MEHARI GEBREMEDHIN, STEPHEN GUROVSKY AND LARS BONDESTAM
Association of Maternal Age and Parity with Birth Weight, Sex Ratio, Stillbirths and Multiple Births* by MEHARI GEBRE-MEDHIN, M.D., M.P.H.,
and LARS BONDESTAM, BSc. From the Ethiopian Nutrition Institute, Ghandi Memorial Hospital and Central Statistical Office, A ddis A baba.
Body size at birth and factors believed to influence it have been the subject of investigation in several geographic regions, to a lesser extent also in Africa, for a good number of years1. In Ethiopia it is only recently that information on birth weight has become available. In 1962 Hofvander reported, a mean weight of 2.95 kg for 554 newborns delivered at a maternity center in Addis Ababa 2 . Five years later Young published a mean birth weight of 3.12 kg and a low birth weight rate of 9.4% for 500 consecutive live single births. Findings by the same author in another smaller city were 3.05 kg and 13.4% respectively3. In connection with an ongoing study in Addis Ababa on the impact of nutrition on reproduction it seemed desirable to obtain further data on relevant attributes of the newborn. For this purpose, the records of a maternity hospital in Addis Ababa were searched for information on birth weights. The availability of good records on age and parity of mother, the sex of the infant, stillbirths and multiple births made it also possible to look at these variables and their association with the size at birth of the newborn. Material and Method The present study is based on 9,070 deliveries consisting of 8,469 consecutive single live births, 170 twin live births, 405 single stillbriths, 25 twin stillbirths and one triplet obtained from the records of the Ghandi Memorial Hospital for the five year period 1964-1968.
'Reprint requests: Dr. Mehari Gebre-Medhin, Ethiopian Nutrition Institute, P.O. Box 5654, Addis Ababa, Ethiopia. Environmental Child Health, June 1976
In the calculation of mean birth weight for single births, stillbirths and caesarian sections were omitted. Results Tables I and II give the total material by age group and parity of mother. Figure 1 gives the distribution of birth weights of all single live births. NO. OF INFANTS 900F
500
300
2500
3500
4500 i BIRTH WEIGHT, Cm.
Fig. 1 The mean birth weight for single live male and female births were 3,180 gm (SD 500.6 gm) and 3,081 gm (SD 496.7 gm) respectively. The mean total birth weight for single live births was 3,132 gm (SD 500.5 gm). The greatest frequency for males occurs between 3,200 gm and 3,400 gm while that forjemales and for the total falls between 3,000 and 3,200 gm. 99
Downloaded from http://tropej.oxfordjournals.org/ at University of California, Santa Barbara on July 10, 2015
STEPHEN GUROVSKY, M.D.
MEHARI GEBRE-MEDHIN, STEPHEN GUROVSKY AND LARS BONDESTAM
Table I. Birth weights, low birth weight rate, sex ratio, twinning and stillbirths by age group of mother Age Group
No. of Births* Male Female Total
10-14
7
10
Mean Birth Weight, gm* LBW rate Sex ratio* Twinning** M/100F N % Male Female Total %
Stillbirths** N %
2,890
17
3,140
2,720
3,054
2,597
3,005
13.4
803
810
1,613
1,361
1,301
2,662
3,145
3,067
3,107
9,7
104.6
25-29
1,163
1,076
2,239
3,225
3,127
3,178
7.5
108.1
30-34
598
552
1,150
3,289
3,164
3,229
6.1
35-39
333
298
631
3,248
3,136
3,195
40-44
80
62
142
3,271
3,203
3,242
45-49
9
6
15
3,170
3,650
3,360
Total
4,354
4,115
8,469
3,180
3,081
3,132
21
1.2
59
3.5
46
1.6
100
3.6
55
2.3
124
5.1
108.3
42
3.3
67
5.3
7.0
111.7
28
4.0
45
6.4
5.9
129.0
3
8.8
105.8
195
99.1
7
2.2
4.5
405
* For single live births ** For total material
Table II. Births weights, sex ratio, twinning and stillbirths by parity of mother
Twinning*** N %
Single Stillbirths*" N %
101.9
38
1.3
128
4.4
3,116
102.8
25
1.6
70
4.4
3,120
3,174
113.6
15
1.2
52
4.2
3,130
3,221
108.1
29
3.2
49
5.4
20
2.8
28
3.9
No. of Births Male Female
Total
Mean Birth Weight, gm»* Male Female Total
1
1,376
1,350
2,726
3,030
2,960
2,997
2
760
739
1,499
3,170
3,060
3
628
553
1.181
3,230
4
429
397
826
3,310
Parity*
Sex ratio** M/100F
5
347
327
674
3,270
3,170
3,223
106.1
6
241
201
442
3,320
3,190
3,262
119.9
17
3.5
23
4.8 .
7
161
172
333
3,230
3,210
3,220
93.6
10
2.8
17
4.7
8
145
140
285
3,300
3,220
3,261
103.6
20
6.3
11
3.5
9
96
76
172
3,280
3,420
3,341
126.3
16
8.0
10
5.0
10
66
54
120
3,330
3,250
3,295
122.2
2
8
• 11
39
29
68
3,350
3,420
3,376
135.5
1
4
12
66
77
143
3,270
3,130
3,198
85.7
2
5
4,354
4,115
8,469
3,180
3,080
3,132
105.8
195
Total
2.1
405
4.47
* Present birth included ** For single live births '** For total material 100
Environmental Child Health, June 1976
Downloaded from http://tropej.oxfordjournals.org/ at University of California, Santa Barbara on July 10, 2015
15-19 20-24
MEHARI GEBRE-MEDHIN, STEPHEN GUROVSKY A N D LARS BONDESTAM
Taking as standard of low birth weight a value of 2,500 gm and below, the overall low birth weight rate in the series is 8.8%. The mean birth weight for single live births increases with increasing age of mother with a coefficient of correlation of 0.15 which is significant on the 95% level of confidence. Figure 2. This trend holds true also for twin births and stillbirths.
LOW BIRTH WEIGHT RATE
A* 2500 gm tt< 2000 gm
BIRTH WEIGHT, Gm. 3700|• FEMALE
•
o MALE
20-21
30-34
43-44
AGE OF MOTHER, YEARS
Fig. 4 The total male/femal sex ratio at birth for single live births is 105.8. This ratio increases with increasing age of mother with a coefficient of correlation of 0.89 which is highly significant. Figure 5. SEX RATIO 150 |
2700U
• 10-14
20-24
30-31 tO-ti AGE.OF MOTHER,YEARS
Fig. 2 The mean birth weight for single live births also increases with parity with a coefficient of correlation of 0.17 giving a significant correlation on the 95% level of confidence. Figure 3. BIRTH WEIGHT, Gm.
3I00F• FEMALE . 10-14
20-24
30-34
40-44
AGE OF MOTHER, YEARS
3000
11
13 PARITY
Fig. 3 The low birth weight rate is highest for the youngest age group but this rate decreases significantly as the maternal age increases. Figure 4. Environmental Child Health, June 1976
Fig. 5 The increasing male/female ratio remains even when parity is held constant. The material is too small to indicate whether parity of mother alone has any significant influence on the sex ratio. The total stillbirth rate is 45 per thousand. A positive correlation between stillbirth rate and increasing maternal age was observed. However, there does not seem to be any correlation between stillbirth rate and parity of mother in this series. Excluding twin births, the male/female sex ratio for stillbirths is 127.5, a ratio significantly higher than that for single live births. The twinning rate is 1:46 and there is increase in frequency of twinning with the age of mother. Discussion The material analysed in the present survey was obtained from the records of an u/ban maternity center for paying patients. Although no accurate 101
Downloaded from http://tropej.oxfordjournals.org/ at University of California, Santa Barbara on July 10, 2015
10-U
MEHARI GEBRE-MEDHIN, STEPHEN GUROVSKY AND LARS DONDESTAM
102
but is considerably more frequent than the rate of one in 300 births observed in Chinese populations10. Table III. Incidence of twins in selected countries. Belgium United States Negroes Whites Italy Greece Japan China Ethiopia (present survey)
1:56 1:70 1:88
1:86 1:130 1:150 1:300 1:46
'(10)
The stillbirth rate of 45 per thousand is five to ten times higher than figures reported from West European sources. The present survey has provided interesting data in a field often neglected in many developing countries and has also drawn attention to how much useful information may be hidden in hospital records. However, only properly designed prospective studies can expose the various determinants which inflence the viability and growth potentials of the neonate. Summary Maternal and newborn records in an urban maternity hospital are analysed. The mean birth weight is found to be 3.132 gm, low birth weight and stillbirth rates 8.8% and 45 per thousand respectively. Birth weight increases with age and parity of mother. Sex ratio and the twinning rate increases with age of mother while low birth weight rate is highest for the youngest age group. The overall stillbirth rate is very high and increases with the age of mother. Acknowledgements We are indebted to Dr. Yohannes Workineh, Director, Ghandi Memorial Hospital, for encouraging us to conduct this survey, and the Central Statistical Office for allowing us free use of its computer. References 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.
Meredith, V.H. (1970), Human Biol, 42,217. Hofvander, Y. (1963), Eth.Med.J., 1,156. Young, P. N. (1968), Eth. Med. J., 6,15. Fraccaro, M. (i968), Ann. Human Genet., 20,282. Abolins, J. A. (1961), Ada Obst. Gynec. Scand., 40,. 339. Mukherjes, S., and Biswas, S. (1959), J. Indian Med. Assoc, 32,389. Roberts, D. F., and Tanner, R. E. S. (1963), Brit. J. Prev. Soc. Med., 17,209. Barrai, I., Fraccaro, M., Lindsten, J. and Zei, G. (1961), Ann. Human Genet. Jeffreys, M. D. W. (1953), S. Afr. J. Med. Sd., 50,89. Nelson, W. E. (1969), Textbook of-Pediatrics, 9th ed., Saunders, Philadelphia. Environmental Child Health, June 1976
Downloaded from http://tropej.oxfordjournals.org/ at University of California, Santa Barbara on July 10, 2015
information is available on the socio-economic status of the subjects studied, there would be a clear preponderance of a fairly homogenous group of the middle to high income bracket. It is therefore realized that the sample suffers from the limitation of being selected and that unqualified application to the population at large cannot be made. Not all women in Ethiopia know their exact age. A slight amassment of females in the age group 20-40 years has been observed in population surveys in Ethiopia. Some women have undoubtedly come to the hospital for repeated deliveries and have thus been counted several times. The estimates of sex ratio are subject only to error in recording while that of the birth weights may be affected by unreliability in weighing also. The mean birth weight of 3,132 gm in this series is only 17 gm greater than that reported by Young, but 175 gm greater than Hofvander's figure for Addis Ababa newborns. Although problems of comparability are great the hospital born Addis Ababa infant scores higher than the majority of African and Asian newborns for whom birth weight approximates 2,700 gm but is lighter than Caucasian neonates of Western Europe and North America, where body weight means are near 3,400 gm1. The low birth weight rate of 8.8% reported in the series is again similar to Young's figure of 9.4% for Addis Ababa infants. When comparisons are made with international findings, Addis Ababa neonates score better than their Mexican and Chinese counterparts (11%) other African counterparts (13%), and Indian and Burmese counterparts (25%), but are at a disadvantage when evaluated against northwest European newborns (3-6%)'. It would have been of great interest to know the proportion of true prematures and/or small-for-dates infants in the present material. The possible effect of maternal age arid parity on the weight of the offspring has stimulated numerous investigations, the results of which have been inconclusive. Fraccaro 4 and Abolins5 have given good indices of references in this field. The results presented here support in general some earlier findings where there is a tendency for the birth weight to increase systematically with maternal age and parity. However, in contrast to other workers we could not see that birth weight diminishes again with advancing age, thus giving a curvilinear relationship6 7. The overall sex ratio for single live births of 105.8 males per 100 females shows un upward trend with increasing age of mother, even when parity is held constant. It is possible, as has been suggested, that there is a parabolic regression of sex ratio on parity with a maximum male frequency between fifth and sixth birth orders8. The total twinning rate of one in 46 births corresponds well with the figure one in 50.9 births collected from a number of other African samples',
Association of Maternal Age and Parity with Birth Weight, Sex Ratio, Stillbirths and Multiple Births* by MEHARI GEBRE-MEDHIN, M.D., M.P.H.,
and LARS BONDESTAM, BSc. From the Ethiopian Nutrition Institute, Ghandi Memorial Hospital and Central Statistical Office, A ddis A baba.
Body size at birth and factors believed to influence it have been the subject of investigation in several geographic regions, to a lesser extent also in Africa, for a good number of years1. In Ethiopia it is only recently that information on birth weight has become available. In 1962 Hofvander reported, a mean weight of 2.95 kg for 554 newborns delivered at a maternity center in Addis Ababa 2 . Five years later Young published a mean birth weight of 3.12 kg and a low birth weight rate of 9.4% for 500 consecutive live single births. Findings by the same author in another smaller city were 3.05 kg and 13.4% respectively3. In connection with an ongoing study in Addis Ababa on the impact of nutrition on reproduction it seemed desirable to obtain further data on relevant attributes of the newborn. For this purpose, the records of a maternity hospital in Addis Ababa were searched for information on birth weights. The availability of good records on age and parity of mother, the sex of the infant, stillbirths and multiple births made it also possible to look at these variables and their association with the size at birth of the newborn. Material and Method The present study is based on 9,070 deliveries consisting of 8,469 consecutive single live births, 170 twin live births, 405 single stillbriths, 25 twin stillbirths and one triplet obtained from the records of the Ghandi Memorial Hospital for the five year period 1964-1968.
'Reprint requests: Dr. Mehari Gebre-Medhin, Ethiopian Nutrition Institute, P.O. Box 5654, Addis Ababa, Ethiopia. Environmental Child Health, June 1976
In the calculation of mean birth weight for single births, stillbirths and caesarian sections were omitted. Results Tables I and II give the total material by age group and parity of mother. Figure 1 gives the distribution of birth weights of all single live births. NO. OF INFANTS 900F
500
300
2500
3500
4500 i BIRTH WEIGHT, Cm.
Fig. 1 The mean birth weight for single live male and female births were 3,180 gm (SD 500.6 gm) and 3,081 gm (SD 496.7 gm) respectively. The mean total birth weight for single live births was 3,132 gm (SD 500.5 gm). The greatest frequency for males occurs between 3,200 gm and 3,400 gm while that forjemales and for the total falls between 3,000 and 3,200 gm. 99
Downloaded from http://tropej.oxfordjournals.org/ at University of California, Santa Barbara on July 10, 2015
STEPHEN GUROVSKY, M.D.
MEHARI GEBRE-MEDHIN, STEPHEN GUROVSKY AND LARS BONDESTAM
Table I. Birth weights, low birth weight rate, sex ratio, twinning and stillbirths by age group of mother Age Group
No. of Births* Male Female Total
10-14
7
10
Mean Birth Weight, gm* LBW rate Sex ratio* Twinning** M/100F N % Male Female Total %
Stillbirths** N %
2,890
17
3,140
2,720
3,054
2,597
3,005
13.4
803
810
1,613
1,361
1,301
2,662
3,145
3,067
3,107
9,7
104.6
25-29
1,163
1,076
2,239
3,225
3,127
3,178
7.5
108.1
30-34
598
552
1,150
3,289
3,164
3,229
6.1
35-39
333
298
631
3,248
3,136
3,195
40-44
80
62
142
3,271
3,203
3,242
45-49
9
6
15
3,170
3,650
3,360
Total
4,354
4,115
8,469
3,180
3,081
3,132
21
1.2
59
3.5
46
1.6
100
3.6
55
2.3
124
5.1
108.3
42
3.3
67
5.3
7.0
111.7
28
4.0
45
6.4
5.9
129.0
3
8.8
105.8
195
99.1
7
2.2
4.5
405
* For single live births ** For total material
Table II. Births weights, sex ratio, twinning and stillbirths by parity of mother
Twinning*** N %
Single Stillbirths*" N %
101.9
38
1.3
128
4.4
3,116
102.8
25
1.6
70
4.4
3,120
3,174
113.6
15
1.2
52
4.2
3,130
3,221
108.1
29
3.2
49
5.4
20
2.8
28
3.9
No. of Births Male Female
Total
Mean Birth Weight, gm»* Male Female Total
1
1,376
1,350
2,726
3,030
2,960
2,997
2
760
739
1,499
3,170
3,060
3
628
553
1.181
3,230
4
429
397
826
3,310
Parity*
Sex ratio** M/100F
5
347
327
674
3,270
3,170
3,223
106.1
6
241
201
442
3,320
3,190
3,262
119.9
17
3.5
23
4.8 .
7
161
172
333
3,230
3,210
3,220
93.6
10
2.8
17
4.7
8
145
140
285
3,300
3,220
3,261
103.6
20
6.3
11
3.5
9
96
76
172
3,280
3,420
3,341
126.3
16
8.0
10
5.0
10
66
54
120
3,330
3,250
3,295
122.2
2
8
• 11
39
29
68
3,350
3,420
3,376
135.5
1
4
12
66
77
143
3,270
3,130
3,198
85.7
2
5
4,354
4,115
8,469
3,180
3,080
3,132
105.8
195
Total
2.1
405
4.47
* Present birth included ** For single live births '** For total material 100
Environmental Child Health, June 1976
Downloaded from http://tropej.oxfordjournals.org/ at University of California, Santa Barbara on July 10, 2015
15-19 20-24
MEHARI GEBRE-MEDHIN, STEPHEN GUROVSKY A N D LARS BONDESTAM
Taking as standard of low birth weight a value of 2,500 gm and below, the overall low birth weight rate in the series is 8.8%. The mean birth weight for single live births increases with increasing age of mother with a coefficient of correlation of 0.15 which is significant on the 95% level of confidence. Figure 2. This trend holds true also for twin births and stillbirths.
LOW BIRTH WEIGHT RATE
A* 2500 gm tt< 2000 gm
BIRTH WEIGHT, Gm. 3700|• FEMALE
•
o MALE
20-21
30-34
43-44
AGE OF MOTHER, YEARS
Fig. 4 The total male/femal sex ratio at birth for single live births is 105.8. This ratio increases with increasing age of mother with a coefficient of correlation of 0.89 which is highly significant. Figure 5. SEX RATIO 150 |
2700U
• 10-14
20-24
30-31 tO-ti AGE.OF MOTHER,YEARS
Fig. 2 The mean birth weight for single live births also increases with parity with a coefficient of correlation of 0.17 giving a significant correlation on the 95% level of confidence. Figure 3. BIRTH WEIGHT, Gm.
3I00F• FEMALE . 10-14
20-24
30-34
40-44
AGE OF MOTHER, YEARS
3000
11
13 PARITY
Fig. 3 The low birth weight rate is highest for the youngest age group but this rate decreases significantly as the maternal age increases. Figure 4. Environmental Child Health, June 1976
Fig. 5 The increasing male/female ratio remains even when parity is held constant. The material is too small to indicate whether parity of mother alone has any significant influence on the sex ratio. The total stillbirth rate is 45 per thousand. A positive correlation between stillbirth rate and increasing maternal age was observed. However, there does not seem to be any correlation between stillbirth rate and parity of mother in this series. Excluding twin births, the male/female sex ratio for stillbirths is 127.5, a ratio significantly higher than that for single live births. The twinning rate is 1:46 and there is increase in frequency of twinning with the age of mother. Discussion The material analysed in the present survey was obtained from the records of an u/ban maternity center for paying patients. Although no accurate 101
Downloaded from http://tropej.oxfordjournals.org/ at University of California, Santa Barbara on July 10, 2015
10-U
MEHARI GEBRE-MEDHIN, STEPHEN GUROVSKY AND LARS DONDESTAM
102
but is considerably more frequent than the rate of one in 300 births observed in Chinese populations10. Table III. Incidence of twins in selected countries. Belgium United States Negroes Whites Italy Greece Japan China Ethiopia (present survey)
1:56 1:70 1:88
1:86 1:130 1:150 1:300 1:46
'(10)
The stillbirth rate of 45 per thousand is five to ten times higher than figures reported from West European sources. The present survey has provided interesting data in a field often neglected in many developing countries and has also drawn attention to how much useful information may be hidden in hospital records. However, only properly designed prospective studies can expose the various determinants which inflence the viability and growth potentials of the neonate. Summary Maternal and newborn records in an urban maternity hospital are analysed. The mean birth weight is found to be 3.132 gm, low birth weight and stillbirth rates 8.8% and 45 per thousand respectively. Birth weight increases with age and parity of mother. Sex ratio and the twinning rate increases with age of mother while low birth weight rate is highest for the youngest age group. The overall stillbirth rate is very high and increases with the age of mother. Acknowledgements We are indebted to Dr. Yohannes Workineh, Director, Ghandi Memorial Hospital, for encouraging us to conduct this survey, and the Central Statistical Office for allowing us free use of its computer. References 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.
Meredith, V.H. (1970), Human Biol, 42,217. Hofvander, Y. (1963), Eth.Med.J., 1,156. Young, P. N. (1968), Eth. Med. J., 6,15. Fraccaro, M. (i968), Ann. Human Genet., 20,282. Abolins, J. A. (1961), Ada Obst. Gynec. Scand., 40,. 339. Mukherjes, S., and Biswas, S. (1959), J. Indian Med. Assoc, 32,389. Roberts, D. F., and Tanner, R. E. S. (1963), Brit. J. Prev. Soc. Med., 17,209. Barrai, I., Fraccaro, M., Lindsten, J. and Zei, G. (1961), Ann. Human Genet. Jeffreys, M. D. W. (1953), S. Afr. J. Med. Sd., 50,89. Nelson, W. E. (1969), Textbook of-Pediatrics, 9th ed., Saunders, Philadelphia. Environmental Child Health, June 1976
Downloaded from http://tropej.oxfordjournals.org/ at University of California, Santa Barbara on July 10, 2015
information is available on the socio-economic status of the subjects studied, there would be a clear preponderance of a fairly homogenous group of the middle to high income bracket. It is therefore realized that the sample suffers from the limitation of being selected and that unqualified application to the population at large cannot be made. Not all women in Ethiopia know their exact age. A slight amassment of females in the age group 20-40 years has been observed in population surveys in Ethiopia. Some women have undoubtedly come to the hospital for repeated deliveries and have thus been counted several times. The estimates of sex ratio are subject only to error in recording while that of the birth weights may be affected by unreliability in weighing also. The mean birth weight of 3,132 gm in this series is only 17 gm greater than that reported by Young, but 175 gm greater than Hofvander's figure for Addis Ababa newborns. Although problems of comparability are great the hospital born Addis Ababa infant scores higher than the majority of African and Asian newborns for whom birth weight approximates 2,700 gm but is lighter than Caucasian neonates of Western Europe and North America, where body weight means are near 3,400 gm1. The low birth weight rate of 8.8% reported in the series is again similar to Young's figure of 9.4% for Addis Ababa infants. When comparisons are made with international findings, Addis Ababa neonates score better than their Mexican and Chinese counterparts (11%) other African counterparts (13%), and Indian and Burmese counterparts (25%), but are at a disadvantage when evaluated against northwest European newborns (3-6%)'. It would have been of great interest to know the proportion of true prematures and/or small-for-dates infants in the present material. The possible effect of maternal age arid parity on the weight of the offspring has stimulated numerous investigations, the results of which have been inconclusive. Fraccaro 4 and Abolins5 have given good indices of references in this field. The results presented here support in general some earlier findings where there is a tendency for the birth weight to increase systematically with maternal age and parity. However, in contrast to other workers we could not see that birth weight diminishes again with advancing age, thus giving a curvilinear relationship6 7. The overall sex ratio for single live births of 105.8 males per 100 females shows un upward trend with increasing age of mother, even when parity is held constant. It is possible, as has been suggested, that there is a parabolic regression of sex ratio on parity with a maximum male frequency between fifth and sixth birth orders8. The total twinning rate of one in 46 births corresponds well with the figure one in 50.9 births collected from a number of other African samples',
