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

Abstract

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.

Miscarriage and early first trimester growth restriction by ultrasound

“…One study demonstrated, that, the rate of miscarriage after visualization of foetal heart is higher in women with threatened miscarriage, when compared with a control group without bleeding (5.5 versus 1.9%). 2 In our study, we did not find that women were more likely to have an early miscarriage if they presented with bleeding, once the foetal heart was visualized in early pregnancy.…”

Correlation analysis between ultrasound findings and abnormal karyotypes in the embryos from early pregnancy loss after in vitro fertilization-embryo transfer

“…The associations between a low fetal heart rate, yolk sac size, and chromosomal abnormalities have been investigated in previous studies [31][32][33]. We did not examine these factors in detail in this study because they overlap with (or are included in) the six categories of ultrasound findings examined here.…”

Evaluation of Early Pregnancy Failure with Ultrasound

“…Pregnancy failure has been determined with sonography using multiple measurements including the mean gestational sac diameter, embryonic pole, and embryonic heart pulsations. The sonographic diagnostic cut-offs for pregnancy failure vary depending the degree specificity, sensitivity and the different author's findings; however, the more common guidelines are summarized in Table 1. 14, 16,[26][27][28] The gestational sac can first be observed by TVS when the sac diameter is 5 mm at approximately 5 weeks gestation (or 3 weeks postconception). Between the fifth and sixth weeks of pregnancy, the MSD increases by approximately l1 mm/day.…”

“…[50][51][52] It has been hypothesized that the higher resistance maternal like flow promotes oxidative stress and then further damage to the embryo which may contribute to pregnancy failure. 27 The abnormal placental resistance patterns documented by Doppler and associated with early pregnancy failure are not clinically useful in diagnosing miscarriage. However, the use of Doppler in the late first trimester may become a more useful tool in predicting other developing placental diseases like pre-eclampsia and molar pregnancies.…”