[Association between maternal plasma one-carbon biomarkers during pregnancy and fetal growth in twin pregnancies].

Objective: To characterize the relationship between the levels of plasma methyl donor and related metabolites (including choline, betaine, methionine, dimethylglycine and homocysteine) and fetal growth in twin pregnancies. Methods: A hospital-based cohort study was used to collect clinical data of 92 pregnant women with twin pregnancies and their fetuses who were admitted to Peking University Third Hospital from March 2017 to January 2018. Fasting blood was collected from the pregnant women with twin pregnancies (median gestational age: 18.9 weeks). The levels of methyl donors and related metabolites in plasma were quantitatively analyzed by high-performance liquid chromatography combined with mass spectrometry. The generalized estimation equation was used to analyze the relationship between maternal plasma methyl donors and related metabolites levels and neonatal outcomes of twins, and the generalized additive mixed model was used to analyze the relationship between maternal plasma methyl donors and related metabolites levels and fetal growth ultrasound indicators. Results: (1) General clinical data: of the 92 women with twin pregnancies, 66 cases (72%) were dichorionic diamniotic (DCDA) twin pregnancies, and 26 cases (28%) were monochorionic diamniotic (MCDA) twin pregnancies. The comparison of the levels of five plasma methyl donors and related metabolites in twin pregnancies with different basic characteristics showed that the median levels of plasma choline and betaine in pregnant women ≥35 years old were higher than those in pregnant women <35 years old, and the differences were statistically significant (all P<0.05). (2) Correlation between plasma methyl donor and related metabolites levels and neonatal growth indicators: after adjusting for confounding factors, plasma homocysteine level in pregnant women with twins was significantly negatively correlated with neonatal birth weight (ß=-47.9, 95%CI:-94.3- -1.6; P=0.043). Elevated methionine level was significantly associated with decreased risks of small for gestational age infants (SGA; OR=0.5, 95%CI: 0.3-0.9; P=0.021) and low birth weight infants (OR=0.6, 95%CI: 0.4-0.9; P=0.020). Increased homocysteine level was associated with increased risks of SGA (OR=1.5, 95%CI: 1.0-2.2; P=0.029) and inconsistent growth in twin fetuses (OR=1.9, 95%CI: 1.0-3.7; P=0.049). (3) Correlation between the levels of plasma methyl donors and related metabolites and intrauterine growth indicators of twins pregnancies: for every 1 standard deviation increase in plasma choline level in pregnant women with twin pregnancies, fetal head circumference, abdominal circumference, femoral length and estimated fetal weight in the second trimester increased by 1.9 mm, 2.6 mm, 0.5 mm and 20.1 g, respectively, and biparietal diameter, abdominal circumference and estimated fetal weight increased by 0.7 mm, 3.0 mm and 38.4 g in the third trimester, respectively, and the differences were statistically significant (all P<0.05). (4) Relationship between plasma methyl donor and related metabolites levels in pregnant women with different chorionicity and neonatal birth weight and length: the negative correlation between plasma homocysteine level and neonatal birth weight was mainly found in DCDA twin pregnancy (ß=-65.9, 95%CI:-110.6- -21.1; P=0.004). The levels of choline, betaine and dimethylglycine in plasma of MCDA twin pregnancy were significantly correlated with the birth weight and length of newborns (all P<0.05). Conclusion: Homocysteine level is associated with low birth weight in twins, methionine is associated with decreased risk of SGA, and choline is associated with fetal growth in the second and third trimesters of pregnancy.

Comparison of maternal third trimester hemodynamics between singleton pregnancy and twin pregnancy.

OBJECTIVES: The impedance cardiography (ICG) technique measures the variation of impedance in the thorax due to the physical contractile activity of the heart. Twin pregnancy is characterized by greater maternal hemodynamic changes than a singleton pregnancy. METHODS: In a study on 121 pregnant women in the last trimester we performed ICG, evaluating the following hemodynamic parameters: stroke volume, heart rate, cardiac output, ventricular ejection time, left ventricular ejection time, thoracic impedance, and systemic vascular resistance. RESULTS: The study included singleton and twin pregnancies. Heart rate values in women with single fetus was lower than in those carrying twins (85 vs. 100 beats/min, p=0.021) as were the stroke volume values (64 vs. 83 mL, p=0.010) and the cardiac output (p<0.0001). Systemic vascular resistance decreased in twin pregnancies compared to singleton pregnancy (p=0.023). CONCLUSIONS: ICG studies are rare, and the validation of their results is an ongoing process. However, the ICG technique is applicable in the third trimester of pregnancy and can yield important information regarding the hemodynamic profile of singleton and twin pregnancies, revealing maternal heart changes specific to twin pregnancies.

Percent Absent End-Diastolic Velocity in the Umbilical Artery and Donor Twin Demise after Laser Surgery for Twin-Twin Transfusion Syndrome.

INTRODUCTION: To examine the association of preoperative absent end-diastolic velocity (AEDV) and percent AEDV (%AEDV) in the umbilical artery (UA) with donor twin intrauterine fetal demise (IUFD) after laser surgery for twin-twin transfusion syndrome (TTTS). METHODS: We performed a retrospective study of stage III/IV TTTS patients who underwent laser surgery from 2006 to 2016. Donors were classified as having preoperative persistent AEDV (yes/no). %AEDV was calculated for those with AEDV as 100× the proportion of the total cardiac cycle in AEDV. Using multiple logistic regression, we tested for an association between the outcome donor IUFD and AEDV risk factors (part 1) and %AEDV (part 2). We stratified these analyses by estimated fetal weight (EFW) discordance ≥20 versus <20%. RESULTS: Of 344 cases, 153 (44.5%) donors had AEDV. Part 1 did not confirm an independent association between AEDV and donor IUFD. In the part 2 analysis of the 153 patients with AEDV, %AEDV was a positive risk factor for donor IUFD only in those with discordance (n = 129) (OR 1.04, 95% CI 1.01-1.08, p = 0.0278) when adjusting for %EFW discordance, presence of arterioarterial anastomoses, and multiparity. DISCUSSION: Among stage III/IV TTTS patients with AEDV, %AEDV was a risk factor for donor IUFD only in the presence of EFW discordance.

Two separate placental masses on ultrasound do not always indicate a dichorionic pregnancy.

Monochorionic pregnancies are associated with a higher risk of perinatal morbidity and mortality than dichorionic pregnancies. Early determination of chorionicity by an ultrasound exam between 11+0 and 14+0 weeks' gestation (WG) is essential for the subsequent management of twin pregnancies. The presence of the T-sign is the most specific sign for determination of monochorionicity. During the second trimester, the presence of two distinct placental masses has a lower specificity in determining the chorionicity. We report here two cases of a monochorionic pregnancy with a bipartite placenta, suggesting that a placenta with two separate masses, each with a distinct cord insertion is not always indicative of a dichorionic pregnancy.'

Twin pregnancy with two live fetuses at 11-13 weeks: effect of one fetal death on pregnancy outcome.

OBJECTIVES: First, to compare the incidence of single and double fetal death between monochorionic (MC) and dichorionic (DC) twin pregnancies with two live fetuses at 11-13 weeks' gestation and no major abnormalities. Second, to investigate the relationship between gestational age at single fetal death and interval to delivery of the cotwin. Third, to determine the rate of early preterm birth in DC and MC twin pregnancies with two live fetuses and those with single fetal death. METHODS: This was a retrospective analysis of prospectively collected data on twin pregnancies undergoing routine ultrasound examination at 11-13 weeks' gestation between 2002 and 2019. The outcome measures, which were stratified by chorionicity, were: first, death of both fetuses at presentation or death of one fetus followed by delivery of a live or dead cotwin within the subsequent 3 days at < 34 weeks' gestation; second, in pregnancies with single fetal death at < 34 weeks' gestation and a live cotwin ≥ 3 days later, the subsequent risk of fetal death and gestational-age distribution at birth of the cotwin; and, third, the gestational-age distribution at birth in pregnancies with two live fetuses. RESULTS: The main findings of this study of 4896 DC and 1329 MC twin pregnancies with two live fetuses at 11-13 weeks' gestation were: first, the rate of death of both twins or death of one fetus and delivery of the live or dead cotwin within 3 days was higher in MC than in DC twin pregnancies; second, the rate of single fetal death with a live cotwin ≥ 3 days later was higher in MC than in DC twin pregnancies, but the rate of subsequent cotwin death in MC twin pregnancies was not significantly different from that in DC twin pregnancies; third, in pregnancies with two live fetuses, the rate of early preterm birth was significantly higher in MC than in DC twin pregnancies; fourth, the rate of early preterm birth in pregnancies with single fetal death and a live cotwin ≥ 3 days later was not significantly different between MC and DC twin pregnancies but the rates were substantially higher than in those with two live fetuses; and, fifth, in both MC and DC pregnancies with single fetal death and a live cotwin ≥ 3 days later, there was a significant inverse association between gestational age at death and interval to delivery (mean interval of 19 weeks for death at 15 weeks and mean interval of 2.5 weeks for death at 30 weeks). CONCLUSIONS: First, in MC twin pregnancies, the risk of single or double fetal death is higher than in DC twins. Second, in both MC and DC twin pregnancies, the rate of early preterm birth is higher in those with one fetal death than in those with two live fetuses. Third, in both MC and DC twins with one fetal death, the interval to delivery is related inversely to gestational age at fetal death. These data should be useful in counseling parents as to the likely outcome of their pregnancy after single fetal death and in defining strategies for surveillance in the management of these types of twin pregnancy. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Association between impedance to blood flow in umbilical arteries and infant survival in twin-to-twin transfusion syndrome.

OBJECTIVE: To evaluate infant survival according to the Doppler pattern of impedance to blood flow in the umbilical arteries (UAs) prior to laser surgery, in pregnancies with twin-to-twin transfusion syndrome (TTTS). METHODS: This was a retrospective study of women with a monochorionic diamniotic twin pregnancy who underwent laser surgery for TTTS between January 2012 and May 2018 at a single institution. Absolute intertwin difference in UA pulsatility index (DUAPI) was measured within 48 h prior to laser surgery. Twins with intermittent or persistent absent/reversed end-diastolic flow (EDF) in the UA (UA-EDF) were analyzed separately. Survival of both or at least one infant at birth and at 30 days postpartum was compared between pregnancies with an intertwin DUAPI of ≥ 0.4 and those with an intertwin DUAPI of < 0.4, as well as between fetuses with intermittent and those with persistent absent/reversed UA-EDF. Parametric and non-parametric tests were used for analysis. Regression analysis was performed to determine if intertwin DUAPI and intermittent or persistent absent/reversed UA-EDF were associated independently with infant survival, while controlling for gestational age at delivery, Quintero stage and other important confounding variables. RESULTS: Of 231 TTTS pregnancies that underwent laser surgery during the study period, UA Doppler information could be retrieved for 206 and delivery information was available for 184, which comprised the study population. Rates of double-twin survival at birth were significantly higher in pregnancies with an intertwin DUAPI of < 0.4 than in those with an intertwin DUAPI of ≥ 0.4 (83.9% (78/93) vs 50.0% (12/24); P < 0.001). Double-infant survival at birth was higher in pregnancies with intermittent compared to those with persistent absent/reversed UA-EDF (73.0% (27/37) vs 36.7% (11/30); P = 0.003). Regression analysis demonstrated that an intertwin DUAPI of < 0.4 was associated with increased survival of both twins at delivery (P < 0.001) and at 30 days postpartum (P = 0.002), as well as increased survival of at least one twin at delivery (P = 0.009). Similarly, intermittent absent/reversed UA-EDF was associated with increased survival of both twins at delivery (P = 0.007) and at 30 days after birth (P = 0.015). CONCLUSIONS: Evaluation of intertwin differences in UA impedance to blood flow as well as identification of intermittent or persistent absent or reversed UA-EDF prior to laser surgery could help in the prediction of double-infant survival at birth and to 30 days in twin pregnancies with TTTS. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Short-Term Flow Changes in Monochorionic Survivor Twins after Ultrasound-Guided Umbilical Cord Occlusion.

OBJECTIVE: To determine hemodynamic changes by Doppler ultrasound of the living fetus during 24 h after umbilical cord occlusion (UCO) in monochorionic diamniotic (MCDA) twin pregnancies. METHOD: We conducted a prospective observational study on fetuses undergoing UCO from 2015 to 2017. Doppler parameters peak systolic velocity (PSV) and umbilical pulsatility index (PI) were obtained in the middle cerebral artery (MCA), umbilical artery (UA) and ductus venosus (DV) before and right after UCO, and at 1, 3, 6, 12, and 24 h after. We used multiple of the median (MoM) to adjust for gestational age. Spaghetti plots visualized flow changes over time. Mixed model adjusting for paired longitudinal data compared the values at different time points. RESULTS: A total of 16 women were included. MCA-PSV dropped within the first hour after surgery from 0.91 to 0.82 MoM (p = 0.08). MCA-PI and UA-PI increased in the first hour from 0.75 to 0.91 MoM (p = 0.02) and 0.94 to 0.98 MoM (p = 0.22), respectively. The DV-PIV increased to 1.14 MoM 3 h after surgery (p = 0.07). The spaghetti plots illustrated the small changes within the first hours and showed a stabilization of flow measurements near initial values 24 h after UCO. CONCLUSION: Within the first hours after UCO the circulation of the survivor twin undergoes small hemodynamic changes.

Co-Twin Control Studies: Natural Events, Experimental Interventions and Rare Happenings/Twin Research: Cancer Risk in Overweight Twins; Prognosis After Fetal Loss of One Twin; Twin Concordance for Parkinson's Disease; Neuroanatomy of Musically Discordant MZ Twins/News Articles: Twin Birth with Two Wombs; Twins' Prenatal Interactions; Switched-at-Birth Twins; Fetus-in-Fetu; Unsolved Paternity.

Co-twin control is a well-known methodological twin research design, but its variations and complexities are less well known. Various issues and illustrations are presented with reference to studies involving natural events, experimental interventions and rare happenings that underlie monozygotic (MZ) twins' environmental differences. This discussion is followed by summaries of recent twin research pertaining to cancer risk in overweight twins, the physical risk to surviving twins after fetal loss of a co-twin, a 20-year update of twin concordance for Parkinson's disease, and neuroanatomical differences in musically discordant MZ twin pairs. Several twin-related items that have attracted attention in the news are also summarized.

Maternal Anemia and Coagulation/Fibrinolysis after Fetoscopic Laser Photocoagulation for Twin-to-Twin Transfusion Syndrome.

AIM: This study was performed to evaluate maternal changes in laboratory characteristics after fetoscopic laser photocoagulation (FLP) for twin-to-twin transfusion syndrome (TTTS). METHODS: A retrospective review was conducted among 30 women with monochorionic diamniotic twin pregnancy with TTTS who underwent FLP at 16-26 weeks of gestation. Maternal laboratory parameters were measured before and after FLP. RESULTS: The pre-FLP mean hemoglobin level (10.0 g/dL), hematocrit level (30.0%), platelet count (229 × 109/mL), fibrinogen level (461 mg/dL), and antithrombin activity (96.8%) decreased after FLP (8.5 g/dL, 25.5%, 204 × 109/mL, 403 mg/dL, and 83.6%, respectively) and returned to normal spontaneously within 2 weeks (9.6 g/dL, 29.4%, 293 × 109/mL, 460 mg/dL, and 102.4%, respectively). The D-dimer level before FLP (2.41 µg/mL) increased after FLP (4.28 µg/mL), and the elevated level was maintained for 2 weeks (3.24 µg/mL). The symptomatic venous thromboembolism (VTE) was not detected after FLP in any of the 30 patients. However, one woman had pulmonary embolism after subsequent cesarean section. CONCLUSION: Changes in maternal anemia and coagulation/fibrinolysis after FLP for TTTS returned to normal spontaneously within 2 weeks. Maternal elevation of D-dimer level after FLP might be a warning indicator of VTE.

[Analysis of clinical characteristics of discordant structural malformations in one of monochorionic diamnionic twins].

Objective: To analyze the clinical characteristics of structural malformations in one of monochorionic diamnionic twins (MCDA). Methods: The clinical data of 77 MCDA patients with structural malformations diagnosed by ultrasound were retrospectively reviewed from January 2012 to May 2017. The distribution of structural malformations, prenatal chromosomal karyotyping and pregnancy outcomes were analyzed. Results: (1)Among the 77 MCDA patients with structural malformations, the single malformation accounted for 79%(61/77), the multiple malformations accounted for 21%(16/77). And there were a total of 94 types of malformations, the top three malformations were neurological malformations (32%, 30/94), cardiovascular malformations (29%, 27/94) and twin reversed arterial perfusion sequence (TRAPS;10%,9/94).(2)Among the 77 patients with structural malformation, 64 cases (83%, 64/77) were examined for fetal chromosomes, of whom 14 cases (22%,14/64) were examined for fetal chromosomes of both twins, with 1 case (1/14) of discordant fetal chromosome. (3)Among the 77 patients, 4 cases (5%, 4/77) with severe fetal malformations terminated pregnancy. Totally 29 cases (38%,29/77) with severe malformations were treated with selective fetal reduction, among whom 7 cases (24%, 7/29) experienced unexplained fetal death within 24 hours after the operation; 2 cases (7%, 2/29) happened inevitable abortion, and 2 cases (7%, 2/29) underwent unexplained fetal death during the late pregnancy. Of the remaining 44 patients (57%,44/77) with expectant treatment, 13 cases (30%,13/44) occurred twin transfusion syndrome (Ⅱ-Ⅳ), and were treated with fetoscopic laser occlusion. Eight patients had 2 survival twins, 4 patients delivered 1 survival twin, and 1 patient had dead twins. Conclusions: The most common malformations in MCDA twins are the nervous malformations, cardiovascular malformations and TRAPS. The chromosome karyotype of MCDA twins with structural malformations are sometimes discordant, and separate samling of the twins is suggested for prenatal diagnosis. Selective fetal reduction could be given to severe structural malformation in MCDA patients safely and effectively. For non-severe structural malformation in MCDA patients with twin transfusion syndrome, fetoscopic laser occlusion is safe and effective.

Maternal and neonatal outcomes according to gestational weight gain in twin pregnancies: Are the Institute of Medicine guidelines associated with better outcomes?

OBJECTIVE: The Institute of Medicine (IOM) recommended a gestational weight gain for full-term twin pregnancies of 17-25 kg for normal Body mass Index patients', and characterize its guidelines on during twin pregnancies as "provisional". Indeed, they are exclusively based on observational epidemiological data. The objective of this study was to investigate whether the IOM's gestational weight gain guidelines are optimal for maternal and neonatal. OUTCOMES STUDY DESIGN: We included all consecutive twin pregnancies delivering two live births retrospectively. Monoamniotic pregnancies, major congenital abnormalities, twin-to-twin transfusion syndrome, patients with missing gestational weight gain data in the last month before delivery, and patients with a body mass index (BMI) ≤18.5 were excluded. To control for gestational length, we divided the total weight gain by the gestational age in weeks at the last weight measurement to obtain the weight gain per week. Patients were classified as having low gestational weight gain, adequate gestational weight gain, or excessive gestational weight gain, with the results adjusted for BMI and tobacco use. RESULTS: There were 878 patients in our level-III university hospital maternity ward who met the inclusion criteria in 1997-2013. Excessive gestational weight gain women had greater rates of preeclampsia than adequate gestational weight gain women did. Low gestational weight gain women showed a lower rate of gestational hypertension than AGWG women did. Delivery before 37 weeks of gestation (26.9% vs. 17.3%, p = 0.009), birth weight <2500 g, respiratory distress syndrome, and transfer to the neonatal intensive care unit were more frequent in the LGWG group compared with the AGWG group. Apgar score <7 at 5 min were more frequent in the EGWG group. CONCLUSION: Adequate gestational weight gain was associated with better outcomes. Our results suggest that the IOM guidelines for twin pregnancy are appropriate and therefore should be routinely used.

Placental weight and birth weight to placental weight ratio in monochorionic and dichorionic growth-restricted and non-growth-restricted twins

OBJECTIVE: The aim of the present study was to compare the placental weight and birth weight/placental weight ratio for intrauterine growth-restricted and non-intrauterine growth-restricted monochorionic and dichorionic twins. METHODS: This was a retrospective analysis of placentas from twin pregnancies. Placental weight and the birth weight/placental weight ratio were compared in intrauterine growth-restricted and non-intrauterine growth-restricted monochorionic and dichorionic twins. The association between cord insertion type and placental lesions in intrauterine growth-restricted and non-intrauterine growth-restricted monochorionic and dichorionic twins was also investigated. RESULTS: A total of 105 monochorionic (intrauterine growth restriction=40; non-intrauterine growth restriction=65) and 219 dichorionic (intrauterine growth restriction=57; non-intrauterine growth restriction=162) placentas were analyzed. A significantly lower placental weight was observed in intrauterine growth-restricted monochorionic (p=0.022) and dichorionic (p<0.001) twins compared to non-intrauterine growth-restricted twins. There was no difference in the birth weight/placental weight ratio between the intrauterine growth restriction and non-intrauterine growth restriction groups for either monochorionic (p=0.36) or dichorionic (p=0.68) twins. Placental weight and the birth weight/placental weight ratio were not associated with cord insertion type or with placental lesions. CONCLUSION: Low placental weight, and consequently reduced functional mass, appears to be involved in fetal growth restriction in monochorionic and dichorionic twins. The mechanism by which low placental weight influences the birth weight/placental weight ratio in intrauterine growth-restricted monochorionic and dichorionic twins needs to be determined in larger prospective studies.

The Relation of Maternal Birth Weight to African-American and Non-Latina White Twin Pregnancy Outcomes: A Population-Based Study.

Objectives The authors investigated the association between maternal birth weight and adverse birth outcome as measured by rates of low birth weight (<2500 g, LBW), preterm birth (<37 weeks, PTB), and small for gestational age (weight <10th percentile for gestational age, SGA) among African American and White twin pregnancies. Methods Stratified and multivariable regression analyses were performed on the Illinois transgenerational dataset of non-Latina African American and non-Latina White twin pairs (born 1989-1991) and their mothers (born 1956-1976). Results Former LBW (n = 104) and non-LBW (n = 742) African American mothers had LBW rates in both twins of 76 and 56 %, respectively; RR (95 % CI) = 1.4 (1.2-1.6). Former LBW (n = 105) and non-LBW (n = 2136) White mothers had LBW rates in both twins of 41 and 34 %, respectively; RR = 1.2 (0.9-1.5). In multivariable regression models, the adjusted (controlling for maternal age, education, marital status, parity, prenatal care usage, and cigarette smoking) RR of LBW in both twins among former LBW (compared to non-LBW) African American and White mothers equaled 1.4 (1.2-1.6) and 1.2 (0.9-1.5), respectively. Maternal LBW was associated with a modestly increased risk of PTB but not SGA among African American twin pregnancies: adjusted RR = 1.3 (1.1-1.4) and 1.1 (0.8-1.5), respectively. Conclusions In African American twin pregnancies, maternal LBW is a risk factor for LBW in both twins. Further research is needed to determine whether a similar generational association occurs among non-Latina White twin pregnancies.

[PROBLEMS OF NEWBORN NEONATAL ADAPTATION FROM A TWINS].

The clinical analysis of multiple pregnancies. The features of neonatal adaptation process in 96 twins, depending on the type of zygosity. It is proved that the adaptation of the newborn with multiple pregnancy depends on the type of placentation. It is found that monozygotic twins is a risk factor syndromes disadaptation. Children from monozygotic twins compared with dizygotic twins have a higher frequency of the syndrome of respiratory disorders, and more prone to jaundice, hemorrhagic syndrome, violation gemolikvorodinamics II and III degrees. The physical development of the twins also determined by the type zygosity. In the group of monozygotic twins are more common heavier versions of intrauterine growth retardation - hypoplastic and dysplastic. The high frequency of asphyxia on the background of immaturity that leads to the development disadaptation syndromes in these children, the most common of which are hypoxic-ischemic CNS disorders, thermoregulation, jaundice and gastrointestinal reactions. Detection disorders of blood coagulation and glucose metabolism certainly play a negative role in the development of adaptation of these newborns. zygosity type must be determined at the time of pregnancy to produce medical tactics and prognosis.

Primary tooth size asymmetry in twins and singletons.

OBJECTIVES: To explore asymmetry values of antimeric deciduous tooth crown dimensions in three types of twins: monozygotic (MZ), dizygotic same-sex (DZ) and opposite-sex (OS) vs. single-born controls. SETTING AND SAMPLE POPULATION: Mesiodistal and labio-lingual crown dimensions of second deciduous molars and mesiodistal canine and first molar crown dimensions of 2159 children at 6-12 years of age were evaluated, originating from the US cross-sectional Collaborative Perinatal Study from the 1970s, including altogether MZ (n = 28), DZ same-sex (n = 33) and OS (n = 39) pairs. Single born (n = 1959) were used as controls. MATERIAL AND METHODS: Dental casts were measured for comparison of variance relationships calculated from antimeric teeth, exhibiting fluctuating (FA), and directional (DA) asymmetry using anova. RESULTS: Significant differences appeared in MZ and OS girls in DA of deciduous canines, which gain size in the first and second trimester, and deciduous second molars, which finally stop crown growth during the early post-natal period. Significantly, increased FA values appeared for lower deciduous canines and second molars, indicating greatest environmental stress in OS girls, MZ girls and DZ boys. Twin girls had more fluctuating and directional crown asymmetry than twin boys, but in some dimensions, the twins were more symmetric than controls. CONCLUSIONS: Transmembrane hormonal influence between opposite-sex twins, and late gestational stress factors, caused by placental malfunction and/or monochorionicity, may be involved in asymmetric growth of antimers, during critical periods of crown size gain.

A review of the mechanisms and evidence for typical and atypical twinning.

The mechanisms responsible for twinning and disorders of twin gestations have been the subject of considerable interest by physicians and scientists, and cases of atypical twinning have called for a reexamination of the fundamental theories invoked to explain twin gestations. This article presents a review of the literature focusing on twinning and atypical twinning with an emphasis on the phenomena of chimeric twins, phenotypically discordant monozygotic twins, mirror-image twins, polar body twins, complete hydatidiform mole with a coexistent twin, vanishing twins, fetus papyraceus, fetus in fetu, superfetation, and superfecundation. The traditional models attributing monozygotic twinning to a fission event, and more recent models describing monozygotic twinning as a fusion event, are critically reviewed. Ethical restrictions on scientific experimentation with human embryos and the rarity of cases of atypical twinning have limited opportunities to elucidate the exact mechanisms by which these phenomena occur. Refinements in the modeling of early embryonic development in twin pregnancies may have significant clinical implications. The article includes a series of figures to illustrate the phenomena described.

Fetal growth according to different reference ranges in twin pregnancies with placental insufficiency

The aim of this study was to compare different fetal growth curves in twin pregnancies with severe placental insufficiency. A retrospective cross-sectional analysis of 47 twin pregnancies with absent or reverse end diastolic flow in the umbilical artery of one fetus was performed. Pregnancies with major fetal abnormalities, twin-twin transfusion or three or more fetuses were not included. The estimated fetal weight zeta-scores were calculated for both fetuses (abnormal Doppler and co-twin) according to the following criteria: Hadlock, Liao and Araújo. The abdominal circumference zeta-scores were calculated according to Hadlock, Liao, Araújo, Ong and Stirrup. The mean estimates of the zeta-score values were calculated using generalized estimating equation regression analysis. The mean gestational age at inclusion was 27.4±4.7 weeks. The fetal sex and the interaction Doppler findings × criteria correlated significantly with the zeta-score values (p <0.001 for both variables). The estimated fetal weight mean zeta-scores (standard error) according to each criteria were as follows: Hadlock - abnormal Doppler: -2.98 (0.18), co-twin: -1.16 (0.15); Liao - abnormal Doppler: -2.89 (0.24), co-twin: -0.58 (0.19); and Araújo - abnormal Doppler: -3.05 (0.29), co-twin: -0.75 (0.18). Values for abdominal circumference were as follows: Hadlock - abnormal Doppler: -3.14 (0.26), co-twin: -1.13 (0.19); Liao - abnormal Doppler: -2.63 (0.27), co-twin: -0.42 (0.19); Araújo - abnormal Doppler: -2.44 (0.22), co-twin: -0.71 (0.14); Ong - abnormal Doppler: -3.36 (0.34), co-twin: -1.48 (0.23); and Stirrup AD -- -2.36 (0.14), co-twin: -1.18 (0.10). Sex- and plurality-specific charts should be used in the evaluation of fetal growth in twin pregnancies with placental insufficiency.

Unconscious dynamics in twin pregnancy emerging from the Lüscher color test.

OBJECTIVE: To investigate unconscious dynamics in women pregnant with twins, using Lüscher's color test to objectively measure subjective color preferences, and compare them with women with singleton pregnancies. METHODS: The color test was administered to 50 Italian women with twin pregnancies and 100 women with singleton pregnancies. RESULTS: Both the twin and singleton pregnancy groups said that violet was their favorite color (50 versus 49%) and brown was their least favorite color (52 versus 44%), indicating that they idealized being pregnant, but also found it physically stressful. The twin pregnancy group chose yellow as their second favorite (28 versus 17%) and were most likely to combine it with their first choice of violet (44 versus 19%, p=0.0006), indicating that they were worried about their relationships with their new babies and wanted to give birth soon. In addition, both groups preferred form 6, the sine curve on a dark background, but rejected the associated brown color 6, revealing that the women felt the need to look after themselves. CONCLUSIONS: Both groups idealized being pregnant, but also found it physically stressful. However, the twin pregnancy group was afraid of building relationships with their babies and wanted to give birth soon.

Pulmonary function in advanced uncomplicated singleton and twin pregnancy / Função pulmonar em mulheres com gestação única ou gemelar avançada e sem complicações

Objective: Pregnancy brings about significant changes in respiratory function, as evidenced by alterations in lung volumes and capacities, which are attributable to the mechanical impediment caused by the growing foetus. This study was undertaken in order to identify changes in respiratory function during normal pregnancy and to determine whether such changes are more pronounced in twin pregnancy than in singleton pregnancy. Methods: Respiratory function was assessed in 50 women with twin pregnancies and in 50 women with singleton pregnancies (during the third trimester in both groups), as well as in 50 non-pregnant women. We measured the following pulmonary function test parameters: FVC; FEV1; PEF rate; FEV1/FVC ratio; FEF25-75%; and maximal voluntary ventilation. Results: All respiratory parameters except the FEV1/FVC ratio were found to be lower in the pregnant women than in the non-pregnant women. We found no significant differences between women with twin pregnancies and those with singleton pregnancies, in terms of respiratory function. Conclusions: Despite its higher physiological demands, twin pregnancy does not appear to impair respiratory function to any greater degree than does singleton pregnancy. .

Objetivo: A gravidez traz mudanças significativas na função respiratória, evidenciada por alterações nos volumes e capacidades pulmonares, que são atribuíveis ao impedimento mecânico causado pelo feto em crescimento. Este estudo foi realizado a fim de identificar alterações na função respiratória durante a gravidez normal e determinar se tais alterações são mais pronunciadas em gestação gemelar que em gestação única. Métodos: Foi avaliada a função respiratória de 50 mulheres com gestações gemelares e de 50 mulheres com gestações únicas (durante o terceiro trimestre em ambos os grupos), bem como de 50 mulheres não grávidas. Medimos os seguintes parâmetros de função pulmonar: CVF, FEV1, taxa do PFE, relação VEF1/CVF, FEF25-75% e ventilação voluntária máxima. Resultados: Todos os parâmetros, exceto a relação VEF1/CVF, foram menores nas mulheres grávidas do que nas mulheres não grávidas.Não foram encontradas diferenças significativas entre as mulheres com gestações gemelares e aquelas com gestações únicas em relação à função respiratória. Conclusões: Apesar das demandas fisiológicas maiores da gestação gemelar, essa não parece causar um comprometimento maior da função respiratória do que a gestação única. .

Improvement in neurodevelopmental outcome in survivors of twin-twin transfusion syndrome treated with laser surgery.

OBJECTIVE: To compare the incidence of neurodevelopmental impairment in surviving children from pregnancies with twin-twin transfusion syndrome (TTTS) treated with laser surgery between 2 time periods. STUDY DESIGN: We compared the neurodevelopmental outcome between the first consecutive cohort of TTTS pregnancies treated with laser surgery from 2000 to 2005, with a cohort treated between 2008 and 2010. Neurologic, cognitive, and motor development was evaluated using Bayley scales at 2 years of age corrected for prematurity. RESULTS: A total of 229 twin pregnancies were treated with laser surgery, 113 in the first cohort and 106 in the recent cohort. Overall survival increased from 70% (158/226) to 80% (170/212) (P = .014). The incidence of neurodevelopmental impairment decreased from 18% (28/152) to 6% (10/155) (P < .01). In multivariate analysis, severe cerebral injury at birth was independently associated with neurodevelopmental impairment (odds ratio, 34.86; 95% confidence interval, 11.83-102.75; P < .01). CONCLUSION: Overall survival in TTTS has improved over time, with a concomitant reduction in the incidence of neurodevelopmental impairment. Research focused on prevention of cerebral injury is needed to further improve outcomes of these complicated twin pregnancies.