by the addition of maternal history factors and 85.7% by the addition of ultrasound findings.

CONCLUSIONS

In early pregnancy a prediction of miscarriage can be provided by a combination of maternal characteristics and ultrasound findings and the estimated risk can be used to rationalize follow-up. Our multivariate model requires prospective evaluation in a new sample population.

Gestational sac volume in missed abortion and anembryonic pregnancy compared to normal pregnancy

PURPOSE

To compare gestational sac (GS) volume (GSV) between normal pregnancies and missed abortions and anembryonic pregnancies and to determine at what gestational age differences in GS volume become evident. METHODS.: GSV in missed abortion and anembryonic pregnancy were measured using three-dimensional ultrasound and the results were compared with GSV in normal pregnancies. Pregnancies between 6 and 12(+6) gestational weeks of age according to last menstrual period were included in normal pregnancies, missed abortions, and anembryonic pregnancies.

RESULTS

There were 141 normal pregnancies and 82 missed or anembryonic abortions. GSV was significantly larger in normal pregnancies than in missed or anembryonic abortion: 27.51 + or - 25.25 cm(3) and 8.04 + or - 10.54 cm(3), respectively (p < 0.001). When stratified by weeks, statistically significant differences were found beginning at 7 weeks, while GSV measurements were not significantly different between the normal and abnormal pregnancies from 6 to 6(+6) weeks.

CONCLUSION

GSV in missed abortion and anembryonic pregnancies is significantly smaller than in normal pregnancies, starting at 7 weeks of gestational age. This finding may be helpful in the diagnosis of missed abortion or anembryonic pregnancies in selected cases.

Three-dimensional sonographic volumetry of the gestational sac and the amniotic sac in the first trimester

OBJECTIVE

The purpose of this study was to measure the volumes of the gestational sac and amniotic sac in normal pregnancies during the first trimester with 3-dimensional sonography to prepare nomograms.

METHODS

One hundred fifty-one patients between 6 and 12 weeks' gestation were studied. Nine aborted and were excluded, leaving 142 patients for evaluation. Inclusion criteria were a singleton viable pregnancy shown by transvaginal sonography and continuation of the pregnancy beyond 24 weeks. Women with known thrombophilia or fetal malformations were excluded. In all patients, gestational sac and amniotic sac volumes were measured by 3-dimensional transvaginal sonography with virtual organ computer-aided analysis software.

RESULTS

The mean gestational sac volume was 20.35 mL (range, 0.7-113 mL) and correlated closely with the gestational age (GA) (r2 = 0.769; P << .001) and crown-rump length (CRL) (r2 = 0.823; P << .001). The mean amniotic sac volume was 3.69 mL (range, 0.01-92.1 mL) and also had a strong correlation with the GA (r2 = 0.869; P << .001) and CRL (r2 = 0.919; P << .001).

CONCLUSIONS

Gestational sac and amniotic sac volumes show excellent correlation with the GA and CRL and hence may be used for determining the GA. Larger studies are needed to determine the importance of these volumes in predicting normal pregnancy outcomes and whether these volumes can be used in the management of pregnancies at risk for abortion.

Doppler examination of uteroplacental circulation in early pregnancy: can it predict adverse outcome?

PURPOSE

To determine whether spectral Doppler measurements obtained from bilateral uterine, arcuate, radial, and spiral arteries in early gestation correlate with adverse pregnancy outcome.

METHODS

One hundred five pregnant women underwent transvaginal Doppler sonographic examination of uteroplacental circulation at 6-12 weeks' gestation. Resistance index (RI) and pulsatility index (PI) of bilateral uterine, arcuate, radial, and spiral arteries were measured. Diameters of gestational sac (GS) and yolk sac, crown-rump length (CRL), GS-CRL difference, and GS/CRL ratio were also recorded. Correlation was made with pregnancy outcome.

RESULTS

Sixteen women developed adverse pregnancy outcome. In these women, right uterine artery PI and RI were significantly higher than in women with normal obstetrical outcome. Spiral artery PI and RI values were also higher, but the difference was not statistically significant. GS-CRL difference, GS/CRL ratio, and yolk sac diameters were significantly lower in this group.

CONCLUSION

Transvaginal Doppler examination can detect hemodynamic changes in uteroplacental circulation associated with subsequent adverse pregnancy outcome.

The role of ultrasound imaging in diagnosing and investigating early pregnancy failure

The advent of high-resolution transvaginal ultrasound (TVS) has revolutionized our understanding of the pathophysiology and the management of early pregnancy failure. Knowledge of the ultrasound appearances of normal early pregnancy development and a good understanding of its pitfalls are essential for the diagnosis and management of early pregnancy failure. Ultrasound imaging has rapidly replaced all other techniques used to study normal human development in the first trimester, and ultrasound features of the early gestational sac have corroborated anatomical studies showing that the first structures to appear are the celomic cavity and the secondary yolk sac. No single ultrasound measurement of the different anatomical features in the first trimester has been shown to have a high predictive value for determining early pregnancy outcome. Similarly, Doppler studies have failed to demonstrate abnormal blood flow indices in the first-trimester uteroplacental circulation of pregnancies that subsequently end in miscarriage. Ultrasound parameters combined with maternal serum hormone levels, maternal age, smoking habits, obstetric history and the occurrence of vaginal bleeding have all been combined in multivariate analyses, with mixed results. Combined ultrasound and in-vitro experiments have demonstrated that the maternal circulation inside the placenta starts at the periphery at around 9 weeks of gestation and that this is associated with a physiological oxidative stress which could be the trigger for the formation of the placental membranes. Abnormal development of these membranes can result in subchorionic hemorrhage and threatened miscarriage with subsequent long-term consequences such as preterm rupture of the membranes and preterm labor, irrespective of the finding of a hematoma on ultrasound. In both euploid and aneuploid missed miscarriages there is clear ultrasound evidence for excessive entry of maternal blood at a very early stage inside the developing placenta resulting in oxidative stress and subsequent degeneration of villous tissue. The finding of blood flow in the intervillous space in cases of first-trimester miscarriage using color Doppler also appears to be useful in the prediction of success of expectant management. Miscarriages with blood flow within the intervillous space are up to four times more likely to complete with expectant management. TVS is considered the gold standard in the diagnosis and management of incomplete miscarriage. Expectant management of miscarriage, using ultrasound parameters to determine eligibility, could significantly reduce the number of unnecessary evacuations of the retained products of conception, depending on the criteria used.

Events from ovulation to implantation studied by three-dimensional ultrasound

During the last decade transvaginal color Doppler has played an important role in increasing understanding of early human development. Although our knowledge of early pregnancy development has recently improved, little is known about the most critical period of human development: between conception and implantation. Recent advances in 3D ultrasound have made studies of follicular development, ovulation and uterine receptivity more accurate. The same method can be used for evaluation of the Fallopian tube patency and assessment of the ovarian and uterine causes of infertility which hamper processes of early human development. Storage capacities, reconstruction of the volume images and simultaneous viewing of all three orthogonal planes are the main advantages of this method. Introducing 3D ultrasound into assessment of early pregnancy has enabled visualization and volume estimation of the gestational sac, yolk sac and embryo. Switching on power Doppler superimposed to 3D gray scale can detect early vasculogenesis within the intervillous space and embryo/fetus. Here we review the potential application of this novel technique in monitoring the morphological and functional processes from ovulation towards implantation and early pregnancy.

Yolk sacs in twin pregnancy

OBJECTIVE

The purpose of this study was to evaluate the relationship between the yolk sacs separated or not separated by septum and chorionicity twin pregnancies scanned early in the first trimester, and the relation between size and morphologic features of the yolk sac and the outcome of twin pregnancies.

RESULTS

In all 38 sets of twins two yolk sacs were identified. During the first trimester of a dichorionic twin pregnancy, the yolk sacs were always separated by a septum and not separated ("Eight" sign) in monochorionic twin pregnancy. In five cases, one of yolk sac was abnormally large (> 8 mm) and had thin wall. Four of the five mothers spontaneously aborted during the next 2-3 weeks. In one case of monochorionic twin ectopic pregnancy two yolk sacs were seen normally.

CONCLUSION

The sonographic identification of yolk sacs in multiple pregnancies allows an early and efficient recognition of presence and chorionicity of twin pregnancy, both in intra- and extrauterine. Identification of abnormal yolk sac or yolk sacs suggests death of one or all embryos.

Volume and vascularity of the yolk sac studied by three-dimensional ultrasound and color Doppler

The aim of our study was to assess the volume of the gestational sac and yolk sac throughout the first trimester of pregnancy, and to establish the relationship between the yolk sac volume measurements and vascularity visualization rates. Eighty women with uncomplicated singleton pregnancies between 5 and 12 weeks were evaluated by three-dimensional and color Doppler ultrasound (Combison 530, Kretztechnik). Regression analysis revealed exponential rise of the gestational sac volume with gestational age throughout the first trimester. An exponential rise of the yolk sac volume was noticed between gestational weeks 5 and 8, followed by gradual increase of the yolk sac volume between the gestational weeks 8 and 10. After reaching the plateau from 10 to 11 weeks, yolk sac volume started to decrease. The highest visualization rates for the yolk sac vessels were obtained between gestational weeks 7 and 8. When yolk sac reached the maximum size between 10 and 11 weeks, reduced vascularity was demonstrated. Three-dimensional ultrasound allowed estimation of the gestational sac and yolk sac volumes throughout the first trimester of pregnancy. Both of these measurements seem to be useful prognostic parameters for the pregnancy outcome. The combination of functional and volumetric data provides much useful information on early human development.

Transvaginal sonography of the yolk sac in normal and abnormal pregnancy

A cross-sectional study comprising 117 consecutive first trimester singleton pregnancies was performed using transvaginal sonography (TVS) to evaluate size abnormalities of the secondary yolk sac (YS) vis-à-vis pregnancy outcome. In normal pregnancy outcome (NPO) the YS diameter showed an increase from the 5th to the 11th week, menstrual age, followed by a decrease and its disappearance after 12 weeks. A YS of abnormal size was statistically significant (p < 0.001) in spontaneous abortion (SA) versus NPO, with a sensitivity of 68.7%, a specificity of 99%, a positive predictive value of 91.6% and a negative predictive value of 95.2%. These preliminary results indicate that a measurement of the YS very early in gestation may be a useful marker of pregnancy outcome.

Yolk sac concentration of prostaglandin E2 in diabetic pregnancy: further clues to the etiology of diabetic embryopathy

Fetal malformation associated with maternal diabetes occurs before the seventh week of pregnancy. Current hypotheses suggest that the diabetic milieu causes a reduction in phosphatidylinositol turnover, leading to a disruption in the arachidonic acid cascade and resulting in a deficiency of prostaglandins, particularly prostaglandin E2. This in turn results in a wide variety of congenital anomalies. This hypothesis has not been tested experimentally in humans. The yolk sac is thought to be the most important source of nutrition in early pregnancy. We sought to compare yolk sac prostaglandin levels in normal and diabetic women. Under ultrasonographic guidance, yolk sacs were aspirated form 8 normal and 12 diabetic women ranging from 8 to 10 weeks gestational age prior to elective abortion. Prostaglandin E2 levels were determined using RIA. The mean prostaglandin E2 level in normal controls was 3605 pg/mL, and was undetected in all of the yolk sacs aspirated from diabetic women (P < 0.001). Yolk sac diameter in diabetic pregnancies was 1.2 mm larger than that of normal pregnancies. The functional and morphological changes demonstrated in this study may increase our understanding of the pathophysiology of diabetic embryopathy.

Early human nutrition

The Human yolk sac has long been considered a vestigial organ, an evolutionary remnant. In the last decade, however, it has been discovered that the human yolk sac plays an active and crucial role during organogenesis. Due to an absent maternal intervillous circulation during the first 12 weeks of pregnancy, the concept of transport of nutrients and oxygen to the embryo must be thoroughly reconsidered. Here the yolk sac plays an essential role by its active and passive transport to the embryo, and by its production of necessary substances. Animal experiments have demonstrated that hyperglycaemia has an initial deleterious effect on yolk sac structure, which then results in embryopathy. Study of the yolk sac by means of ultrasound has not become an important diagnostic method yet. On the basis of clinical studies and animal experiments, however, it may be expected that this organ plays a crucial role in the development of spontaneous abortion and structural congenital defects.

Vascularization of yolk sac and vitelline duct in normal pregnancies studied by transvaginal color and pulsed Doppler

The yolk sac is an organ of increasingly recognized importance in the initial mechanisms of pregnancy maintenance and the early growth and welfare of the embryo. Having a complex protein secretion and an equally intricate ultrastructure, it is the primary source of blood and germ cells. This small and to date largely ignored structure may have a vital and interesting part to play in human embryonic development, which may be comparable to its proven evolutionary importance in other animals. The aim of our study was to assess the vascularity of the yolk sac and vitelline duct in 105 patients between the 6th and 10th weeks of gestation who were scheduled for termination of pregnancy for psychosocial reasons. The patients were divided in five subgroups depending on the duration of gestation. All of them had a normal developing pregnancy with no clinical symptoms of pathology (e.g. bleeding in early pregnancy). Gestational age was calculated from the first day of the last menstrual period and substantiated by crown-rump (CRL) measurements. After exploration of the gestational sac and embryo by transvaginal sonography, color Doppler was used to image the yolk sac and vitelline duct vascularity. The visualized vessels were analyzed with pulsed Doppler using the sample volume unit set of 1 mm. The assessment of obtained waveform signals was made by means of peak systolic Doppler shift (PSV) and pulsatility index (PI). The pulsatility index was calculated as a difference between peak systolic and end diastolic Doppler shift divided by the mean maximum velocity. At least 5 separate cardiac cycles were measured, and the mean value was calculated.(ABSTRACT TRUNCATED AT 250 WORDS)

Alpha-fetoprotein levels and yolk sac size in the first trimester of pregnancy

Transvaginal ultrasound measurement of the yolk sac and transvaginal amniocentesis were carried out on 94 women prior to first-trimester termination of pregnancy. Maternal serum and fluids from the amniotic cavity and extraembryonic coelom were analysed for alpha-fetoprotein (AFP). No correlation was found between the yolk sac size and the levels of AFP in any of these sites.

Ectopic somatic endoderm in secondary human yolk sac

Three secondary human yolk sacs (SHYSs) showing heterotopic endodermal tubular structures of the gut-forming type were analyzed from a series of 180 SHYSs. These structures were similar to the early somatic endoderm involved in the formation of gut and lung. They may have arisen either as sequestrations in growth-disorganized embryos or as a phenomenon of differentiation from extraembryonal endoderm, which would indicate that extraembryonal tissues such as the SHYSs retain the capacity to differentiate somatic endoderm in developmentally altered embryos. It is possible that these structures may be the precursors of placental hepatic tissue and teratomas. Their morphologic resemblance to similar structures found in glandular, polyvesicular, and intestinal human yolk sac tumors provides yet another example of the similarity between SHYSs and yolk sac tumors.