Slow fetal heart rate may predict pregnancy outcome in first-trimester threatened abortion

Assessing the predictive value of first trimester ultrasound and biochemical markers in miscarriage: A scoping review

INTRODUCTION

Vaginal bleeding in the first trimester of pregnancy generates anxiety and uncertainty for expecting parents. The ability to determine pregnancy outcome through a first trimester ultrasound scan remains a challenge in obstetrics. Several first trimester ultrasound markers used individually or in combination, as well as ultrasound markers used in combination with biochemical markers, have been studied to determine their predictive value in pregnancy outcome. This scoping review was performed to determine which markers have already been investigated for this purpose.

METHODS

An extensive and systematic database search was performed using four different categories of keywords which were combined using Boolean terms. A total of 14 variables were included on the final data charting forms. Data was synthesised collectively for each variable and then separately for the studies analysing only one marker. For the studies which analysed multiple markers, data was synthesised based on the number of markers per study.

RESULTS

The search yielded 3608 studies, of which 128 were ultimately used for this review. Data extraction, based on predetermined eligibility criteria, was performed by two authors independently. Seventy-seven (62.6%) studies investigated the predictive value of a single ultrasound marker. The remaining 46 (37.4%) studies explored multiple markers, of which at least one was an ultrasound marker.

CONCLUSION

This review identified several discrepancies among different studies. This highlights the need for better consensus among researchers to allow for the design of a predictive model which enables extrapolation of findings to all pregnant women.

IMPLICATIONS FOR PRACTICE

Through the study of ultrasound and biochemical markers in the first trimester of pregnancy, clinicians may provide a more accurate prediction of pregnancy outcome following threatened miscarriage.

Combining early pregnancy bleeding with ultrasound measurements to assess spontaneous abortion risk among infertile patients

BACKGROUND

Approximately 15% of all clinically recognized pregnancies in patients with infertility result in spontaneous abortion. However, despite its potential to have a profound and lasting effect on physical and emotional well-being, the natural history of spontaneous abortion in women with infertility has not been described. Although vaginal bleeding is a common symptom in pregnancies conceived via reproductive technologies, its prognostic value is not well understood.

OBJECTIVE

This study aimed to evaluate the combination of early pregnancy bleeding and first-trimester ultrasound measurements to determine spontaneous abortion risk.

STUDY DESIGN

This was a retrospective cohort study of patients with infertility who underwent autologous embryo transfer resulting in singleton intrauterine pregnancy confirmed by ultrasound from January 1, 2017, to December 31, 2019. Early pregnancy symptoms of bleeding occurring before gestational week 8 and measurements of crown-rump length and fetal heart rate from ultrasounds performed during gestational week 6 (6 0/7 to 6 6/7 weeks of gestation) and gestational week 7 (7 0/7 to 7 6/7 weeks of gestation) were recorded. Modified Poisson regression with robust error variance was adjusted a priori for patient age, embryo transfer day, and transfer of a preimplantation genetic-tested embryo to estimate the relative risk and 95% confidence interval of spontaneous abortion for dichotomous variables. The relative risks and positive predictive values for early pregnancy bleeding combined with ultrasound measurements on the occurrence of spontaneous abortion were calculated for patients who had an ultrasound performed during gestational week 6 and separately for patients who had an ultrasound performed during gestational week 7. The primary outcome was spontaneous abortion in the setting of vaginal bleeding with normal ultrasound parameters. The secondary outcomes were spontaneous abortion with vaginal bleeding and (1) abnormal crown-rump length, (2) abnormal fetal heart rate, and (3) both abnormal crown-rump length and abnormal fetal heart rate.

RESULTS

Of the 1858 patients who were included (359 cases resulted in abortions and 1499 resulted in live births), 315 patients (17.0%) reported vaginal bleeding. When combined with ultrasound measurements from gestational week 6, bleeding was significantly associated with increased spontaneous abortion only when accompanied by absent fetal heart rate (relative risk, 5.36; 95% confidence interval, 3.36-8.55) or both absent fetal heart rate and absent fetal pole (relative risk, 9.67; 95% confidence interval, 7.45-12.56). Similarly, when combined with ultrasound measurements from gestational week 7, bleeding was significantly associated with increased spontaneous abortion only when accompanied by an abnormal assessment of fetal heart rate or crown-rump length (relative risk, 5.09; 95% confidence interval, 1.83-14.19) or both fetal heart rate and crown-rump length (relative risk, 14.82; 95% confidence interval, 10.54-20.83). With normal ultrasound measurements, bleeding was not associated with increased spontaneous abortion risk (relative risk: 1.05 [95% confidence interval, 0.61-1.78] in gestational week 6 and 0.80 [95% confidence interval, 0.36-1.74] in gestational week 7), and the live birth rate was comparable with that in patients with normal ultrasound measurements and no bleeding.

CONCLUSION

Patients with a history of infertility who present after embryo transfer with symptoms of vaginal bleeding should be evaluated with a pregnancy ultrasound to accurately assess spontaneous abortion risk. In the setting of normal ultrasound measurements, patients can be reassured that their risk of spontaneous abortion is not increased and that their live birth rate is not decreased.

Automated prediction of early spontaneous miscarriage based on the analyzing ultrasonographic gestational sac imaging by the convolutional neural network: a case-control and cohort study

Background

It is challenging to predict the outcome of the pregnancy when fetal heart activity is detected in early pregnancy. However, an accurate prediction is of importance for obstetricians as it helps to provide appropriate consultancy and determine the frequency of ultrasound examinations. The purpose of this study was to investigate the role of the convolutional neural network (CNN) in the prediction of spontaneous miscarriage risk through the analysis of early ultrasound gestational sac images.

Methods

A total of 2196 ultrasound images from 1098 women with early singleton pregnancies of gestational age between 6 and 8 weeks were used for training a CNN for the prediction of the miscarriage in the retrospective study. The patients who had positive fetal cardiac activity on their first ultrasound but then experienced a miscarriage were enrolled. The control group was randomly selected in the same database from the fetuses confirmed to be normal during follow-up. Diagnostic performance of the algorithm was validated and tested in two separate test sets of 136 patients with 272 images, respectively. Performance in prediction of the miscarriage was compared between the CNN and the manual measurement of ultrasound characteristics in the prospective study.

Results

The accuracy of the predictive model was 80.32% and 78.1% in the retrospective and prospective study, respectively. The area under the receiver operating characteristic curve (AUC) for classification was 0.857 (95% confidence interval [CI], 0.793–0.922) in the retrospective study and 0.885 (95%CI, 0.846–0.925) in the prospective study, respectively. Correspondingly, the predictive power of the CNN was higher compared with manual ultrasound characteristics, for which the AUCs of the crown-rump length combined with fetal heart rate was 0.687 (95%CI, 0.587–0.775).

Conclusions

The CNN model showed high accuracy for predicting miscarriage through the analysis of early pregnancy ultrasound images and achieved better performance than that of manual measurement.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12884-022-04936-0.

Clinical and Ultrasound Evaluation of Early Threatened Miscarriage to Predict Pregnancy Continuation up to 28 Weeks: A Prospective Cohort Study

OBJECTIVES

(1) To study the predictors of pregnancy continuation up to 28 weeks in first-trimester threatened miscarriage after a single clinical and ultrasound (US) evaluation. (2) To assess the role of both clinical and US predictors in counseling and decreasing repeated emergency follow-up scans.

METHODS

A prospective observational study that included a cohort of 241 patients with threatened miscarriage (≥6-12 weeks) was conducted. They had a single clinical and US evaluation, and then they were contacted by weekly phone calls until completing 28 weeks' gestation or reporting miscarriage. Independently, all patients were followed by the recommended routine US scanning with or without emergency visits.

RESULTS

Two hundred thirty-three patients completed the study, of whom 193 patients continued up to 28 weeks' gestation, and 40 miscarried (17.1%). Only spotting/mild bleeding episodes and progesterone treatment were the clinical predictors of fetal viability. The embryonic/fetal heart rate (E/FHR) was the best single US predictor, with a specificity and positive predictive value of 95.3% and 97.2%, respectively. Combining 3 US parameters, at their best cutoff points (E/FHR >113 beats per minute, crown-rump length >19.9 mm, and gestational sac diameter >27.3 mm), had a specificity and positive predictive value of 98% and 99% (first-trimester US triad of fetal viability).

CONCLUSIONS

[1] In first-trimester threatened miscarriage, clinical parameters that could predict fetal viability included spotting/ mild bleeding and progesterone treatment. [2] After a single US scan, the presence of at least an E/FHR of greater than 113 bpm or the suggested first-trimester US triad appeared as a simple, measurable, and effective predictor of pregnancy continuation up to 28 weeks. [3] These US predictors are not to replace the recommended scheduled scanning during pregnancy. [4] This can improve patients' counseling and decrease the need for repeated emergency follow-up scans. Otherwise, there is an indication for repeating US scans at a 1-week to 10-day interval.

Failed Intrauterine Pregnancy: What Is a Failed Pregnancy, What Is Not?

Pregnancy failure is defined as a lack of sonographic evidence of current or expected viability. Technologic advances in ultrasound imaging continue to redefine diagnostic criteria of pregnancy failure or success. When evaluating a pregnancy, the first step is an assessment of maternal risk factors for failure. Imaging clues such as an empty gestational sac measuring ≥25 mm or an embryo ≥7 mm without cardiac activity are reliable signs of pregnancy failure, whereas embryonic growth <1 mm/d is not. Combinations of sonographic findings can be used for a more accurate prediction of pregnancy success or failure.

Control of the heart rate of rat embryos during the organogenic period

The aim of this study was to gain insight into whether the first trimester embryo could control its own heart rate (HR) in response to hypoxia. The gestational day 13 rat embryo is a good model for the human embryo at 5–6 weeks gestation, as the heart is comparable in development and, like the human embryo, has no functional autonomic nerve supply at this stage. Utilizing a whole-embryo culture technique, we examined the effects of different pharmacological agents on HR under normoxic (95% oxygen) and hypoxic (20% oxygen) conditions. Oxygen concentrations ≤60% caused a concentration-dependent decrease in HR from normal levels of ~210 bpm. An adenosine agonist, AMP-activated protein kinase (AMPK) activator and K_ATP channel opener all caused bradycardia in normoxic conditions; however, putative antagonists for these systems failed to prevent or ameliorate hypoxia-induced bradycardia. This suggests that the activation of one or more of these systems is not the primary cause of the observed hypoxia-induced bradycardia. Inhibition of oxidative phosphorylation also decreased HR in normoxic conditions, highlighting the importance of ATP levels. The β-blocker metoprolol caused a concentration-dependent reduction in HR supporting reports that β₁-adrenergic receptors are present in the early rat embryonic heart. The cAMP inducer colforsin induced a positive chronotropic effect in both normoxic and hypoxic conditions. Overall, the embryonic HR at this stage of development is responsive to the level of oxygenation, probably as a consequence of its influence on ATP production.

Sonographic Parameters for Prediction of Miscarriage: Role of 3-Dimensional Volume Measurement

OBJECTIVES

To evaluate the value of volume measurement using 3-dimensional sonography for prediction of miscarriage.

METHODS

We prospectively enrolled 188 singleton pregnant women at 5 to 9 weeks' gestation. The 3-dimensional sonographic gestational sac volume and yolk sac volume were measured together with the fetal heart rate, gestational sac diameter, and yolk sac diameter. For each sonographic parameter, nomograms were created; z scores were calculated for each measurement, and the values were compared between miscarriage and ongoing pregnancy groups. Sonographic parameters for prediction of miscarriage were evaluated by multivariate analysis, and the screening performance was assessed by a receiver operating characteristic curve.

RESULTS

Among the 188 pregnancies, 30 (16.0%) had miscarriage. Multivariate analysis showed that fetal heart rate below the 5th percentile (odds ratio, 6.43), gestational sac diameter below the 5th percentile (odds ratio, 4.87), gestational sac volume below the 5th percentile (odds ratio, 5.25), and yolk sac diameter below the 2.5th or above the 97.5th percentile (odds ratio, 15.86) were significant predictors of miscarriage (P = .018; P = .018; P = .033; and P < .001, respectively). At a false-positive rate of 30%, the detection rate for miscarriage in screening by a combination of fetal heart rate, gestational sac diameter, gestational sac volume, and yolk sac diameter was 77.8%.

CONCLUSIONS

A small-for-gestational-age gestational sac volume is a significant sonographic predictor of miscarriage, as are fetal bradycardia, a small gestational sac diameter, and a small or large yolk sac diameter.

Cell-free fetal DNA and cell-free total DNA levels in spontaneous abortion with fetal chromosomal aneuploidy

Background

Cell-free fetal DNA and cell-free total DNA in maternal circulation have been proposed as potential markers for noninvasive monitoring of the placental condition during the pregnancy. However, the correlation of and change in cell-free fetal DNA and cell-free total DNA in spontaneous abortion (SA) with fetal chromosomal aneuploidy have not yet been reported. Therefore, we investigated cell-free fetal DNA and cell-free total DNA levels in SA women with fetal chromosomal aneuploidy.

Methodology/Principal Findings

A nested case-control study was conducted with maternal plasma collected from 268 women in their first trimester of pregnancy. Subjects included 41 SA with normal fetal karyotype, 26 SA with fetal chromosomal aneuploidy, and 201 normal controls. The unmethylated PDE9A gene was used to measure the maternal plasma levels of cell-free fetal DNA. The GAPDH gene was used to measure the maternal plasma levels of cell-free total DNA. The diagnostic accuracy was measured using receiver-operating characteristic (ROC) curves. Levels of cell-free fetal DNA and cell-free total DNA were significantly higher in both SA women with normal fetal karyotype and SA women with fetal chromosomal aneuploidy in comparison with the normal controls (P<0.001 in both). The correlation between cell-free fetal DNA and cell-free total DNA levels was stronger in the normal controls (r = 0.843, P<0.001) than in SA women with normal karyotype (r = 0.465, P = 0.002) and SA women with fetal chromosomal aneuploidy (r = 0.412, P = 0.037). The area under the ROC curve for cell-free fetal DNA and cell-free total DNA was 0.898 (95% CI, 0.852–0.945) and 0.939 (95% CI, 0.903–0.975), respectively.

Conclusions

Significantly high levels of cell-free fetal DNA and cell-free total DNA were found in SA women with fetal chromosomal aneuploidy. Our findings suggest that cell-free fetal DNA and cell-free total DNA may be useful biomarkers for the prediction of SA with fetal chromosomal aneuploidy, regardless of fetal gender.

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.

Correlation of maternal plasma total cell-free DNA and fetal DNA levels with short term outcome of first-trimester vaginal bleeding

BACKGROUND

The current methods using sonographic parameters and/or maternal serum beta-HCG levels to predict spontaneous abortion are not satisfactory. The aim of this study was to determine whether maternal plasma fetal DNA and total DNA levels could be used to predict spontaneous abortion.

METHODS

We prospectively studied pregnant women who presented with vaginal bleeding in the first trimester of pregnancy, and those who had no vaginal bleeding (controls). DYS14 and the beta-globin gene were used to measure the maternal plasma levels of fetal and total DNA, respectively, by real-time PCR.

RESULTS

A total of 1114 women were studied. Both maternal plasma fetal and total DNA concentrations increased with gestation from 6 to 11.6 weeks in the controls. The multiple of medians (MoMs) of fetal and total DNA concentration in those who miscarried were significantly greater (P < 0.001) than in the normal controls by about 5- and 4-fold respectively. Using a cut-off value of 1.6 MoMs for total DNA to predict spontaneous abortion, the sensitivity was 98.2% and false positive rate was 4.7%. However, using a cut-off value of 1.8 MoMs for fetal DNA, the corresponding figures were 97% and 44.3%, respectively.

CONCLUSIONS

Both maternal plasma fetal and total DNA concentrations increased throughout the first trimester. Significantly high levels of fetal and total DNA were found in those who miscarried.

Ultrasonography in the Diagnosis and Management of Abnormal Early Pregnancy

The demand for ultrasound in early pregnancy has been increasing steadily, and is now a routine investigation for most women within the first trimester of their pregnancy. It is a safe investigation which provides reassurance, charts normal development, and identifies women with abnormal or high risk pregnancies. Transvaginal ultrasound has revolutionized the diagnosis of early pregnancy as it can detect a pregnancy at an earlier stage, whether it is normal and therefore reassuring, or abnormal and require intervention. Ultrasound is also a useful tool to aid decisions regarding management of abnormal pregnancy, such as ectopic pregnancy or miscarriage. This chapter looks at the important role ultrasound plays in the diagnosis and management of abnormal pregnancy.

First trimester embryonic/fetal heart rate in normal pregnant women

OBJECTIVE

To establish reference ranges for first trimester embryonic/fetal heart rate in normal pregnant women.

MATERIALS AND METHODS

This was a cross-sectional study. We performed ultrasonogram in 319 normal pregnant women, gestation age between 6(+0) and 14(+6) weeks and measured embryonic/fetal heart rates using M-mode. The embryonic/fetal heart rates were analyzed according to gestational ages (GA).

RESULTS

Data of 319 pregnancies were analyzed and the outcome revealed the mean of fetal heart rate according to gestational age. The mean embryonic heart rates during the 6th-7th week of gestation are lower when compared with the other gestational ages. At the 8th week of gestation, the embryonic heart rate is maximum. Then the embryonic/fetal heart rate gradually decreased to 161 beats/min at the 14th week of gestation. The regression equation for embryonic/fetal heart rate (beat/min) [y] according to GA (day) [x] was y = -53.124 + 6.1333x + (-0.0407)x ( 2 )(r (2) = 0.525; P < 0.001).

CONCLUSION

Embryonic/fetal heart rates during the 6(+0) and 14(+6) week of gestation are related to GA. Our reference ranges may be useful for further studies such as for prediction of adverse pregnancy outcome in threatened abortion.

Updated and revised nomenclature for description of early pregnancy events

The nomenclature used to describe clinical events in early pregnancy has been criticized for lack of clarity and promoting confusion. There is no agreed glossary of terms or consensus regarding important gestational milestones. In particular there are old and poorly descriptive terms such as 'missed abortion' and 'blighted ovum', which have persisted since their introduction many years ago (Robinson, 1975) and have not undergone revision despite the widespread application of ultrasound for accurate clinical assessment and diagnosis. The authors are aware of these shortcomings in terminology and are keen to provide an updated glossary. We hope that this paper will facilitate the introduction of a revised terminology in an attempt to provide clarity and to enhance uptake and use in the literature as well as clinical assessment and documentation.

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.