| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
ORIGINAL RESEARCH |
From the Perinatal Epidemiological Research Unit, Department of Obstetrics and Gynaecology, and Department of Paediatrics, Aarhus University Hospital, Aarhus, Denmark; Department of Epidemiology and Social Medicine, University of Aarhus, Aarhus, Denmark; and Department of Obstetrics and Gynecology, King Faisal Specialist Hospital and Research Center, Riyadh, Kingdom of Saudi Arabia.
Address reprint requests to: Janne Ørskou, Perinatal Epidemiological Research Unit, Department of Obstetrics and Gynaecology, Skejby Sygehus, Aarhus University Hospital, 8200 Aarhus N, Denmark; E-mail: joerskou{at}hotmail.com.
 |
ABSTRACT |
|---|
TOP
 ABSTRACT MATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
METHODS: Our analyses included 24,093 pregnancies of nondiabetic women with information on potential risk factors for high birth weight: maternal prepregnancy weight, height, age, parity, smoking habits, alcohol and caffeine intake, marital status, educational level, gestational age, and infant gender. Information was obtained from questionnaires completed during pregnancy and birth registration forms at the Department of Obstetrics and Gynaecology, Aarhus University Hospital, Aarhus, Denmark, from 1990 to 1999.
RESULTS: We found a statistically significantly increased risk of giving birth to infants weighing more than 4000 g for women with high prepregnancy weight and height, parity greater than 2, gestational age greater than 42 weeks, and male infant gender and for nonsmokers. Women with a low caffeine intake or 10 or more years of education were also at statistically significantly higher risk. The variation found in birth weight over the past 10-year period was explained by changes in maternal prepregnancy weight, height, smoking habits, educational level, and caffeine intake over the same period.
CONCLUSION: Risk factors associated with a higher proportion of high birth weight infants may be clinically significant and have an impact on public health. High birth weight increases the risk of adverse outcomes of delivery as well as the risk of childhood morbidity.
During the past generation mean birth weight has increased, and simultaneously an increasing proportion of infants are born with a birth weight of more than 4000 g.1–3 In a previous study in Denmark we found that the proportion of infants born with a birth weight above 4000 g increased from 16.7% to 20.0% during the 1990s.1
When birth weight exceeds 4000 g, the risks of perinatal mortality, brachial palsy, meconium aspiration, clavicular fracture, shoulder dystocia, and low Apgar score increase.4–7 This makes identification of risk factors for delivery of large infants important.
Several researchers have demonstrated that the accuracy of estimation of birth weight in normal and high weight fetuses in the third trimester is poor, whether the method is ultrasound or clinical estimation.8–10 Thus, the need to find additional ways to prevent or identify large fetuses grows. Identification of potential risk factors for birth of large infants may be helpful, and at the public health level identification of risk factors may guide potential prevention of perinatal pathology in mother and child.
Many researchers have evaluated the association between birth weight and maternal, obstetric, or lifestyle factors that might potentially affect birth weight, but there is some divergence in the findings.11–20
Our aim was to identify factors associated with an increased risk of giving birth to infants weighing more than 4000 g and to study whether changes in these factors could explain the increasing proportion of high birth weight infants over the last decade.
|
MATERIALS AND METHODS |
|---|
|
TOP
ABSTRACTMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
At approximately 16 weeks’ gestation the women were asked to complete two self-administered questionnaires. Information from the first questionnaire was used to generate the women’s medical record and provided information on age, height, prepregnancy weight, parity, chronic diseases, smoking habits, and alcohol consumption. The second questionnaire was used for research purposes and provided information on marital status, education, and intake of caffeinated beverages.
Information concerning birth weight, gestational age, and infant gender was obtained from birth registration forms, completed by the attending midwife immediately after delivery. The birth registration forms were manually checked and compared with the medical record by a research midwife before data entry. For validation purposes data on birth weight were entered twice into the database.
All singleton, nondiabetic pregnant women with a known date of delivery and for whom the first questionnaire was returned were included in the study (n = 36,424).
We excluded pregnancies with no information on birth weight (n = 146) or gestational age (n = 13). The final population available for analyses included 36,265 pregnancies. For a total of 24,093 pregnancies information on all variables mentioned below was available.
The potential risk factors for high birth weight were maternal weight before pregnancy, height, age, parity, smoking habits, alcohol consumption and caffeine intake, marital status, educational level, gestational age, and infant gender.
We categorized smoking habits into nonsmoking groups and smoking one to four, five to nine, ten to 14, and 15 or more cigarettes a day. Alcohol consumption was categorized into the groups less than one drink, one to two, three to four, and five or more drinks per week. Caffeine intake was calculated on the basis of daily average consumption of coffee (one cup = 104 mg), tea (one cup = 46 mg), cocoa (one cup = 13 mg), and cola (one bottle = 45 mg)21 and was then categorized as less than 200 mg a day, 200–399 mg a day, and 400 or more mg a day. Other potential risk factors were categorized as seen in Table 1
.
|
Gestational age was calculated from early (before 21 weeks’ gestation) ultrasonographically determined biparietal diameter in 23,519 pregnancies (64.9%). In 11,610 pregnancies (32.0%) without an early ultrasound scan, we calculated gestational age from the last menstrual period, and for 1136 pregnancies (3.1%) with no early ultrasound scan and no date of the last menstrual period, we used the gestational age as reported on the birth registration form.
The unadjusted and adjusted associations between the potential risk factors and delivery of a high birth weight infant are presented as odds ratios with 95% confidence intervals.
Results from the unadjusted analyses included all of the 36,265 pregnancies. Missing values for each potential risk factor were analyzed as a separate category. Performing the unadjusted analyses on the smaller sample of pregnancies with information for all variables gave no substantial or statistically significant differences in results versus the unadjusted results found for all pregnancies. We restricted the adjusted analyses to pregnancies with no missing information in the questionnaires (n = 24,093). The potential risk factors listed in Table 1
were all considered in a multivariable logistic regression analysis. They were entered in the logistic regression model as a number of dummy variables equal to the number of categories minus one, and the mutually adjusted odds ratios are presented.
Changes in maternal characteristics from 1990 to 1999 are shown in Table 2. Significance was tested by t test for data of normal distribution; for data without normal distribution, significance was tested by the Mann–Whitney U test.
|
All analyses were performed using SPSS 9.0 statistical software (SPSS Inc., Chicago, IL).
|
RESULTS |
|---|
|
TOP
ABSTRACTMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
Table 1 shows the distribution of maternal characteristics and lifestyle factors for all pregnancies in the period 1990–1999.
In the unadjusted analyses, high maternal prepregnancy weight and height, age 30 or more years, and high parity were associated with a higher risk of having a high birth weight infant (Table 1). Women with a prepregnancy weight exceeding 80 kg, a height above 190 cm, or two or more previous childbirths had nearly twice the risk of having a high birth weight infant than women of normal weight or normal height or nulliparous women, respectively (Table 1). Compared with birth at term, a gestational age of more than 42 weeks was associated with more than twice the risk of delivering a high birth weight infant.
Smoking, alcohol intake of five or more drinks per week, caffeine intake of 400 or more mg per day, living alone, 10 or less years of education, and female child gender were associated with a reduced risk of giving birth to an infant weighing more than 4000 g (Table 1). Entering maternal body mass index into the model instead of height and weight did not change the result.
During the 10-year period of the study, pregnant women increased their weight, height, age, and years of education, on average. They became less likely to smoke cigarettes and reduced their alcohol and coffee consumption. Parity, marital status, and gestational age remained essentially unchanged (Table 2).
After mutual adjustment for the variables in a multivariable logistic regression analysis, there was a statistically significantly increased risk of giving birth to an infant weighing more than 4000 g for women with high maternal prepregnancy weight and height, high parity, high gestational age, and male infant gender and for nonsmokers (Table 1). Women with caffeine intake of 200 or less mg per day or 10 or more years of education were also at statistically significantly increased risk, whereas maternal age, alcohol consumption, and marital status were not associated with the risk of having a high birth weight infant.
To investigate if the potential risk factors could explain the increased proportion of infants above 4000 g found in the 10-year period, we looked upon the changes in these factors over the same period. Maternal prepregnancy weight, height, smoking habits, educational level, and caffeine intake did change over the decade and can thus be considered possible explanations for the increase found in birth weight over time (Table 2).
Accordingly, inclusion of these factors in the multivariable logistic regression model showed that the increase in birth weight over the years was explained.
|
DISCUSSION |
|---|
|
TOP
ABSTRACTMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
Many researchers have consistently found variables such as maternal weight before pregnancy, total weight gain during pregnancy, gestational age, and smoking during pregnancy to be associated with birth weight, whereas findings related to the mother’s and father’s own birth weight, parity, maternal age, and height were less consistent.* It has also previously been suggested that a high intake of caffeine and alcohol may influence average birth weight.14,28
Compared with previous studies, ours was of considerable size, leaving sufficient statistical power to consider a large number of potential risk factors. Thus, we were able to study the mutual influence of a variety of potential risk factors, as opposed to the few variables taken into account in the majority of previous studies.
We tested whether cutoff for high birth weight at 4500 g instead of 4000 g would change the results, but the tendency in our risk estimates remained the same, and the same risk factors showed significance but with less precision on the estimates because of the lesser data set.
A substantial number of previous studies on birth weight obtained the information on risk factors postpartum, with recall bias as a potential explanation of their findings. Our information was collected before the women knew about the pregnancy outcome, and differential recall is therefore avoided.
Most previous studies on birth weight have focused on average or low birth weight. However, changes in average birth weight may not reflect shifts in the entire birth weight distribution. Furthermore, significant changes in the proportion of low and high birth weight infants may not be disclosed by studying average birth weight. Also, although risk factors leading to an increase in average birth weight of 50 or even some 100 g may not seem clinically meaningful, risk factors associated with a higher proportion of high birth weight infants may be clinically significant and have an impact on public health.
High birth weight may have different consequences for the individual infant. Some high birth weight infants may not have reached their genetic growth potential, whereas, for the same birth weight, others may have reached—for those individual infants—an unnaturally high birth weight. However, as birth weight increases, the likelihood that the limit for the genetic growth potential has been reached also increases. More researchers have shown that high birth weight increases the risk of adverse outcomes of delivery as well as the risk of childhood and adult morbidity.29–31
The risk of giving birth to high weight infants may be minimized by intervention before or during pregnancy addressed to high-risk women. Among the risk factors identified in our study, high maternal prepregnancy weight seems to be the most obvious to try to modify, whereas other factors are less obvious to manipulate, meaning that high weight women who are planning pregnancy should attempt to reduce their weight before it.
Previous studies have shown that even moderate physical activity during pregnancy reduced the risk of having a large for gestational age infant.32,33 Unfortunately, we had no information on exercise during pregnancy, but future research should encounter this aspect.
|
Footnotes |
|---|
* References 5, 11–13, 15, 16, 18–20, 22–27. 
Received September 17, 2002. Received in revised form February 17, 2003. Accepted February 27, 2003.
|
REFERENCES |
|---|
|
TOP
ABSTRACTMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
2. Johar R, Rayburn W, Weir D, Eggert L. Birth weights in term infants. A 50-year perspective. J Reprod Med 1988; 33:813–6.[Medline]
3. Meeuwisse G, Olausson PO. Increased birth weights in the Nordic countries. A growing proportion of neonates weigh more than four kilos. Lakartidningen 1998;95:5488–92.[Medline]
4. Rydhstrom H, Ingemarsson I. The extremely large fetus—antenatal identification, risks, and proposed management. Acta Obstet Gynecol Scand 1989;68:59–63.[Medline]
5. Spellacy WN, Miller S, Winegar A, Peterson PQ. Macrosomia—maternal characteristics and infant complications. Obstet Gynecol 1985;66:158–61.[Medline]
6. Boyd ME, Usher RH, McLean FH. Fetal macrosomia: Prediction, risks, proposed management. Obstet Gynecol 1983;61:715–22.
7. Golditch IM, Kirkman K. The large fetus. Management and outcome. Obstet Gynecol 1978;52:26–30.
8. Niswander KR, Capraro VJ, Van Coevering RJ. Estimation of birth weight by quantified external uterine measurements. Obstet Gynecol 1970;36:294–8.
9. Watson WJ, Soisson AP, Harlass FE. Estimated weight of the term fetus. Accuracy of ultrasound vs. clinical examination. J Reprod Med 1988;33:369–71.[Medline]
10. Benacerraf BR, Gelman R, Frigoletto FD Jr. Sonographically estimated fetal weights: Accuracy and limitation. Am J Obstet Gynecol 1988;159:1118–21.[Medline]
11. Eriksson M, Cnattingius S, Svardsudd K, Tibblin G. Factors associated with birth weight in Sweden: The study of men born in 1913. J Epidemiol Community Health 1997; 51:19–23.[Abstract]
12. Klebanoff MA, Mednick BR, Schulsinger C, Secher NJ, Shiono PH. Father’s effect on infant birth weight. Am J Obstet Gynecol 1998;178:1022–6.[Medline]
13. Klebanoff MA, Mills JL, Berendes HW. Mother’s birth weight as a predictor of macrosomia. Am J Obstet Gynecol 1985;153:253–7.[Medline]
14. Vlajinac HD, Petrovic RR, Marinkovic JM, Sipetic SB, Adanja BJ. Effect of caffeine intake during pregnancy on birth weight. Am J Epidemiol 1997;145:335–8.
15. Wikstrom I, Axelsson O, Bergstrom R. Maternal factors associated with high birth weight. Acta Obstet Gynecol Scand 1991;70:55–61.[Medline]
16. Mitchell MC, Lerner E. Factors that influence the outcome of pregnancy in middle-class women. J Am Diet Assoc 1987;87:731–5.[Medline]
17. Winikoff B, Debrovner CH. Anthropometric determinants of birth weight. Obstet Gynecol 1981;58:678–84.
18. Abrams BF, Laros RKJ. Prepregnancy weight, weight gain, and birth weight. Am J Obstet Gynecol 1986;154:503–9.[Medline]
19. Rossner S, Ohlin A. Maternal body weight and relation to birth weight. Acta Obstet Gynecol Scand 1990;69:475–8.[Medline]
20. Johnson JW, Longmate JA, Frentzen B. Excessive maternal weight and pregnancy outcome. Am J Obstet Gynecol 1992;167:353–70.[Medline]
21. Bunker ML, Mc Williams M. Caffeine content of common beverages. J Am Diet Assoc 1979;74:28–32.[Medline]
22. Langhoff-Roos J, Lindmark G, Gustavson KH, Gebre-Medhin M, Meirik O. Relative effect of parental birth weight on infant birth weight at term. Clin Genet 1987;32: 240–8.[Medline]
23. Lieberman E, Gremy I, Lang JM, Cohen AP. Low birth-weight at term and the timing of fetal exposure to maternal smoking. Am J Public Health 1994;84:1127–31.
24. Davies DP, Abernethy M. Cigarette smoking in pregnancy: Associations with maternal weight gain and fetal growth. Lancet 1976;1:385–7.[Medline]
25. Dougherty CR, Jones AD. The determinants of birth weight. Am J Obstet Gynecol 1982;144:190–200.[Medline]
26. Sexton M, Hebel JR. A clinical trial of change in maternal smoking and its effect on birth weight. JAMA 1984;251: 911–5.[Abstract]
27. Cnattingius S, Axelsson O, Eklund G, Lindmark G. Smoking, maternal age, and fetal growth. Obstet Gynecol 1985; 66:449–52.
28. Wright JT, Waterson EJ, Barrison IG, Toplis PJ, Lewis IG, Gordon MG, et al. Alcohol consumption, pregnancy, and low birthweight. Lancet 1983;1:663–5.[Medline]
29. Daling JR, Starzyk P, Olshan AF, Weiss NS. Birth weight and the incidence of childhood cancer. J Natl Cancer Inst 1984;72:1039–41.
30. Cnattingius S, Zack M, Ekbom A, Gunnarskog J, Linet M, Adami HO. Prenatal and neonatal risk factors for childhood myeloid leukemia. Cancer Epidemiol Biomarkers Prev 1995;4:441–5.[Abstract]
31. Stene LC, Magnus P, Lie RT, Sovik O, Joner G. Birth weight and childhood onset type 1 diabetes: Population based cohort study. BMJ 2001;322:889–92.
32. Alderman BW, Zhao H, Holt VL, Watts DH, Beresford SA. Maternal physical activity in pregnancy and infant size for gestational age. Ann Epidemiol 1998;8:513–9.[Medline]
33. Campbell MK, Mottola MF. Recreational exercise and occupational activity during pregnancy and birth weight: A case-control study. Am J Obstet Gynecol 2001;184: 403–8.[Medline]
This article has been cited by other articles:
|
|
 |
|
  E Koch, M Bogado, F Araya, T Romero, C Diaz, L Manriquez, M Paredes, C Roman, A Taylor, and A Kirschbaum Impact of parity on anthropometric measures of obesity controlling by multiple confounders: a cross-sectional study in Chilean women J. Epidemiol. Community Health, May 1, 2008; 62(5): 461 - 470. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 L. Rode, H. K. Hegaard, H. Kjaergaard, L. F. Moller, A. Tabor, and B. Ottesen Association Between Maternal Weight Gain and Birth Weight Obstet. Gynecol., June 1, 2007; 109(6): 1309 - 1315. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
N. E. Stotland, Y. W. Cheng, L. M. Hopkins, and A. B. Caughey Gestational Weight Gain and Adverse Neonatal Outcome Among Term Infants. Obstet. Gynecol., September 1, 2006; 108(3): 635 - 643. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T Clausen, T K Burski, N Oyen, K Godang, J Bollerslev, and T Henriksen Maternal anthropometric and metabolic factors in the first half of pregnancy and risk of neonatal macrosomia in term pregnancies. A prospective study Eur. J. Endocrinol., December 1, 2005; 153(6): 887 - 894. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. J. Rosenberg, S. Garbers, W. Chavkin, and M. A. Chiasson Prepregnancy Weight and Adverse Perinatal Outcomes in an Ethnically Diverse Population Obstet. Gynecol., November 1, 2003; 102(5): 1022 - 1027. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
