The relationship between maternal birthweight and gestational age in twins and singletons and those of their offspring in Norway

In order to elucidate whether maternal plurality affects offspring intrauterine growth, the relationship between birthweight and gestational age of twins and singletons and those of their first singleton liveborn children in Norway was studied using data from the Medical Birth Registry. The population-based sample consisted of 49 698 mother–offspring pairs (48 842 with singleton and 856 with twin-mothers). In bivariate analyses, no significant differences in mean birthweight and gestational age of offspring of twin and singleton mothers were found, although the mean birthweight and gestational age of the twin-mothers themselves were significantly lower than those of singletons (819 g and 14 days respectively). In multiple regression analysis, the expected birthweight of offspring was 230.3 g (95% CI: 193.2–267.4 g) higher when the mother was a twin than when the mother was a singleton, when controlling for non-standardised maternal birthweight. When adjusting for relative maternal birthweight ( z -score), the association between maternal plurality and offspring birthweight was not statistically significant. The results suggest that being born as a twin has no substantial consequences on offspring growth in utero and show that mean differences in birthweight between twins and singletons should be standardised when both groups are included in multivariate studies.     

Maternal sociodemographic characteristics as risk factors for preterm birth in twins versus singletons

Many studies have examined associations between sociodemographic variables and preterm birth in singletons. However, almost no research has been published on whether variables such as maternal age, race, ethnicity, level of education and smoking are associated with preterm birth among twins in the same way. The purpose of this study was to examine such associations in twins and singletons comparatively. The study population consisted of all 567796 twins and 23297909 singleton births recorded in the US birth records for 1990-95. Gestational age data were rigorously 'cleaned' to solve the problem of biologically implausible birthweight/gestation combinations in vital records. Preterm birth was defined as gestational age < 35 weeks. Some 25.8% of twins and 3.2% of singletons were preterm by this definition. Crude and adjusted relative risks (RR) were estimated using a modified Mantel-Haenszel procedure. We found several characteristics associated with preterm birth in both twins and singletons, e.g. for twins: race (black adjusted RR = 1.30 compared with white non-Hispanic); marital status (unmarried adjusted RR = 1.15 compared with married); and age (< or = 17 years adjusted RR = 1.39 compared with 20-29 years). A similar analysis of singletons revealed stronger associations between the same characteristics and preterm birth, e.g. the adjusted RR for black race was 2.3. These differences in RRs suggest that sociodemographic characteristics have weaker effects on preterm birth among twins than among singletons. Care must be taken in interpreting differences in preterm birth in twins and singletons, as their gestational age distributions differ so markedly.     

Maternal smoking and adverse birth outcomes among singletons and twins

OBJECTIVES: This study assessed the effects of maternal smoking on birth outcomes among singletons and twins. METHODS: An algorithm was developed to link twins with their siblings in the 1995 Perinatal Mortality Data Set. A random-effects logistic regression model was then used to estimate the association between maternal smoking and several adverse outcomes for a random sample of singletons and for all twins with available maternal smoking information. RESULTS: The algorithm successfully linked sibling pairs for 91% of the twin sample. Maternal smoking was associated with a significantly increased risk of low birthweight, very low birthweight, and gestation of less than 33 weeks for both singletons and twins and with an increased risk of gestation of less than 38 weeks, infant mortality, and placental abruption for singletons. Among smokers, negative impacts on the risk of low birthweight, very low birthweight, and extreme premature delivery were significantly higher for women carrying twins. CONCLUSIONS: Some of the negative effects of smoking on low birthweight and preterm delivery are greater for twins than for singletons. Women carrying twins should be warned that smoking increases their already high risk of serious infant health problems.     

Teen Maternal Age and Very Preterm Birth of Twins

Background: As teen singleton pregnancy is associated with higher risks of adverse birth outcome, and twin pregnancy, regardless of maternal age, may result in poor outcome, teens pregnant with twins may represent a particularly vulnerable group. However, little has been documented regarding teen twin pregnancy outcome. Objective: To characterize the risk of very preterm birth among teens having twins. Design: Cross-sectional analysis of the US 1995–2000 Matched Multiple Birth Data Set. Methods: We calculated the risk of very preterm birth (<33 weeks' gestation) for teen and young adult mothers of twins (≤16 years, 17–18 years, 19–20 years), compared to 21–24 year olds, stratified by race/ethnicity. Adjusted odds ratios were estimated controlling for marital status and entry into prenatal care. Results: Odds of very preterm birth decreased significantly with increasing age. Odds ratios ranged from 2.07 (1.73,2.48) to 1.20 (1.11,1.29) according to maternal age for White teen mothers, from 1.76 (1.48,2.09) to 1.13 (1.03,1.24) for Black teen mothers, and from 2.19 (1.77,2.72) to 1.15 (1.02,1.31) for Hispanic teen mothers. Odds of very preterm birth among teen mothers of twins were about the same as those for teen mothers of singletons. Conclusions: Teens having twins have higher odds of very preterm birth than young adult mothers. However, the association between age and preterm birth was similar among teen mothers having twins as for those having singletons.     

Fetal growth and neonatal mortality in Korea

The fetal growth curve and neonatal mortality rate, based on gestational age and birthweight, are important for identifying groups of high-risk neonates and developing appropriate medical services and health-care programmes. The purpose of this study was to develop a national fetal growth curve for neonates in Korea, and examine the Korean national references for fetal growth and death according to their characteristics. Data of Korean vital statistics linked National Infant Mortality Survey conducted on births in 1999 were used in this study. The total livebirths were 621,764 in 1999, which were grouped into singletons (n = 609,643) and twins (n = 9805) for analysis. Birthweight/gestational age-specific fetal growth curves and neonatal mortality rates were based on 250 g of birthweight and weekly gestational age intervals for each characteristic of the birth. The features of high-risk neonates such as small-for-gestational-age and the limit of viability in Korea were different from those of Western countries. Difference in fetal growth and death was also detected in other characteristics of the fetus (gender and plurality of birth) besides race. The fetal growth curve of males was higher than that of females, and was higher in singleton than in twins. The neonatal mortality rate was higher in males (singleton, 2.6; twin, 23.5) than females (singleton, 2.1; twin, 15.9), and higher in twins (19.8/1000) than in singletons (2.4/1000). However, in neonates with gestational age >29 weeks and birthweight >1000 g, the neonatal mortality rate was lower in twins than in singletons. The limit of viability was gestational age 27 weeks and birthweight 1000 g, which was similar in singletons and twins regardless of gender. To improve the health of neonates in a country, it is imperative to investigate the characteristics of fetal growth and death under the particular circumstances of the country. When risk is defined for neonates account must be taken of differences in race, gender and plurality of birth, as the neonatal mortality rate varies depending on those factors.     

Twin–singleton influence on infant development: a national birth cohort study

Background While studying the development of twins, gestational age and birthweight were suggested as two of the major mediators to be considered. In addition, maternal age, maternal education, parental income and assisted reproductive technologies (ART) also should be considered as moderators. Thus the purpose of this study was to investigate the mediators and moderators of twin and singleton development. Methods Being a national birth cohort study, 21 648 infants were randomly selected and developmental measures were assessed at 6 and 18 months post partum. Children's development at 6 and 18 months were measured using the high reliable Taiwan Birth Cohort Study instrument, which measures children's development in four domains of gross motor, fine motor, language and social development. Additionally, maternal sociodemographics including maternal age, maternal education and parental income; children's characteristics including gender, birthweight, gestational age, single or multiple births, ART or natural conception information were also collected. These data were analysed using a three‐step multiple linear regression analysis and further validated using structural equation modelling. Results Parental sociodemographics, children characteristics and being twin all had effect on children's development. Additionally, ART and twin were mediators between maternal age and children's development. Mothers aged over 40 were more likely to choose ART, thus increases their likelihood of having twins. Additionally, mothers aged over 40 were more likely to give birth to premature or low‐birthweight babies, regardless if they were twin or not. Twins had a higher prevalence of prematurity or low birthweight, which also affected their development in all four domains at 6 and 18 months. Thus prematurity and low birthweight were mediating factors between twin and children's development; with these two mediating factors controlled, there were no difference between twin and singleton development. Conclusions The conceptual construct of structural equation modelling showed these factors interacted and influenced children's development through multiple pathways. Medical intervention may facilitate children's development through prenatal growth and premature care.     

活产双胎低出生体重儿影响因素分析

目的探讨活产双胎低出生体重与相关因素关系。方法将657对活产双胎按出生体重分为体重均低组、单低体重组和体重正常组,配对分析双胎性别、出生次序与低出生体重的关系;分析母亲因素（孕龄、孕周、孕次、产次、血压、血红蛋白等）与出生体重的关系。结果双胎中第2个出生胎儿为低体重者明显多于第1个出生胎儿,女婴显著多于男婴。各体重组母亲孕周、产次比较差异有统计学意义;低体重组母亲孕初舒张压显著低于正常组,血红蛋白值始终高于体重正常组。结论双胎低出生体重与胎儿性别、出生顺序、母亲孕周、产次有关。双胎母亲孕期血压、血红蛋白与胎儿低出生体重间的关系是否属于对双胎妊娠的一种适应,有待进一步探讨。     

The cost of prematurity: a case-control study of twins vs singletons.

OBJECTIVES: This study evaluated the extent to which morbidity and costs at birth were associated with plurality, gestational age, and birth-weight with a sample of twins from a large urban hospital. METHODS: Each twin infant was matched to two singleton infants (control [ctrl]-singletons) for payor status and race, and to one singleton infant (gestation [ga]-singleton) for payor status, race, and gestational age; after exclusion of infants who were transferred, the study population included 111 twins, 242 ctrl-singletons, and 106 ga-singletons. Data were stratified by five gestational categories and compared across study groups. Outcomes included birthweight, neonatal diagnoses, infant length of stay, infant costs per day, and total infant and total birth costs. RESULTS: Total birth costs ranged from $280,146 at 25 to 27 weeks to $9,803 at 39 to 42 weeks, decreasing with advancing gestation to means of $88,891 (twins), $43,041 (ga-singletons), and $9,326 (ctrl-singletons). Twins did not differ from either group of singletons in prematurity-related diagnoses, length of stay, or costs until after 34 weeks' gestation. CONCLUSIONS: In this sample, prematurity, not plurality, was the predominant cost factor at birth. Compared with singletons, twins experienced increased morbidity and associated costs after 38 weeks' gestation.     

The influence of maternal age on very preterm birth of twins: differential effects by parity

For singleton births, parity can modify the effect of maternal age on birth outcomes such as low birthweight and preterm birth; however, it is unknown whether this relationship exists for twin births. As the rate of twin births increases among older women, it is important to understand how parity may influence the relationship between maternal age and adverse birth outcomes. The NCHS Matched Multiple Birth Data Set, which contains all twin births in the USA from 1995 to 1998, was analysed. Parity was grouped into two levels (primiparous--no prior live births, and multiparous--at least one prior live birth), and maternal age was divided into the following groups: 20-24, 25-29, 30-34, 35-39, and 40 years or more. Very preterm birth was defined as births occurring before 33 weeks. Logistic regression was used to obtain odds ratios (OR) to estimate the risk of very preterm birth, and to determine the relationships between parity, maternal age, and very preterm birth. Among primiparae, women 40 years and older had a reduced risk of very preterm birth compared with women of 25-29 years (OR 0.74 [95% CI=0.66, 0.84]). Among multiparae, women 40 years and older had the same risk of very preterm birth compared with women of 25-29 years (OR 1.00 [95% CI=0.90, 1.12]). However, stratification by education revealed that the age gradient was limited to women with >12 years education among primiparae. The effect of maternal age on very preterm birth of twins differs according to parity. To some extent, that effect is further modified by education. Therefore, future analyses of maternal age and twin birth outcomes should account for measures of obstetric history and other factors, which may influence these results.     

Comparison of infant mortality among twins and singletons: United States 1960 and 1983

Infant mortality among US black and white twins and singletons was compared for 1960 and 1983 using the Linked Birth/Infant Death Data Sets from the National Center for Health Statistics. Both twin and singleton infant mortality rates showed impressive declines since 1960 but almost all of the improvement in survival for both twins and singletons was related to increased birth weight-specific survival rather than improved birth weight distribution. One-half of white twins and two-thirds of black twins weighed less than 2,500 g at birth, and 9% of white twin births and 16% of black twin births were in the very low (less than 1,500g) birth weight category. In 1983, twin infant mortality rates were still four to five times that of singletons. However, twins had a survival advantage in the 1,250-3,000 g range, which persisted after adjustment for gestational age. Cause-specific mortality among twins was considerably higher for every major cause of death: twin mortality risks due to newborn respiratory disease, maternal causes, neonatal hemorrhage, and short gestation/low birth weight were six to 15 times that of singletons. The lowest twin-to-singleton mortality ratios observed were for congenital anomalies and sudden infant death syndrome with relative risks twice that of singletons. The data underscore the need to develop effective strategies to decrease infant mortality among twins.     

Gestational age-specific birthweight of twins in vital records

Analysis of singleton preterm birth from vital statistics data is hampered by inaccurate gestational age dating. This is most notably evidenced by the large fraction of implausibly high birthweights for gestational age given in birth records. Using natality statistics for New England, 1977–88, birthweight distributions were plotted for representative preterm gestations. Confounding by improbable birthweights was observed to be considerably less among preterm twin births than among preterm singleton births.     

Obesity subtypes and risk of spontaneous versus medically indicated preterm births in singletons and twins

Using data from the Missouri maternally linked files (1989-1997), the authors examined the association among maternal obesity, obesity subtypes, and spontaneous and medically indicated preterm (<37 weeks) and very preterm (<33 weeks) births in singletons and twins. Adjusted odds ratios were obtained with correction for intracluster correlation. The prevalence of obesity increased by 77% over the study period (p(trend) < 0.001). Obese mothers had a lower risk for spontaneous preterm birth, and this was more pronounced among twins (odds ratio = 0.68, 95% confidence interval: 0.62, 0.75) than singletons (odds ratio = 0.84, 95% confidence interval: 0.82, 0.87). However, this association was present only among obese women who gained less than 0.69 kg/week for singletons and between 0.23 and 0.69 kg/week for twins. By contrast, obese mothers with singleton gestation had about 50% greater odds of medically indicated preterm (odds ratio = 1.46, 95% confidence interval: 1.39, 1.54) and very preterm (odds ratio = 1.49, 95% confidence interval: 1.34, 1.65) births, and the risk increases with ascending severity of obesity (p(trend) < 0.01). For extreme obesity, the risk of medically indicated preterm and very preterm births was almost double that for nonobese women. Similar findings were observed in twins. These data suggest that obesity increases the risk for medically indicated but not spontaneous preterm birth in both singletons and twins.     

Changing patterns of low birthweight and preterm birth in the United States, 1981-98

Low birthweight (LBW) and preterm birth are primary risk factors for infant morbidity and mortality in the US. With increasing multiple births and delayed childbearing, it is important to examine the separate contributions of these characteristics to the increases in LBW and preterm birth rates. US natality records from 1981, 1990 and 1998 were used to calculate LBW (% births <1500, 1500-2499, <2500 g) and preterm (% births <29, 29-32, 33-36, <37 weeks gestation) rates. Data were stratified by maternal race (black or white) and plurality (singleton vs. multiple birth). LBW and preterm rates among singletons were adjusted for maternal age to examine the influence of demographic shifts on LBW trends. From 1981 to 1998, LBW increased 12% among white infants, but remained relatively stable among black infants. During the same time, preterm birth increased 23% among white infants compared with 3% among black infants. For both black and white infants, the increase in LBW and preterm births was greater among multiple births than among singletons. Adjustment for maternal age did not reduce the temporal increase in LBW or preterm birth among singletons. Black infants continue to experience a markedly higher incidence of LBW and preterm birth, but the racial gap in these outcomes has narrowed slightly in recent years as a result of increasing LBW and preterm birth among white births. The differing trends for white and black infants are the consequence of a disparate trend in the incidence and outcome of multiple births coupled with increases in LBW and preterm birth among white singletons. Understanding the differential patterns in birth outcomes among white and black infants is necessary to develop effective interventions designed to decrease racial disparities in pregnancy outcome.     

Infant mortality rates in single, twin and triplet births, and influencing factors in Japan, 1995–98

The infant mortality rate (IMR) was analysed among single, twin and triplet births during the period from 1995 to 1998 using Japanese Vital Statistics. This study also investigated the effects of order of multiple births and of birthweight on the IMR. Proportions of neonatal deaths among total infant deaths were about 1/2 for singletons and 3/4 for both twins and triplets. Thus, to reduce the IMR, intensive care of multiple births is likely to be very important during the first month of life. The IMR was higher in males than females for both singletons and twins, but not in triplets. Relative risks of the IMR in multiples relative to singletons were 5-fold in twins and 12-fold in triplets. The IMR was higher in the second-born (18 per 1000 live births) than the first-born (16) twin and higher in the third-born (51) than the first-born (31) and the second-born (34) triplet. The higher risk in the second-born than the first-born twin may be related to delivery complications. The IMR decreased rapidly as birthweight increased in singletons, twins, and triplets. IMRs for < or =1500 g were 2.4 per 1000 live births in singletons, 5.9 in twins and 6.1 in triplets. The corresponding proportions of infant deaths were 75%, 33% and 10% respectively. The higher relative risks of multiple births are almost entirely the result of the lower birthweight distribution among twins and triplets. To reduce the IMR, birthweight is an important factor in twins, triplets and singletons. The overall early neonatal death rate decreased as gestational age rose in singletons, twins and triplets. For birthweights <1000 g, higher IMRs were related to gestational ages of <28 weeks.     

Assisted reproductive technologies and birth outcomes: overview of recent systematic reviews

Several systematic reviews have been published recently on birth outcomes of infants conceived through assisted reproductive technologies (ART), compared with infants conceived spontaneously. These outcomes include perinatal mortality, preterm birth, low birthweight and birth defects. Methodological limitations of many of the individual studies (including small sample size, potential for bias in ascertainment of outcomes and considering singletons and multiples together) were obviated in these reviews by excluding studies where methods were considered inadequate, by conducting meta-analyses using data from all methodologically sound studies (small and large) and by examining singletons separately. Overall, the reviews indicate few differences between outcomes in ART twins compared with twins conceived spontaneously. However, in singleton ART infants, there are around two-fold increases in risk of perinatal mortality, low birthweight and preterm birth, about a 50% increase in small for gestational age and a 30-35% increase in birth defects, compared with singletons conceived spontaneously. Couples considering ART should be counselled about the increased risk of adverse outcomes. Epidemiologists, in conjunction with clinical and laboratory colleagues, should now focus on large, methodologically sound studies with long-term follow up that seek to identify the reasons for these increased risks and their long-term consequences, whether they are associated with particular technologies and causes of infertility, and how they might be reduced.     

Reference birthweight for multiple births in Japan

PURPOSE: Intrauterine growth curves of twins, that is, birth weights according to gestational age, were calculated from birth certificate data. METHODS: Multiple births were identified by birthplace, ages of the parents, gestational age, and year and month of birth. There were 49,240 twin births in Japan between 1988 and 1991. Of these, 32,232 livebirth-livebirth pairs, 679 livebirth-stillbirth pairs, and 278 stillbirth-livebirth pairs were included in this analysis. There were also 1894 triplet live births from 744 sets of triplets and 206 quadruplet live births analyzed. For all, access was made to the database of birth certificates in the form of magnetic tapes giving birthweights in hundred gram categories. RESULTS: For all gestational ages, median birthweights of males were ca. 0.05 kg-0.1 kg larger than female values. Compared to singleton births in Japan, median birthweights of twins remained ca. 0.15 kg smaller until gestational age of 34 weeks, the difference then increasing to ca. 0.5 kg at 42 weeks of gestation. As for birth order, mean birthweight of the first twin was larger than that of the second and the standard deviation was larger for the second. Birthweights of twins from multiparous mothers were greater than those from primiparous mothers. Among the multiple births, median birthweight for gestational age was found to be greatest in twins, lower in triplets and lowest in quadruplets. In triplets, the 50th centile for boys was 0.08 kg larger than for girls. DISCUSSION: With regard to perinatal growth, the fetus is affected more or less by the limitation of uterine expansion in the late gestational weeks. Reference birthweights for exclusive use for multiple births are different from that for singletons.     

Long-term cardiovascular mortality in women with twin pregnancies by lifetime reproductive history

Background

Women with one lifetime singleton pregnancy have increased risk of cardiovascular disease (CVD) mortality compared with women who continue reproduction particularly if the pregnancy had complications. Women with twins have higher risk of pregnancy complications, but CVD mortality risk in women with twin pregnancies has not been fully described.

Objectives

We estimated risk of long-term CVD mortality in women with naturally conceived twins compared to women with singleton pregnancies, accounting for lifetime number of pregnancies and pregnancy complications.

Methods

Using linked data from the Medical Birth Registry of Norway and the Norwegian Cause of Death Registry, we identified 974,892 women with first pregnancy registered between 1967 and 2013, followed to 2020. Adjusted hazard ratios (aHR) with 95% confidence intervals (CI) for maternal CVD mortality were estimated by Cox regression for various reproductive history (exposure categories): (1) Only one twin pregnancy, (2) Only one singleton pregnancy, (3) Only two singleton pregnancies, (4) A first twin pregnancy and continued reproduction, (5) A first singleton pregnancy and twins in later reproduction and (6) Three singleton pregnancies (the referent group). Exposure categories were also stratified by pregnancy complications (pre-eclampsia, preterm delivery or perinatal loss).

Results

Women with one lifetime pregnancy, twin or singleton, had increased risk of CVD mortality (adjusted hazard [HR] 1.72, 95% confidence interval [CI] 1.21, 2.43 and aHR 1.92, 95% CI 1.78, 2.07, respectively), compared with the referent of three singleton pregnancies. The hazard ratios for CVD mortality among women with one lifetime pregnancy with any complication were 2.36 (95% CI 1.49, 3.71) and 3.56 (95% CI 3.12, 4.06) for twins and singletons, respectively.

Conclusions

Women with only one pregnancy, twin or singleton, had increased long-term CVD mortality, however highest in women with singletons. In addition, twin mothers who continued reproduction had similar CVD mortality compared to women with three singleton pregnancies.     

Social determinants of birthweight and length of gestation in Estonia during the transition to democracy

BACKGROUND: To investigate social variation in birthweight and length of gestation in Estonia in the period of transition to a democracy and market economy. METHODS: All live births resulting from singleton pregnancies reported to the Estonian Medical Birth Registry in 1992-1997 (n = 84, 629) were studied with respect to social variation in birthweight and preterm delivery (<37 weeks gestation). The results were adjusted for maternal age, parity, education, nationality, marital status, smoking in pregnancy, sex of the infant (and gestational age). RESULTS: Between 1992 and 1997, mean birthweight increased from 3,465g to 3,497g (P < 0.001) and the preterm rate fell from 5.8% to 5.1% (P = 0.001). Maternal education, marital status and nationality were all independently related to the mean birthweight and the risk of preterm birth. The mean difference in birthweight between children of mothers with basic and university education was 87 g (95% CI : 74-100). Children born to mothers of non-Estonian compared to Estonian nationality were on average 77 g lighter (95% CI: 70-84). While the effect of nationality and marital status on birthweight was relatively stable during the study period, differences in birth outcome by maternal education became stronger. CONCLUSIONS: The mean birthweight increased and the preterm rate decreased in Estonia as a whole during the transition. However, the improvements were not shared equally by all social groups. An increase in variation in birthweight by maternal education was particularly notable.     

Twinning rates and survival of twins in rural Nepal

BACKGROUND: Twin pregnancies are common but there are few data on rates of twinning or survival of liveborn twin infants in developing countries. METHODS: The rates of multiple births were calculated in a population-based cohort of married women of childbearing age who were enrolled in a randomized community trial to assess the impact of vitamin A or beta-carotene on maternal and infant health and survival. RESULTS: The rate of twinning was 16.1 per 1000 pregnancies (7.4 if only twin pregnancies resulting in two liveborn infants were used). The rate for triplets and quadruplets was 0.19 and 0.06 per 1000 pregnancies. Twinning rates were higher among women of higher parity, but were not associated with maternal age. Twinning rates among twins where at least one was live born (or increased in utero survival) were 30% (95% CI : -1%, 71%) and 44% (95% CI : 9%, 89%) higher among women receiving vitamin A and beta-carotene supplements than placebo, after adjusting for maternal age, gestational age, and parity. The perinatal mortality rate was 8.54 times higher for twins than singletons, 7.32 higher for neonatal mortality, and 5.84 higher for cumulative 24-week mortality. This difference was reduced but not erased by adjusting for gestational age. No difference in survival of liveborn twin infants was seen by supplement group. A higher mortality rate among male twins was largely explained by gestational age. CONCLUSIONS: Multiple births are relatively common occurrences in rural Nepal, and carry a much higher mortality risk for the infants than for singletons. Vitamin A or beta-carotene supplementation appeared to increase the rate of twinning, or improve the survival of twins in utero, but did not increase twin survival after birth.     

Undiagnosed coeliac disease in a father does not influence birthweight and preterm birth

Khashan AS, Kenny LC, McNamee R, Mortensen PB, Pedersen MG, McCarthy FP, Henriksen TB. Undiagnosed coeliac disease in a father does not influence birthweight and preterm birth. Paediatric and Perinatal Epidemiology 2010. There is conflicting evidence regarding the effect of coeliac disease (CD) in the father on birthweight and preterm birth. We investigated the association between paternal CD and birthweight and preterm birth. Medical records of all singleton live‐born children in Denmark between 1 January 1979 and 31 December 2004 were linked to information about parents' diseases. Fathers who were diagnosed with CD were then identified. Fathers with CD were considered treated if they were diagnosed before pregnancy and untreated if they were diagnosed after the date of conception. The outcome measures were: birthweight, small‐for‐gestational age (birthweight<10th centile for gestational age) and preterm birth (<37 weeks). We compared the offspring of men without CD (n = 1 472 352) and offspring of those with CD [untreated (n = 138) and treated (n = 473)]. There was no significant association between untreated CD in the father and birthweight (adjusted mean difference = ?3 g; [95% CI ?46, 40]) or preterm birth (adjusted odds ratio (OR) = 0.86, [95% CI 0.53, 1.37]) (compared with no CD). There was some evidence for an association between treated paternal CD and birthweight (adjusted mean difference = ?81 g; [95% CI ?161, ?3]), but not preterm birth (adjusted OR = 1.76, [95% CI 0.95, 3.26]). Untreated paternal CD was not associated with an increased risk of reduced birthweight, or of preterm birth. There was some evidence that diagnosis and presumed treatment of paternal CD with a gluten‐free diet is associated with reduced birthweight.