Screening and diagnosis of chromosomal abnormalities in twin pregnancy

Twin pregnancies are at an increased risk of adverse pregnancy and perinatal outcome as compared to singleton gestations, mainly as the consequence of the higher rate of preterm birth, chromosomal as well as structural anomalies, placental abnormalities, and complications unique to monochorionic placentation.Screening for chromosomal anomalies poses diagnostic and management challenges when applied to twin pregnancies. The recent implementation of cell-free fetal DNA (cffDNA) in clinical practice raises the questions whether a more accurate test should be offered to twin pregnancies in view of the higher false positive rate of traditional screening and the higher risk of fetal loss following amniocentesis or chorionic villus sampling (CVS) in multiple gestations. Finally, twin pregnancies require a tailored approach for aneuploidy screening, such as nuchal translucency (NT) or crown rump length discordance, discordant fetal anomalies, or monoamniotic gestations.The present review aims to provide an up-to-date critical appraisal of screening and prenatal diagnosis of chromosomal abnormalities in twin pregnancies.     

Antenatal nonstress test in complicated and uncomplicated pregnancies in type-1-diabetic women

111 pregnant women with type-1 diabetes were cared for at the Karolinska Hospital from 1979 to 1986. As routine fetal monitoring, a non-stress test (NST) was performed twice weekly from the 35th or 36th week of gestation to delivery. If pregnancy complications occurred, an NST was still used for fetal monitoring, but more frequently. The median gestational age at delivery was 270 days. The mean maternal blood glucose during the third trimester was 6.0 mmol/l. In 88 of the totally 111 women the only indication for an NST was the patient's diabetes. In this routinely monitored group, 2/88 patients had abnormal NSTs and cesarean sections were performed. The neonatal outcome was good in both cases. Twenty-three had such complications as pre-eclampsia or IUGR, and in these cases the frequency of an NST was individualized. Four of these 23 had abnormal NSTs leading to cesarean sections. There were no signs of asphyxia among these four infants. Thus, in diabetic pregnancies with a well-regulated blood glucose, intervention due to abnormal fetal monitoring is more associated with acute pregnancy complications than the diabetes per se. The results of this study suggest that antenatal NSTs twice a week from week 35-36 is sufficient in well blood-glucose regulated type-1-diabetic women with a well-regulated blood glucose. If pregnancy complications occur, the NST, in an individualized frequency, seems to be a safe way of fetal monitoring.     

Predictive value of antepartum fetal heart rate non-stress test in high-risk pregnancy

For antepartum evaluation of high-risk pregnancies the non-stress test (NST) was performed in order to predict favorable or adverse fetal outcome. Between January 1, 1980 and December 31, 1980, 4078 NSTs were performed on 454 women with high-risk pregnancies. The NSTs were evaluated for pathology by a CTG pathology score. The NST interpretation were normal 95%, slight pathological 4% and severe pathological 1%. The group of women in whom all NST results were normal gave birth to healthy babies. In tact with an increasing number of pathologica-NSTs and with worsening CTG pathology score, a significant increase was found for cesarean section rate, acute operative delivery, low Apgar score, low umbilical cord artery pH and infants born small for gestational age or clinically dysmature. The frequence of perinatal morbidity was almost the same, irrespective of whether the NSTs showed accelarations or not on one or more occasions. To identify fetuses suffering from retarded intra-uterine growth the predictive value of normal NST was 97.3% and the predictive value of pathological NST was 34.8%. To identify perinatal morbidity the predictive values were 87.4% and 55.1% respectively. The NST appears to be a reliable test for antepartum assessment of fetal well-being in high-risk pregnancies.     

Effects of prenatal care on twin gestations

Twin pregnancies are known to have a higher risk of prematurity, uteroplacental insufficiency and increased perinatal mortality. An almost universally held tenet is that prenatal care is helpful in reducing those risks. In an attempt to support that belief, the records of all twins delivered at R. E. Thomason General Hospital between 1982 and 1985 were reviewed. Thirty-seven twin pregnancies received appropriate antepartum care, and 25 did not. There were statistically significant differences in the perinatal mortality rate of the clinic patients (68/1,000) versus the nonclinic patients (160/1,000). Also, significant differences were demonstrated between the mean birth weights: 2,007 g in the nonclinic group and 2,546 in the clinic group. The results suggest that intensive prenatal care in twin gestations promotes fetal growth and improves perinatal outcome.     

Multifetal pregnancy in older women and perinatal outcomes

OBJECTIVE: To examine multifetal pregnancy in older women and perinatal outcomes.DESIGN: A cross-sectional study.SETTING: A nationwide vital registry.PATIENT(S): A national population-based database that links the live birth, fetal, and infant death certificates reported of multiple gestations in the United States from 1995 to 1997. It includes 155,777 twin and 5,630 triplet pregnancies.INTERVENTION(S): None.MAIN OUTCOME MEASURE(S): Very preterm birth (<33 weeks), very low birthweight (<1,500 g), and perinatal and infant deaths.RESULT(S): Compared with those with singleton pregnancies, women with multifetal gestation tended to be older, non-Hispanic white, better educated, married, and nulliparous and to have earlier and more frequent prenatal care. Pregnancies conceived by assisted reproductive technology accounted for an increasing number of multiple gestations in older women. In women with lower socioeconomic status, older age was associated with higher risks of poor perinatal outcomes in twin pregnancy (relative risks ranging from 1.0 to 1.9 with a dose-response pattern). However, in women with higher socioeconomic status, older women did not have a higher risk of poor perinatal outcomes than younger women.CONCLUSION(S): The effect of older maternal age on perinatal outcomes in multifetal pregnancies may have been altered by assisted reproductive technology, frequent prenatal surveillance, and advanced neonatal care.     

双绒毛膜及单绒毛膜双胎与妊娠期并发症及围生儿结局分析

目的:探讨双胎妊娠绒毛膜性对孕妇妊娠期并发症及围生儿预后的影响及意义。方法:对我院定期随诊并分娩的472例双胎临床资料进行回顾性分析,根据绒毛膜性分为单绒毛膜双羊膜囊组(MCDA组)和双绒毛膜双羊膜囊组(DCDA组),对两组孕妇的分娩孕周、并发症以及围生儿预后等进行比较分析。结果:两组孕产妇妊娠并发症的发生率比较,差异无统计学意义(P>0.05)。MCDA组低出生体重儿、极低出生体重儿、新生儿窒息及围生儿死亡的发生率均明显高于DCDA组,其差异有统计学意义(P<0.05),MCDA组中双胎输血综合征发生率为7.32%。结论:绒毛膜性对孕妇妊娠并发症的发生无明显影响,而双胎孕妇于孕早期行B超检查诊断单绒毛膜或双绒毛膜对预测围生儿预后具有重要意义。尽早确定双胎类型,加强对单绒毛膜双胎的监护及干预,是改善胎儿和新生儿预后的关键。     

Accuracy of ultrasonographic fetal weight estimation in twin pregnancies

OBJECTIVE: To compare the accuracy of fetal weight estimations between normal and growth-restricted twin and singleton pregnancies in a single tertiary center. METHODS: The computerized ultrasound database of a tertiary center was searched for all fetal weight estimations made in twin pregnancies from 2001 to 2006, which were performed up to 3 days before delivery. Accuracy was compared with a control group of singleton pregnancies at a 3:1 ratio. Estimated fetal weight was calculated by the Hadlock formula. Analyses were performed for the whole group and for pregnancies associated with fetal growth restriction and discordancy. RESULTS: The study groups included 278 twins and 834 singleton pregnancies. The twins group was characterized by a higher mean absolute percentage error compared with the singleton group (8.9% compared with 6.8%). Accuracy was lower for the second twins than for the first twins. When comparing the subgroup of fetal growth restriction, differences in sensitivity and specificity were small for singleton compared with overall twins (47.5% compared with 48.9% and 97.7% compared with 95.7%, respectively). Overall accuracy was better in the singleton group (95% compared with 88%), mainly due to relatively low accuracy in the second twin (86%). For detection of discordancy, estimated fetal weight had a sensitivity of 52%, specificity of 88%, and overall accuracy of 81%. CONCLUSION: The accuracy of the ultrasonographic estimated fetal weight seems to be lower for twin gestations than for singleton gestations, especially for second twins. These data should be considered by clinicians when making decisions based on ultrasonographic characteristics.     

Studies on the interrelation of fetal heart rate change, placental findings and fetal outcome

The relation between antepartum fetal heart rate (FHR) non stress test (NST), maternal serum estriol, intrapartum FHR change, birth weight, placental findings and Apgar score were studied in 168 normal gestations and 36 high-risk pregnancies including 25 EPH-gestosis cases. The frequency of placental infarcts was higher in severe gestosis than in other high-risk pregnancies and normal gestation. Abnormal NST was more frequent in high-risk pregnancy than normal. Light for date (LFD) infants were more numerous in high-risk pregnancy than normal, and also frequent in the cases of placental infarcts. Particularly in high-risk pregnancy patients with abnormal NST and placental infarcts, 3 out of 5 showed LFD infants. Intrapartum fetal distress was more common in the cases of abnormal NST than normal. The five minute Apgar score was lower in the patients with abnormal NST and in the cases of placental infarcts than normal. The placental infarct ratio was higher in high-risk pregnancies with abnormal NST than normal. The maternal serum estriol level was not changed in cases of high-risk pregnancy, abnormal NST or placental infarcts when compared to normal gestation. The cases of succeeding fetal death, however, showed a low serum estriol level. In conclusion, antepartum abnormal NST suggests severe placental dysfunction caused by its infarcts and the prognosis is poor in patients with high-risk pregnancies, particularly EPH-gestosis. Coping with abnormal antepartum NST is regarded as important in fetal management.     

Maternal physiology and complications of multiple pregnancy

Approximately 1% to 3% of all pregnancies in the United States are multiple gestations. The vast majority (97-98%) are twin pregnancies. Multiple pregnancies constitute significant risk to both mother and fetuses. Antepartum complications-including preterm labor, preterm premature rupture of the membranes, intrauterine growth restriction, intrauterine fetal demise, gestational diabetes, and preeclampsia-develop in over 80% of multiple pregnancies as compared with approximately 25% of singleton gestations. This article reviews in detail the maternal physiologic adaptations required to support a multiple pregnancy and the maternal complications that develop when these systems fail or are overwhelmed.     

Perinatal outcome of twin pregnancies with one structurally affected fetus: a case-control study.

OBJECTIVE: To determine whether one structurally affected fetus of a twin pregnancy further increases the risk of preterm delivery and to compare perinatal morbidity and mortality in these pregnancies with twin gestations with structurally normal fetuses. STUDY DESIGN: The cases (n = 25) included all twin gestations diagnosed from 1991 to 1994 with a sonographically detected fetal anomaly and a structurally normal co-twin delivered after 24 completed weeks' gestation. The control group consisted of 547 twin gestations delivered during the study period with no sonographically detected structural anomalies in either twin. RESULTS: Compared with controls, pregnancies with a single anomalous fetus (cases) delivered at a significantly lower gestational age (mean +/- SD: 34.0 +/- 3.2 weeks versus 35.6 +/- 3.2 weeks; p = 0.019) and had a significantly increased preterm delivery rate (76.0% vs 55.4%; p = 0.042). There was no significant difference in the incidence of intraventricular hemorrhage or respiratory distress syndrome, yet the perinatal mortality (80.0/1000 vs 6.4/1000; p = 0.000) and the average nursery stay (45.5 +/- 43.3 days versus 17.0 +/- 24.0 days; p = 0.003) were significantly increased for cases compared with controls. In addition, a significantly greater birth weight discordancy (> or = 30%) was seen in cases compared with controls (32.0% versus 9.1%; p = 0.002). The normal co-twin did not show any significant difference in the perinatal outcome variables studied when compared with controls. CONCLUSION: Compared with structurally normal twin pairs, twin gestations with a single anomalous fetus are at a significantly increased risk for preterm delivery. In addition, the anomalous fetus, but not the structurally normal co-twin, has a significantly increased mortality rate and a longer nursery stay. Finally, despite the increased risk for preterm delivery in twin pregnancies with one anomalous fetus, it is the nature of the anomaly itself that dictates the perinatal outcome.     

Prenatal diagnosis in twin gestations

Twin gestations face an increased risk of structural abnormalities compared with singleton gestations, as well as an increased risk of aneuploidy. Accordingly, there is a need for accurate prenatal diagnosis of fetal genetic disorders and structural anomalies in twin gestations. Given the increased risk of congenital anomalies, a detailed sonographic survey of fetal anatomy is recommended in the early second trimester of twin gestations. In addition, fetal echocardiography should be considered in monochorionic twin gestations and in dichorionic twin pregnancies conceived using assisted reproductive technologies given the increased risk of congenital heart disease in these populations. Although first- and second-trimester aneuploidy screening in twin gestations is available, screening is less accurate than in singleton gestations. Invasive prenatal diagnosis in twin pregnancies is associated with a risk of pregnancy loss that is higher than the baseline risk of loss among twin gestations. Precise procedure-related loss rates in twin gestations undergoing chorionic villus sampling or amniocentesis, however, remain unclear because of methodological differences between published studies investigating diagnostic procedures in twins.     

Multiple pregnancies with single intrauterine demise. Description of twenty-eight pregnancies

METHODS: Retrospective study of multiple pregnancies and deliveries with single intrauterine demise, in a five years' study period. RESULTS: Of a total of 13,840 deliveries in the study period, 355 represented multiple pregnancies with two or more fetuses from conception: 310 twin pregnancies and 45 triplets or higher. Twenty-eight multiple pregnancies were complicated by single intrauterine death: in six cases (group A) as first trimester spontaneous fetal loss, in nine cases (group B) due to selective fetal reduction, and in thirteen pregnancies as spontaneous intrauterine demise occurring in the second or third trimester (group C). In group A, no specific cause of death was proven. In group C, four cases of death were caused by twin transfusion syndrome, three cases by severe intrauterine growth retardation, four cases by placental insufficiency, one case by placental abruption striking one of the twins, whereas the last death was undefined. In group A, mean gestational age at delivery was 33 completed weeks. In group C, five monochorionic pregnancies were delivered at median gestational age 30 weeks and seven dichorionic pregnancies at 34 weeks (the chorionicity was indefinite in one case). The neonatal complications of the forty-two live born babies included prematurity problems only, except for one case of congenital anemia in a transfusion syndrome donor twin. None of the mothers showed signs of intravascular coagulopathy. CONCLUSION: The main problem for the surviving twin was prematurity - not the sibling's death.     

双胎之一胎死宫内的诊治

随着促排卵技术和辅助生殖技术的发展，多胎妊娠发生率逐年增多。与单胎妊娠相比，多胎妊娠围产儿病死率更高。双胎之一胎死宫内属于双胎妊娠的严重并发症，一胎死亡后会对存活胎儿有潜在、长期的影响，可引起存活胎儿死亡、神经系统损伤、早产及相关后遗症等，因此，孕期应加强母儿监护。及时诊断和处理是改善围产儿结局的关键。     

Analysis of 104 twin pregnancies conceived with assisted reproductive technologies and 193 spontaneously conceived twin pregnancies

OBJECTIVE: To evaluate pregnancy outcome of assisted reproductive technology (ART)-conceived twin pregnancies. DESIGN: Retrospective study. SETTING: A tertiary obstetric care center. PATIENT(S): All twin pregnancies delivered > or = 24 weeks of gestation from January 1, 1996, to December 31, 1997. INTERVENTION(S): Maternal and neonatal record review. MAIN OUTCOME MEASURE(S): Pregnancy and perinatal outcome. RESULT(S): The study group comprised 104 ART-conceived twin pregnancies, and 193 non-ART-conceived pregnancies served as controls. Mean maternal age, the proportion of nulliparae, and the percentage of women who delivered before 34 weeks' gestation was higher among the study women, whereas mean gestational age was younger. The incidences of pregnancy-induced hypertension, uterine bleeding, premature contractions, intrauterine growth retardation, fetal death, discordance, and cesarean section were significantly higher in the study group. Correspondingly, in the study group, the mean birth weight of both twins was lower; more neonates weighed < 1, 500 g, more had Apgar scores of < 7 at 5 minutes, more were admitted to the intensive care unit, and more second twin neonates died. The outcome of twin pregnancies conceived spontaneously was comparable with those conceived by ovulation induction. CONCLUSION(S): Assisted reproductive technology-conceived twin pregnancies are at greater risk than non-ART-conceived ones for pregnancy complications and adverse perinatal outcome.     

Twins--twice more trouble?

Twin gestations are fascinating and are also high-risk pregnancies. They account for approximately 3% of all pregnancies in the United States. Major obstetrical complications associated with twin pregnancies include hypertensive disorders of pregnancy, gestational diabetes, and preterm delivery. In addition, the death rate for twins and the rate of severe handicap in very low birth weight survivors of twin pregnancies is greater than that for singleton pregnancies. Ultrasound allows for stepwise evaluations at any time during a twin gestation. Current evidence suggests that uncomplicated diamniotic twins with concordant and appropriate growth beyond 24 weeks' gestation should be managed conservatively and the time and mode of delivery should be determined on the basis of obstetrical history and fetal presentations. Perinatal management of the remaining twin pregnancies depends on good clinical judgment, which is improved by the use of ultrasound imaging.     

Ultrasound in twins: Dichorionic and monochorionic

The objective of this review is to assess the evidence that supports the use of ultrasound in twin pregnancies. Although many of the indications for obstetric ultrasound are the same in both singleton and multiple gestations, there are special considerations as well as unique conditions in twins that require additional imaging studies. The reasons for ultrasound in twins include pregnancy dating, determination of chorionicity, nuchal translucency assessment, anatomical survey, placental evaluation, cervical length assessment, routine fetal growth, and serial surveillance of pregnancies complicated by anomalies, cervical shortening, fetal growth disturbances, and amniotic fluid abnormalities. Twins with monochorionic placentation require heightened scrutiny for monoamnionicity, conjoined twins, twin reversed arterial perfusion (TRAP) syndrome, twin–twin transfusion syndrome, unequal placental sharing with discordant twin growth or selective intrauterine fetal growth restriction (IUGR), twin anemia–polycythemia sequence (TAPS), and single fetal demise. Ultrasound is essential for the detection and management of conditions that can complicate dichorionic and monochorionic twin pregnancies.     

Differences in TDx fetal lung maturity assay values between twin and singleton gestations

OBJECTIVE: The purpose of this study was to quantify differences in indexes of pulmonary maturity between singleton and twin gestations by means of the TDx fetal lung maturity assay.Study Design: We identified records of a total of 830 singleton and twin pregnancies not complicated by diabetes and delivered between 28 and 37 weeks' gestation from December 1994 through August 1995. Among these, 170 (20%) had TDx fetal lung maturity measurements performed within 72 hours of delivery. Linear regression was used to assess differences in TDx fetal lung maturity assay values between singleton gestations (n = 143 gestations) and twin gestations (n = 27 gestations) while controlling for potential confounding factors. RESULTS: Twin gestations were no more likely than singleton gestations to undergo TDx fetal lung maturity screening (odds ratio, 1.3; 95% confidence interval, 0.8-2.2). Pregnancy complications and corticosteroid treatment were similar in the two groups. After 31 weeks' gestation the twin gestations had significantly higher TDx fetal lung maturity values. Linear regression with controls for gestational age indicated that twin gestations on average had a TDx fetal lung maturity value that was 22.0 mg/g (95% confidence interval, 9.8-34.6 mg/g) higher than that of gestational age-matched singleton gestations. CONCLUSION: Beyond 31 weeks' gestation twin pregnancies appeared to have a TDx fetal lung maturity value that was 22 mg/g higher than that of singleton pregnancies. If the underlying incidences of respiratory distress syndrome are similar between twin and singleton gestations, then the potential exists for false-positive prediction of adequate lung maturity values among twin gestations.     

Twin pregnancy complicated by intrauterine death of one twin

In twin pregnancies single intrauterine death of one fetus is associated with significant morbidity and mortality of the surviving infant. The aims of our retrospective study were to review conditions of twin pregnancies complicated with SIUD in Polish Mother's Memorial Hospital in ?ód? between 1989-1999 and to assess the fetal outcome when conservative management had undergone. In this study we reviewed 30 twin gestations involving the intrauterine death of one fetus. The incidence of preterm delivery among pregnancies with fetal death was 83.3%; Caesarean section was the method of delivery in 53.3% cases. Monochorionic placentation was found in 60%. Conservative management until there is no risk for the fetus is apt.     

Monoamnotic twin pregnancy. Multicenter study

OBJECTIVE: The purpose of this study was to evaluate of perinatal mortality and morbidity of monoamniotic twins. STUDY DESIGN: This was a multicenter retrospective analysis of 26 monoamniotic twin gestations identified between 1985 and 2004 in a 3 perinatal departments. Of these 26 pregnancies, 11 women were admitted electively for inpatient fetal monitoring. Overall mortality rates, the risk of intrauterine fetal death and neonatal mortality and morbidity, pregnancy complications and fetal anomalies were calculated. RESULTS: Monoamniotic twin pregnancies were diagnosed reliably prenatally by ultrasound in 22 women and at delivery in 4 cases. Of the 26 gestations, spontaneous fetal losses before 22 weeks of gestation were 4 cases. The overall loss rate and the perinatal mortality rate were 52% and 19.4%, respectively. Twenty-two women had both twins alive at 24 weeks of gestation; 11 women were admitted electively for inpatient fetal monitoring at 26-27 week of gestation. In this group there were 2 neonatal deaths. No intrauterine fetal death occurred in any hospitalized patient. In our series there were 100% incidence of prematurity, 38,5% of umbilical cord entaglement, 23% of TTTS, 3.6% of TRAP and 9.6% fetal congenital anomalies. CONCLUSION: Monoamniotic twins are at extremly risk of pregnancy complications and fetal loss. These pregnancies can be diagnosed reliably by ultrasound in most cases. Electively admitted women for inpatient fetal monitoring could be improved neonatal survival and decreased perinatal morbidity.     

Clinical significance of first trimester crown-rump length disparity in dichorionic twin gestations

OBJECTIVE: The purpose of this study was to determine the clinical significance of first trimester crown-rump disparity in dichorionic twin gestations. STUDY DESIGN: Ultrasound examinations of dichorionic twin pregnancies between 11 and 14 weeks of gestation were evaluated for growth discordance using crown-rump length. Medical records were reviewed for antenatal complications that included spontaneous abortion, fetal death, fetal structural or chromosomal anomalies, and preterm delivery. Fisher's exact test was used for statistical analysis; a probability value of <.05 was considered significant. RESULTS: Of 159 twin pregnancies, there were 7 fetal structural anomalies, 2 fetal chromosomal anomalies, 5 second-trimester spontaneous abortions, 3 second-trimester fetal deaths, and 1 third-trimester fetal death. Pregnancies that were complicated by fetal structural or chromosomal anomalies had significantly greater median crown-rump length discordance than pregnancies without fetal anomalies (4.0 mm vs 2.0 mm; P = .02). Crown-rump length discordance >10%, which is the 90th percentile for intertwin crown-rump length disparity in our population, was associated with a significantly higher incidence of fetal anomalies (22.2% vs 2.8%; P = .01). CONCLUSION: First trimester crown-rump length disparity in dichorionic twin gestations is associated with an increased risk of fetal structural and chromosomal anomalies.