1 Department of Epidemiology, School of Public Health, University of Michigan, Ann Arbor Michigan, USA
2 Department of Community Medicine, Medical School, University of Zimbabwe, Harare, Zimbabwe
Correspondence: Dr Shingairai A. Feresu, c/o Dr SD Harlow, University of Michigan, Department of Epidemiology, School of Public Health, 611 Church Street, Ann Arbor, MI 481043028, USA. E-mail: sferesu{at}umich.edu
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Abstract |
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Methods This case-control study examined risk factors for PTD, at Harare Maternity Hospital between March and June 1999.
Results The frequency of PTD among live birth was 16.4%. Prior history of stillbirth or abortion was associated with PTD (adjusted relative risk [ARR] 1.50; 95% CI: 1.06, 2.11). Nutritional factors, including drinking a local non-alcoholic beverage (mahewu) during pregnancy and mother's increasing mid-arm circumference reduced the risk of PTD (ARR = 0.75; 95% CI: 0.60, 0.93 and ARR = 0.95; 95% CI: 0.92, 0.99 per cm of circumference, respectively). Obstetric conditions including eclampsia, anaemia, ante-partum haemorrhage, and placenta praevia were infrequent, but when present, were strongly associated with PTD (ARR = 3.57; 95% CI: 1.67, 7.63; ARR = 4.12; 95% CI: 1.80, 9.43; ARR = 3.05; 95% CI: 1.86, 5.00 and ARR = 3.30; 95% CI: 1.34, 8.14, respectively). Malaria, although less frequent, nonetheless was associated with an increased risk of PTD (ARR = 2.93; 95% CI: 1.70, 5.04). These results suggest that in addition to established obstetric risk factors, nutrition and malarial infection are important. About 43% of the mothers initiated prenatal care after 28 weeks of gestation.
Conclusion Addressing prematurity in this population will require earlier initiation of prenatal care to allow for early detection and management of complications of pregnancy, and improving nutritional status of reproductive age with locally available foods. Further exploration of the potential benefits of mahewu, is warranted.
Accepted 19 January 2004
The pre-term delivery (PTD) of an infant has been and continues to be one of the most serious problems encountered in the care of pregnant women in both developed and developing countries.14 Prematurity accounts for more than 35% of infant mortality world-wide.1 In the US pre-term births account for more than 75% of fetal and neonatal deaths annually in infants without congenital abnormalities.5 Limited data from Zimbabwe suggests that prematurity is a common obstetric problem,4,6 and an important contributor to infant mortality.7 Levels of infant mortality in Zimbabwe (73 per1000 live births) are high compared with South Africa (55 per 1000 live births), mid-income countries such as and Mexico (25 per 1000 live births), and to developed countries including the US, UK, or Sweden (7,6, and 3 per 1000 live births, respectively).7
Although prematurity has been well studied in developed countries,13 data from developing countries is limited.13 This preliminary study is among the first to assess risk factors for prematurity in Zimbabwe. Our aim was to describe the socio-demographic, reproductive, medical, and obstetrical risk factors of pre-term birth among live births over a 3-month period at Harare Maternity Hospital.
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Methods |
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The main outcome of interest was pre-term birth. Since gestational age is difficult to assess if last menstrual period (LMP) is inaccurate or not known, the Ballard method11,12 was administered within 248 hours post delivery to estimate gestational age. Cases were all women who delivered a liveborn singleton infant before 37 completed weeks but after 20 weeks of pregnancy.1,3,5,8,9,13 Controls included all women who delivered a liveborn singleton baby at term.
Each day at 8 a.m. and 2 p.m., a list of women was made from the delivery logbook. Eligible women who agreed to participate and who signed the consent form completed a short interview regarding demographic and lifestyle factors, had their baby examined for maturity, and had their medical records abstracted. Six registered nurses and one woman with 4 years of secondary education were trained to administer the Ballard method of assessing gestational age.11,12 This training involved simulations, piloting of the instruments, and evaluation of intra and inter-observer variation for each item of the Ballard scale. To maintain data quality, weekly spot checks and meetings of the research team were held.
Age of mother was calculated as the number of years from her date of birth to her previous birthday. Marital status (currently married or living as married, never married, separated, divorced or widowed), education of mother and father (less than primary education, having achieved primary education which is 7 years of schooling, secondary education and above), employment status of father and mother (yes/no) and residence (urban/rural) were obtained by interview. Women were asked whether or not they smoked, drank alcohol (chibuku, beer, spirits, or wine), or drank home brew (mahewu) during pregnancy. Mahewu is a local non-alcoholic nutritious beverage made from corn meal, rapoko or sorghum, beans, and sugar. Weight and height were collected from medical records. Body mass index (BMI) was calculated as weight (kg) divided by height (m2). Mid-arm circumference was obtained by measuring the length between shoulder and the elbow with arm bend, with circumference measured at the midpoint.14 Midarm circumference was later categorized, using Jellife standards at cut off of 28.5, and <28.5 denoting undernutrition.15
A mother was considered booked when she had received any prenatal care during her pregnancy, and unbooked otherwise. Once a patient is booked, they receive a booklet containing their complete obstetric record, which they bring to delivery. Patients maintain their booking status irrespective of where they deliver. Parity (0, 12, >2 pregnancies), prior history of abortion, stillbirth, or low birthweight birth defined as delivering an infant 500 g<2500 g at birth (yes/no), and sex of the infant was abstracted from obstetric records. Information on whether the woman had been diagnosed with a chronic medical condition or obstetric complication including diabetes, hypertension, anaemia, pregnancy induced hypertension, eclampsia, cardiovascular disease, ante-partum haemorrhage, and placenta praevia was abstracted from obstetric records. History of infections during pregnancy including diagnosis of and treatment for malaria, urinary tract infection, or syphilis was also obtained.
The population delivering at Harare Central Hospital Maternity Unit is composed of referrals from the 12 Harare Municipal clinics and women who receive prenatal care at the hospital, and women who deliver at the hospital because it is the closest facility. All women with risk factors or obstetric complications are referred to Harare Maternity, often late in pregnancy or during labour. The referral criteria are not strictly adhered to and many patients without any significant complications deliver at Harare Maternity Hospital.16
As the complete population of births over a 3-month period within the hospital was ascertained, we first estimated the incidence of prematurity in live births. Crude relative risks and 95% CI were calculated to assess the association between each potential risk factor and prematurity. Cross-tabulations with each pair of covariates were examined and 2 tests were calculated using EPINFO 2000 to assess associations between independent variables. Generalized linear regression models with a complimentary log-log link function were used to estimate the adjusted relative risks of preterm birth for potential demographic, reproductive, and nutritional risk factors, for medical and obstetric complications, and for infections. We first looked at all the potential risk factors in their subsets including, socio-demographic, anthropometric and nutritional factors; reproductive factors, medical and obstetric complications, and infections. We then built a model, of socio-demographic, anthropometric and nutritional factors, and reproductive factors, using a cut-off of a P-value of 0.10 for variables to be included and also taking into consideration their contribution to the model. In the final model we adjusted for whether the mother was referred to Harare Maternity Hospital or not. We also examined the risk associated with medical and obstetric complications and for infections after adjustment for those relevant covariates including socio-demographic, anthropometric, and nutritional factors, and reproductive factors. In our final models, we excluded mid-arm circumference because it had been introduced late in the study and about 15% of women did not have their mid-arm circumference measured, thus estimates were not stable with its inclusion. Data were analysed using SAS versions 6.12 and 8.1 (SAS Institute, Cary, NC).
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Results |
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Reproductive factors
Although the majority of women (87%) received prenatal care (Table 2), 43% of these women initiated care after 28 weeks of gestation with 10% initiating care after 37 weeks of gestation. As expected, lack of prenatal care was associated with a twofold increase in the risk of pre-term birth. Nearly 86% of women were referred to Harare Maternity Hospital for delivery, with 77% referred from Harare Municipal clinics. Referral was not associated with risk of pre-term birth (data not shown). Parity ranged from 0 to 9 with about half of the women having their first child. About 10.1% reported having a previous history of abortion, 6.4% a stillbirth, and 10.7% a low birthweight (LBW) birth. These women had a slightly increased risk of delivering a preterm birth, but the 95% confidence intervals include one.
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Discussion |
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In agreement with reports from several studies,1,2,8,9,17 nutritional factors remain important determinants of pre-term birth in Zimbabwe. Poor nutrition, as measured through BMI and mid-arm circumference, was adversely associated with pre-term, as elsewhere.8,9,18 Newer studies19 suggest that undernutrition in women at the time of conception results in a precocious fetal cortisol surge and preterm birth. In a population where chronic malnutrition of mothers is not uncommon, the adverse effects on birth outcomes cannot be negated.10 Unlike some other populations,20,21 few mothers in our study drank alcohol during pregnancy. However, about 60% drank mahewu, a nutritious drink that appears to have provided some protection against pre-term birth. Anaemia was associated pre-term birth in this population, a finding also reported by other studies.22,23 Programmes aimed at improving women's health should target improving nutrition, and increased screening for anaemia during pregnancy is needed. Further exploration of the potential benefits of drinking mahewu is also warranted.
As would be expected, in a developing country setting,2427 lack of prenatal care was associated with pre-term birth as women who deliver prematurely often deliver before their intended date of initiating care.28 Only 18.2% of women received prenatal care before 20 weeks gestation. A comparable proportion of unbooked mothers (10.5%) was reported by DHS29 and Feresu and colleagues.10 Effective interventions are likely to necessitate women entering into prenatal programmes by 20 weeks of pregnancy.
Obstetric complications of pregnancy, although relatively infrequent, remain important risk factors for pre-term birth in this and other13,26,30 populations. Unlike in the US where African American women with essential hypertension31,32 have been found to have an increased risk of pre-term birth, neither essential nor pregnancy-induced hypertension were associated with pre-term birth among live births in this population.
Although Harare is an urban setting, malaria appears to remain an important determinant of pre-term birth in this population as has been shown previously33,34 especially in primigravidae.35 In a setting were malaria is not endemic, women are not likely to be screened for parasites, raising a concern about missed cases, particularly among women arriving from rural endemic areas. Urinary tract (UTI) is not routinely screened for, but the few reported cases were associated with pre-term birth as has been shown in other studies.36,37 Screening and management of UTI in pregnancy has been recommended as an important component of the WHO essential programme for prenatal care.38
In Zimbabwe, screening for syphilis during pregnancy is poor.39,40 The relationship between human immunodeficiency virus (HIV) and pre-term birth in Zimbabwe has yet to be evaluated, but HIV infection was poorly reported in obstetric records, and voluntary testing and counselling had not been initiated at the time of this study. Reports on the association between HIV infection and pre-term birth are conflicting and further research on this question is needed.4143 Reproductive tract infections were not consistently screened for, thus under-diagnosis and inadequate treatment for these conditions is likely. Focused studies to evaluate the role of infections and their association with pre-term birth in Zimbabwe are warranted.9,4447
In this preliminary study we focused on live births. Excluding stillbirth and early neonatal deaths underestimates the true burden of pre-term delivery and may have biased our results towards the null. Using the obstetrician/midwife gestational age assessment, 62.8% of stillbirths, 61.5% of very ill babies, and 61.5% of infants who died within the first hour of life at Harare Maternity Hospital are born prematurely.10 If we use this information to estimate the frequency of pre-term deliveries among all births during the study period, 20.2% of all births were pre-term, further emphasizing the need for more studies of the aetiology of PTD in Zimbabwe and the development of appropriate intervention programmes.
Some potential limitations in our study warrant consideration. Focusing solely on births within Harare Maternity Unit raises concerns about potential selection bias, however, the risk of pre-term birth did not differ between those referred and not referred, and referral status was controlled for in the final regression model. Nevertheless, this population may represent a high risk group and estimates may not be generalizable to the rest of Zimbabwe. Rural women may experience more preterm birth given that malnutrition is more frequent in that setting. Exclusion of twin deliveries and stillbirth underestimates the rate of preterm birth slightly at this hospital.10 Lack of data on the number of prenatal care visits limited our ability to assess the adequacy of prenatal care.
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Acknowledgments |
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References |
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2 Kramer MS. Intrauterine growth and gestational duration determinants. Pediatrics 1987;80:50211.[Abstract]
3 Villar J, Belizan JM. The relative contribution of prematurity and fetal growth retardation to low birth weight in developing and developed societies. Am J Obstet Gynecol 1982;143:79398.[ISI][Medline]
4 De Muylder X. Perinatal mortality audit in Zimbabwean district. Paediatr Perinat Epidemiol 1989;3:28493.[Medline]
5 Mercer BM, Lewis R. Pre-term labor and pre-term premature rupture of the membranes: Diagnosis and management. Infect Dis Clin North Am 1997;11:177201.[ISI][Medline]
6 Aiken CG. The causes of perinatal mortality in Bulawayo, Zimbabwe. Centr Afr J Med 1992;38:26381.[ISI][Medline]
7 United Nations Children's Fund. 2000 Child Statistics; Child Mortality, Infant Mortality. http://www.childinfo.org/cmr/revis/db1.htm
8 Witter FR, Keith LG. Textbook of Prematurity. 1st Edn. Boston/Toronto/London: Little Brown and Company, 1993. pp. 35, 2538, 11526.
9 Elder MG, Romero R, Lamont RF. Pre-term Labor. 1st Edn. New York Edinburgh, London, Melbourne, San Francisco, Tokyo: Churchill Livingstone, 1997, pp. 6583, 195205.
10 Feresu SA, Welch K, Gillespie B, Harlow SD. Incidence of and sociodemographic risk factors for stillbirth, pre-term birth and low birthweight in Zimbabwean women. Paediatr Perinat Epidemiol 2003. In Press.
11 Ballard JL, Khoury JC, Wedig K et al. New Ballard Score: expanded to include extremely premature infants. J Pediatr 1991;119:41723.[ISI][Medline]
12 Feresu SA, Gillespie BW, Sowers MF, Johnson TRB, Welch K, Harlow SD. Improving the assessment of gestational age in a Zimbabwean population. Int J Gynecol Obstet 2002;78:718.[CrossRef][ISI][Medline]
13 Lumely J. The epidemiology of pre-term birth. Baillieres Clin Obstet Gynaecol 1993;7:47798.[ISI][Medline]
14 Zerfas AJ. The insertion tape: a new circumference tape for use in nutritional assessment. Am J Clin Nutr 1975;28:78287.[Abstract]
15 Bishop CW, Pitchey SJ. Evaluating upper arm anthropometric measurements. J Am Diet Assoc 1984;84:33035.[ISI][Medline]
16 Tshimanga M, Makunike B, Wellington M. An audit of maternity referrals in labour from primary health care clinics to a central hospital in Harare, Zimbabwe. Cent Afr J Med 1997;43:27983.
17 Kramer MS, Mclean FH, Eason FH et al. Maternal nutrition and spontaneous pre-term birth. Am J Epidemiol 1992;136:57483.[Abstract]
18 Siega-Riz AM, Adair LS, Hobel CJ. Maternal underweight status and inadequate rate of weight gain during the third trimester of pregnancy increases the risk of pre-term delivery. J Nutr 1995;126:14653.[ISI]
19 Bloomfield FH, Oliver MH, Hawkins P et al. A periconceptual nutritional origin for noninfectious preterm birth. Science 2003;300:606.
20 Borges G, Lopez-Carvantes M, Medina-Mora ME et al. Alcohol consumption, low birth weight, and pre-term delivery in the National Addiction Survey (Mexico). Int J Addict 1993;28:35568.[ISI][Medline]
21 Lundsberg LS, Bracken MB, Saftlas AF. Low-to-moderate gestational alcohol use and intrauterine growth retardation, low birth and pre-term delivery. Ann Epidemiol 1997;7:498508.[CrossRef][ISI][Medline]
22 Siega-Riz AM, Adair LS, Hobel CJ. Maternal hematologic changes during pregnancy and the effect of iron status on pre-term delivery in a West Los Angels population. Am J Perinatol 1998;15:51522.[ISI][Medline]
23 Scholl TO, Reilly T. Anemia and pregnancy outcome. J Nutr 2000;130(2S Suppl.):44347S.
24 Fairbrother P, Connolly MD. The quality of perinatal care received by patients in the Greater Harare area during 1973. S Afr Med J 1975;49:15862.[ISI][Medline]
25 Prazuck T, Tall F, Roisin AJ et al. Risk factors for pre-term delivery in Burkina Faso (West Africa). Int J Epidemiol 1993;22:48994.[Abstract]
26 Ferraz EM, Gray RH, Cunha TM. Determinants of pre-term delivery and intrauterine growth retardation in Northeast Brazil. Int J Epidemiol 1990;19:10107.[Abstract]
27 Gomez-Olmedo M, Delgado-Rodriguez M, Bueno-Cavanillas A, Molina-Font JA, Galvez-Vargas R. Prenatal care and prevention of preterm birth: A case-control study in southern Spain. Eur J Epidemiol 1996;12:3744.[CrossRef][ISI][Medline]
28 Galvin J, Woelk GB, Mahomed K, Wagner N, Mudzamari S, Williams MA. Prenatal care utilization and fetal outcomes at Harare maternity Hospital, Zimbabwe. Cent Afr J Med 2000;47:8792.
29 CSO Zimbabwe Demographic and Health Survey 1994. Institute for Resource Dev/Macro System, Inc Columbia Maryland, 1994, p. 109.
30 Fahim HI, Abdel Maeboud KH, Ashour HA et al. A study of the epidemiology of pre-term labor. J Egypt Public Health Assoc 1992;67:34155.[Medline]
31 Samadi AR, Mayberry RM. Maternal hypertension and spontaneous pre-term births among black women. Obstet Gynecol 1998;91:899904.
32 Samadi AR, Mayberry RM, Reed JW. Preeclampsia associated with chronic hypertension among African-American and White women. Ethn Dis 2001;11:192200.[Medline]
33 Steketee RW, Wirima JJ, Hightower AW et al. The effect of malaria and malaria prevention in pregnancy on offspring birthweight, prematurity, and intrauterine growth retardation in rural Malawi. Am Soc Trop Med Hyg 1996;55(Suppl.1):3341.
34 Sullivan AD, Nyirenda T, Cullinan T et al. Malaria infection during pregnancy: intrauterine growth retardation and pre-term delivery in Malawi. J Infect Dis 1999;179:158083.[CrossRef][ISI][Medline]
35 Brabin BJ. An analysis of malaria in pregnancy in Africa. Bull World Health Organ 1983;61:100516.[ISI][Medline]
36 Schieve LA, Handler A, Hershow R et al. Urinary tract infection during pregnancy: its association with maternal morbidity and perinatal outcome. Am J Public Health 1994;84:40510.[Abstract]
37 Mackenzie H, Donnet ML, Howie PW et al. Risk of pre-term delivery in pregnant women with group B streptococcal urinary infections or urinary antibodies to group B streptococcal and E.coli antigens. Br J Obstet Gynaecol 1994;101:10713.[ISI][Medline]
38 World Health Organization Antenatal Care. Report of a Technical Working Group, 1994WHO/FRH/MSM/96.8. 1996.
39 Kambarami RA, Manyame B, Macq J. Syphilis in Murehwa district, Zimbabwe: an old problem that rages on. Cent Afr J Med 1998;44:22932.[Medline]
40 Gwanzura L, Latif A, Bassett M et al. Syphilis serology and HIV infection in Harare, Zimbabwe. Sex Transm Infect 1999;75:42630.[Abstract]
41 Brocklehurst P, French R. The association between maternal HIV infection and perinatal outcome: a systematic review of literature and meta-analysis. Br J Obstet Gynaecol 1998;105:83648.[ISI][Medline]
42 Coley JL, Msamanga GI, Fawazi MC et al. The association between maternal HIV-1 infection and pregnancy outcomes in Dar es Salaam, Tanzania. BJOG: an International Journal of Obstetrics & Gynaecology 2001;108:112533.[CrossRef]
43 Ellis J, Graves W, Lindsay MK. Human immunodeficiency virus infection is a risk factor for adverse perinatal outcome. Am J Obstet Gynecol 2002:186: 90306.[CrossRef][ISI][Medline]
44 Romero R, Mazor M, Wu KK et al. Infection in the pathogenisis of pre-term labor. Semin Perinatol 1988;12:26279.[ISI][Medline]
45 Gibbs RS, Romero R, Hillier SL et al. Current development: A review of premature birth and subclinical infection. Am J Obstet Gynecol 1992;166:151528.[ISI][Medline]
46 Martius J, Roos T. The role of urogenital tract infections in the etiology of pre-term birth: a review. Arch Gynecol Obstet 1996;285:119.[CrossRef]
47 Andrews WW, Hauth JC, Goldenberg RL. Infection and pre-term birth. Am J Perinatol 2000;17:35765.[CrossRef][ISI][Medline]