Evaluación del índice de riesgo del primer trimestre en casos de embarazo múltiple con presencia de un feto perdido / Evaluation of the risk index of the first-trimester combined screening test in cases of multiple pregnancy with a «vanishing twin»

Fundamento y objetivo. Justificar una evaluación correcta del test combinado de cribado prenatal del primer trimestre, en casos especiales de embarazos gemelares con pérdida de uno de los embriones, debido al aumento de estos casos, sobre todo en gestantes sometidas a técnicas de reproducción in vitro. Paciente y métodos. Se documenta un caso clínico de gestación gemelar bicorial biamniótica con pérdida del primer feto en la semana 12. Se le solicita cribado prenatal en el que la estimación del índice de riesgo del primer trimestre no se pudo valorar como tal. Discusión y conclusiones. El índice de riesgo no es calculable debido a la pérdida de uno de los fetos. Los niveles de la fracción libre de la subunidad beta de la gonadotropina coriónica humana (Beta-hCG) en suero no se ven afectados pero sí se produce un aumento significativo de los niveles de la proteína plasmática A asociada al embarazo (PAPP-A), que depende del tiempo transcurrido desde la pérdida fetal, por lo que no puede considerarse ni como un feto aislado ni como 2. Por tanto, para evaluar el riesgo se recomienda una estimación de la translucencia nucal fetal (TN) y la Beta-hCG libre, o únicamente la TN, atendiendo también a unos múltiplos de la mediana (MoM) dentro de la normalidad(AU)

Background and purpose. To justify an accurate assessment of the first-trimester combined screening test, in special cases of twin pregnancies with a vanishing twin; because the increase in such cases specially is being seen in pregnant women undergoing in vitro fertilization techniques. Patients and methods. We report a case of biamniotic bichorionic twin pregnancy with loss of the first fetus at week 12. Prenatal screening was asked in wich it couldn’t been estimated the risk index for the first trimester screening test. Discussion and conclusions. The risk index is not calculable due to the loss of one fetus. The levels of the free fraction of the beta subunit of human chorionic gonadotropin (Beta-hCG) in serum are not affected but there is a significant increase in the levels of pregnancy associated plasma protein-A (PAPP-A), which depends on the time since fetal loss; so the serum levels cannot be regarded neither as an isolated fetus or as 2. Therefore to assess the risk of the first-trimester combined screening test, it is recommended to estimate the fetal nuchal translucency thickness (NT) and Beta-hCG, or just only NT, also considering the median multiples (MoM) within the normal limits(AU)

Urinary hCG patterns during the week following implantation.

BACKGROUND: Human chorionic gonadotrophin (hCG) is used to monitor pregnancy status. Yet the pattern of hCG excretion in the first week following implantation has not been adequately described. Therefore the aim of this study was to describe the average profile of hCG and its variability during the 7 days following estimated implantation in a population of naturally conceived pregnancies. METHODS: We measured daily hCG concentrations in first-morning urine for 142 clinical pregnancies from women with no known fertility problems. Mixed-effects regression models were used to estimate the hCG trajectory and its variability in relation to pregnancy outcomes. RESULTS: hCG rose 3-fold between the day of detection and the next day (95% CI = 2.7-3.4). The relative rate of rise decreased thereafter, reaching 1.6-fold (95% CI = 1.5-1.8) between days 6 and 7. HCG levels followed a log-quadratic trajectory, and the patterns of rise were unrelated to number of fetuses, risk of spontaneous abortion or sex of the baby. Later implantations (after 10 luteal days) produced slower rates of increase. CONCLUSIONS: Although mean hCG follows a log-quadratic trajectory during the first week of detectability, there is high variability across pregnancies. Later implantation may reflect characteristics of the uterus or conceptus that slow hCG production.

Prostanoid excretion in incipient singleton and twin pregnancies.

OBJECTIVE: Our purpose was to examine the urinary excretion of metabolites of prostacyclin, 6-keto-prostaglandin F(1 alpha) and 2,3-dinor-6-keto-prostaglandin F(1 alpha), and thromboxane A2, thromboxane B2 and 2,3-dinor-thromboxane B2, in early twin and singleton pregnancies resulting from in vitro fertilization-embryo transfer. STUDY DESIGN: Overnight urine samples were obtained from 23 women at regular intervals for 20 weeks after embryo transfer. Prostanoids were measured by high-pressure liquid chromatography-radioimmunoassay. RESULTS: All prostanoids, most markedly 6-keto-prostaglandin F(1 alpha) and 2,3-dinor-6-keto-prostaglandin F(1 alpha), increased in both singleton and twin pregnancies. This resulted in an increased ratio of prostacyclin over thromboxane A2 both in the dinor compounds (from 1.3 to 2.8) and the total metabolites (from 1.7 to 3.5). No marked differences were observed between twin and singleton pregnancies. CONCLUSIONS: Twin and singleton pregnancies show a similar increase in the prostacyclin to thromboxane A2 ratio in the first half of pregnancy.