Further defining the risks confronting twins

Early-life mortality risks in opposite-sex and same-sex twins: a Danish cohort study of the twin testosterone transfer hypothesis

PURPOSE

To investigate the twin testosterone transfer (TTT) hypothesis by comparing early-life mortality risks of opposite-sex (OS) and same-sex (SS) twins during the first 15 years of life.

METHODS

We performed a population-based cohort study to compare mortality in OS and SS twins. We included 68,629 live-born Danish twins from 1973 to 2009 identified through the Danish Twin Registry and performed piecewise stratified Cox regression and log-binomial regression.

RESULTS

Among 1933 deaths, we found significantly higher mortality for twin boys than for twin girls. For both sexes, OS twins had lower mortality than SS twins; the difference persisted for the first year of life for boys and for the first week of life for girls.

CONCLUSIONS

Although the mortality risk for OS boys was in the expected direction according to the TTT hypothesis, the results for OS girls pointed in the opposite direction, providing no clear evidence for the TTT hypothesis.

Gestational Duration, and Fetal and Infant Mortality for Twins vs Singletons

The aim of this research was to study fetal and infant mortality in Sweden between 1973 and 1996 in twins vs singletons in relation to gestational duration. Analysis was of fetal and infant mortality based on the number of pregnancies at risk as the denominator rather than the number of deliveries each week. The analysis was based on information stored at the Medical Birth Registry (MBR), the National Board of Health and Welfare, Stockholm. The MBR keeps records on virtually all pregnancies (> 99%) regarding delivery and neonatal information, and for infant mortality up to 1 year of age. During the study period, 2,206,738 singleton and 52,658 twin births were registered. Risk evaluation was made as odds ratio (OR) with a 95% confidence interval. The material was stratified according to parity, maternal age, year of delivery, and delivery unit. Results showed the OR for twin births before 34 weeks gestation was 6 to 8-fold increased compared with singletons. The OR for fetal mortality was increased in all gestational weeks, and like-sexed twins had a consistently poorer prognosis compared to unlike-sexed. Between 1989–96, unlike-sexed twins had a fetal mortality approaching that of singletons. In conclusion, real progress in reduction of infant mortality in twins may be impossible until the high incidence of preterm births can be decreased. Hypothetically, about 100 twin labors would have to be induced to avoid one fetal death in like-sexed twin pregnancies.

Should all Twins be Delivered by Caesarean Section? A Preliminary Report

The aim was to analyse the neonatal mortality related to mode of delivery for twins using a population-based registry. In all, 18,125 twins delivered in Sweden between 1991 and 1997, after excluding those with unknown gestational duration, were used to analyse the differences between groups of twins. Results showed the OR for neonatal death, breech vaginal delivery versus caesarean section (all indications) was 1.47 (95% CI 0.99-2.17). The OR at vaginal delivery for neonatal death, twin I in breech versus cephalic presentation was 5.60 (2.62-11.94) and for twin II the corresponding figures were 1.85 (1.03-3.32). Analyses using population-based registries from other countries are needed to confirm or reject the present findings of an increased neonatal mortality for twins in breech presentation delivered vaginally.

The contribution of maternal race/ethnicity and fetal sex to prematurity in twins

OBJECTIVE

The contribution of male fetal sex to twin preterm birth (PTB) rates was evaluated in the United States.

STUDY DESIGN

The 2002 National Center for Health Statistics Natality database was analyzed for fetal sex and twin gestations based on birth sex for MM and FF pairs (M, male; F, female). Multivariable Cox proportional hazards regression was applied to estimate the hazard ratio for PTB with adjustments for known risks.

RESULTS

Thirty-three thousand nine hundred twenty-six pairs were analyzed. PTBs between 20-36 completed weeks occurred in 59.1% MM pairs and 57.5% FF pairs. MM sex was an independent risk factor for PTB. This effect was greatest for deliveries between 20-29 weeks (hazard ratio, 1.224; 95% CI, 1.113-1.346). The effect was most pronounced in non-Hispanic white MM pairs.

CONCLUSION

In the United States, MM pairs are at greater risk for PTB. Race and ethnicity modulate sex effects. Further studies are needed to understand potential mechanisms.

Genetic and environmental contributions to common psychopathologies of childhood and adolescence: a study of twins and their siblings

We report findings based on analyses of self-reports of six common adolescent psychopathologies (attention deficit/hyperactivity disorder, ADHD; conduct disorder, CD; oppositional defiant disorder, ODD; generalized anxiety disorder, GAD; separation anxiety disorder, SAD; and major depressive disorder, MDD) in a sample of 1,162 male and female adolescent (12-19 years) twin pairs and 426 siblings. Prevalence statistics for past year and lifetime reports confirm differences between genders for CD, GAD, SAD, and MDD, and a lack of differences between twins and their non-twin siblings. Biometrical modeling was conducted to ascertain the relative influences of genes, and shared and non-shared environments contributing to these disorders. A more robust estimate of these parameters was obtained by including non-twin siblings. Age-specific thresholds were integrated into the analyses to appropriately model the developmental patterns of behavior. We found evidence for both genetic and non-shared environmental influences for all disorders. Shared environmental influences also seem to be important for MDD and lifetime GAD.

Neonatal mortality and morbidity in vertex-vertex second twins according to mode of delivery and birth weight

OBJECTIVE

To assess the risk of neonatal mortality and morbidity in vertex-vertex second twins according to mode of delivery and birth weight.

STUDY DESIGN

Data from a historical cohort study based on a twin registry in the US (1995-1997) were used. Multivariate logistic regression was used to control for maternal age, race, marital status, cigarette smoking during pregnancy, parity, medical complications, gestational age, and other confounders.

RESULTS

A total of 86 041 vertex-vertex second twins were classified into two groups: second twins delivered by cesarean section after cesarean delivery of first twin (C-C) (43.0%), second twins whose co-twins delivered vaginally (V-X) (57.0%). In infants of birth weight>or=2500 g group, the risks of noncongenital anomaly-related death (adjusted odds ratio (aOR): 4.64, 95% confidence interval (95% CI): 1.90, 13.92), low Apgar score (aOR: 2.39, 95% CI: 1.43, 4.14), and ventilation use (aOR: 1.31, 95% CI: 1.18, 1.47) were higher in the V-X group compared with the C-C group. No asphyxia-related neonatal deaths occurred in C-C group, whereas the incidence of this death was 0.04% in the V-X group.

CONCLUSION

The risks of neonatal mortality and morbidity are increased in vertex-vertex second twins with birth weight>or=2500 g whose co-twins delivered vaginally compared with second twins delivered by cesarean section after cesarean delivery of first twin.

Breech presenting twin A: is vaginal delivery safe?

The aim of our study was to compare the neonatal outcome of vaginally delivered breech-presenting twins (VD) to those delivered by cesarean (CS). Maternal and neonatal charts of all live, non-anomalous twins delivered at > or =25 weeks of gestation, in a single tertiary care center, over an 11-year period were reviewed. Of 517 twins delivered, 130 breech-presenting twins were analyzed. Thirty-five (26.9%) were delivered vaginally and 95 (73.1%) by cesarean. More patients presented in labor with advanced cervical dilation in the VD compared to the CS group. There was no difference in the incidence of respiratory distress syndrome, intraventricular hemorrhage, need for mechanical ventilation, length of nursery stay or neonatal mortality rate when twin A was compared in the two groups. However, one breech-presenting twin in the VD group had a traumatic delivery at 32 weeks of gestation that caused a spine fracture followed by immediate neonatal death. Although there seems to be no compromise in the immediate neonatal outcome of breech-presenting twins delivered vaginally compared to those delivered by cesarean, the case of head entrapment that led to intrapartum death is quite alarming. Based on our study, we cannot advocate normal vaginal delivery when twin A is non-vertex: cesarean seems to be a safer route of delivery.

Relationship of Maternal Body Mass Index and Height to Twinning

OBJECTIVE

Increasing use of fertility drugs is considered the primary cause for the recent increase in dizygotic twinning in developed countries. However, dizygotic twinning has also been related to obesity in foreign populations. We sought to confirm this relationship in U.S. pregnancies, which predated widespread use of fertility drugs.

METHODS

We analyzed 51,783 pregnancies (561 twin) in the Collaborative Perinatal Project, which took place at 12 hospitals in the United States from 1959 to 1966. The occurrence of twinning was compared according to maternal self-reported prepregnant body mass index (BMI) of less than 20, 20-24.99, 25-29.99, and 30 kg/m(2) or greater, before and after adjustment for confounding factors.

RESULTS

There was a statistically significant trend for increased risk of total twinning with increasing BMI (P < .001). The odds of monozygous twinning were not significantly related to BMI, but the odds of dizygous twinning were significantly related to increased BMI. After adjusting for maternal race, age, parity, and height, the odds of dizygous twinning were still significantly elevated among women with a BMI of 30 or more, and the trend for increasing risk of dizygous twinning with increasing BMI was significant (P = .001). The trend for increased twinning with increasing height was also significant. Women in the tallest quartile of height had a significantly increased odds ratio for dizygous twin pregnancies, although not of the same magnitude as women with BMI over 30.

CONCLUSION

We confirmed the association of maternal weight and height with dizygotic twinning in a U.S. population among which fertility drugs were not a factor.

Nucleated red blood cells in concordant, appropriate-for-gestational age twins

OBJECTIVES

The purpose of this study was to test the hypothesis that neonatal nucleated red blood cell (RBC) counts are elevated in nondiscordant twins compared with singletons.

STUDY DESIGN

We compared absolute nucleated RBC counts taken after birth in 2 groups of term, appropriate-for-gestational age infants; 74 concordant twins, and 29 singleton control infants. We excluded infants with factors associated with a potential increase in absolute nucleated RBC counts.

RESULTS

Birth weight and gestational age were significantly lower in twins than in singletons (P < .01). Hematocrit, absolute nucleated RBC count, and corrected lymphocyte counts were significantly higher in twins (P < .01). In multiple regression, the significantly higher absolute nucleated RBC count in twins remained significantly higher even after taking into account gestational age and Apgar scores.

CONCLUSION

Concordant, appropriate-for-gestational age twins have increased nucleated RBCs at birth compared with singleton control infants.

Risk factors for low birth weight: a review

Low birth weight (LBW) is one of the main predictors of infant mortality. The global incidence of LBW is around 17%, although estimates vary from 19% in the developing countries (countries where it is an important public health problem) to 5-7% in the developed countries. The incidence in Spain in the decade 1980-1989 was about 5.7%. LBW is generally associated with situations in which uterine malnutrition is produced due to alterations in placental circulation. There are many known risk factors, the most important of which are socio-economic factors, medical risks before or during gestation and maternal lifestyles. However, although interventions exist to prevent many of these factors before and during pregnancy, the incidence of LBW has not decreased.

Preterm male infants need more initial respiratory and circulatory support than female infants

AIM

The aim of this study was to investigate possible gender-related differences in clinical parameters during the first week of life that could explain the higher morbidity and mortality of preterm male infants.

METHODS

In total, 130 clinical variables were collected from 236 inborn infants (130 male and 106 female infants) with gestational age (GA) < 29 wk. A subgroup of 175 extremely low birthweight infants (ELBW) < 1000 g (n = 86 males; n = 89 females) was analysed separately.

RESULTS

At 6 postnatal h, 60.8% of the male infants needed mechanical ventilation versus 46.2% of the females (p = 0.026). Chronic lung disease (CLD) developed in 36.2% of males versus 9.8% of female infants (p = 0.004). Inotrope support with dopamine was used in more than 50% of the infants; additional inotrope support to dopamine was needed by 19.4% of male and 9.7% of female infants (p = 0.041). The gender-related difference in need for inotrope support was more evident among the ELBW infants; 67.1% of male infants needed inotrope support versus 50.6% of females (p = 0.028). At 12-24 h, male ELBW infants had lower minimum mean arterial blood pressure (mean (SD) 25(4) mmHg vs 28(6) mmHg, p = 0.004)) and lower minimum PaCO2 than females infants (4.3 (1.1) kPa vs 4.7 (0.9) kPa, p = 0.043).

CONCLUSIONS

There are early gender-related differences in need for ventilatory and circulatory support that may contribute to the worse long-term outcome in prematurely born male infants.

The risk of mortality or cerebral palsy in twins: a collaborative population-based study

The purpose of the paper was to describe demographic and clinical factors associated with fetal or neonatal death or cerebral palsy (CP) in twins. Vital statistics from five populations in the United States and Australia, which included information on CP diagnosed after 1 y of age. Information on zygosity was not available. In 1,141,351 births, 25,772 of whom were twins, significant secular trends from 1980 to 1989 included increasing prevalence of twins, increasing proportion of unlike-sex twins, and increasing maternal age. Overall, twins were at an approximately 5-fold increased risk of fetal death, 7-fold increased risk of neonatal death, and 4-fold increased risk of CP compared with singletons. However, at birth weight <2500 g, twins generally did better than singletons, both with respect to mortality and to CP rates. Second-born twins and twins from same-sex pairs were at increased risk of early death but not of CP. Twins from growth-discordant pairs and twins whose co-twin died were at increased risk of both mortality and CP. The highest rates of CP were in surviving twins whose co-twin was still-born (4.7%), died shortly after birth (6.3%) or had CP (11.8%). In this large data set spanning a 10-y period, overall rates of death or cerebral palsy were higher in twins than singletons, although small twins generally did better than small singletons. Co-twin death was a strong predictor of CP in surviving twins. This risk was the same for same- and different-sex pairs, and observed both for preterm and term infants.

Perinatal mortality and neonatal morbidity rates among twin pairs at different gestational ages: optimal delivery timing at 37 to 38 weeks' gestation

OBJECTIVE

The aim of this study was to determine the gestational age at delivery associated with the lowest rates of perinatal mortality, respiratory distress syndrome, and long hospital stays among twins, with pair rates used to account for both infants in each twin pregnancy.

STUDY DESIGN

We conducted a population-based retrospective study that analyzed linked birth certificates, fetal and infant death certificates, and hospital discharge data for 8150 twin pairs born in Washington State during 1987 through 1997. The chi2 or Fisher exact test was used to assess the statistical significance.

RESULTS

The nadirs of perinatal mortality rate, respiratory distress syndrome incidence, and long hospital stay rate were seen at delivery dates of 39, 40, and 38 weeks' gestation, respectively. Restriction to pairs delivered vaginally without the induction of labor revealed that the perinatal mortality rate was lowest for delivery at 37 weeks' gestation, the gestational age at which the highest numbers of such spontaneously timed pairs were born.

CONCLUSION

Induction of labor should be routinely considered for twins at 37 to 38 weeks' gestation.

Early parental interactions with and perceptions of multiple birth infants

The perceptions and interactions of mothers and fathers of seven sets of twins and one set of triplets were compared to those of parents of 49 singleton infants. Couples were typically interviewed together three times during the pregnancy and at 1 week and 3 months post-partum. Two-weekly observations of mother-father-infant interactions were conducted after the first postnatal interview. Three major themes were apparent in the interviews--the positive and negative specialness for multiple births, difficulties involved in managing more than one infant, and attachment issues--that were also evident during the observations. Although there were few differences in care-giving and interactive behaviours between the multiple birth and singleton parents, the logistics of caring for more than one infant dictated that multiple birth infants were left alone more and looked at, talked to and held less often. Couples used different strategies to care for their infants, varying in both the extent to which they interacted preferentially with the infants and in the relative involvement of the mother, father and others.

Effects of fetal sex and race on risk of very preterm birth in twins

OBJECTIVE

Our purpose was to determine whether the risk of twin preterm birth correlates with the number of male fetuses.

STUDY DESIGN

Among 8109 white and 1884 black twin pregnancies in the Missouri Successive Pregnancy Birth/Death Data Set, 1978 through 1990, risk for preterm birth at various gestational ages was determined with 0, 1, or 2 male infants.

RESULTS

Studied as individuals, white preterm twins <35 weeks' gestation demonstrated a 9.2% excess of male fetuses (P < .001). Adjusted for monozygosity, risk for preterm birth <35 weeks' gestation was 15.7% in white female-female pairs, 17.9% in unlike-sex white fetuses, and 20.2% in white male-male pairs (r = .999, P = .01). The effect was absent in black pregnancies and was unrelated to birth order, cesarean delivery, parity, twins' weight differential, year, or season.

CONCLUSIONS

In white twin gestations the observed linear relationship between the number of male fetuses and the likelihood of preterm birth <35 weeks' gestation suggests a fetal mechanism for preterm birth <35 weeks' gestation linked to fetal sex. Studies of mechanisms for preterm birth must stratify by fetal sex and race.

The multiple birth explosion: implications for nursing practice

An explosion in multiple birth rates has generated record numbers of multiple pregnancies and infants. Obstetric and neonatal nurses and those in related practice areas, such as reproductive endocrinology, perinatal education, home health, and lactation services, need special knowledge and resources to provide optimal care for these high-risk families. Multiple birth families have a number of unique health care problems that require directed nursing interventions throughout the perinatal continuum.

Delivery of twins

The delivery of twins presents considerable challenges to the obstetric team, particularly in terms of decision-making, technical skills required and the need to respond quickly to changing circumstances. There is a serious lack of sound evidence upon which to base decisions concerning the method of delivery of twins. The trend towards the routine use of caesarean section is not supported by evidence of improved outcome for the infants, while maternal outcome is compromised. Specific circumstances that may have a bearing on the need for caesarean section include gestational age, presentation of the twins and chorionicity/amnionicity. Caesarean section does not eliminate the chance of fetal trauma during delivery, particularly for premature twins. The techniques of twin delivery, whether vaginal or by caesarean section, require thorough preparation for all possible eventualities, and skilled teamwork. Particular attention should be paid to emotional needs during labour, birth and afterwards, of the parents of twins.

Adverse outcome after multiple pregnancy

There is increasing interest in the outcomes of multiple pregnancies as their numbers rise, mainly owing to advances in fertility-enhancing techniques. In addition, the numbers of multiple births surviving the perinatal period is increasing with the increasing survival of very tiny babies. In order to investigate these outcomes or to evaluate procedures that may improve them, it is important to consider a number of methodological issues that affect the comparability of data both between and within populations. How a birth and a multiple birth are defined, data sources, whether multiple pregnancies or individual births are being counted and the identification of multiple gestations by zygosity and chorionicity will all affect the reported outcome rates. In light of this, perinatal mortality and neurodevelopmental disabilities are examined as adverse outcomes of multiple pregnancies.