CC BY
37
ПЕДИАТРИЯ
*
twin BIRTH ORDER, BIRTHwEIGHT AND BIRTHwEIGHT DISCORDANCE: ANY Relationship?
A.N. Onyiriuka - Nigeria, Benin City, University of Benin Teaching Hospital, Department of Child Health.
УДК 618.492:618.291-07 Оригинальная статья
соотношение между последовательностью рождения близнецов и несоответствием их массы тела
А.Н. Онириука - Нигерия, Бенин-Сити, Университет при клинике в Бенине, кафедра детского здоровья.
Дата поступления - 10.10. 2010 г. Дата принятия в печать - 14.12.2010 г.
Onyiriuka A.N. Twin birth order, birthweight and birthweight discordance: any relationship // Saratov Journal of Medical Scientific Research. 2010. Vol. 6, № 4. P. 807-811.
Background: It is widely believed that in twin pairs, at birth, the first-born weigh more than the second-born but this concept has been challenged. Objective: To assess the truthfulness of this common concept that first-born twins are usually heavier than their second-born siblings at birth. Methods: In a series of 104 sets of live-born twins, the birth weights of first-born twins were compared with those of their second-born siblings, after controlling for gender. Their intra-pair birthweight differences were determined and twin pairs whose birthweight difference was 15% or more were designated as discordant. Results: Twin I was heavier than Twin II in 61.5% of cases while Twin II was heavier than Twin I in 28.9% of cases. Twins I and II had equal birthweights in 9.6% of cases. Comparing the mean birthweight of the first-born-male twin with that of second-born- male twin, it was 2515+427g (95% Confidence Interval, CI=2402-2628) versus 2432 +435g (95% CI=2321-2543) p>0.05. The mean birthweight of first-born-female twin was 2326+445g (95% CI=2214-2439) while that of the second-born-female twin was 2325+501g (95% CI=2197-2453) p>0.05. When the birthweight difference exceeded 750g, the probability that Twin I will be heavier than Twin II was 83.3% (5 of 6). Conclusion: Although the first-born twin was more often heavier than their second-born siblings, either could weigh more or less at birth. The larger the birthweight difference between growth-discordant twin pair, the greater the probability that the heavier twin would be delivered first.
Key words: Twins, Birth order, Relative birthweights, Birthweight discordance.
Онириука А.Н. Соотношение между последовательностью рождения близнецов и несоответствием их массы тела // Саратовский научно-медицинский журнал. 2010. Т. 6, № 4. С. 807-811.
Широко известно, что при рождении близнецов младенец, появившийся первым на свет, имеет массу выше, чем второй. Однако это утверждение может быть опровергнуто. Данная статья является доказательством взаимосвязи массы тела и порядка рождения близнецов. Исследование включало 104 случая рождения близнецов с разницей в весе 15% и более. Учитывался пол новорожденного. В 61,5% случаев первый младенец обладал большей массой тела, в 28,9% случаев - второй. Близнецы с одинаковым весом составили 9,6%. Средняя масса тела у первых младенцев мужского пола 2515+427 г, у вторых младенцев мужского пола 2432+435 г. Средняя масса тела у новорожденных женского пола, появившихся первыми на свет, составила 2326+445 г, у новорожденных, появившихся вторыми на свет, 2325 + 501 г. Если несоответствие в весе новорожденных близнецов превышало 750 г, вероятность того, что масса тела первого младенца будет больше второго, составляла 83,3% (5 из шести случаев). Таким образом, первый младенец чаще всего обладает большей массой тела, чем второй, не принимая во внимание их весовое несоответствие при рождении. Чем больше разница в весе у близнецов, тем выше вероятность рождения первым младенца с большей массой тела.
Ключевые слова: близнецы, последовательность рождения, относительный вес при рождении, несоответствие массы тела.
introduction. The concept that first-born twins are usually heavier than their second-born siblings at birth is widely believed. Various studies aimed at assessing the truthfulness of this concept have produced conflicting conclusions, both in developed and developing countries. For instance, in Nigeria, Ilesanmi et al [1] reported that among 212 twin pairs the first-born twin was heavier in 42.6% of cases while the second-born twin was heavier in 42.2% of cases. In another Nigerian study, Swende and Hwande [2] reported that the first-born was heavier in 48.7% of cases while the second-born twin was heavier in 43.6% of cases. Similarly, a study from Germany reported that mean birthweight was higher in first-born twins than in their second-born siblings [3]. Another German study involving 177 live-born twin pairs reported that the first twin was on the average heavier by 54g [4].
In contrast, a Nigerian study reported that second-born twins had weight advantage more often than their
Corresponding author: Alphonsus N. Onyiriuka.
E-mail: alpndiony@yahoo.com
corresponding first-born siblings [5]. Friedman et al [6] in USA, reported that second-born twins were heavier than first-born twins in 55% of cases. Similar finding has been reported in another study in a developed country [7]. Oyawoye and Fakeye [8] reported that in low birthweight twin gestations, the second-born twin was heavier than the first-born twin in 57.3% of cases. However, in these studies, the investigators did not control for gender which is well known to influence birthweight both in singletons [9, 10] and in twins [11].
Although the phenomenon of birthweight discordance is common in twin gestations, various studies on birthweight discordance were silent on which one of the discordant pair is likely to be delivered first [12-14]. This is an issue of practical clinical importance because it has been shown that twin infants with birthweight-discordance [13-15] and second-born twins [16-18] are both at increased risk of adverse perinatal outcome. Some investigators have reported that the threshold for clinically significant birthweight discordance is 15% or more [12].
808
педиатрия
The present study sought to assess the truthfulness of the concept that first-born twins are usually heavier than their second-born siblings at birth.
Methods. This cross-sectional study involved all twin babies delivered at St Philomena Catholic Hospital (SPCH) between 1st January, 2000 and 31st December, 2003.
All twin babies delivered at SPCH during the 4-year study period were weighed naked by a trained midwife, within the first 30 minutes after birth, using a mechanical Waymaster weighing scale calibrated to the nearest 50 grammes. The scale was periodically standardized with known weights for reliability and daily for zero error to ensure accuracy. The order of delivery of the twins and their sexes were carefully recorded. Excluded from the study were twin babies delivered by Caesarean section and twin pairs where one or both were still-born. Only live-born pairs of twins were studied. In this study, Twin I refers to the first-born while Twin II refers to the second-born twin. The data on birth weight were analysed according to birth order to determine their relative distribution collectively. Also the difference in birth weights (weight of Twin I minus weight of Twin II) were examined to determine the magnitude and direction of such differences.
In this study, a twin pair was designated discordant if one of the pair was smaller by 15% or more. The level of discordance was calculated for each pair as a percentage of the birthweight of the heavier twin:
Level of discordance (%) = Birthweight difference*100 Birthweight of heavier twin
Intra-pair birthweight percentage differences was stratified into the following categories: 15-24.9, 2534.9 and 35% or more, which roughly corresponded to moderate, severe and extreme discordance. A percentage difference in birthweight of 14.9% and below was regarded as mild level of discordance. A twin pair was called discordant-first when the smaller was firstborn and discordant-second when the smaller was second-born. One-minute Apgar Score of 3 and below was designated as severe birth asphyxia.
The Student's t test was used in ascertaining the level of significance of two differences, which was set at p<0.05.
Results. During the 4-year study period, a total of 104 (2.3%) sets of live-born twins were delivered (not by caesarean section) in an obstetric population of 4,544. Overall male-to-female ratio was 0.98:1.
Ratio of male Twin I to female Twin I was 1:1. The same ratio was obtained for male Twin II and female twin II. As shown in Table 1, Twin I was more frequently heavier than Twin II (61.5% versus 28.9%). Overall, the mean birthweight of male Twin I was greater than that of male Twin II by an average difference of 83g (Table 2) p>0.05. Table 3 compared mean birthweight of female Twin I with that of female Twin II. Overall, there was no statistically significant difference in birthweight distribution. As shown in Tables 2 and 3, there was a trend towards higher mean birthweight of twin babies over the years of study, even after controlling for gender. As shown in Table 4, when both sexes were combined, Twin I was heavier by an average of 34g. The mean birthweight of male Twin I was greater than that of female Twin I by 189g (t statistic=0.862; p>0.05). Similarly, the mean birthweight of male Twin II was greater than that of female Twin II by 107g (t statistic=0.444; p>0.05) (Tables 2, 3).
Among the 30 birthweight discordant twins pairs, the mean birthweight of Twin I was 1973±423g (95% confidence interval CI=1753-2193) while the mean birthweight of Twin II was 2312±480g (95% CI=2090-2534)±2.123 p>0.05. Of the 30 birthweight discordant twin pairs, 14(46.7%) were discordant-first and 16 (53.3%) were discordant-second. Table 5 showed twin birth order in relation to levels of birthweight discordance. Each of the three sets of twins in which both foetuses were stillborn exhibited severe levels of birthweight discordance greater than 25% (specifically, their levels of birthweight discordance were 26.7, 36.6 and 60% in first, second and third twin pairs respectively ). As shown in Table 6, Twin I is more likely to be heavier than Twin II when the birthweight difference between the pair is between 500-750 g. when the birthweight difference exceeds 750 g, the probability that Twin I will be heavier than Twin II is 83.3% (5 of 6). The risk of breech delivery and 1-minute Apgar Score of 3 and below were each 1.8 times higher in Twin II than in Twin I (Table 7).
Discussion. Data from the present study showed that the widely held view that first-born twins were usually heavier than their second-born siblings was incorrect. The differences in mean birthweights between the first-born and the second-born twins were small and statistically not significant, making it less likely to be important clinically. However, this does not imply that significant clinical problem could never occur.
In the present study, excluding twins of equal birthweight, first-born twins had weight advantage more often than their second-born siblings at birth. Other previous studies [1, 2, 19] in Nigeria have reported similar trend but with differing percentages. In contrast, some other investigators [5-7] have reported that second-born twins were more often heavier than their first-born siblings. There is no readily available explanation for this finding. It is possible that it is an integral part of the discordant phenomenon. This view is reinforced by the finding in this study that the probability that Twin I will be heavier that Twin II was 83.3% when the birthweight difference between the twin pair was greater than 750 g.
Overall, comparing the mean birthweight of male twins I and II, the former was heavier than the latter by an average of 83 g. However, this difference was not statistically significant. On the other hand, similar comparison between female twins I and II, showed that both had similar birthweight distribution with a difference of only one gramme. Comparison with previous studies [1-3, 5, 6] was not possible because the authors did not control for gender in their analysis of relative birthweights of Twins I and II. In both singletons [10] and twins [11], it has consistently been shown that males were significantly heavier than females at birth. It is possible that failure to control for gender in relative birthweight data analysis may have partly contributed to the conflicting reports in literature concerning relative birthweights in twins. Consequently, it is suggested that future studies aimed at verifying the truthfulness of the concept that first-born twins were usually heavier than second-born twins should take gender into consideration in their data analysis.
Conclusion. The results of the present study indicated that second-born twins demonstrated a higher tendency toward low birth weight, breech presentation and low Apgar Score compared to their first-born counterparts. Similar finding has been reported by other investigators [3, 8, 17, 20]. These three factors above may account for the higher perinatal death rate in second-born twins compared to their first-born counterparts.
Table 1
Relative birthweights of Twins I and II
Table 2
Comparison of mean birthweight of male Twin I and male Twin II.
Year of Mean Birthweight in grammes
Study Twin I Twin II *Dlfference t-statistic P value
2000 2175±402 2297±411 -122 0.832 >0.05
2GG1 2430±417 2348±420 82 0.493 >0.05
2GG2 2638±503 2422±427 216 1.309 >0.05
2003 2925±518 2657±513 268 1.272 >0.05
total 2515±427 2432±435 S3 1.028 >0.05
* Difference = mean birthweight Twin I minus mean birthweight of Twin II.
Table 3
Comparison of mean birthweight of female Twin I and female Twin II
Year of Mean Birthweight in grammes
Study Twin I Twin II *Dlfference t-statistic P value
2000 2154±479 2157±481 -3 0.019 >0.05
2GG1 2150±493 2175±487 -25 0.123 >0.05
2GG2 2388±487 2642±553 -254 1.243 >0.05
2GG3 2609±523 2GG5±517 204 1.003 >0.05
total 2326±445 2325±5G1 1 0.011 >0.05
Comparison of mean birthweight of Twin i and Twin ii (both sexes combined) Table 4
Year of Mean Birthweight in grammes
Study Twin I Twin II Difference t-statistic P value
2000 2162±382 2225±403 -63 0.671 >0.05
2GG1 2318±445 2251±479 67 0.512 >0.05
2GG2 1878±332 1874±359 4 0.011 >0.05
2GG3 2731±6G3 2550±586 181 1.159 >0.05
total 2416±467 2380±472 36 0.276 >0.05
Table 5
Birth order in 30 birthweight-discordant twin pairs
Relative birthweights of Twins I and II Levels of birthweigt discordane in percentage
15-24.9 (moderate) No (%) 25-34.9 (severe) No (%) 35 or more (Extreme) No (%) Total No (%)
Twin I greater than Twin II 11 (36.7) 4 (13.3) 1 (3.3) 16 (53.3)
Twin I less than Twin II 8 (26.7) 4 (13.3) 2 (6.7) 14 (46.7)
Table 6
Distribution of birthweights differences according to relative birth weight in 30 birthweight-discordant twin pairs
Relative birthweights of Twins I and II Birthweight difference (g) in twin pairs
<500g 500-750g >750g
No (%) No (%) No (%)
Twin I greater than Twin II 2(6.6) 11 (36.7) 5 (16.7)
Twin I less than Twin II 6 (20.0) 5 (16.7) 1 (3.3)
Twins I and II combined 8 (26.6) 16 (53.4) 6 (20.0)
Table 7
Twin birth order and perinatal outcome
A. Low birth weight n=119 No of babies Percentage
Twin I less than 2500g 55 46.2
Twin II less than 2500g 64 53.8
B. Twin birth order and presentation
Twin I: n=104
-73 Cephalic 76 73.1
-74 Breech 25 24.0
-75 Transverse Э 2.9
Twin II: n=104
-76 Cephalic 59 55.7
-77 Breech 44 42.3
-78 Transverse 1 0.1
C. One-minute Apgar Score=or<3 n=14
Twin I 5 35.7
Twin II 9 64.3
D. Perinatal death n=8
Twin I 2 25.0
Twin II 6 75.0
One limitation of the present study was its failure to assess the effects of monozygosity versus dizygosity on this phenomenon. This represents an area of future study. Despite this limitation, the present study focused on assessment of the truthfulness of the concept that the first-born twin was usually heavier than its second-born sibling and our data have shown that irrespective of birth order any one of the twin pairs could weigh more or less at birth.
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УДК 612.648 (470.324-201) Оригинальная статья
физическое развитие новорожденных воронежской области за последние 25 ЛЕТ
О.Н. Оводкова - Воронежская ГМА им. Н.Н. Бурденко, аспирант кафедры неонатологии; Л.И. Ипполитова - Воронежская ГМА им. Н.Н. Бурденко, доцент кафедры неонатологии, кандидат медицинских наук.
PHYSICAL DEVELOPMENT OF NEWBORNS OF VORONEZH REGION OVER THE LAST 25 YEARS
O.N. Ovodkova - Voronezh State Medical Academy n.a. N.N.Burdenko, Department of Neonatology, Post-graduate; L.I. Ippoli-tova - Voronezh State Medical Academy n.a. N.N. Burdenko, Department of Neonatology, Assistant Professor, Candidate of Medical Science.
Дата поступления - 24.08.2010 г. Дата принятия в печать - 14.12.2010 г.
Оводкова О.Н., Ипполитова Л.И. Физическое развитие новорожденных Воронежской области за последние 25 лет // Саратовский научно-медицинский журнал. 2010. Т. 6, № 4. С. 811-814.
Изменения в физических размерах и внешнем виде ребенка считаются видимыми проявлениями комплекса клинических, биохимических, неврологических и физиологических изменений, происходящих в детстве. Целью исследования стал сравнительный анализ показателей физического развития у 11 437 новорожденных г. Воронежа и Воронежской области за последние 25 лет. Изучены четыре основных антропометрических признака у новорожденных - масса тела, длина тела, окружность головы, окружность груди; проведен анализ данных акушерско-гинекологического анамнеза их матерей. Установлено различие в показателях, характеризующих физическое развитие младенцев, рожденных в г. Воронеже и в Воронежской области. Определена взаимосвязь между физическим развитием новорожденных и антропометрическими показателями рожениц. Выявлена сезонная тенденция в изменении показателей окружности головы.
Ключевые слова: физическое развитие, новорожденные, масса тела, длина тела, окружность головы, окружность грудной клетки.
Ovodkova O.N., Ippolitova L.I. Physical development of newborns of Voronezh region over the last 25 years // Saratov Journal of Medical Scientific Research. 2010. Vol. 6. № 4. P. 811-814.
Changes in physical sizes and appearance of the child are manifestations of clinical, biochemical, neurologic and physiological changes which take place in childhood. The aim of the research is a comparative analysis of indicators of physical development of 11 437 newborns from Voronezh and Voronezh region over the last 25 years. Four basic anthropometrical signs in newborns - body mass, body length, head circumference, breast circumference - have been studied. Obstetric-gynecologic analysis of mothers anamneses have been carried. It was established that indicators of physical development differ in Voronezh and Voronezh region. Also the interrelation between physical development of newborns and anthropometrical indicators of women has been determined. The seasonal tendency of indicators of head circumference has been revealed.
Key words: physical development, newborns, body mass, body length, head circumference, breast circumference.
Введение. Развитие организма до рождения улучшение здоровья плода, новорожденного путем
представляет собой сложный и длительный внутри- снижения их заболеваемости [1].
утробный процесс. В течение девяти месяцев плод Изменения в физических размерах и внешнем
испытывает самые быстрые и самые рискованные виде ребенка считаются видимыми пр°явлениями
трансформации влияющие на его будущее Его мас- комплекса клинических, невр°л°ги-
са увеличивается более чем в 40 000 раз, количество ческих и физиологических изменений, пр°исх°дящих
клеток достигает нескольких миллиардов, и они диф- в детстве [2]- Любые отклонения антропометриче-
ских показателей от нормы при рождении ребенка
ференцируются в большое число высокоспециализированных органов. Все это является предметом
могут стать одной из причин снижения иммунологической резистентности, повышая вероятность воз-изучения перинатальной цель которой - никновения болезни на первом году жизни вдвое, а
Ответственный автор - Оводкова Ольга Николаевна. вероятность смерти - в четыре раза [3]. Осложнен-
394036, г. Воронеж, ул. Студенческая, 10.
Тел : з_92о-46о-47-00 ное течение беременности приводит к изменению
E-mail: doc.pon@mail.ru физического развития у новорожденных и оказывает
