Prediction of pre-eclampsia in twin pregnancy by maternal factors and biomarkers at 11-13 weeks' gestation: data from EVENTS trial.

OBJECTIVES: First, to validate a previously developed model for screening for pre-eclampsia (PE) by maternal characteristics and medical history in twin pregnancies; second, to compare the distributions of mean arterial pressure (MAP), uterine artery pulsatility index (UtA-PI), serum placental growth factor (PlGF) and serum pregnancy-associated plasma protein-A (PAPP-A) in twin pregnancies that delivered with PE to those in singleton pregnancies and to develop new models based on these results; and, third, to examine the predictive performance of these models in screening for PE with delivery at < 32 and < 37 weeks' gestation. METHODS: Two datasets of prospective non-intervention multicenter screening studies for PE in twin pregnancies at 11 + 0 to 13 + 6 weeks' gestation were used. The first dataset was from the EVENTS (Early vaginal progesterone for the preVention of spontaneous prEterm birth iN TwinS) trial and the second was from a previously reported study that examined the distributions of biomarkers in twin pregnancies. Maternal demographic characteristics and medical history from the EVENTS-trial dataset were used to assess the validity of risks from our previously developed model. The combined data from the first and second datasets were used to compare the distributional properties of log10 multiples of the median (MoM) values of UtA-PI, MAP, PlGF and PAPP-A in twin pregnancies that delivered with PE to those in singleton pregnancies and develop new models based on these results. The competing-risks model was used to estimate the individual patient-specific risks of delivery with PE at < 32 and < 37 weeks' gestation. Screening performance was measured by detection rates (DR) and areas under the receiver-operating-characteristics curve. RESULTS: The EVENTS-trial dataset comprised 1798 pregnancies, including 168 (9.3%) that developed PE. In the validation of the prior model based on maternal characteristics and medical history, calibration plots demonstrated very good agreement between the predicted risks and the observed incidence of PE (calibration slope and intercept for PE < 32 weeks were 0.827 and 0.009, respectively, and for PE < 37 weeks they were 0.942 and -0.207, respectively). In the combined data, there were 3938 pregnancies, including 339 (8.6%) that developed PE and 253 (6.4%) that delivered with PE at < 37 weeks' gestation. In twin pregnancies that delivered with PE, MAP, UtA-PI and PlGF were, at earlier gestational ages, more discriminative than in singleton pregnancies and at later gestational ages they were less so. For PAPP-A, there was little difference between PE and unaffected pregnancies. The best performance of screening for PE was achieved by a combination of maternal factors, MAP, UtA-PI and PlGF. In screening by maternal factors alone, the DR, at a 10% false-positive rate, was 30.6% for delivery with PE at < 32 weeks' gestation and this increased to 86.4% when screening by the combined test; the respective values for PE < 37 weeks were 24.9% and 41.1%. CONCLUSIONS: In the assessment of risk for PE in twin pregnancy, we can use the same prior model based on maternal characteristics and medical history as reported previously, but in the calculation of posterior risks it is necessary to use the new distributions of log10 MoM values of UtA-PI, MAP and PlGF according to gestational age at delivery with PE. © 2020 International Society of Ultrasound in Obstetrics and Gynecology.

Increased nuchal translucency at 11-13 weeks' gestation and outcome in twin pregnancy.

OBJECTIVE: To investigate the value of increased fetal nuchal translucency thickness (NT) at the 11-13-week scan in the prediction of adverse outcome in dichorionic (DC), monochorionic diamniotic (MCDA) and monochorionic monoamniotic (MCMA) twin pregnancies. 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. In pregnancies with no major defects or chromosomal abnormalities, we examined the value of increased NT ≥ 95th percentile in one or both fetuses in the prediction of, first, miscarriage or death of one or both fetuses at < 20 and < 24 weeks' gestation in DC, MCDA and MCMA twin pregnancies, second, death of one or both fetuses or neonates at ≥ 24 weeks in DC, MCDA and MCMA twin pregnancies, third, development of twin-twin transfusion syndrome (TTTS) or selective fetal growth restriction (sFGR) treated by endoscopic laser surgery at < 20 and ≥ 20 weeks' gestation in MCDA pregnancies, and, fourth, either fetal loss or laser surgery at < 20 weeks' gestation in MCDA pregnancies. RESULTS: The study population of 6225 twin pregnancies included 4896 (78.7%) DC, 1274 (20.5%) MCDA and 55 (0.9%) MCMA pregnancies. The incidence of NT ≥ 95th percentile in one or both fetuses in DC twin pregnancies was 8.3%; in MCDA twins the incidence was significantly higher (10.4%; P = 0.016), but in MCMA twins it was not significantly different (9.1%; P = 0.804) from that in DC twins. In DC twin pregnancies, the incidence of high NT was not significantly different between those with two survivors and those with adverse outcome. In MCMA twin pregnancies, the number of cases was too small for meaningful assessment of the relationship between high NT and adverse outcome. In MCDA twin pregnancies with at least one fetal death or need for endoscopic laser surgery at < 20 weeks' gestation, the incidence of NT ≥ 95th percentile was significantly higher than in those with two survivors (23.5% vs 9.8%; P < 0.0001). Kaplan-Meier analysis in MCDA twin pregnancies showed that, in those with NT ≥ 95th percentile, there was significantly lower survival at < 20 weeks' gestation than in those with NT < 95th percentile (P = 0.001); this was not the case for survival at ≥ 20 weeks (P = 0.960). The performance of screening by fetal NT ≥ 95th percentile for prediction of either fetal loss or need for endoscopic laser surgery at < 20 weeks' gestation was poor, with a detection rate of 23.5% at a false-positive rate of 8.9%, and the relative risk, in comparison to fetal NT < 95th percentile, was 2.640 (95% CI, 1.854-3.758; P < 0.0001). In MCDA twin pregnancies, the overall rate of fetal loss or need for laser surgery at < 20 weeks' gestation was 10.7% but, in the subgroups with NT ≥ 95th and NT ≥ 99th percentiles, which constituted 10.4% and 3.3% of the total, the rates increased to 24.1% and 40.5%, respectively. CONCLUSIONS: In MCDA twin pregnancies with no major fetal abnormalities, measurement of NT at the 11-13-week scan is a poor screening test for adverse pregnancy outcome. However, the finding in one or both fetuses of NT ≥ 95th percentile, and more so ≥ 99th percentile, is associated with a substantially increased risk of fetal loss or need for endoscopic laser surgery at < 20 weeks' gestation. The extent to which closer monitoring and earlier intervention in the high-risk group can reduce these complications remains to be determined. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Intertwin discordance in fetal size at 11-13 weeks' gestation and pregnancy outcome.

OBJECTIVE: To investigate the value of intertwin discordance in fetal crown-rump length (CRL) at the 11-13-week scan in the prediction of adverse outcome in dichorionic (DC), monochorionic diamniotic (MCDA) and monochorionic monoamniotic (MCMA) twin pregnancies. 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. In pregnancies with no major abnormalities, we examined the value of intertwin discordance in fetal CRL in DC, MCDA and MCMA twins in the prediction of fetal loss at < 20 and < 24 weeks' gestation, perinatal death at ≥ 24 weeks, preterm delivery at < 32 and < 37 weeks, birth of at least one small-for-gestational-age (SGA) neonate with birth weight < 5th percentile and intertwin birth-weight discordance of ≥ 20% and ≥ 25%. RESULTS: First, the study population of 6225 twin pregnancies included 4896 (78.7%) DC, 1274 (20.4%) MCDA and 55 (0.9%) MCMA twin pregnancies. Second, median CRL discordance in DC twin pregnancies (3.2%; interquartile range (IQR), 1.4-5.8%) was lower than in MCDA twins (3.6%; IQR, 1.6-6.2%; P = 0.0008), but was not significantly different from that in MCMA twins (2.9%; IQR, 1.2-5.1%; P = 0.269). Third, compared to CRL discordance in DC twin pregnancies with two non-SGA live births at ≥ 37 weeks' gestation, there was significantly larger CRL discordance in both DC and MCDA twin pregnancies complicated by fetal death at < 20 and < 24 weeks' gestation, perinatal death at ≥ 24 weeks, preterm birth at < 32 and < 37 weeks, birth of at least one SGA neonate and birth-weight discordance ≥ 20% and ≥ 25%, and in MCDA twin pregnancies undergoing endoscopic laser surgery. Fourth, the predictive performance of CRL discordance for each adverse pregnancy outcome was poor, with areas under the receiver-operating-characteristics curves ranging from 0.533 to 0.624. However, in both DC and MCDA twin pregnancies with large CRL discordance, there was a high risk of fetal loss. Fifth, in DC twin pregnancies, the overall rate of fetal loss at < 20 weeks' gestation was 1.3% but, in the small subgroup with CRL discordance of ≥ 15%, which constituted 1.9% of the total, the rate increased to 5.3%. Sixth, in MCDA twin pregnancies, the rate of fetal loss or endoscopic laser surgery at < 20 weeks was about 11%, but, in the small subgroups with CRL discordance of ≥ 10%, ≥ 15% and ≥ 20%, which constituted 9%, < 3% and < 1% of the total, the risk was increased to about 32%, 49% and 70%, respectively. Seventh, in MCMA twin pregnancies, there were no significant differences in CRL discordance for any of the adverse outcome measures, but this may be the consequence of the small number of cases in the study population. CONCLUSIONS: In both DC and MCDA twin pregnancies, increased CRL discordance is associated with an increased risk of fetal death at < 20 and < 24 weeks' gestation, perinatal death at ≥ 24 weeks, preterm birth at < 37 and < 32 weeks, birth of at least one SGA neonate and birth-weight discordance ≥ 20% and ≥ 25%, but CRL discordance is a poor screening test for adverse pregnancy outcome. However, in DC twins, CRL discordance of ≥ 15% is associated with an increased risk of fetal loss at < 20 and < 24 weeks' gestation and, in MCDA twins, CRL discordance of ≥ 10%, and more so discordance of ≥ 15% and ≥ 20%, is associated with a very high risk of fetal loss or endoscopic laser surgery at < 20 and < 24 weeks and this information is useful in counseling women and defining the timing for subsequent assessment and possible intervention. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

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.

Diagnosis of fetal defects in twin pregnancies at routine 11-13-week ultrasound examination.

OBJECTIVES: To examine the performance of the routine 11-13-week scan in detecting fetal defects in twin pregnancies and to examine if, in pregnancies with a fetal defect, compared to those with normal fetuses, there is increased incidence of nuchal translucency thickness (NT) ≥ 95th and ≥ 99th percentiles or intertwin discordance in crown-rump length (CRL) ≥ 10% and ≥ 15%. METHODS: This was a retrospective analysis of prospectively collected data in twin pregnancies undergoing routine ultrasound examination for fetal anatomy, according to standardized protocols, at 11-13 weeks' gestation between 2002 and 2019. Pregnancies with known chromosomal abnormality were excluded. The final diagnosis of fetal defect was based on the results of postnatal examination in cases of live birth and on the findings of the last ultrasound examination in cases of pregnancy termination, miscarriage or stillbirth. The performance of the 11-13-week scan in the detection of fetal defects was determined. RESULTS: The study population of 6366 twin pregnancies with two live fetuses at 11-13 weeks' gestation included 4979 (78.2%) dichorionic (DC) and 1387 (21.8%) monochorionic (MC) twin pregnancies. The main findings were: first, the overall incidence of fetal defects was higher in MC than in DC twins (2.8% vs 1.3%); second, the proportion of defects diagnosed in the first trimester was higher in MC than in DC twins (52.6% vs 27.1%); third, the pattern of defects in relation to detectability at the 11-13-week scan (always detectable, sometimes detectable and never detectable) was similar to that reported previously in singleton pregnancies; fourth, always-detectable defects included acrania, alobar holoprosencephaly, encephalocele, pentalogy of Cantrell, exomphalos, body-stalk anomaly, twin reversed arterial perfusion sequence and conjoined twins; fifth, the incidence of fetal NT ≥ 95th percentile was higher in those with than in those without a defect (16.5% vs 4.5% in DC twins and 19.2% vs 5.9% in MC twins) and this was also true for NT ≥ 99th percentile (8.3% vs 1.0% in DC twins and 15.4% vs 2.0% in MC twins); and sixth, the incidence of CRL discordance ≥ 10% was higher in those with than in those without a defect (20.2% vs 7.9% in DC twins and 33.8% vs 9.3% in MC twins) and this was also true for CRL discordance ≥ 15% (10.1% vs 1.9% in DC twins and 28.2% vs 2.8% in MC twins). CONCLUSIONS: First, fetal defects are more common in MC than in DC twin pregnancies. Second, first-trimester detection of fetal defects in DC twin pregnancies is similar to that in singleton pregnancies. Third, first-trimester detectability of defects in MC twins is higher than in DC twins. Fourth, in twin pregnancies with a fetal defect, there is higher intertwin discordance in CRL and incidence of increased NT, but the predictive performance of screening by these markers is poor. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Diagnóstico de defectos del feto en embarazos de gemelos en el examen ecográfico de rutina de las 11-13 semanas OBJETIVOS: Examinar la eficacia del examen rutinario de 11-13 semanas para detectar defectos fetales en embarazos de gemelos y examinar si, en los embarazos con un defecto fetal, en comparación con los de fetos normales, hay una mayor incidencia del grosor de la translucencia nucal (TN) ≥ percentil 95o y ≥ percentil 99o o una discordancia entre gemelos en la longitud céfalo-caudal (LCC) ≥10% y ≥15%. MÉTODOS: Este estudio fue un análisis retrospectivo de datos recogidos prospectivamente de embarazos de gemelos sometidos a exámenes ecográficos de rutina entre 2002 y 2019 para determinar la anatomía del feto, según protocolos estándar a las 11-13 semanas de gestación. Se excluyeron los embarazos con anomalías cromosómicas conocidas. El diagnóstico final de la anomalía fetal se basó en los resultados del examen posnatal en los casos de nacimientos vivos y en los hallazgos del último examen ecográfico en los casos de interrupción del embarazo, aborto o éxitus fetal. Se determinó la eficacia de la exploración de las 11-13 semanas en la detección de anomalías fetales. RESULTADOS: La población de estudio fue de 6366 embarazos de gemelos con dos fetos vivos a las 11-13 semanas de gestación e incluyó 4979 (78,2%) embarazos bicoriales (BC) y 1387 (21,8%) monocoriales (MC). Los principales hallazgos fueron: primero, la prevalencia total de defectos fetales fue mayor en los gemelos MC que en los gemelos BC (2,8% vs. 1,3%); segundo, la proporción de defectos diagnosticados en el primer trimestre fue mayor en los gemelos MC que en los gemelos BC (52,6% vs. 27,1%); tercero, la pauta de defectos en relación con la detectabilidad en la exploración de 11-13 semanas (siempre detectable, a veces detectable y nunca detectable) fue similar a la reportada previamente para los embarazos con feto único; cuarto, entre los defectos siempre detectables estaban la acrania, la holoprosencefalia alobar, el encefalocele, la pentalogía de Cantrell, el onfalocele, la anomalía del pedículo embrionario, la secuencia de perfusión arterial inversa de los gemelos y los gemelos unidos; quinto, la frecuencia del percentil de la TN fetal ≥95o fue mayor en los que tenían un defecto que en los que no lo tenían (16,5% vs 4,5% en los gemelos BC y 19,2% vs 5,9% en los gemelos MC) y esto también fue cierto para el percentil de la TN ≥99o (8,3% vs 1,0% en gemelos BC y 15,4% vs 2,0% en gemelos MC); y sexto, la frecuencia de una discordancia de la LCC ≥10% fue mayor en los que tenían un defecto que en los que no lo tenían (20,2% vs 7,9% en los gemelos BC y 33,8% vs 9,3% en los gemelos MC) y esto también fue cierto para la discordancia de la LCC ≥15% (10,1% vs 1,9% en los gemelos BC y 28,2% vs 2,8% en los gemelos MC). CONCLUSIONES: Primero, los defectos fetales son más comunes en embarazos de gemelos MC que en los de gemelos BC. Segundo, la detección en el primer trimestre de defectos fetales en los embarazos de gemelos BC es similar a la de los embarazos con feto único. Tercero, la detectabilidad en el primer trimestre de los defectos en los gemelos MC es mayor que en los gemelos BC. Cuarto, en los embarazos de gemelos con un defecto fetal, hay mayor discordancia entre los gemelos en la LCC y prevalencia de una mayor TN, pero la eficacia predictiva del cribado mediante estos marcadores es escasa.

Outcome of twin pregnancy with two live fetuses at 11-13 weeks' gestation.

OBJECTIVES: To report and compare pregnancy outcome in dichorionic (DC), monochorionic diamniotic (MCDA) and monochorionic monoamniotic (MCMA) twin pregnancies with two live fetuses at 11-13 weeks' gestation and to examine the impact of endoscopic laser surgery for severe twin-twin transfusion syndrome (TTTS) and/or selective fetal growth restriction (sFGR) on the outcome of MCDA twins. 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. In pregnancies with no major abnormalities, we compared overall survival, fetal loss at < 24 weeks' gestation, perinatal death at ≥ 24 weeks, delivery at < 37 and < 32 weeks, and birth weight < 5th percentile between DC, MCDA and MCMA twins. RESULTS: The study population of 6225 twin pregnancies with two live fetuses at 11-13 weeks' gestation with no major abnormalities included 4896 (78.7%) DC, 1274 (20.5%) MCDA and 55 (0.9%) MCMA twins. In DC twins, the rate of loss at < 24 weeks' gestation in all fetuses was 2.3%; this rate was higher in MCDA twins (7.7%; relative risk (RR), 3.258; 95% CI, 2.706-3.923) and more so in MCMA twins (21.8%; RR, 9.289; 95% CI, 6.377-13.530). In DC twins, the rate of perinatal death at ≥ 24 weeks in all twins that were alive at 24 weeks was 1.0%; this rate was higher in MCDA twins (2.5%; RR, 2.456; 95% CI, 1.779-3.389) and more so in MCMA twins (9.3%; RR, 9.130; 95% CI, 4.584-18.184). In DC twins, the rate of preterm birth at < 37 weeks' gestation in pregnancies with at least one liveborn twin was 48.6%; this rate was higher in MCDA twins (88.5%; RR, 1.824; 95% CI, 1.760-1.890) and more so in MCMA twins (100%; RR, 2.060; 95% CI, 2.000-2.121). In DC twins, the rate of preterm birth at < 32 weeks was 7.4%; this rate was higher in MCDA twins (14.2%; RR, 1.920; 95% CI, 1.616-2.281) and more so in MCMA twins (26.8%; RR, 3.637; 95% CI, 2.172-6.089). In DC twin pregnancies with at least one liveborn twin, the rate of a small-for-gestational-age neonate among all liveborn twins was 31.2% and in MCDA twins this rate was higher (37.8%; RR, 1.209; 95% CI, 1.138-1.284); in MCMA twins, the rate was not significantly different (33.3%; RR, 1.067; 95% CI, 0.783-1.455). Kaplan-Meier analysis showed a significant difference in survival in MCDA and MCMA twins, compared to DC twins, for both the interval of 12 to < 24 weeks' gestation (log-rank test, P < 0.0001 for both) and that of ≥ 24 to 38 weeks (log-rank test, P < 0.0001 for both). Endoscopic laser ablation of intertwin communicating placental vessels was carried out in 127 (10.0%) MCDA twin pregnancies for TTTS and/or sFGR and, in 111 of these, surgery was performed at < 24 weeks; both fetuses survived in 62 (55.9%) cases, one fetus survived in 25 (22.5%) cases and there were no survivors in 24 (21.6%) cases. On the extreme assumption that, had laser surgery not been carried out in these cases, all fetuses would have died, the total fetal loss rate at < 24 weeks' gestation in MCDA twins would have been 13.5%. CONCLUSIONS: The rates of fetal loss at < 24 weeks' gestation, perinatal death at ≥ 24 weeks and preterm birth are higher in MCDA and more so in MCMA twins than in DC twins. In MCDA twins, the rate of fetal loss may have been reduced by endoscopic laser surgery in those that developed early TTTS and/or sFGR. These data would be useful in counseling parents as to the likely outcome of their pregnancy and in defining strategies for surveillance and interventions in the management of the different types of twin pregnancy. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Resultado del embarazo de gemelos con dos fetos vivos a las 11-13 semanas de gestación OBJETIVOS: Informar y comparar el resultado de embarazos de gemelos dicoriales (DC), monocoriales diamnióticos (MCDA) y monocoriales monoamnióticos (MCMA) con dos fetos vivos a las 11-13 semanas de gestación y examinar la repercusión de la cirugía endoscópica con láser para los casos graves del síndrome de transfusión gemelo a gemelo (STGG) y/o la restricción selectiva del crecimiento fetal (RsCF) en el resultado de gemelos MCDA. MÉTODOS: Este estudio fue un análisis retrospectivo de datos recogidos prospectivamente sobre embarazos de gemelos sometidos a un examen ecográfico rutinario a las 11-13 semanas de gestación entre 2002 y 2019. En los embarazos sin anomalías importantes, se comparó la supervivencia general, la pérdida del feto a <24 semanas de gestación, la muerte perinatal a ≥24 semanas, el parto a <37 y <32 semanas, y el peso al nacer <5o percentil entre gemelos DC, MCDA y MCMA. RESULTADOS: La población de estudio fue de 6225 embarazos de gemelos con dos fetos vivos a las 11-13 semanas de gestación sin anomalías importantes y estaba formada por 4896 (78,7%) gemelos DC, 1274 (20,5%) gemelos MCDA y 55 (0,9%) gemelos MCMA. En los gemelos DC, la tasa de pérdida a <24 semanas de gestación, en el total de los fetos fue del 2,3%; esta tasa fue más alta en gemelos MCDA (7,7%; riesgo relativo (RR), 3,258; IC 95%, 2,706-3,923) y mayor aun en gemelos MCMA (21,8%; RR, 9,289; IC 95%, 6,377-13,530). En los gemelos DC, la tasa de muerte perinatal a ≥24 semanas en todos los gemelos que estaban vivos a las 24 semanas fue del 1,0%; esta tasa fue mayor en gemelos MCDA (2,5%; RR, 2,456; IC 95%, 1,779-3,389) y mayor aun en los gemelos MCMA (9,3%; RR, 9,130; IC 95%, 4,584-18,184). En los gemelos DC, la tasa de parto pretérmino a <37 semanas de gestación en embarazos con al menos un gemelo nacido vivo fue del 48,6%; esta tasa fue mayor en gemelos MCDA (88,5%; RR, 1,824; IC 95%, 1,760-1,890) y mayor aun en los gemelos MCMA (100%; RR, 2,060; IC 95%, 2,000-2,121). En los gemelos DC, la tasa de parto pretérmino a <32 semanas de gestación fue del 7,4%; esta tasa fue mayor en gemelos MCDA (14,2%; RR, 1,920; IC 95%, 1,616-2,281) y mayor aun en los gemelos MCMA (26,8%; RR, 3,637; IC 95%, 2,172-6,089). En los embarazos de gemelos DC con al menos un gemelo nacido vivo, la tasa de un recién nacido pequeño para la edad gestacional entre todos los gemelos nacidos vivos fue del 31,2% y en los gemelos MCDA esta tasa fue mayor (37,8%; RR, 1,209; IC 95%, 1,138-1,284); en los gemelos MCMA, la tasa no fue significativamente diferente (33,3%; RR, 1,067; IC 95%, 0,783-1,455). El análisis de Kaplan-Meier mostró una diferencia significativa en la supervivencia de los gemelos MCDA y MCMA, en comparación con los gemelos DC, tanto para el intervalo de 12 a <24 semanas de gestación (prueba logarítmico-ordinal, P<0,0001 para ambos) como para el de ≥24 a 38 semanas (prueba logarítmico-ordinal, P<0,0001 para ambos). La ablación endoscópica con láser de los vasos placentarios comunicantes entre gemelos se llevó a cabo en 127 (10,0%) embarazos de gemelos MCDA para STGG y/o RsCF y, en 111 de ellos, la cirugía se realizó a <24 semanas; en 62 (55,.9%) casos sobrevivieron ambos fetos, en 25 (22,5%) casos sobrevivió uno de los fetos y en 24 (21,6%) casos no hubo sobrevivientes. En la suposición extrema de que, si no se hubiera utilizado la cirugía láser en estos casos, todos los fetos habrían muerto, la tasa de pérdida fetal total a <24 semanas de gestación in gemelos MCDA hubiera sido del 13,5%. CONCLUSIONES: Las tasas de pérdida fetal a <24 semanas de gestación, de muerte perinatal a ≥24 semanas y de parto pretérmino son mayores en gemelos MCDA y más aun en gemelos MCMA que en gemelos DC. En los gemelos MCDA, la tasa de pérdida fetal podría haberse reducido mediante la cirugía endoscópica láser en aquellos que desarrollaron STGG y/o RsCF de forma temprana. Estos datos podrían ser útiles para asesorar a los padres en cuanto al resultado probable de su embarazo y para definir las estrategias de vigilancia e intervenciones en el tratamiento de los diferentes tipos de embarazo de gemelos.