Twin birth weight discordance and risk of preterm birth

Long-term adverse neurodevelopmental outcomes of discordant twins delivered at term: A nationwide population-based study

OBJECTIVE

To evaluate long-term adverse neurodevelopmental outcomes of discordant twins delivered at term.

DESIGN

Retrospective cohort study.

SETTING

Nationwide (Republic of Korea).

POPULATION

All twin children delivered at term between 2007 and 2010.

METHODS

The study population was divided into two groups according to inter-twin birthweight discordancy: the 'concordant twin group', twin pairs with inter-twin birthweight discordancy less than 20%; and the 'discordant twin group', twin pairs with inter-twin birthweight discordancy of 20% or more. The risk of long-term adverse neurodevelopmental outcomes was compared between the concordant twin group and the discordant twin group. Long-term adverse neurodevelopmental outcomes between smaller and larger twin children within twin pairs were further analysed. The composite adverse neurodevelopmental outcome was defined as the presence of at least one of the following: motor developmental delay, cognitive developmental delay, autism spectrum disorders/attention deficit hyperactivity disorders, tics/stereotypical behaviour or epileptic/febrile seizure.

MAIN OUTCOME MEASURES

Long-term adverse neurodevelopmental outcome.

RESULTS

Of 22 468 twin children (11 234 pairs) included, 3412 (15.19%) twin children were discordant. The risk of composite adverse neurodevelopmental outcome was higher in the discordant twin group than in the concordant twin group (adjusted hazard ratio [HR] 1.13, 95% CI 1.03-1.24). The long-term adverse neurodevelopmental outcomes were not significantly different between smaller and larger twin children in discordant twin pairs (adjusted HR 1.01, 95% CI 0.81-1.28).

CONCLUSION

In twin pairs delivered at term, an inter-twin birthweight discordancy of 20% or greater was associated with long-term adverse neurodevelopmental outcomes; and long-term adverse neurodevelopmental outcomes were not significantly different in smaller or larger twin children in discordant twin pairs.

Birth weight discordance in very low birth weight twins: mortality, morbidity, and neurodevelopment

OBJECTIVE

Examine outcomes among birth weight concordant and discordant 401-1500 g twins.

STUDY DESIGN

Twins (n = 8,114) at NICHD Neonatal Research Network (1994-2011) were studied. Discordance (birth weight difference/larger twin birth weight x 100%) was categorized into: ≤ 14, > 14-20, > 20-30, and > 30%. Separate logistic regression models for the smaller and larger infants assessed the adjusted association between discordance and outcomes.

RESULTS

Compared with the smaller twin with ≤ 14% discordance, mortality, necrotizing enterocolitis, severe retinopathy of prematurity, bronchopulmonary dysplasia, and neurodevelopmental impairment or death were highest among the smaller twins with discordance > 30%. The larger twins with discordance > 30% had higher odds of patent ductus arteriosus, moderate-to-severe cerebral palsy, blindness, cognitive and motor scores < 70. Odds of cerebral palsy and blindness were also higher among the larger twins with discordance > 14-20%.

CONCLUSIONS

Discordance > 30% was associated with higher mortality in the smaller twin and higher morbidities among the smaller and larger twins.

Association Between Twin Discordance at 6–9 Weeks' of Gestation and Birthweight Complications

Twins achieved through in-vitro fertilisation often undergo a viability ultrasound at 6–9 weeks of gestation. The presence of inter-twin crown-rump length discordance at this stage is not an uncommon finding; however the clinical significance of this is unknown. We analyzed 218 dichorionic twin pregnancies, producing two live fetuses > 24 weeks gestation, to determine whether inter-twin discordance (≥ 85th centile) in the mid-first trimester was associated with birthweight discordance (> 20%), or small for gestational age (< 10th centile). The incidence of birthweight discordance and small for gestational age infants were determined, with no increased risk found for the discordant population. This may provide some reassurance to treating clinicians.

The association between intratwin birthweight discordance and preterm birth in twin pregnancy

BACKGROUND

Previous studies found that increased birthweight discordance among twins was associated with increased risk of perinatal mortality and morbidity, but there is disagreement regarding the relationship between birthweight discordance and the risk of preterm birth.

AIMS

To examine the relationship between intratwin birthweight discordance and preterm birth, and the influence of total birthweight as a confounding factor.

METHODS

We conducted a historical cohort study to assess the relationship between intratwin birthweight discordance and preterm birth, using the 1995-1997 twin registry data of the USA. Parallel analyses with and without adjustment for total birthweight were performed.

RESULTS

A total of 147,262 eligible twin sets were included in the analysis. In the non-stratified analysis, preterm birth (< 37 weeks) rates were 64.3 and 51.8%, respectively, in subjects with a birthweight discordance > 25% and in those < or = 25%. In the analysis stratified by total birthweight, the rates of preterm birth were higher in subjects with a birthweight discordance > 25% than in those < or = 25% at every total birthweight stratum. Changing the thresholds to define preterm birth or treating gestational age as a continuously distributed variable yielded similar results. Using other methods to adjust for total birthweight also reversed the direction of this relationship.

CONCLUSIONS

Increased intratwin birthweight discordance is associated with increased risk of preterm birth, and adjustment for total birthweight biases the relationship to the wrong direction. Clinicians should be aware of the possibility of a preterm birth when there are signs of discordance in birthweight between the two twins.

A new method for measuring misclassification of maternal sets in maternally linked birth records: true and false linkage proportions

OBJECTIVES

Numerous studies have used maternally linked birth records to investigate perinatal outcomes, maternal behaviors, and the quality of vital records birth data. Little attention has been given to assessing errors in the linkages and to understanding how such errors affect estimates derived from the linked data. The author developed a framework for conceptualizing maternal linkage error and measures for quantifying it, and examined the behavior of the new measures in a maternally linked file.

METHODS

Linkage errors were conceptualized as misclassification, with the classes being the maternal sets (records classified as representing different births to the same woman). The true linkage proportion, analogous to sensitivity, was used to capture the degree to which all of a woman's births were assigned to a single maternal set; the false linkage proportion, analogous to specificity, was used to capture the degree to which the assigned maternal sets combined births from different women. The behavior of the two proportions was examined by introducing increasing degrees of linkage error into a maternally linked file.

RESULTS

Both measures indicated greater misclassification with increasing simulated linkage errors.

CONCLUSIONS

The new measures may be a useful tool for assessing the quality of maternally linked data, as well as other types of linked records where the linkages are within a single file. This is a necessary step towards developing methods for addressing misclassification bias in studies of maternally linked records through sensitivity analysis, adjustment, and other means.

Birth weight discordance in spontaneous versus induced twins: impact on perinatal outcome

PURPOSE

To compare the rate of birth weight discordance and perinatal outcome of twin pregnancies after assisted reproduction with that of spontaneous twins.

METHOD

A total of 12,920 deliveries were analyzed retrospectively. Seventy-five twin pregnancies after ART were compared to the 94 spontaneous counterparts. Birth weight discordance was defined as a difference of 20% or more.

RESULTS

Discordance rate was elevated (25.3% vs. 17.0%) among ART twins. SGA was increased and NICU admission was more frequent in discordant group. Unlike-sexed twins were more prevalent (73.7% vs. 37.5%) among discordants after ART.

CONCLUSIONS

ART can increase discordance rate which can elevate perinatal risk.

Decreased phagocytic capacity of cord blood monocytes in second- and third-born multiplets

OBJECTIVE

To assess the risk to second- and third-borns of developing perinatal infections based on a diminished first-line immune response in comparison to the first-born.

STUDY DESIGN

11 sets of twins and 2 sets of triplets (27-39 weeks of gestation, 740-3,560 g birth weight) admitted consecutively to our neonatal care unit were investigated. All were delivered by cesarean section. Phagocytosis and the expression of TNF-alpha and IL-1 in cord blood were determined immediately and 72 h after birth from peripheral blood monocytes by FACS analysis and ELISA.

RESULTS

In all second- and third-borns, phagocytosis of cord blood monocytes was significantly decreased in comparison to the first-borns (p < 0.001, p < 0.015). 72 h after birth phagocytosis determined from peripheral blood showed no significant difference between the first-borns and the second- and third-borns. Cytokine expression revealed no significant differences dependent on birth order.

CONCLUSION

We suggest that the observed temporarily diminished first-line immune response of second- and third-born multiplets might be the result of a short-term reduced cellular oxygenation during delivery, but has no influence on further immunological deficiency leading to a higher risk of perinatal infections.