Contribution of Gestational Age and Birth Weight to Perinatal Viability in Singletons Versus Twins

The objective of this study was to determine the effects of birth weight and gestational age on twin vs. singleton mortality. Population-based analysis of live births, fetal deaths, and infant deaths by plurality in the United States from 1983 to 1986 was conducted. Seven mortality rates and relative risks (RRs) of twin vs. singleton mortality were calculated by birth weight, gestational age, and combined birth weight and gestational age. The mortality rates included fetal, perinatal, early neonatal, late neonatal, neonatal, postneonatal, and infant. Twins had 3–4 times the RRs of mortality compared to singletons, ranging from a RR of 2.71 for postneonatal mortality to a RR of 3.73 for late neonatal mortality. Generally, for birth weights of 2,800 g or less and gestational ages of 38 weeks or less, twins had lower combined birth weight and gestational age mortality rates and lower RRs. Between 1,900 and 2,799 g, mortality rates decreased then increased with advancing gestation between 31 and 42 weeks both more severely and consistently for twins than for singletons. In conclusion, twins have lower birth weight and gestational age-specific mortality rates and RRs than singletons below 2,800 g and 39 weeks. The “U”-shaped pattern of mortality beyond 38 weeks gestation, particularly for twins with birth weights below 2,500 g, reflects the combined influence of growth retardation and advancing gestation on mortality. The lowest mortalityfor twins is achieved at birth weights of 2,500-2,799gat35-38 weeks gestation. Only 1 in 7 twins is born within this “ideal window.” Efforts at reducing twin mortality should be directed toward reducing intrauterine growth retardation and achieving optimal timing for delivery.     

A case-control study of 1253 twin pregnancies from a 1982-1987 perinatal data base

In one regional perinatal network between 1982-1987, 101,506 women delivered infants greater than 500 g, of which 1253 were twin pregnancies (1.2%). This latter group was compared statistically with a 5% random sample of the singletons (N = 5119). The results showed that the women with twin pregnancies were slightly older, had a higher parity, gained more weight during the gestation, and had a heavier body weight at delivery. Twin pregnancies were complicated by increases in hypertension (odds ratio 2.5; 95% confidence interval 2.1-3.1), abruption (odds ratio 3.0; 95% confidence interval 1.9-4.7), and anemia (odds ratio 2.4; 95% confidence interval 1.9-3.0). There was no increased risk of pyelonephritis, placenta previa, or diabetes mellitus in mothers with twins. The twin pregnancies delivered earlier and the infants were smaller, had lower Apgar scores, and were at increased risk for congenital anomalies. Fetal and neonatal mortality rates were significantly increased in the twin infants; the perinatal mortality rates for twin A and twin B were 48.8 and 64.1, respectively, compared with 10.4 per 1000 births for the singleton controls. When the twin infants A and B were of similar weight, they had a similar perinatal mortality (odds ratio 1.0; 95% confidence interval 0.6-1.8). For infants less than 2500 g, twins A and B had lower fetal and neonatal mortality rates than did singletons, but twins heavier than 2500 g were at increased risk of perinatal death.     

Prospective risk of fetal death in singleton, twin, and triplet gestations: implications for practice

OBJECTIVE: To evaluate the prospective risk of fetal death in singleton, twin, and triplet pregnancies and to compare this risk with fetal and neonatal death rates. METHODS: We analyzed 11,061,599 singleton, 297,622 twin, and 15,375 triplet gestations drawn from the 1995-1998 National Center for Health Statistics linked birth and death files. Prospective risk of fetal death was expressed as a proportion of all fetuses still at risk at a given gestational age and compared with fetal death rate. Fetal death risk and neonatal death rates were represented graphically for singletons, twins, and triplets. RESULTS: The prospective risk of fetal death at 24 weeks was 0.28 per 1000, 0.92 per 1000, and 1.30 per 1000 for singletons, twins, and triplets, respectively. At 40 weeks, the corresponding risk was 0.57 per 1000 and 3.09 per 1000 for singletons and twins, respectively and, at 38 or more weeks, 13.18 per 1000 for triplets. Plots of gestation-specific prospective risk of fetal death and neonatal mortality converged for singletons and twins at term but crossed for triplets at approximately 36 weeks' gestation. CONCLUSION: Prospective risk of fetal death is greater for triplets and twins than for singletons and greater for triplets than for twins during the third trimester. The pattern corroborates with uteroplacental insufficiency as a suspected underlying mechanism. When prospective risk of fetal death exceeds neonatal mortality risk, delivery might be indicated. When this model is used, this data set suggests that it might be reasonable to consider delivery of twins by 39 weeks and triplets by 36 weeks to improve perinatal outcome.     

Perinatal mortality and morbidity rates among singleton,twin, and triplet gestations

Objective: To determine rates of perinatal mortality and morbidity from 24 to 43 weeks gestation among singletons, twins, and triplets.Methods: Successfully linked data from 1992 Californian maternal and infant discharge records as well as birth and death certificates from acute care civilian hospitals were examined for perinatal mortality and morbidity. Perinatal mortality was defined as the sum of all stillbirths and neonatal deaths. Deliveries from 24 to 43 weeks gestation among singleton, twin, and triplet pregnancies were collected as separate data sets. Perinatal mortality was identified using birth certificate death indicators excluding deaths caused by congenital anomalies. Neonatal deaths were identified from death indicators found in the death certificates. For the purpose of this study, perinatal morbidities were identified by ICD-9 codes and limited to respiratory distress syndrome (RDS), intraventricular hemorrhage (IVH), and necrotizing enterocolitis (NEC). Perinatal mortality and morbidity rates were expressed as a percent of live births stratified by gestational age. Perinatal mortality data were expressed in log scale and perinatal morbidity rates were statistically compared.Results: There were 571,390 total births in California of which 527,677 (92%) were singleton, 12,535 (2%) were twin, and 367 (0.06%) were triplet gestations. Across gestation, the rate of RDS between triplets and twins was comparable (6.6% vs 6.8%). However, the rates of IVH and NEC were significantly greater in triplets than in twins (20% vs 8%, P < .0001, and 25% vs 9%, P < .0001, respectively). The perinatal mortality rates are shown below.

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Conclusions: Perinatal mortality rates were comparable among singleton, twin, and triplet gestations delivered between 24 and 30 weeks gestation. Unlike singletons and twins, the triplet perinatal mortality rate did not fall between 31 and 36 weeks gestation and remained at 2.6%. Twin perinatal mortality rate was equivalent to singletons until 36 weeks gestation. IVH and NEC were significantly greater among triplets regardless of gestational age. These data suggest that antepartum fetal surveillance of triplet pregnancies should start as early as 30 weeks gestation while testing for twin pregnancies can begin at 36 weeks gestation.     

Stillbirth and neonatal outcomes in South Australia, 1991-2000

OBJECTIVES: The purpose of this study was to determine the effect of maternal factors associated with impaired placental function on stillbirth and neonatal death rates in South Australia. STUDY DESIGN: From 1991 to 2000, the South Australian Pregnancy Outcome Unit's population database was searched to identify stillbirths and neonatal deaths in women with maternal medical conditions during pregnancy and in twin and singleton pregnancies. RESULTS: Women with hypertension and carbohydrate intolerance and who smoked during pregnancy had an increased risk of stillbirth. Women with twin pregnancies had a significantly higher stillbirth rate than for singletons at each week of gestational age. An increase in stillbirth rate at later gestations was seen with singletons, with a similar trend in twins but rising from 36 weeks' gestation. CONCLUSION: There is a clinical correlation between maternal factors associated with impaired placental function and increased risk of stillbirth, suggesting that intrauterine fetal death represents the mortality end point in a spectrum of intrauterine hypoxia.     

Perinatal mortality and route of delivery in term breech presentations

Objective To compare intrapartum related infant mortality in term (> 34 weeks) breech presentations in relation to vaginal delivery or delivery by caesarean section.
Design Register based nationwide study.
Setting Sweden from 1991 to 1992.
Participants 6542 singleton fetuses born in the breech presentation.
Main outcome measures Intrapartum and early neonatal deaths, stillbirths and congenital malformations, low Apgar score < 7 at 5 min, mode of delivery.
Results After exclusion of antepartum stillbirths and congenital malformation, the intrapartum and early neonatal mortality rate was 2/2248 (0.09%) in the group delivered vaginally and 2/4029 (0.05%) in the group delivered by caesarean section. The relative risk was 1.81 (95% CI 0.26–12.84). Thus the difference was not statistically significant. This result was further supported after reviewing individual cases.
Conclusions The intrapartum related mortality in the group delivered vaginally was low and the result could not verify an increased mortality in term breech presentations delivered vaginally compared with those delivered by caesarean section.     

The Principal Pregnancy Complications Resulting in Preterm Birth in Singleton and Twin Gestations

Preterm birth is the major cause of perinatal mortality for both singleton and twin gestations in the United States; most preterm birth prevention programs are primarily structured to detect and treat preterm labor. Most of these programs have had limited success, and the preterm birth rate for twins has remained well above that for singletons. Little attention has been paid to the question of whether the frequency of conditions that result in preterm twin delivery differs from those that result in the delivery of preterm singletons. Delivery records were reviewed for all 1,976 preterm (24–36 completed gestational weeks) singleton pregnancies and 221 preterm twin pregnancies delivered at the University of Connecticut Health Center, 1980–1989, to determine the primary complication that resulted in preterm delivery. Premature rupture of membranes was responsible for 46% of these singleton preterm deliveries, while the other causes were preterm labor with intact membranes (20%), pregnancy-induced hypertension (15%), antepartum hemorrhage (9%), and other maternal-fetal indications (10%). The five groups differed significantly in maternal and neonatal characteristics. The principal pregnancy complications resulting in preterm delivery of twins were preterm rupture of membranes (42%), preterm labor (31%), antepartum hemorrhage (4%), pregnancy-induced hypertension (11%), and other maternal-fetal indications (12%). Compared to preterm singletons, the preterm twins were significantly more likely to deliver because of preterm labor and less likely to deliver because of hemorrhage. Substantial reduction in the preterm birth rate requires programs tailored to the specific population and etiologies involved and should not solely address preterm labor.     

The effect of single or multiple courses of antenatal corticosteroid therapy on neonatal respiratory distress syndrome in singleton versus twin pregnancies

Background: Antenatal corticosteroid (ACS) treatment is widely used for the prevention of respiratory distress syndrome (RDS) in preterm infants. However, the efficacy and safety of ACS treatment remains controversial in twin pregnancies.
Aims: To investigate the effect of ACS therapy, single or multiple courses, on the incidence of neonatal RDS in singleton and twin pregnancies.
Methods: We retrospectively evaluated the pregnancy and neonatal outcomes of 450 singleton and 117 twin pregnancies delivered at 24–34 weeks of gestation due to preterm labour or preterm premature rupture of membranes. The subjects were categorised into four groups according to ACS exposure: 0, 1, 2 and ≥ 3 courses.
Results: Overall, RDS occurred more frequently in twins compared to singletons (41.0% vs 25.3%, P  < 0.001). In singleton pregnancy, the incidence of RDS was significantly lower in the ACS user groups than in the non-user group, with the lowest incidence in the multiple course groups. An increase in the number of courses of ACS was associated with a reduction in the incidence of RDS (odds ratio 0.349, 95% confidence interval 0.226, 0.537, P  < 0.001) independent of confounding variables. In twin pregnancies, however, the incidence of RDS was not significantly different in comparisons among the four groups.
Conclusion: Multiple courses of ACS were associated with a significantly decreased risk of RDS in singleton pregnancies. However, the current standard dose or interval for ACS administration in singleton pregnancy, as either a single or multiple courses, did not reduce RDS in twins.     

Perinatal outcome and peripartum complications in preterm singleton and twins deliveries: a comparative study

OBJECTIVE: Multiple pregnancy is one of the major risk factors for preterm births. The aim of the present study was to compare perinatal outcome and peripartum complications between twins and singletons, born preterm. STUDY DESIGN: The study population consisted of preterm deliveries of 435 pairs of twins (870 neonates) and the comparison group included 4754 preterm deliveries of singletons, born in the same period (January 1, 1989-December 31, 1996). Exclusion criteria were lack of prenatal care and births following infertility treatments. The three steps in statistical analysis consisted of (1) degree of concordance between the twins; (2) comparison between each twin (I and II) to their singleton comparison groups using SPSS computer program; (3) stratified analysis to examine perinatal mortality rates at different gestational age groups. RESULTS: The prevalence of preterm deliveries was 7.9% (6192/77610). Perinatal mortality was lower in twins of both birth orders, however, it was statistically significant only when APD is considered. Mortality rates in all gestational age groups and for both twin groups were lower than that of singleton [OR=0.45 (0.26-0.75; 95% CI) for twin-I; OR=0.36 (0.21-0.59; 95% CI) for twin-II]. Compared to singletons, twin gestations had less congenital malformations. Twin gestation had statistically lower rates of preterm premature rupture of membranes, severe pregnancy induced hypertension, oligohydramnios, placenta previa, placental abruption and clinical chorioamnionitis [12.2 vs.17.3%, 2.5 vs. 6.3%, 2.3 vs. 4.7%, 0.9 vs. 2.9%, 1.8 vs. 5%, 1.8 vs. 5.2%, respectively (P<0.01)]. Mothers of twins had less diabetes mellitus class B-R, hydramnios and chronic hypertension than that of singleton (1.8 vs. 2.6%, 5.5 vs. 7.4%, 3.7 vs. 4.8%, respectively). Cesarean section rates were significantly higher in twin's gestation. Mothers of twins tended to be older and of higher birth and gravidity order. CONCLUSIONS: Perinatal mortality rates and peripartum complications were lower in twin compared to singleton gestations.     

Trends in the cause of late fetal death, 1982-2000

BACKGROUND: Progress in reducing late fetal deaths has slowed in recent years, despite changes in intrapartum and antepartum care. OBJECTIVES: To describe recent trends in cause-specific fetal death rates. DESIGN: Retrospective cohort study. SETTING: North of England. POPULATION/SAMPLE: 3,386 late fetal deaths (> or = 28 weeks of gestation and at least 500 g), occuring between 1982 and 2000. METHODS: Data on deaths were obtained from the Northern Perinatal Mortality Survey. Data on live births were obtained from national birth registration statistics. Rate ratios (RR) and 95% confidence intervals (CI) for fetal deaths in 1991-2000 compared with 1982-1990 were calculated. MAIN OUTCOME MEASURES: Cause-specific late fetal death rates per 10,000 total births. RESULTS: Mortality in singletons declined from 51.5 per 10,000 births in 1982-1990 to 42.0 in 1991-2000 (RR 0.82, 95% CI 0.76-0.87). There was a greater decline in multiples, from 197.9 to 128.0 per 10,000 (RR 0.65, 95% CI 0.51-0.83). In singletons, the largest reductions occurred in intrapartum-related deaths, and deaths due to congenital anomalies, antepartum haemorrhage and pre-eclampsia. There was little change in the rate of unexplained antepartum death occurring at term (RR 0.97, 95% CI 0.84-1.11) or preterm (RR 0.94, 95% CI 0.82-1.07), these accounting for about half of all late fetal deaths. Unexplained antepartum deaths declined in multiple births and in singletons of birthweight < 1500 g. CONCLUSIONS: While late fetal mortality due to many specific causes has declined, unexplained antepartum death rates have remained largely unchanged. Improved identification of deaths due to growth restriction and infection, which may otherwise be classified as unexplained, is important. Further investigation of the underlying aetiologies of genuinely unexplained deaths is needed.     

Monoamniotic twin pregnancies: antenatal management and perinatal results of 19 consecutive cases

Objective   To describe the obstetric management and perinatal outcome of antenatally diagnosed monoamniotic twin pregnancies (MATP) in a tertiary level maternity unit.
Setting   Port-Royal Maternity Hospital, Paris, France.
Population   MATP that progressed beyond 22 weeks seen from 1993 to 2001.
Methods   A retrospective chart review of all twin pregnancies. Diagnosis of MATP was made by ultrasonography and confirmed by placental pathology.
Main outcome measure   Perinatal mortality.
Results   Among the 1242 twins pregnancies delivered during the study period, 19 were monoamniotic. Four fetuses (10% of all births) had malformations. Perinatal mortality was high ( n = 12, 32%) because of fetal deaths (nine cases) and very preterm births (three neonatal deaths). No fetal deaths occurred after 29 weeks. Of the 15 women with at least one live fetus before labour, 6 gave birth by vaginal delivery (40%). No obstetric accidents occurred during vaginal deliveries.
Conclusion   Perinatal mortality of MATP is still very high, even with accurate, early antenatal diagnosis, intensified surveillance and delivery provided in a tertiary level hospital. The main causes of perinatal deaths are cord accidents in utero , congenital anomalies and very preterm births.     

Perinatal outcome of ICSI pregnancies compared with a matched group of natural conception pregnancies in Flanders (Belgium): a cohort study

A retrospective cohort study was conducted with an intracytoplasmic sperm injection (ICSI) group and a naturally conceived comparison group. A total of 1655 singleton and 1102 twin ICSI births were studied with regard to perinatal outcome. Control subjects (naturally conceived pregnancies) were selected from a regional registry and were matched for maternal age, parity, place of delivery, year of birth and fetal sex. The main outcome measures were duration of pregnancy, birth weight, Apgar score <5 after 5 min, neonatal complications, perinatal death and congenital malformations. Twin births, when compared with singletons, carry a much higher risk of poor perinatal outcome. For both ICSI singletons and ICSI twins, no significant difference was found between ICSI and naturally conceived pregnancies for all investigated parameters. After excluding like-sex twin pairs, ICSI twin pregnancies were at increased risk for perinatal mortality (OR = 2.74, CI = 1.26-5.98), prematurity (OR = 1.38, CI = 1.10-1.75) and low birth weight (OR = 1.34, CI = 1.06-1.69) compared with spontaneously conceived different-sex twin pairs. In conclusion, the perinatal outcome of ICSI singleton and twin pregnancies was very similar to that of spontaneously conceived pregnancies in this large cohort study. After excluding like-sex twin pairs, ICSI twins were at increased risk for prematurity, low birth weight and higher perinatal mortality compared with the natural conception comparison group.     

Assessment of fetal growth in twins: Which method to use?

Fetal growth restriction contributes to the excess perinatal mortality and morbidity associated with twin pregnancies. Regular ultrasound monitoring for fetal growth restriction is an essential component of antenatal care of twin gestations. It is accepted that twins have divergent growth trajectories around 28–30 weeks’ gestation and are born smaller compared to singletons. Despite this well-established difference in fetal growth, twin pregnancies have been traditionally managed using growth standards developed for singleton pregnancies. Numerous recent studies have demonstrated a strong case supporting the use of twin-specific growth standards, but clinical implementation has been lacking. In this paper, we will review the evidence on factors affecting fetal growth, the rationale for twin-specific reference charts, clinical evidence for their use, and future direction of research. Applying singleton growth standards to twin pregnancies inflates the abnormal growth rate, and recent clinical evidence from several studies suggests that they are too stringent for classification of twins. The association of adverse perinatal and maternal outcomes such as perinatal death, preterm birth, neonatal care unit admission, hypertensive disorders of pregnancy, and composite neonatal morbidity is stronger when classification is made using twin-specific standards compared to singletons.     

Screening for trisomy 21 in twin pregnancies by maternal age and fetal nuchal translucency thickness at 10–14 weeks of gestation

Objective To determine the prevalence of increased fetal nuchal translucency thickness in twin pregnancies and to evaluate screening for trisomy 21 by a combination of translucency thickness and maternal age.
Design Prospective screening study at 10 to 14 weeks of gestation.
Setting Fetal Medicine Centre.
Population 22,518 self-selected pregnant women at 10 to 14 weeks of gestation, including 21,477 singleton and 448 twin pregnancies with live fetuses.
Methods Fetal nuchal translucency thickness was measured by ultrasound examination at 10–14 weeks. Sensitivity and false positive rates of screening for trisomy 21 by a combination of fetal nuchal translucency thickness and maternal age were calculated.
Main outcome measures Prevalence of increased nuchal translucency thickness and detection of trisomy 21.
Results In the 448 twin pregnancies the nuchal translucency thickness was above the 95th centile of the normal range (for crown-rump length in singletons) in 65/896 fetuses (7.3%), including 7/8 (88%) with trisomy 21. Increased translucency was also present in four fetuses with other chromosomal abnormalities. In the chromosomally normal twin prebmancies the prevalence of increased nuchal translucency was higher in fetuses from monochorionic (8.4%; 16/190) than in those with dichori-onic pregnancies (5.4%; 37/688). The minimum estimated risk for trisomy 21, based on maternal age and fetal nuchal translucency thickness, was 1 in 300 in 19.5% (175/896) of the twins including all eight of those with trisomy 21.
Conclusions In twin pregnancies the sensitivity of fetal nuchal translucency thickness in screening for trisomy 21 is similar to that in singleton pregnancies, but the specificity is lower because translucency is also increased in chromosomally normal monochorionic twin pregnancies.     

Twin versus singleton pregnancies complicated by preterm premature rupture of membranes

Objective: To compare latency period, infectious morbidity, neonatal morbidity and neonatal mortality in twin versus singleton pregnancies complicated by preterm premature rupture of membranes (PPROM) remote from term. Methods: A retrospective, matched cohort study comparing 41 twin and 82 singleton pregnancies complicated by PPROM between 24-0/7 and 31-6/7 weeks’ gestation. The data were obtained by reviewing maternal and neonatal charts. Results: The median latency periods were 3.6 days (interquartile range 1.5–13.9 days) for twins and 6.2 days (interquartile range 2.9–11.8 days) for singletons (p?=?0.86). Twins were less likely to be complicated by clinical chorioamnionitis when compared with singletons (4/41 [9.8%] vs. 19/82 [23.2%], relative risk [RR] 0.42, 95% confidence interval [CI] 0.18–0.96). Histological evidence of chorioamnionitis was also lower in twins compared with singletons (14/39 [35.9%] vs. 46/68 [67.7%], RR 0.56, 95% CI, 0.34–0.92). These differences persisted after adjusting for race, insurance status, latency period and route of delivery. Neonatal morbidity and mortality rates were similar between the two groups. Conclusions: There was not a statistically significant difference in the latency periods for twin and singleton pregnancies complicated by PPROM. Clinical chorioamnionitis and histological evidence of infection were significantly less common in twins compared with singletons.     

Fetal Monitoring of Twins

Perinatal mortality for twins is five to seven times that for singletons. This disparity is related to a variety of risk factors that may alter the health of the woman and her fetuses. With twin pregnancies, antepartum surveillance frequently begins earlier in gestation. Although extensive antepartum and intrapartum nursing care is required for women with twins, little has been published in the nursing literature to provide direction for caregivers. Factors such as zygosity and gestational age influence monitoring in twin pregnancies. Current clinical and technical nursing issues are reviewed and related to the antepartum and intrapartum electronic fetal monitoring of twins.     

Fetal growth and perinatal mortality in twin pregnancy - effect of sick leave and hospitalization

Fetal growth, birth weight specific mortality rates and effect of sick leave or hospitalization on the fetal growth were investigated in a material of 476 twin pregnancies managed at University Central Hospital of Turku in year 1970–1981. Birth weights of twin babies at any gestational age were slightly but not significantly higher than in earlier materials. When compared to growth curve of singleton fetuses, the growth rate of both twins is equal to singletons up to 30th week of pregnancy, being thereafter slower than in singleton pregnancies.Although duration of sick leave and hospitalization increased considerably during the study period, no change in the duration of pregnancy nor in the weight of twin babies occurred. Instead perinatal mortality decreased from 101/per thousand to 36.2/ per thousand. Birth weight specific mortality rates did not differ from those in singleton fetuses.     

Medical and economic effects of twin gestations

OBJECTIVE: To determine the incidence and trends of twinning in the United States and to review the medical and economic effects of twin versus singleton gestations. METHODS: Pertinent and recent studies on twin gestations were obtained through a MEDLINE database search of the English language between December 1987 and December 1999. Data from the 1995-1996 National Center for Health Statistics were also used to compare gestational age at delivery, fetal growth restriction, and perinatal mortality for twin and singleton gestations. Studies that have evaluated perinatal risks in relation to advanced reproductive technology also were reviewed and summarized. The economic implications of twinning from a societal perspective and infant quality of life issues of twins compared with singleton gestations are reviewed. RESULTS: Due to delayed childbearing and increased use of reproductive technologies, the incidence of twin gestations in the United States has been increasing. Twin pregnancies have a higher risk of complications, including pregnancy-induced hypertension, anemia, antepartum and postpartum hemorrhage, and maternal mortality. In addition, twin infants are more likely to deliver preterm, have low birth weight and greater perinatal mortality rates. These outcomes influence health care costs and quality of life for both parents and children. CONCLUSIONS: Women carrying twin fetuses are at increased risk for perinatal and obstetric complications. The increased perinatal risks that accompany twin fetuses may be partly due to the increasing use of advanced reproductive technologies. The economic burdens, as well as the potential for decreased quality of life among twins, needs careful evaluation.     

Perinatal mortality in twin pregnancy: an analysis of birth weight-specific mortality rates and adjusted mortality rates for birth weight distributions

The objective of this study is to compare the fetal mortality rate (FMR), early neonatal mortality rate (ENMR) and perinatal mortality rate (PMR) of twin and single births. It is based on a survey which was carried out in 22 Hospital Centers in Spain in 1980, and covered 1,956 twins born and 110,734 singletons born. The FMR in twins was 36.3/1000 and 8.8/1000 for singletons. The ENMR in twins was 36.1/1000 and 5.7/1000 for singletons. The PMR in twins was 71.1/1000 and 14.4/1000 for singletons. When birthweight-specific PMR in twin and singletons births are compared, there were no differences between the rates for groups 500-999 g and 1000-1499 g. For birthweight groups of 1500-1999 g (124.4 vs 283.8/1000) and 2000-2999 g (29.6 vs 73.2/1000) the rates for twins were about twice lower than those for single births. The PMR for 2500 g and over birthweight was about twice higher in twins than in singletons (12.5 vs 5.5/1000). After we adjusted for birthweight there was a difference in the FMR (12.6 vs 9.8/1000) and the PMR (19.1 vs 16.0/1000, and no difference in the ENMR between twins and singletons (5.9 vs 6.4/1000), indicating that most of the differences among crude rates are due to differences in distribution of birthweight.     

Twin deliveries and place of birth in NSW 2001–2005

Background:  Twin pregnancies have an elevated risk of adverse outcomes, particularly preterm twins.
Aims:  Describe the distribution of twin deliveries by hospital level, the associated perinatal and maternal morbidity, and determine predictors of perinatal morbidity and urgent transfer to a neonatal intensive care unit.
Methods:  Longitudinally linked New South Wales delivery and hospital records for the years 2001–2005 were used to identify perinatal and maternal morbidity/mortality in twin pregnancies. Regression analysis was used to examine predictive factors, including birth hospital volume.
Results:  At ≤ 32 weeks, 88.1% of twins were delivered in tertiary referral hospitals. By 34–35 weeks, only 39.7% of twins were delivered in tertiary units. Gestational age was the primary predictor of perinatal morbidity/mortality. Perinatal morbidity/mortality and maternal morbidity were lowest for deliveries at 38 weeks. There was no evidence that planned caesarean section at ≤ 38 weeks was protective against perinatal morbidity/mortality. There was an increased risk of perinatal morbidity/mortality (odds ratio (OR) = 2.22) for twins delivered at 33–35 weeks gestation at hospitals with < 500 deliveries per annum, and an increased risk of urgent neonatal transfer (OR = 2.06). Twin pairs for whom there was a ≥ 20% discordance in birthweight had an increased risk of morbidity/mortality at 36–38 weeks (OR = 1.79).
Conclusions:  Both infant and maternal morbidity increase from 39 weeks gestation. Delivery of twins before 36 weeks at smaller hospitals (< 500 deliveries per annum) should be avoided. A twin pregnancy where there is a ≥ 20% difference in estimated fetal weights should be considered for referral to a tertiary obstetric unit.