Twin pregnancy: the impact of the Higgins Nutrition Intervention Program on maternal and neonatal outcomes

Does Dietitian Involvement During Pregnancy Improve Birth Outcomes? A Systematic Review

Maternal diet during pregnancy can have a significant impact on maternal and offspring health. As nutrition counselling is an important component of prenatal care, registered dietitians (RDs) are uniquely trained professionals who can provide personalized nutrition counselling customized to an individual's sociocultural needs. The objective of this systematic review was to determine if RD involvement during pregnancy is associated with a lower prevalence of adverse birth outcomes in the United States and Canada. The review was conducted through a search of four databases: PubMed, CINAHL, Embase, and Web of Science. A total of 14 studies were identified. Women had a lower prevalence of low birth weight and preterm infants when RDs were involved during prenatal care. While RD involvement during pregnancy was not associated with macrosomia, more research is needed to assess its relationship with small for gestational age, large for gestational age, and infant mortality. Future research should also investigate the specific dietary advice provided by RDs and the extent and timing of their involvement throughout pregnancy to better understand the mechanisms surrounding nutrition counselling, in utero development, and health outcomes.

A new care pathway to optimize gestational weight gain in twin pregnancies

BACKGROUND

Maternal gestational weight gain is an important determinant of pregnancy outcomes and may have an even greater role in twin pregnancies because of their higher rate of pregnancy complications and greater nutritional demands. However, data on the optimal week-specific gestational weight gain in twin pregnancies and on interventions that should be applied in cases of inadequate gestational weight gain are limited.

OBJECTIVE

This study aimed to determine whether a new care pathway that involves monitoring gestational weight gain using a week-specific chart, along with a standardized protocol for managing cases with inadequate gestational weight gain, can optimize maternal gestational weight gain in twin pregnancies.

METHODS

In this study, patients with twin pregnancies followed in a single tertiary center between February 2021 and May 2022 were exposed to the new care pathway (postintervention group). Gestational weight gain and clinical outcomes were compared with those of a previously described cohort of patients with twins followed in our clinic before the implementation of the new care pathway (preintervention group). The new care pathway targeted patients and care providers and included educational material, a newly developed body mass index group-specific gestational weight gain chart, and a stepwise management algorithm in cases of inadequate gestational weight gain. The body mass index group-specific gestational weight gain charts were divided into 3 zones: (1) green zone (optimal gestational weight gain at 25th-75th centiles); (2) yellow zone (suboptimal gestational weight gain at 5th-24th or 76th-95th centiles); and (3) gray zone (abnormal gestational weight gain, at <5th or >95th centile). The primary outcome was the overall proportion of patients achieving optimal gestational weight gain at birth.

RESULTS

A total of 123 patients were exposed to the new care pathway and were compared with 1079 patients from the preintervention period. Patients in the postintervention group were more likely to achieve optimal gestational weight gain at birth (60.2% vs 47.7%; adjusted odds ratio, 1.91; 95% confidence interval, 1.28-2.86) and were less likely to achieve low-suboptimal gestational weight gain (7.3% vs 14.7%; adjusted odds ratio, 0.41; 95% confidence interval, 0.20-0.85) or any suboptimal gestational weight gain (26.8% vs 34.8%; adjusted odds ratio, 0.60; 95% confidence interval, 0.39-0.93) at birth. In addition, patients in the postintervention group were less likely to have low-abnormal gestational weight gain anytime during gestation (18.9% vs 29.1%; P=.017) and were more likely to have normal gestational weight gain throughout pregnancy (21.3% vs 14.0%; P=.031) or high-abnormal gestational weight gain anytime during gestation (18.0% vs 11.1%; P=.025), suggesting that in comparison with standard care, the new care pathway is more effective in preventing patients from moving into the low-abnormal zone than the high-abnormal zone. Furthermore, the new care pathway was more effective than standard care in correcting high-suboptimal gestational weight gain and high-abnormal gestational weight gain.

CONCLUSION

Our findings suggest that the new care pathway may be effective in optimizing maternal gestational weight gain in twin gestations, which may in turn contribute to better clinical outcomes. This is a simple, low-cost intervention that can be easily disseminated among providers caring for patients with twin pregnancies.

A Community Prenatal Intervention in Social Nutrition: Evaluating the Impact on Pregnancy and Birthweight Outcomes

This study aims to assess the associations between structural features of the Montreal Diet Dispensary’s social nutrition intervention and pregnancy (i.e., anemia, gestational diabetes mellitus (GDM), gestational weight gain (GWG), hypertension) and birthweight outcomes (i.e., small- or large-for-gestational-age) among pregnant women, most of them recent immigrants. The study consists of a secondary analysis of the digital client database of the Montreal Diet Dispensary (n = 2925). Logistic regressions were used to estimate the odds of pregnancy and birthweight outcomes, depending on structural features of the intervention. Pregnant women who attended a welcoming group session presented lower odds of GDM and anemia compared to those who did not attend. A longer duration of intervention was also associated with lower odds of GDM and anemia. Each additional appointment with a dietitian was associated with higher odds of excessive GWG and lower odds of insufficient GWG only among women with a pre-pregnancy BMI lower than 25 kg/m². This study emphasizes the importance of providing nutritional services early in pregnancy to reduce the risk of GDM and anemia. It also stresses the importance of using appropriate nutritional guidelines to avoid increasing the risk of excessive GWG.

Review of Dietary Recommendations for Twin Pregnancy: Does Nutrition Science Keep Up with the Growing Incidence of Multiple Gestations?

Recommendations for nutrition and the use of dietary supplements for pregnant women are updated on regular basis but it remains to be seen to what extent they may be applicable in twin pregnancies. The aim of this narrative review is to present the current state of knowledge about the energy and nutrient demand in twin pregnancy. There is general consensus in literature that the energy demand is higher than in a singleton pregnancy, but there is a lack of position statements from scientific societies on specific energy intake that is required. In turn, recommended maternal weight gain, which favors the normal weight of the neonate, has been determined. There is even a larger knowledge gap when it comes to vitamins and minerals, the body stores of which are theoretically used up faster. The greatest number of studies so far focused on vitamin D, and most of them concluded that its concentration in maternal blood is lower in twin as compared to singleton pregnancy. Few randomized studies focus on iron supplementation and there are no other studies that would assess dietary interventions. In light of a growing incidence of multiple pregnancies, more studies are necessary to establish the nutritional demands of the mother and the course of action for adequate supplementation.

Micronutrients in Multiple Pregnancies-The Knowns and Unknowns: A Systematic Review

Maternal diet and nutritional status are of key importance with regard to the short- and long-term health outcomes of both the mother and the fetus. Multiple pregnancies are a special phenomenon in the context of nutrition. The presence of more than one fetus may lead to increased metabolic requirements and a faster depletion of maternal macro- and micro- nutrient reserves than in a singleton pregnancy. The aim of this systematic review was to gather available knowledge on the supply and needs of mothers with multiple pregnancies in terms of micronutrients and the epidemiology of deficiencies in that population. It was constructed in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses Statement (PRISMA). The authors conducted a systematic literature search with the use of three databases: PubMed/MEDLINE, Scopus and Embase. The last search was run on the 18 October 2020 and identified 1379 articles. Finally, 12 articles and 1 series of publications met the inclusion criteria. Based on the retrieved studies, it may be concluded that women with multiple pregnancies might be at risk of vitamin D and iron deficiencies. With regard to other microelements, the evidence is either inconsistent, scarce or absent. Further in-depth prospective and population studies are necessary to determine if nutritional recommendations addressed to pregnant women require adjustments in cases of multiple gestations.

Gestational Weight Gain and Adverse Birth Outcomes in Twin Pregnancies

OBJECTIVE

To evaluate the association between gestational weight gain in twin pregnancies and small-for-gestational-age (SGA) and large-for-gestational-age (LGA) birth, preterm birth before 32 weeks of gestation, cesarean delivery, and infant death within each prepregnancy body mass index (BMI) category.

METHODS

Data in this population-based study came from Pennsylvania-linked infant birth and death records (2003-2013). We studied 54,836 twins born alive before 39 weeks of gestation. Total pregnancy weight gain (kg) was converted to gestational age-standardized z scores. Multivariable modified Poisson regression models stratified by prepregnancy BMI were used to estimate associations between z scores and outcomes. A probabilistic bias analysis, informed by an internal validation study, evaluated the effect of BMI and weight gain misclassification.

RESULTS

Gestational weight gain z score was negatively associated with SGA and positively associated with LGA and cesarean delivery in all BMI groups. The relation between weight gain and preterm birth was U-shaped in nonobese women. An increased risk of infant death was observed for very low weight gain among normal-weight women and for high weight gain among women without obesity. Most excess risks of these outcomes were observed at weight gains at 37 weeks of gestation that are equivalent to less than 14 kg or more than 27 kg in underweight or normal-weight women, less than 11 kg or more than 28 kg in overweight women, and less than 6.4 kg or more than 26 kg in women with obesity. The bias analysis supported the validity of the conventional analysis.

CONCLUSION

Very low or very high weight gains were associated with the adverse outcomes we studied. If the associations we observed are even partially reflective of causality, targeted modification of pregnancy weight gain in women carrying twins might improve pregnancy outcomes.

Nutrition for Multiples

In 2012 there were 135,943 infants of multiple pregnancies born in the United States, nearly a 2-fold increase since 1980, with twins accounting for 96% of all multiple births. To date, most perinatal morbidities associated with multiple births have proven resistant to technological or pharmaceutical interventions. Maternal nutrition can have a profound effect on the course and outcome of multiple pregnancy, with the goal of achieving optimal intrauterine growth and birthweights, and minimizing prenatal and perinatal complications for the mother and her children.

[Twin pregnancies: where should we manage them? Where should they deliver?]

OBJECTIVES

To define where should twin pregnancies be managed and delivered.

MATERIALS AND METHODS

A literature search was performed using the Pubmed and Cochrane database. Foreign societies guidelines were also consulted.

RESULTS

There is little or no evidence to answer the question. Risk of premature labor and chorionicity are the two main factors involved in twin management. When there is a risk of prematurity, in utero transfer is recommended. Twin care must be performed by a team trained in the specificity of management according to chorionicity. There is not enough evidence to support specialized clinics. Labor and delivery need permanent and immediate disponibility of a perinatal team including an OB-gyn, an anesthesiologist and a pediatrician.

CONCLUSION

Needs assessment and chorionicity are the best indicators to define the optimal place of care and delivery for twin pregnancies. More than a specific location, it seems more logical to define all necessary means to enforce an optimal management of these pregnancies.

Optimal nutrition for improved twin pregnancy outcome

Twin pregnancies contribute a disproportionate degree to perinatal morbidity, partly because of increased risks of low birth weight and prematurity. Although the cause of the morbidity is multifactorial, attention to twin-specific maternal nutrition may be beneficial in achieving optimal fetal growth and birth weight. Achievement of body mass index (BMI)-specific weight gain goals, micronutrient and macronutrient supplementation specific to the physiology of twin gestations, and carbohydrate-controlled diets are recommended for optimal twin growth and pregnancy outcomes. The daily recommended caloric intake for normal-BMI women with twins is 40-45 kcal/kg each day, and iron, folate, calcium, magnesium, and zinc supplementation is recommended beyond a usual prenatal vitamin. Daily supplementation of docosahexaenoic acid and vitamin D should also be considered. Multiple gestation-specific prenatal care settings with a focus on nutritional interventions improve birth weight and length of gestation and should be considered for the care of women carrying multiples. Antepartum lactation consultation can also improve the rate of postpartum breastfeeding in twin pregnancies. Twin gestation-specific nutritional interventions seem effective in improving the outcome of these pregnancies and should be emphasized in the antepartum care of multiple gestations. This review examines the available evidence and offers recommendations for twin pregnancy-specific nutritional interventions.

Validation of a screening tool to identify the nutritionally at-risk pregnancy

OBJECTIVE

To assess the efficacy of a screening tool to be used by nurses to determine which economically disadvantaged pregnant women are most likely to benefit from a dietitian's intensive intervention.

METHODS

The 26-variable screening tool was used by 53 nurses in 17 Montreal primary care facilities at first contact with 300 subjects who were eligible for prenatal programs for low-income women. Among these, 259 subjects were subsequently interviewed by a Montreal Diet Dispensary (MDD) dietitian using the Higgins Method, established as the gold standard for the detection of a nutritionally at-risk pregnancy. Comparisons of the results obtained by dietitians using the Higgins Method with scores obtained by nurses using the screening tool to determine risk levels and individual variables were analyzed using the Pearson correlation coefficient, receiver operating characteristic (ROC) curves, and predictive indices such as sensitivity, specificity, and predictive values.

RESULTS

Because of low agreement between the findings of MDD dietitians and nurses using the screening tool, 10 variables were excluded. The resulting 16-variable tool showed a correlation coefficient of 0.70. The ROC cut-off for this simplified tool was 8, meaning that a woman would be considered at nutritional risk if her score was 8 or more. This score optimized sensitivity (85%) with rather low specificity (50%), but retained a positive predictive value of 87% and a negative predictive value of 55%.

CONCLUSION

Revisions of the screening tool to identify nutritionally at-risk pregnant women led to the development of a simplified screening tool with an acceptable measure of nutritional risk in pregnancy. Hence, the use of this tool by any health professional will identify the majority of the nutritionally at-risk pregnant women most likely to benefit from a dietitian's intensive intervention.

Nutrition in multiple gestations

Multiple pregnancies represent a state of magnified nutritional requirements, resulting in a greater nutrient drain on maternal resources and an accelerated depletion of nutritional reserves. Maternal weight gain to 20 weeks and between 20 and 28 weeks has the greatest effect on birthweight in twin and triplet pregnancies, particularly among underweight women. Parity, which most likely represents a higher proportion of body fat, has a positive effect on pregnancy outcome, with an average 7 to 10 days longer gestation for multiparous versus nulliparous women. In addition to being the nutrients most often lacking in a woman's diet, calcium, magnesium, and zinc have been identified as having the most potential for reducing pregnancy complications and improving outcomes.

Specialized prenatal care and maternal and infant outcomes in twin pregnancy

OBJECTIVE

This study was undertaken to evaluate the effect of a prenatal nutrition and education program on twin pregnancy, neonatal, and early childhood outcomes.

STUDY DESIGN

This prospective intervention study of women who participated in a specialized program (Program Pregnancies) versus nonparticipants included twice-monthly visits, dietary prescription of 3000 to 4000 kcal per day, multimineral supplementation, and patient education.

RESULTS

Program Pregnancies were associated with improved pregnancy outcomes (preeclampsia, adjusted odds ratio [AOR] 0.41, 95% CI, 0.23-0.75; preterm premature rupture of membranes, AOR 0.35, 95% CI, 0.20-0.60; delivery <36 weeks, AOR 0.62, 95% CI, 0.43-0.89; low birth weight, AOR 0.42, 95% CI, 0.29-0.61), significantly longer gestations (+7.6 days), higher birth weights (+220 g), lower neonatal morbidity (retinopathy of prematurity, necrotizing enterocolitis, intraventricular hemorrhage, or ventilator support, AOR 0.44, 95% CI, 0.31-0.62), length of stay (-5.3 days), and cost per twin (-14,023 dollars). Through 3 years of age, program children were significantly less likely to be rehospitalized (AOR 0.31, 95% CI, 0.11-0.91) or to be developmentally delayed (AOR 0.65, 95% CI, 0.44-0.96).

CONCLUSION

Program participation was associated with improved outcomes at birth and through age 3 years.

Nutritional assessment and support during pregnancy

This article thoroughly updates the authors' previous review of nutritional assessment and support during pregnancy. After briefly reviewing nutrient metabolism and requirements, the authors discuss the nutritional assessment of the pregnant woman and review the nutritional support principles in hyperemesis gravidarum and other conditions that can compromise the nutritional health of mother or fetus.

Clinical usefulness of maternal body mass index in twin pregnancies

OBJECTIVE

We examined whether maternal body mass index (BMI) during prepregnancy is useful for prediction of maternal preeclampsia in twin pregnancies.

METHODS

We studied 250 dichorionic twin pregnancies and 3196 singleton pregnancies. Maternal BMI was calculated during prepregnancy in both twin and singleton pregnancies. The incidence of maternal preeclampsia was compared among three groups, low-BMI [< -1.5 standard deviations (SD)], normal-BMI, and high-BMI (> + 1.5 SD) groups, in both singleton and twin pregnancies.

RESULTS

In singleton pregnancies, the incidence of maternal preeclampsia in the high-BMI group was significantly higher than that in the normal-BMI group (p < 0.05). The relative risk by high BMI was 8.5 (95% confidence interval: 5.6-12.0). However, in twin pregnancies, no significant differences were observed in these values.

CONCLUSIONS

Body mass index during prepregnancy was not useful for the prediction of preeclampsia in twin pregnancies. Mechanisms other than maternal weight may be associated with the beginning of preeclampsia in twin pregnancies.

Nutrition and multifetal pregnancy

Largely because of assisted reproduction, the rate of multifetal pregnancy is rising rapidly in the United States. Accordingly, dietitians are increasingly being called upon to provide nutrition services for these high-risk pregnancies. This article gives an overview of the incidence of and risks associated with multifetal pregnancy and reviews studies that contribute to our knowledge of nutrition and multifetal pregnancy. Practice guidelines for promoting healthy outcomes based on the best available scientific data are suggested. Guidelines for weight gain for twin and triplet pregnancy, dietary intake, and supplement use are included. Suggested practice guidelines for multifetal pregnancy include a positive rate of weight gain early in pregnancy, the use of prepregnancy weight status to determine total weight gain goals in twin pregnancy, a 50-lb weight gain goal for triplet pregnancy, and higher minimal number of servings of foods from several of the Food Guide Pyramid groups. The need for additional information on the effects of nutritional status on the course and outcome of multifetal pregnancy is critical. Preliminary evidence of the benefits of nutrition services suggests that both the incorporation of dietetics services into care programs and additional research on nutrition and multifetal gestation are warranted.

Growth, development and differentiation: a functional food science approach

Few other aspects of food supply and metabolism are of greater biological importance than the feeding of mothers during pregnancy and lactation, and of their infants and young children. Nutritional factors during early development not only have short-term effects on growth, body composition and body functions but also exert long-term effects on health, disease and mortality risks in adulthood, as well as development of neural functions and behaviour, a phenomenon called 'metabolic programming'. The interaction of nutrients and gene expression may form the basis of many of these programming effects and needs to be investigated in more detail. The relation between availability of food ingredients and cell and tissue differentiation and its possible uses for promoting health and development requires further exploration. The course of pregnancy, childbirth and lactation as well as human milk composition and the short- and long-term outcome of the child are influenced by the intake of foods and particularly micronutrients, e.g. polyunsaturated fatty acids, Fe, Zn and I. Folic acid supplementation from before conception through the first weeks of pregnancy can markedly reduce the occurrence of severe embryonic malformations; other potential benefits of modulating nutrient supply on maternal and child health should be further evaluated. The evaluation of dietary effects on child growth requires epidemiological and field studies as well as evaluation of specific cell and tissue growth. Novel substrates, growth factors and conditionally essential nutrients (e.g. growth factors, amino acids, polyunsaturated fatty acids) may be potentially useful as ingredients in functional foods and need to be assessed carefully. Intestinal growth, maturation, and adaptation as well as long-term function may be influenced by food ingredients such as oligosaccharides, gangliosides, high-molecular-mass glycoproteins, bile salt-activated lipase, pre- and probiotics. There are indications for some beneficial effects of functional foods on the developing immune response, for example induced by antioxidant vitamins, trace elements, fatty acids, arginine, nucleotides, and altered antigen contents in infant foods. Peak bone mass at the end of adolescence can be increased by dietary means, which is expected to be of long-term importance for the prevention of osteoporosis at older ages. Future studies should be directed to the combined effects of Ca and other constituents of growing bone, such as P, Mg and Zn, as well as vitamins D and K, and the trace elements F and B. Pregnancy and the first postnatal months are critical time periods for the growth and development of the human nervous system, processes for which adequate substrate supplies are essential. Early diet seems to have long-term effects on sensory and cognitive abilities as well as behaviour. The potential beneficial effects of a balanced supply of nutrients such as I, Fe, Zn and polyunsaturated fatty acids should be further evaluated. Possible long-term effects of early exposure to tastes and flavours on later food choice preferences may have a major impact on public health and need to be further elucidated. The use of biotechnology and recombinant techniques may offer the opportunity to include various bioactive substances in special dietary products, such as human milk proteins, peptides, growth factors, which may have beneficial physiological effects, particularly in infancy and early childhood.

Ability of the Higgins Nutrition Intervention Program to improve adolescent pregnancy outcome

OBJECTIVES

To determine the extent to which birth weight can be increased and the risk for adverse pregnancy outcome decreased when pregnant adolescents participated in the Higgins Nutrition Intervention Program; and to describe the dietary components of the program, including their variation as a function of diagnosed risk for adverse pregnancy outcome.

DESIGN

Retrospective cohort study involving review of medical charts.

SUBJECTS/SETTING

Developed as an adjunct to routine prenatal care, the Higgins Nutrition Intervention Program consists of an assessment of each pregnant adolescent's risk profile for adverse pregnancy outcomes and an individualized nutritional rehabilitation program based on that profile. The intervention group for this evaluation consisted of 1,203 pregnant adolescents who participated in the Higgins program at the Montreal Diet Dispensary between 1981 and 1991. The nonintervention group consisted of a randomly selected group of 1,203 pregnant adolescents known not to have participated in the program.

OUTCOMES MEASURED

Birth weight; rates of low birth weight, very low birth weight, preterm delivery, fetal growth retardation, perinatal morbidity and mortality; and maternal morbidity.

STATISTICAL ANALYSIS

Means and proportions were used to describe risk profiles and pregnancy outcomes in the two groups. Analysis of covariance and logistic regression were used to compare pregnancy outcomes while controlling for the effect of key confounding variables.

RESULTS

Results from multivariable analyses showed that infants in the intervention group weighed an average of 55 g more (P < .05) than infants in the nonintervention group; their low-birth-weight rate was 39% lower (P < .001) and their very-low-birth-weight rate was 56% lower (P < .01). Individually determined dietary prescriptions for the adolescents in the intervention group recommended increases in daily consumption averaging approximately 900 kcal energy and 52 g protein. The lowest daily increases (approximately 150 kcal energy and 2 g protein) were recommended to the group with no diagnosed risks; the greatest increases (approximately 1,300 kcal energy and 76 g protein) were recommended to the group with multiple risk conditions. Although none of the risk/intervention groups achieved their prescribed increases during intervention, increases in actual intake generally followed the pattern of the prescribed increases; that is, the greater the prescribed increase, the greater the actual increase.

CONCLUSIONS

These results suggest that the Higgins Nutrition Intervention Program, in which nutrition intervention is individualized as a function of diagnosed risk, significantly improves the outcome of adolescent pregnancy.

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.

The risks confronting twins: a national perspective

OBJECTIVES

Our objectives were twofold: (1) to report the relative risks and population-attributable risks of twins compared with singletons for several adverse pregnancy outcomes and (2) to describe the association between having been of low or very low birth weight and death in the neonatal, postneonatal, and infant periods for twins compared with singletons.

STUDY DESIGN

We performed population-based analysis of all live births and infant deaths from 1985 to 1986 birth cohorts, as reported in the U.S. Linked Birth/Infant Death Data Sets.

RESULTS

With singletons as the referent group, twins of all races had relative risk for very low birth weight, low birth weight, and neonatal, postneonatal, and infant death of 9.97, 8.61, 7.06, 2.75, and 5.43, respectively. Although twins make up only 2.09% of live births, the population-attributable risks of twins (the proportion of the population's adverse outcome associated with being a twin) for very low birth weight, low birth weight, and neonatal, postneonatal, and infant death was 15.8%, 13.7%, 11.2%, 3.4%, and 8.4%, respectively.

CONCLUSIONS

These population-based data show that although twins are relatively infrequent they account for a disproportionately large share of adverse pregnancy outcomes. Given the relative ease with which twins can be identified early in the course of pregnancy, development and testing of interventions to postpone preterm delivery in twin pregnancy should become a national public health priority.