Monozygotic twin pregnancy: diagnostic and Doppler ultrasound studies

No advantage of fresh blastocyst versus cleavage stage embryo transfer in women under the age of 39: a randomized controlled study

PURPOSE

Is there a difference in implantation and pregnancy rates between embryos transferred electively at cleavage or blastocyst stage in infertile women ≤ 38 years with at least four zygotes on day 1 post retrieval?

METHODS

A randomized clinical trial was conducted in a single tertiary care hospital with a sample size of 194 patients in each arm for a total population of 388 women. Patients less than 39 years of age with more than three fertilized oocytes and less than four previous assisted reproductive technology (ART) attempts were inclusion criteria.

RESULTS

The two groups were similar for age, years of infertility, indication to treatment, basal antimüllerian hormone and FSH, number of previous ART cycles, primary or secondary infertility, type of induction protocol, days of stimulation, total gonadotrophin dose, and estradiol (E2) and progesterone (P) levels at trigger. No statistically significant differences were found in terms of number of retrieved oocytes, inseminated oocytes, fertilization rate, canceled transfers (7.73% in blastocyst and 3.61% in cleavage stage group), and cycles with frozen embryos and/or oocytes. Although a higher number of fertilized oocytes were in the blastocyst stage group (6.18 ± 1.46 vs 5.89 ± 1.54, p = 0.052), a statistically greater number of embryos/randomized cycle were transferred at cleavage stage (1.93 ± 0.371) compared with the number of transferred blastocysts (1.80 ± 0.56), probably due to the number of embryos not reaching blastocyst stage (3.09%). The implantation rate (28.37 vs 25.67%), pregnancy rate per cycle (36.06 vs38.66%), transfer (39.66 vs 40.11%), spontaneous abortions (19.72% vs 12.00%), delivery rate per cycle (27.84 vs 32.99%), and transfer (30.17 vs 34.22%) were not significantly different between the blastocyst and cleavage stage groups. The twin delivery rate was higher in the blastocyst stage group, although not significant (42.59 vs 28.12%). The mean numbers of frozen blastocyst (2.30 ± 1.40 vs 2.02 ± 1.00) and frozen oocytes (7.09 ± 3.55vs 6.79 ± 3.26) were not significantly different between the two groups.

CONCLUSIONS

Fresh blastocyst-stage transfer versus cleavage-stage transfer did not show any significant difference in terms of implantation and pregnancy rate in this selected group of patients. A high twin delivery rate in both groups (35.59%) was registered, and although not significant, they were higher in the blastocyst transfer group (42.59 vs 28.12%). Our conclusion supports considering single embryo transfer (SET) policy, even in cleavage stage in patients younger than 39 years with at least four zygotes.

TRIAL REGISTRATION

ClinicalTrials.gov registration number NCT02639000.

Do Doppler studies enhance surveillance of uncomplicated monochorionic diamniotic twins?

OBJECTIVES

To determine whether isolated abnormal Doppler indices before 28 weeks predict adverse pregnancy outcomes in uncomplicated monochorionic diamniotic (MCDA) twins.

METHODS

A retrospective cohort study of MCDA twin pregnancies receiving antenatal testing at a single center between 2007 and 2013 was conducted. Sonographic surveillance, including Doppler velocimetric studies of the umbilical artery, ductus venosus, and middle cerebral artery of each twin, was initiated by 28 weeks and repeated at least every 2 weeks. All pregnancies were deemed "uncomplicated" at initial sonography, without evidence of polyhydramnios, oligohydramnios, intrauterine growth restriction, twin growth discordance of at least 20%, structural or chromosomal anomalies, or unclear chorionicity. Pregnancies were divided into 2 groups: those with isolated Doppler abnormalities before 28 weeks and those with normal Doppler indices. The primary outcome was a composite including twin-twin transfusion syndrome, intrauterine growth restriction of more than 1 twin, growth discordance of at least 20%, preterm delivery before 34 weeks for fetal indications, or demise of more than 1 fetus.

RESULTS

Ninety-six patients were included, with 22 (22.9%) having isolated Doppler abnormalities before 28 weeks. The incidence of the primary outcome did not differ between groups (36.4% versus 28.4%; P = .47). The abnormal Doppler group underwent a greater number of sonographic examinations (15 versus 10; P= .001) and more antenatal admissions for fetal concerns (50.0% versus 12.2%; P < .001).

CONCLUSIONS

Isolated Doppler abnormalities are commonly encountered in uncomplicated MCDA pregnancies before 28 weeks yet are not clearly predictive of twin-specific complications. Doppler abnormalities were associated with increased sonographic surveillance and antenatal hospitalizations, suggesting an influence on physician practice patterns. Data may not support Doppler studies before 28 weeks for routine MCDA twin monitoring.

The East Flanders Prospective Twin Survey (Belgium): a population-based registe

The East Flanders Prospective Twin Survey (EFPTS), started in 1964, is unique among the 17 major European twin registers because it is population based, the twins (and higher order births) are ascertained at birth, basic perinatal data are collected, chorion type is established and, when appropriate, genetic markers including DNA fingerprints, are determined. The total number of sets is 5089 twin, 158 triplet and 14 of higher order. Zygosity has been diagnosed on the basis of sex, placental structure and genetic markers in more than 95% of pairs. The EFPTS is the only large register that includes placental data and allows differentiation of three subtypes of monozygotic twins based on the time of the initial zygotic division: the dichorionic—diamnionic pairs (early), the monochorionic—diamnionic pairs (intermediate), and the monochorionic—monoamnionic pairs (late). Methodology and basic results in twins are considered in this article; detailed studies will be reported later. The sex proportion in dizygotic (DZ) twins is the same as in singletons, whereas monozygotic (MZ) twins number more girls than boys. The difference in perinatal mortality between DZ and MZ twins is limited to the monochorionic MZ subgroup. Birth weight is highest in DZ twins and diminishes stepwise in MZ dichorionic and MZ monochorionic twins. Duration of pregnancy follows the same trend but is limited to a few days. Iatrogenic pregnancies are increasing to the point of representing almost 50% of the twin births in 1997.

Monoamniotic twins discordant for anencephaly managed conservatively with good outcomes: two case reports and a review of the literature

Monoamniotic twin pregnancy discordant for anencephaly (MATDA) is a rare occurrence with only seven prior reported cases. Selective termination has been advocated in managing discordant monoamniotic twins. We report two cases managed expectantly with good outcomes and review other previously reported cases. The first case was a primigravid woman diagnosed with MATDA at 18 weeks. She was managed expectantly until 32 + 5 weeks when a Cesarean section was performed for preterm labor. The surviving female infant weighed 1610 g. The second case was a multigravid woman who was diagnosed with MATDA at 17 + 5 weeks and was managed as an outpatient. An emergency Cesarean section was performed at 31 weeks for non-reassuring monitoring and the surviving male infant weighed 1790 g. In both cases, the survivors were discharged home in good condition. A review of these two cases and those in the literature suggests that expectant management should be considered among management options for this rare condition.

Diamnionic monochorionic twin gestations: an overview

Monochorionic (MC) twins account for about 20-30% of all twins, but contribute disproportionately to mortality, intrauterine growth restriction, and preterm delivery compared with dichorionic (DC) twins. This higher mortality in MC twins is likely due to the effects of placental morphologic characteristics, which include complex vascular communications between the twins associated with twin-twin transfusion syndrome (TTTS), and the tendency for the common placenta to be shared either symmetrically or asymmetrically. In assessment of clinical outcomes for TTTS, artery to vein anastomoses in the absence of artery to artery or vein to vein, especially if present with placental asymmetry, carry the worse prognosis. Chorion status in twins forms the basis for clinical risk assessment and can be determined by 7 menstrual weeks using transvaginal sonography. The variable results reported in the literature for intertwin umbilical artery Doppler findings in MC twins may be explained by differences between sonographic and clinical criteria (including differential hemoglobin concentrations) reported by various investigators. Antenatal fetal Doppler assessment of the umbilical artery and cerebral arteries can help distinguish between TTTS and placental insufficiency in MC twins. Significant restriction of fetal growth occurs in about 25% of multiple gestations, accounting for about 17% of all growth-retarded infants. Redistribution of fetal blood (brain-sparing effect), as determined by Doppler interrogation of fetal cerebral and umbilical arteries, occurs more commonly in MC twins compared to DC twins and in growth-restricted MC twins compared to nongrowth-restricted MC twins. Overall, the prognosis is poorer for the donor twins in TTTS and there is a greater prenatal death rate for the donor (18-35%), and a higher overall survival rate for recipients following fetoscopic laser treatment. Finally, the clinical and sonographic findings suggest that the polyhydramnios/oligohydramnios sequence seen in MC twins likely represents a spectrum strongly linked to placental variables.

Sonographic considerations with multiple gestation

Determination of chorionicity is of paramount importance in risk assessment and management. Best performed in the first trimester, dichorionic placentation can be reliably assumed when the membrane is easily seen, there is a "twin peak" sign, there are clearly separate placentas, and there is discordant fetal gender. In a monochorionic twin pregnancy, there is a single placental mass, the dividing membrane is difficult to visualize until the end of the first trimester, and the membrane inserts onto the placental surface without a peaked appearance. Amniotic fluid volume assessment is important in the management of twin pregnancy. Polyhydramnios-oligohydramnios may be a manifestation of twin-twin transfusion syndrome, although oligohydramnios with normal amniotic fluid volume in the other twin's sac may more likely be a sign of velamentous cord insertion, infection, or chromosomal or structural abnormality. Fetal growth discordance is common in twin pregnancy and is associated with increased perinatal mortality and morbidity. The most sensitive indicator of discordant twin growth is thought to be estimated fetal weight, and an intertwin difference of > or = 20% is considered significant. In the clinical care of a patient with twins, it is reasonably standard to confirm chorionicity with ultrasonography in the first or early second trimester. At about 20 weeks, a level II ultrasound for anatomic survey is indicated. In dichorionic pregnancies, ultrasound examinations are then performed at 26 to 28 weeks and every 3 to 4 weeks thereafter to follow growth and amniotic fluid volume. In monochorionic twins, we generally do an additional ultrasound at about 23 to 24 weeks, because of the risk of twin-twin transfusion syndrome. In the late third trimester, careful attention should also be given to fetal position, to help with delivery planning.

The consequences of monochorionic placentation

Monochorionic (MC) placentation occurs in two-thirds of monozygous twins and approximately 0.3% of all spontaneous conceptions. Vascular anastomoses within the placenta allow intertwin transfusion to occur, which is in most cases a normal event. However, imbalance in this flow may lead to the clinical sequelae observed, with acute, chronic or reverse intertwin transfusion. Acute transfusion describes the events following the death of one of an MC twin pair in utero, with an approximately 1 in 4 chance of demise or neurological damage in the co-twin. Chronic intertwin transfusion, otherwise termed feto-fetal transfusion syndrome, arises following the gradual flux of blood from one twin (the donor) to its sibling fetus (the recipient). The ensuing polyhydramnios places the pregnancy at risk of preterm amniorrhexis and/or labour, notwithstanding the specific sequelae seen in these fetuses following chronic in utero insult. Reverse transfusion describes the most bizarre form of intertwin transfusion: acardiac twinning. Retrograde perfusion of one of the twins with deoxygenated blood leads to the formation of a non-viable acardiac parasite and a 'pump twin' struggling to maintain the cardiac output required to perfuse both twins.

Doppler ultrasound in multiple pregnancies

This chapter aims to provide a current review of the use of Doppler ultrasound in the management of multiple pregnancies. OVID and Medline searches were undertaken. Randomized controlled trials, where available, were assessed by the Cochrane Review Manager (RevMan-version 3.0). The specific multiple pregnancy problems of fetal growth restriction (FGR), twin reversed arterial perfusion sequence and twin-twin transfusion syndrome (TTTS) were also reviewed. Historically, controlled and randomized controlled trials show a promising reduction in perinatal mortality in twin pregnancies where Doppler ultrasound is used. However, the numbers are small and further trials are recommended. In those twin pregnancies in which there is FGR as a result of placental dysfunction, Doppler ultrasonography will show intertwin discordancy. In those twin pairs where development is complicated by TTTS, there is often discordant fetal size, with concordant fetal Doppler results. Thus Doppler ultrasound appears to be useful in the management of twin pregnancies and in delineating those complicated by FGR and TTTS.

The relationship of birth weight and birth weight discordance to cerebral palsy or mental retardation later in life for twins weighing less than 2500 grams

OBJECTIVE

This study tested the hypothesis that twins with a birth weight < 2500 gm who subsequently had cerebral palsy or mental retardation had a birth weight distribution or birth weight discordance distribution differing from that of the total live-born twin population also weighing < 2500 gm at birth.

STUDY DESIGN

All twins born in Sweden between 1973 and 1980 (n = 5382) and having a birth weight < 2500 gm were identified by using information stored at the Medical Birth Registry, the National Board of Health and Welfare, Stockholm, or at Statistics Sweden. To identify twins with cerebral palsy or mental retardation, a questionnaire bearing the personal identification number (given to all newborns in Sweden shortly after birth) was distributed to all rehabilitation centers, all county school boards, all local boards of education, and to all County Councils for the Provisions and Services for the Mentally Retarded. The questionnaire was distributed in 1988 and 1989 when the twins were > or = 8 years old.

RESULTS

Altogether 115 disabled twins resulting from 99 pregnancies were identified. The incidence of disabled twins per 1000 was 21.4 (95% confidence interval 17.5 to 25.2). No obvious difference was evident in the distribution of birth weight discordance when the twins with disability were compared with the population of all live-born twins having a birth weight < 2500 gm. Disabled twins had a significantly lower birth weight for gestational age (t = -3.5, p < 0.001), but in fact only 10 (8.7%) twins had a birth weight < -2 SD. No difference in the incidence of disability was found for twin A versus twin B (relative risk 1.3, 95% confidence interval 0.8 to 1.9) or for like-sex versus unlike-sex twins (relative risk 1.0, 95% confidence interval 0.6 to 1.6). However, the larger twin in the pair had a significantly higher incidence of cerebral palsy than the smaller one did (relative risk 2.6, 95% confidence interval 1.4 to 4.8).

CONCLUSIONS

Birth weight discordance for twins seems not to be related to disability later in life. The great majority of twins with a birth weight < 2500 gm who later became disabled were appropriate for gestational age at birth.

Screening for the compromised fetus: a randomized trial of umbilical artery velocimetry in unselected pregnancies

OBJECTIVE

Meta-analysis of randomized trials of Doppler ultrasonography in high-risk pregnancies has showed reduced mortality rates among normally formed fetuses. This trial addressed the impact on outcome of umbilical artery velocimetry in a nonselected population (i.e., as a screening test in low-risk and high-risk pregnancies).

STUDY DESIGN

A randomized, controlled trial with Doppler ultrasonographic investigation was performed at two gestational age windows: 26 to 30 weeks and 34 to 36 weeks. The 2986 women were randomly allocated to revealed or concealed groups in which the Doppler results were either made available or not made available to clinicians; 1056 women were studied at only the first window, 544 at only the second, and 1386 at both.

RESULTS

There were no significant differences between groups in antenatal admissions to hospital, preterm deliveries, rates of cesarean section, admission to the neonatal unit, and need for assisted ventilation. There was, however, a trend toward fewer stillbirths in the "revealed" group (three vs eight, odds ratio 0.34, confidence interval 0.10 to 1.07).

CONCLUSIONS

The incidence of stillbirths was reduced by more than half in the Doppler-revealed group, but the confidence intervals were wide and these findings could be compatible with chance.

Term birth after midtrimester hysterotomy and selective delivery of an acardiac twin

OBJECTIVE

Our aim was to determine whether hysterotomy and selective removal of an acardiac twin could improve the outcome of the "pump" twin.

STUDY DESIGN

A literature and case review of the outcome of the acardiac twin malformation was performed. When an acardiac malformation was diagnosed at 19 weeks' gestation the patient was monitored with weekly ultrasonographic examinations. At 23 weeks' gestation, no blood flow could be demonstrated to the acardiac twin and it was thought that the continued presence of the acardiac twin posed a risk to the "pump" twin. A midtrimester hysterotomy was performed and the acardiac twin was delivered.

RESULTS

After the midtrimester hysterotomy, the pregnancy progressed to term and a healthy female infant was delivered by elective cesarean section at 37 weeks' gestation.

CONCLUSION

Midtrimester hysterotomy may be a useful intervention in cases of twinning when one fetus is a threat to the health of the other.