The risks confronting twins: a national perspective

Multifetal pregnancy reduction: a review of the world results for the period 1993-1996

The objective of this work was to evaluate the outcome of multifetal pregnancy reduction and to provide an analysis of the ethical dilemmas associated with its application. The study design was based on data on over 1400 completed pregnancies that underwent multifetal pregnancy reduction as reported in the world literature during 1993-1996. The results were: A total of 1453 completed cases of multifetal pregnancy reduction are presented. The total survival rate was estimated to be 87.7%, resulting in a total pregnancy loss rate of 12.3%. The lowest survival rate is found to be in higher-order pregnancies of five or more fetuses (75.2%), whereas pregnancy loss rate seems to be similar for quadruplets, triplets and twins that underwent reduction (11.3%, 8.3% and 13.6%, respectively). A 33.3% of the total pregnancy loss rate occurred within four weeks from the procedure, whereas 66.7% occurred after the four weeks but at 24 weeks of gestation or earlier. The mean gestational age at delivery was estimated to be 33 weeks for pregnancies reduced to triplets, 35.8 weeks for those reduced to twins and 36.9 weeks for singletons, with 5% delivering at less than 28 weeks and 9.6% at 29-32 weeks. We conclude that multifetal pregnancy reduction has been established as an efficient and safe way to improve outcome of multifetal gestations, especially those with four or more fetuses and likely of triplets. As the experience from the procedure increases, it seems that reduction of triplets to twins can be offered to patients with satisfactory results. The reduction to singletons has not yet been established and is being performed only when medical indications exist. Prenatal genetic diagnosis should become an integral part of counselling on multiple pregnancy. Physicians should take whenever possible measures designed to prevent high multiple birth pregnancies. We also note that although multifetal pregnancy reduction improves significantly the outcome of multiple pregnancies, several ethical dilemmas arising from its application are still under dispute.

Do twins mature earlier than singletons? Results from a matched cohort study

OBJECTIVE

Our purpose was to determine whether, as a consequence of advanced maturity, preterm twin infants have a more favorable neonatal outcome than matched singleton infants.

STUDY DESIGN

A matched cohort study design was used. Two hundred twenty-four twin infants (112 sets) were matched for gestational age, race, gender, and mode of delivery with singleton infants who were delivered because of refractory preterm labor. Pregnancies with maternal medical disease including preeclampsia, premature rupture of membranes, twin-twin transfusion syndrome, and known fetal anomalies were excluded. Information was obtained by review of maternal and neonatal charts.

RESULTS

There was no difference in the incidence of neonatal death (5% vs 7%, p = 0.66), respiratory distress syndrome (38% vs 35%, p = 0.54), grades 3 and 4 intraventricular hemorrhage (5% vs 4%, p = 0.63), grades 2 and 3 necrotizing enterocolitis (4% vs 6%, p = 0.52), and 5-minute Apgar score < or = 6 (21% vs 21%, p = 1.00). Twins had a higher incidence of admission to the Special Care Unit (88% vs 72%, p < 0.001). Results were similar when analysis was limited to presenting twins, nonpresenting twins, and twins concordant with controls for antenatal glucocorticoid exposure.

CONCLUSION

Twin infants do not have accelerated maturation and improved neonatal outcome compared with matched singleton infants born at the same gestational age because of preterm labor.

Further defining the risks confronting twins

OBJECTIVE

We report the absolute and relative risks for neonatal and infant death, low and very low birth weight, and delivery at < 33 and < 35 weeks' gestation in twin pregnancy stratified by maternal race and age, as well as gender pair combinations of the twins.

STUDY DESIGN

Data on 324,141 twin infants were obtained from the 1985 to 1988 U.S. Linked Birth/ Infant, Death Data Sets. In this observational cohort study, we analyzed the outcomes of 138,779 twin pregnancies of white and black women that ended with the delivery of two live-born infants.

RESULTS

Rates for the aforementioned outcomes are increased for black infants, for male-male pairs compared with male-female pairs (with female-female pairs being intermediate), and for young mothers. For male-male twins born to young (< or = 22 years old) black women, relative risks range from 2.1 for both pair members being low birth weight (< 2500 gm) to 5.0 for both pair members dying in infancy, when male-female pairs born to older (> or = 28 years) white women served as the reference group.

CONCLUSIONS

Although all twin pregnancies are at higher risk than singletons, risk is influenced by maternal race and age, as well as gender pair combination. These analyses provide useful information for counseling women pregnant with twins. Furthermore, they suggest that failure to consider variations in baseline risk may have seriously flawed studies evaluating prophylactic interventions in twin pregnancy.

Sonographic determination of first trimester twin chorionicity and amnionicity

OBJECTIVE

To determine the reliability of first trimester sonography in the detection of twin chorionicity and amnionicity.

MATERIALS AND METHODS

Sets of twins (179) were evaluated sonographically in the first trimester. Chorionicity was determined by identifying the number of gestational sacs. The presence or absence of an amnion about each embryo/fetus was also recorded. The placentas for each case were evaluated to determine chorionicity and amnionicity.

RESULTS

Of the 179 twin pairs, 158 were dichorionic/diamniotic; 19 were monochorionic/diamniotic, and two pairs were monochorionic/monoamniotic. Chorionicity and amnionicity were correctly determined in each case.

CONCLUSION

The chorionicity of twin pregnancies can be determined from the time that the gestational sacs are visualized within the uterus. Transvaginal sonography can reliably determine the amnionicity of monochorionic twin pregnancies after 7 weeks, menstrual age.

Prognostic significance of prior preterm twin delivery on subsequent singleton pregnancy

OBJECTIVE

Our purpose was to determine whether preterm birth of twins is associated with an increased risk of preterm birth in a subsequent singleton pregnancy.

STUDY DESIGN

The Medical University of South Carolina perinatal database was accessed to identify a cohort of patients who were delivered of twins followed by a singleton gestation (1981 to 1993). Maternal transports were excluded to minimize referral bias. Preterm birth was defined as < 37 weeks' gestation. Relative risks with 95% confidence intervals were calculated.

RESULTS

One hundred forty-four patients were identified who were delivered of twins followed by a singleton gestation. Preterm delivery occurred in 86 (59.7%) of the twins and 21 (14.6%) of the subsequent singletons. Preterm birth of twins was associated with a significantly increased risk of preterm delivery in a subsequent singleton pregnancy (relative risk 2.87, 95% confidence interval 1.02 to 8.09). In the subset of women who were delivered of twins at < 30 weeks' gestation, 42% of the subsequent singletons were delivered preterm (relative risk 6.11, 95% confidence interval 2.07 to 18.02). The relative risk of preterm birth of a singleton after delivery of twins between 30 and 34 weeks' gestation was 3.63 (95% confidence interval 1.02 to 12.92). However, if the preceding twins delivered between 34 and 37 weeks' gestation, the relative risk of preterm birth of the subsequent singleton was not significantly increased (relative risk 1.42, 95% confidence interval 0.40 to 5.01).

CONCLUSIONS

Preterm birth of twins before 34 weeks' gestation is associated with a significant risk for preterm delivery in a subsequent singleton pregnancy. The magnitude of risk increases with decreasing gestational age of the preceding twin delivery.

Antepartum management of the multiple gestation: the case for specialized care

Multiple gestations are increasingly more common and represent one of the highest risk conditions faced in pregnancy. The population-attributable fetal and newborn risks of twin and triplet gestations are compelling. This article is dedicated to a discussion of the antepartum management of multiple gestations and a conclusion that specialized care can improve both perinatal morbidity and mortality in these pregnancies. Prenatal care for multiple gestations should be provided by an experienced and dedicated staff that can anticipate and manage the various and complex problems presented by the multifetal gestation. Specialized care for multiple gestations should include components such as consistent evaluation of maternal symptoms and cervical status by a single care-provider, intensive preterm birth prevention education, individualized modification of maternal activity, increased attention to nutrition, ultrasonography, tracking of clinic nonattenders, and a supportive clinical environment. This sort of specialization and individualization of antepartum care for multiple gestations provides the best opportunity to maximize intrauterine fetal growth, identify congenital anomalies, prevent extremely preterm or very low birth weight deliveries, and identify fetal or maternal complications that may necessitate more intensive fetal surveillance or even delivery to reduce adverse perinatal outcome.

Evaluation of twin growth status at birth using individualized growth assessment: comparison with conventional methods

OBJECTIVE

We sought to evaluate the growth status of twins at birth using individualized growth assessment methods and to compare this assessment with that obtained with conventional methods.

STUDY DESIGN

Twenty twin pregnancies were studied longitudinally with ultrasound. Measurements of the head and abdominal cubes (A,B), head circumference (HC), abdominal circumference (AC), thigh circumference (ThC), and femur diaphysis length (FDL) made in the 2nd trimester were used to specify Rossavik growth models for each parameter in each fetus. These models were used to predict weight (WT), HC, AC, ThC, and crown-head length (CHL) at birth. Actual birth measurements made within 24 hours of delivery were compared to predicted values, the latter corrected using singleton [corrects for both technical problems (TP)] or twin [corrects for both technical problems (TP) and decreased soft-tissue deposition (DSTD)] correction factors where appropriate. Two sets of growth potential realization index (GPRI) values and their corresponding neonatal growth assessment scores (NGAS) were calculated and compared to previously established normal values. Birth measurements were compared with appropriate population age-specific size curves. These data were used to characterize and classify the growth status of each twin neonate.

RESULTS

Individualized growth assessment identified five primary types of growth outcomes: normal (Group I, 45%); primarily DSTD (Group II, 22.5%); IUGR (Group III, 15%); above average soft-tissue deposition (Group IV, 5%); and growth acceleration (Group V, 7.5%). Within Group I was a subgroup with evidence of DSTD (Group Ib, 33.3% of Group I). Group II could be divided into two subgroups, one with only DSTD (Group IIa, 44.4% of Group II) and one with both DSTD and other growth abnormalities (Group IIb, 55.6% of Group II). Group III had multiple growth abnormalities which were more severe than those seen in Group II. All normal neonates were AGA and had virtually all anatomic parameters within their respective normal ranges. Of the neonates with definite evidence of IUGR (Groups IIb and III), only 4 of 11 (36.4%) were SGA and only 6 of 11 (54.5%) had any of the five anatomic parameters below their respective normal ranges. Only 1 of 3 (33.3%) of neonates with growth acceleration was LGA and none (0%) of the five anatomic parameters were above their respective normal ranges.

CONCLUSIONS

Individualized growth assessment methods provide a more comprehensive assessment of growth outcome in twins and detect a decrease in soft-tissue deposition not identifiable with conventional growth assessment procedures. The latter procedures are also less sensitive in the detection of both IUGR and growth acceleration.