Vasa praevia after IVF: should there be guidelines? Report of two cases and literature review

Clinical characteristics of a novel "Type 3" vasa previa: case series at a single center

OBJECTIVE

Vasa previa is a condition in which fetal blood vessels are located on fetal membranes within 2 cm of the internal cervical os. Vasa previa has been classified into two types: Type 1, in which vessels connect a velamentous umbilical cord to the placenta, and Type 2, in which vessels connect the lobes of a bilobed placenta or the placenta to a succenturiate lobe. However, there are also atypical cases that cannot be classified into these two types. These cases are manifested by a center or marginal cord insertion with a normal shaped placenta, and fetal vessels were also located on membranes around the internal cervical os. These cases were recently proposed as Type 3 vasa previa. The present study investigated the incidence of Type 3 vasa previa and elucidated differences in clinical and ultrasonographical characteristics between traditional types and Type 3.

METHODS

This was a single-center observational study using a cohort of all vasa previa cases between January 2010 and April 2020.

RESULTS

Among 8,723 deliveries, there were 14 cases (0.16%) of vasa previa, all of which were diagnosed prenatally by US, not after vaginal delivery or CS. There were 9 (64%), 0, and 5 (36%) cases of Types 1, 2, and 3, respectively. All 5 Type 3 cases had only one fetal aberrant vessel of vasa previa, while 6 out of 9 Type 1 cases (67%) had two or more aberrant vessels. Seven Type 1 cases (78%) possessed two or more known risk factors, such as velamentous cord insertion, whereas all Type 3 cases only had one. Difficulties were associated with diagnosing two out of the 14 cases of vasa previa using routine transvaginal ultrasonography (TVUS). In these cases, the aberrant fetal vessel of vasa previa was only one vein with a thin wall that was not clearly visualized by gray-scale TVUS as well as slow flow that was easily misread by color-Doppler. These cases were ultimately diagnosed as vasa previa based on non-pulsatile flow detected by color and pulsed Doppler.

CONCLUSIONS

The present results suggest that Type 3 may account for a large proportion of vasa previa cases. Most Type 3 cases may present with only one fetal aberrant vessel of vasa previa and fewer risk factors, suggesting that the diagnosis of vasa previa may be more challenging in Type 3 cases than in the other types. Vasa previa with a venous vasa previa needs to be considered because of the difficulties associated with an antenatal diagnosis due to unclear imaging of the vasculature or the lack of specific color Doppler flow patterns. Pulsed Doppler imaging may be helpful for the diagnosis of these cases.

Variations in reported outcomes in studies on vasa previa: a systematic review

OBJECTIVE

To evaluate reported outcomes of published studies on the diagnosis and management of vasa previa in pregnancy.

MATERIALS AND METHODS

Databases such as MEDLINE, Embase, Cochrane, PubMed, and ClinicalTrials.gov were searched up to March 2018 for all published studies on vasa previa using combinations of the following medical subject headings and key words: vasa previa, placenta previa, low-lying placenta, succenturiate lobe or placenta, bilobed or bilobate placenta, and velamentous insertion. All original human research that described maternal, obstetric, placental, fetal or neonatal outcomes relating to pregnancies with vasa previa were included for analysis. Title and abstract screening and data extraction was conducted independently and in duplicate by 2 reviewers for all studies until total agreement for eligibility was achieved. Data extraction was also conducted in duplicate in approximately 50% of studies reviewed.

RESULTS

A total of 160 published studies (1004 pregnancies) were included. There was a wide range of reported outcomes, many of which were sparingly reported. The most commonly reported maternal outcomes included mode of delivery, presence of antepartum hemorrhage, time of diagnosis, and rupture of membranes. The presence of known risk factors for vasa previa such as a low-lying placenta, succenturiate or bilobed placenta, and (velamentous) cord insertion was incorrectly reported as "outcomes" in many studies. The most commonly reported fetal/neonatal outcomes included fetal heart rate, gestational age at delivery, birthweight, Apgar score, presence of neonatal anemia, cord blood gas measurements, need for blood transfusion, and death. Of note, only 3 studies reported outcomes related to life impact, maternal social and emotional functioning, perceived delivery of care, or resource utilization.

CONCLUSION

Despite the profound effect the diagnosis of vasa previa has on pregnant women, families, and healthcare systems, studies on vasa previa seldom report outcomes related to life impact and resource utilization. There is a need for the development of a core outcome set-a minimum standard set of outcomes deemed important by pregnant women and other stakeholders involved in their care-to standardize outcome reporting in future studies on vasa previa.

Is IVF/ICSI [corrected] an Independent Risk Factor for Spontaneous Preterm Birth in Singletons? A Population-Based Cohort Study

The aim of our study was to explore the risk factors for very preterm (gestation under 32 weeks) and moderate preterm birth (gestation weeks 32-36 6/7) in singleton pregnancies in a national retrospective cohort study. We also wanted to establish whether IVF/ICSI is an independent risk factor for preterm birth after adjusting for already known confounders. We used data for 267 718 singleton births from 2002-2015 from the National Perinatal Information System of Slovenia, containing data on woman, pregnancy, birth, the postpartum period, and the neonate for each mother-infant pair. Mode of conception, maternal age, education, BMI, parity, smoking, history of cervical excision procedure, history of hysteroscopic resection of uterine septum, presence of other congenital uterine malformations, bleeding in pregnancy, preeclampsia or HELLP and maternal heart, and pulmonary or renal illness were included in the analyses. Unadjusted OR for very preterm birth after IVF-ICSI [corrected] was 2.8 and for moderate preterm birth was 1.7. After adjusting for known confounders, the OR was still significantly elevated (1.6 and 1.3, respectively). Risk factors for very preterm birth with OR higher than 2.4 were history of cervical excision procedure, resection of uterine septum, operation or having other congenital uterine malformations, and bleeding in pregnancy. Risk factors for very preterm birth with OR between 1.4 and 2.1 were age >35 years, being underweight or obese, not having professional education, smoking, first birth, preeclampsia/HELLP, and IVF/ICSI. Risk factors for moderate preterm birth with OR higher than 2.4 were history of cold knife conization and other congenital uterine malformations. We found that even after adjustment, IVF/ICSI represents a single risk factor for early and late preterm birth even after adjustment with other risks such as maternal age, smoking, or a history of invasive procedures for either cervical intraepithelial neoplasia or infertility treatment.

Is ultrasound screening for vasa praevia clinically justified and a financially viable screening test? A literature review

Vasa praevia is an obstetric complication currently not screened for within the United Kingdom, which if undetected prenatally can lead to fetal death when the membranes rupture. Internationally, guidelines are available providing guidance on the best screening policy and management pathways. However, the UK National Screening Committee and Royal College of Obstetricians and Gynaecologists do not support screening due to a lack of evidence. Recent studies explore the ability of ultrasound to detect vasa praevia prenatally in both the general and high-risk populations. Whilst there is no consensus on the 'best' screening strategy, the majority of authors note that targeted screening of the high-risk population is the most achievable and cost-effective strategy. Although not infallible, a standard screening protocol could identify the majority of cases in the high-risk group. Introduction of a screening strategy would affect training needs of professionals within the UK and would have implications on the need to produce guidelines on management and quality assurance. Further research is also needed to define a relevant high-risk population and explore how this would impact on service provision. This review explores the current evidence base for systematic screening and the implications for service.

No. 231-Guidelines for the Management of Vasa Previa

OBJECTIVES

To describe the etiology of vasa previa and the risk factors and associated condition, to identify the various clinical presentations of vasa previa, to describe the ultrasound tools used in its diagnosis, and to describe the management of vasa previa.

OUTCOMES

Reduction of perinatal mortality, short-term neonatal morbidity, long-term infant morbidity, and short-term and long-term maternal morbidity and mortality.

EVIDENCE

Published literature on randomized trials, prospective cohort studies, and selected retrospective cohort studies was retrieved through searches of PubMed or Medline, CINAHL, and the Cochrane Library, using appropriate controlled vocabulary (e.g., selected epidemiological studies comparing delivery by Caesarean section with vaginal delivery; studies comparing outcomes when vasa previa is diagnosed antenatally vs. intrapartum) and key words (e.g., vasa previa). Results were restricted to systematic reviews, randomized control trials/controlled clinical trials, and observational studies. Searches were updated on a regular basis and incorporated into the guideline to October 1, 2008. Grey (unpublished) literature was identified through searching the websites of health technology assessment and health technology assessment-related agencies, clinical practice guideline collections, clinical trial registries, and from national and international medical specialty societies.

VALUES

The evidence collected was reviewed by the Diagnostic Imaging Committee and the Maternal Fetal Medicine Committee of the Society of Obstetricians and Gynaecologists of Canada (SOGC) and quantified using the evaluation of evidence guidelines developed by the Canadian Task Force on Preventive Health Care.

BENEFITS, HARMS, AND COSTS

The benefit expected from this guideline is facilitation of optimal and uniform care for pregnancies complicated by vasa previa.

SPONSORS

The Society of Obstetricians and Gynaecologists of Canada.

SUMMARY STATEMENT

A comparison of women who were diagnosed antenatally and those who were not shows respective neonatal survival rates of 97% and 44%, and neonatal blood transfusion rates of 3.4% and 58.5%, respectively. Vasa previa can be diagnosed antenatally, using combined abdominal and transvaginal ultrasound and colour flow mapping; however, many cases are not diagnosed, and not making such a diagnosis is still acceptable. Even under the best circumstances the false positive rate is extremely low. (II-2) RECOMMENDATIONS.

Independent factors influencing large-for-gestation birth weight in singletons born after in vitro fertilization

PURPOSE

Higher risk for birth of singletons being large for gestational age (LGA) has been revealed after in vitro fertilization (IVF) frozen-thawed embryo-transfer (FET). This phenomenon is now being investigated, since there is a speculation that these neonates could suffer from underlying epigenetic disturbances. The aim of the study was to expose independent LGA risk factors and to identify those connected to the IVF techniques.

METHODS

Altogether, 4508 singleton pregnancies and births were included in the cohort case-matched study. Two hundred eleven singleton pregnancies and births after FET and 916 after fresh embryo transfer (ET) were included into two study groups. The IVF procedures were performed at the University Medical Centre Ljubljana between 2004 and 2011. For each IVF pregnancy, three matched consecutive controls after natural conception were included. Using logistic regression models, we observed LGA connection to maternal parameters (smoking, hypertension, parity, BMI, gestational diabetes, IVF conception, FET, double ET, and ICSI procedure).

RESULTS

Singletons born after FET had a significantly higher risk for being LGA (p = 0.032; OR 1.697; 95 % CI 1.047-2.752). BMI 25-30 was a significant independent risk factor for LGA in the IVF groups (FET p = 0.041, OR 2.460, 95 % CI 1.030-5.857 and fresh ET p = 0.003; OR 2.188, 95 % CI 1.297-3.691). ICSI and double ET had no significant effect on LGA occurrence.

CONCLUSIONS

Besides maternal BMI, FET is a significant independent LGA risk factor in IVF patients. Other observed factors (smoking, hypertension, multiparity, GDM, ICSI procedure, or number of embryos transferred) do not influence LGA risk significantly.

Assisted reproduction causes placental maldevelopment and dysfunction linked to reduced fetal weight in mice

Compelling evidence indicates that stress in utero, as manifested by low birth weight (LBW), increases the risk of metabolic syndrome in adulthood. Singletons conceived by assisted reproductive technology (ART) display a significant increase in LBW risk and ART offspring have a different metabolic profile starting at birth. Here, used mouse as a model, we found that ART resulted in reduced fetal weight and placental overgrowth at embryonic day 18.5 (E18.5). The ART placentae exhibited histomorphological alterations with defects in placental layer segregation and glycogen cells migration at E18.5. Further, ART treatments resulted in downregulation of a majority of placental nutrient transporters and reduction in placental efficiency. Moreover, the ART placentae were associated with increased methylation levels at imprinting control regions of H19, KvDMR1 and disrupted expression of a majority of imprinted genes important for placental development and function at E18.5. Our results from the mouse model show the first piece of evidence that ART treatment could affect fetal growth by disrupting placental development and function, suggests that perturbation of genomic imprinting resulted from embryo manipulation may contribute to these problems.

Singleton pregnancy outcomes after in vitro fertilization with fresh or frozen-thawed embryo transfer and incidence of placenta praevia

The aim of the study was to compare the single pregnancy and neonate outcome after fresh and frozen-thawed embryo transfer in the in vitro fertilization programme (IVF). The study focused on clinical and laboratory factors affecting the abnormal placentation, especially placenta praevia, in patients conceiving in the IVF programme. The results confirm that neonates born after frozen-thawed embryo transfer had significantly higher mean birth weight than after fresh embryo transfer (ET). Moreover, the birth weight distribution in singletons was found to shift towards “large for gestation” (LGA) after frozen-thawed ET. On the other hand, the pregnancies after fresh ET were characterized by a higher incidence of placenta praevia and 3rd trimester bleeding. Placenta praevia was more common in IVF patients with fresh ET in a stimulated cycle than in patients with ET in a spontaneous cycle. It occurred more frequently in patients with transfer of 2 embryos. From this point of view, single ET and ET in a spontaneous cycle should be encouraged in good prognosis patients in the future with more than two good quality embryos developed. An important issue arose of how the ovarian hormonal stimulation relates to abnormal placentation and if the serum hormone levels interfere with in the IVF treatment results.

Is assisted reproduction associated with abnormal placentation?

Artificial reproductive technologies (ART) and conception following a period of untreated infertility (>1 year) are independently associated with increased pregnancy complications in both singleton and multiple pregnancies. It is unknown if placental dysfunction associated with macroscopic and/or microscopic histological discrepancies might explain some of these variances. Our aim was to compare the histopathology of placentae from singleton pregnancies belonging to 3 groups, as follows: conception as a result of ART; spontaneous conception (<1 year of trying); and conception following untreated infertility (>1 year). Pathological examination of placentae from singleton pregnancies of nonsmoking, age-matched primiparous women with no significant medical history and no known uterine congenital anomalies was performed by a single pathologist blinded to the groups. Features were compared using analysis of variance and chi-square tests. A total of 89 placental pathology reports were available (control  =  39, infertility  =  17, ART  =  33). The mean placental thickness was significantly higher in the ART group when compared to the spontaneous conception group (P  =  0.02). There were significantly more placental hematomas in the ART group (P  =  0.04) compared to the other groups. There were no significant differences in rates of abnormal placental shapes or abnormal cord insertions. There were no statistically significant differences in the incidence of microscopic placental lesions, nor were there any statistically significant differences in the incidence of macroscopic and microscopic placental lesions between the infertility group and the other groups. Placentae of ART pregnancies show significantly increased thickness and a higher incidence of hematomas. Increased placental thickness has previously been linked to increased perinatal risk.

A case of vasa previa diagnosed prenatally, and review of the literature

The perinatal mortality rate of vasa previa is high if it is not prenatally diagnosed. In this report, a case of vasa previa diagnosed prenatally is presented. Antepartum hemorrhage at 24 weeks of gestation prompted a close investigation of the uterine cervix, internal os, and placenta. We detected a low-lying bilobed placenta with umbilical cord insertion in the lower uterine segment. Furthermore, one of the connecting vessels of the bilobed placenta passed directly above the internal os. Vasa previa was suspected and confirmed with color Doppler and MRI. The fetus was delivered uneventfully by planned Cesarean section at 38 weeks of gestation. It should be considered that placenta previa (including low-lying placenta), bilobed placenta, and umbilical cord insertion in the lower uterine segment are associated with high risk of vasa previa. Ultrasound screening for cord insertion and placenta around the internal os enables efficient and certain detection of vasa previa.

Effect of the method of conception and embryo transfer procedure on mid-gestation placenta and fetal development in an IVF mouse model

BACKGROUND

Abnormal placentation is a potential mechanism to explain the increased incidence of low birthweight observed after IVF. This study evaluates, in a mouse model, whether the method of conception and embryo transfer affect placentation and fetal development.

METHODS

IVF blastocysts (CF1 x B6D2F1/J) were cultured in Whitten's medium (IVF(WM), n = 55) or K modified simplex optimized medium with amino acids (IVF(KAA), n = 56). Embryos were transferred to the uteri of pseudo-pregnant recipients. Two control groups were created: unmanipulated embryos produced by natural mating (in vivo group, n = 64) and embryos produced by natural mating that were flushed from uterus and immediately transferred to pseudo-pregnant recipients (flushed blastocysts, FB group, n = 57). At gestation age 12.5 days, implantation sites were collected and fixed; fetuses and placentas were weighed and their developmental stage (DS) evaluated. Placental areas and vascular volume fractions were calculated; parametric statistics were applied as appropriate.

RESULTS

IVF fetuses showed a modest but significant delay in development compared with FB mice (P < 0.05). In addition, IVF conceptuses were consistently smaller than FB (P < 0.05). Importantly, these differences persisted when analyzing fetuses of similar DS. The placenta/fetus ratio was larger in the IVF group (IVF(WM) 0.95; IVF(KAA) = 0.90) than the FB group (0.72) (P < 0.05 for all comparisons). Gross morphology of the placenta and ratio labyrinth/fetal area were equivalent in the IVF and FB groups, as were percentage of fetal blood vessels, maternal blood spaces and trophoblastic components.

CONCLUSIONS

In vitro embryo culture affects fetal and placental development; this could explain the lower birthweight in IVF offspring.