Birth weight and prematurity in Tanzania

791 TRANSACTIONS OF THE ROYAL SOCIETY OF TROPICAL MEDICINE AND HYGIENE. Vol. 60. No. 6. 1966.

BIRTH WEIGHT A N D P R E M A T U R I T Y IN TANZANIA BY

M. C. LATHAM* AND

J. R. K. ROBSON~ There are still all too few reports on birth weights of infants in many developing countries, and particularly in Africa. Considerable evidence suggests that the weight of an infant at birth is influenced by the diet of the mother. A record of birth weights may therefore to some extent reflect the nutritional status of women in any area. Data of this kind are then of more importance where there is doubt about the adequacy of diets, than where people have a high standard of living. No conclusive proof exists to incriminate a deficiency of one particular nutrient as a cause of low birth weight, but the assumption is widely made that a generally poor or inadequate diet is involved. Protein is the deficient nutrient most commonly blamed, but vitamins and minerals taken during pregnancy have been claimed to reduce the incidence of prematurity. In Massachusetts a study of 216 pregnancies in which the diet was rated as good, fair or poor, showed that the weight of the infant was significantly lower in those mothers on a poor than those on a good diet (BURKE et al., 1943). In another American study, JEANSand her colleagues (1965) classified the diets of 227 mothers as very poor to excellent. In this study a protein intake of 50 to 60 g. daily was rated poor, and an intake of less than 50 g. as very poor. Defining a premature infant as one with a birth weight of less than 5½ lb., they found that 4% of mothers on an excellent diet, 9.6% of mothers on a poor diet and 13.4% of mothers on a very poor diet gave birth to premature infants. Where weight alone is used as the basis for defining prematurity, any factor related to a reduction in mean birth weight will clearly also be related to an increase in the incidence of prematurity. The lack of statistics of birth weights from developing countries leaves us with inadequate knowledge to judge the significance of ethnic and geographical factors with regard to birth weight. Without more data it is difficult to establish the relative roles of genetics and environment as determinants of birth weight. In a study in South Africa, SALBERand BRADSHAW(1951) showed that mean birth weights of European infants were 7.47 lb., coloured (mixed races) 6.85 lb., Bantu 6.77 lb. and Indians 6.471b. Theincidence of prematurity for these four groups was 4.2%, 9.6 %, 11.5% and 18.3% respectively. They suggest that the differences run parallel with the economic status of each group when this is based on the per caput income of each family. Presumably the principal economic factor which has an effect on birth weight is diet. *Now at Department of Nutrition, Harvard University, 665 Huntington Avenue, Boston, U.S.A. tWHO Regional Office, Alexandria, U.A.R.

792

BIRTH WEIGHT AND PREMATURITY I N TANZANIA

The only previous study of birth weights of infants in Tanzania is that by MCLARErr (1959) which was based on 2471 live births in Mwanza, a town in the north-west of the country on the shores of Lake Victoria. The present paper reports the birth weights of 7528 infants from 3 other areas of Tanzania: Nzega, Moshi and Tanga. The data from Moshi are broken down to illustrate differences in weight with birth rank and also to show the rate of prematurity.

The study The tables presented here are records of birth weights from 3 hospitals in Tanzania. All the infants were weighed on a reliable apparatus within 12 hours of birth. Only singleton live births have been included. Nzega is a small town and the headquarters of a district with a population of 205,299, mainly peasant farmers and their families living near subsistence level. The hospital is well known to provide a good maternity service and it has for many years been used as a training centre for village midwives. By far the majority of mothers attending were from rural areas. Moshi is a regional headquarters and the centre of a district where coffee, grown mainly on individually owned small holdings, is an important cash crop. The population of the district is 364,941. The Chagga people who inhabit the area have the highest per caput income of any tribe in Tanzania, although this is still extremely low by North American or European standards. The town itself is a commercial and marketing centre with a population of 13,726. Women giving birth in the hospital are partly urban wives and partly wives of coffee growers from the slopes of Mount Kilimanjaro, at whose base the town lies. A minority, perhaps 8%, consists of pastoral people from the Masai steppe which stretches southward from Moshi. Tanga is a port city on the Indian Ocean, the second largest town in Tanzania, with a population of 38,053. It is also the centre of the sisal industry and of a district with 199,673 inhabitants. Most women giving birth in Tanga hospital are from the town or from surrounding sisal estates. However, a considerable number are the wives of farmers who grow coconuts, maize, and other crops in the environs of Tanga township, or the wives of fishermen from along the coast. At all three hospitals any woman who comes for antenatal examination is encouraged to have her baby in the hospital. Similarly, any woman in labour who presents herself at the hospital for delivery is admitted. There was no conscious attempt, therefore, to encourage only primiparae or women believed to have a high risk of abnormal delivery, to enter the hospital. However, as in all areas of the country, by far the most deliveries are conducted in the family home, and not in the hospital. Inevitably, the hospitals receive many patients who did not intend to be delivered in the hospital but who have had difficulties during labour at home. Despite this fact the vast majority of the 7528 deliveries in this series were normal births. We are also fully aware that those women who have their babies in the hospital are not a random sample of the population of a district. Inevitably, factors such as faith in western medicine, levels of education, proximity of residence to the hospital, and many cultural factors, have influenced the selection of the infants who form a part of this study. However, as long as the majority of women continue to be delivered in their own homes without any medical attention there will be no way of getting accurate data of a truly representative sample of birth weights. The Statistical Abstract published by the Government of Tanzania states that, based on the sample census of 1957, the birth rate per 1000 in Tanzania is 46. The full census of that year showed that the population

M. C. LATHAMAND J. R. K. ROBSON

793

of Tanzania was 8,759,000 and so the expected number of births in 1958 would be 402,914. The Tanzania Medical Report for 1958 gives the total number of live births in government, mission and native authority hospitals and clinics as 48,178 for that year. This, therefore constitutes 11.96% of total expected births as having occurred in recognized institutions. The number of deliveries in private nursing homes, or conducted by physicians in peoples' homes, is extremely small in Tanzania and probably represents about 0.2 o / o f the total.

Results Table I shows the mean birth weight by sex in each of the 3 areas. As in studies from other parts of the world the mean weight of male infants was greater than of female infants. Similarly, in all three hospitals the total number of males born exceeded TABLE I.

Birth weight by sex in different areas Mean Birth Weight

NZEGA Males

Years of study

No. of infants

1o of Total

1959-1960

1027

51.2

980

48' 8

Females Total Mosm Males Females

2007

O/

lb.

kg.

8.~

6.52

2.96

4

6-25

2.83

6

6,1-

6.39

2.90

, 12~

6"80

3" 08

! 9~

6"61

3"00

6"71

3 '04

I@

100

1960-1963

1143

52.8

i 6

,,

1023

47"2

1 6 i

Total TANGA Males

,,

2166

i00

.....

'

! 6

I

1955-1960

Females

,,

Total

,,

F1753

52.25

6

101

6"66 i 3-02., 6'41

6

2 "91

8--T 6.5

2'97 ,.i

TOTALS Males

3923

Females Total

7528

52.1

10~

6.66

3.02

47"9

6~

6.42

2.91

100

8~

6.55 ,2 - - ~ - 9 7

I the total number of females. There were thus 521 male and 479 female births per 1000 live births in the study. The highest birth weights are recorded at Moshi and the lowest at Nzega. This is consistent with what is known of the relative economic status of the people in the three areas.

794

BIRTH WEIGHT AND PREMATURITY IN TANZANIA

Evidence from many studies shows that birth weight increases with birth rank. There is, however, a difference of opinion concerning up to what birth rank this statement holds true. DONALD(1939) stated that "most investigators agree that there is an increase in weight up to the third child. What happens after that has not been satisfactorily determined owing to the inadequacy of the available numbers but it seems likely that there is but slight change from the fourth onwards." The weights of infants born in Moshi were analysed by birth rank because good records of this were kept there, but were not available at the other two hospitals. Table II shows clearly that in both males and females, mean birth weights for the first-born child are considerably lower than TABLE II.

Birth weight by birth rank and sex, Moshi Males

Birth Rank

Females Mean Wt.

Mean Wt. No.

No. lb.

1st

445

I oz.

i

kg.

lb.

I oz.

394

6

I

3.08

180

6

11{

3.05

[ 3.23

144

6

11½

3"04

104

6

121

3"08

201

6

10~

9½ i 2-99

I

kg.

6½ j 2'90

i

2nd

208

12½

3rd

171

2

q

4th

132

5th +

187

15½

3.16

0½!3.19

L

"3 "03 k

birth weights of subsequent children. In males there is an increase from second to third, and so the mean birth weight of third infants is 8.5 ounces higher than that of first born infants. In the case of female infants in this series there is no significant increase beyond the second born infant. In neither males nor females is there a clear increase beyond the third child. In 1950 a World Health Organization Expert Group on prematurity recognized the need for uniform terminology and definition for prematurity. The Group suggested that for international use "a premature infant be defined as one whose birth weight is 2500 grams (5.5 pounds) or less." This has been widely accepted by those who present statistics relating to rates of prematurity in different parts of the world. However, many obstetricians and paediatricians argue that if weight is used as the only criterion of prematurity, then many infants labelled as premature will not in fact be immature. This is true, and maturity is certainly a useful criterion for the physician as a guide to the treatment of an individual case. However, maturity is difficult to define with exactitude so that it seems better to use the criterion of weight alone for surveys and for national statistics. Moreover, there is evidence that African infants at birth are on the average more mature than either European or American infants of equal weight (GEBER and DEAN, 1957). Using the definition of prematurity suggested by the WHO Group we present in Table III the incidence of prematurity by birth rank for Moshi. The overall total of I0. I% of premature infants is similar to the 11.5% for Bantu mothers in South Africa reported by SALBERet al., (1951), and is lower than the I3.4% for mothers on a very poor diet in America as reported by JEANS et al., (1955).

795

M. C. L A T H A M A N D J. R. K. ROBSON

TABLE III.

Prematurity by sex and birth rank, Moshi

Birth Rank

1st

2nd

3rd

_ 4th _

445

208

171

132

187

1143

No. Premature

48

14

10

10

13

95

% Premature

10"8

I 5th ÷

Total

I

MALES Total Births

FEMALES Total Births

394

No. Premature

63

% Premature

16'0

TOTALS Total Births No. Premature

6-7

~'8

7.61

7.0

8.3

180 f

19 10.6

839

I 388

315

236

111

33

21

18

6'7

% Premature

[ 388

]

2166

36

219

9"3 ]

i

10- 1

The records of birth weights were for different years in each of the three areas (see Table I). I f there is a chronological year-by-year increase in mean birth weights in all areas this would give Moshi an advantage and Tanga the main disadvantage. However, it seems highly doubtful that the very small annual rise in personal incomes and total food production in these areas would have a measurable effect on birth weights over so short a period of time. In 1961 there was a drought in Tanzania which might be expected to offset any advantage accruing to Moshi as this was the median year for collection of birth weights there, whereas 1960 was the last year in which data from Nzega and Tanga has been used.

Summary The importance of birth weight as an index of nutritional status is discussed. The birth weights of 7528 singleton live births from 3 hospitals in Tanzania are reported. The overall mean weight for males was 6 lb. 10½ oz. and for females 6 lb. 6~ oz. Birth weights in hospitals are not necessarily typical of birth weights for the whole country. From the census report and other statistical data we estimate that approximately 12% of births in Tanzania take place in hospitals and other recognized medical institutions. Mean birth weights were lowest at Nzega, highest at Moshi and intermediate at Tanga. They run parallel with the economic status of the people in the three areas. As in studies elsewhere there were more male infants (52.1 °4) than female infants (47.9%) in the series. Birth weight by birth rank was investigated at Moshi. Birth weights of both males and females were significantly higher in second and subsequent births than in first-born

796

BIRTH WEIGHT AND PREMATURITY IN TANZANIA

infants. Birth weights were higher for third-born infants than for second-born infants in males, but not in females. Using the international standard for prematurity we found that 10.1% of births at Moshi were premature. NOTE

In 1964 a union was formed between the Republic of Tanganyika and the Peoples' Republic of Zanzibar. The newly created state was later named the United Republic of Tanzania. In this paper we deal only with that part of Tanzania which up to 1964 was known as Tanganyika. Unless otherwise stated national statistics quoted in this paper are based on the 1957 Tanganyika Census Report. REFERENCES BURKE, B. S., HARDING,V. V. & STUART, H. C. (1943). J. Pediat., 23, 506. , KmKWOOD, S. B. & STUART,H. C. (1943). Amer. J. Obstet. Gynec., 46, 38. DONALD, H. P. (1939). Proc. R. Soc., 59, 91. GEBER, M. & DEAN, R. F. A. (1957). Lancet, 1, 1216. JEANS, P. C., SMITH, M. S. & SLEARNS, G. (1955). ft. Amer. diet. Ass., 31, 576. McL/~tEN, D. S. (1959). Trans. R. Soc. trop. Med. Hyg., 53, 173. SALBER, E. J. & BRADSHAW,E. S. (1951). Brit. ff. Soc. Med., 5, 113. Tanganyika Statistical Abstract (1962). Government Printer, D a r e s Salaam. WORLD HEALTH ORGANIZATION(1950). Tech. Rep. Ser., No. 27. Expert Group on Prematurity, pp. 1-11.