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Malaria Research and Training Center, Department of Epidemiology and Parasitic Diseases, Faculty of Medicine and Dentistry, University of Bamako, Bamako, Mali
Malaria Branch, Division of Parasitic Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia
Background.
Malaria during pregnancy contributes to maternal anemia and low birth weight. In East Africa, several studies have demonstrated that intermittent preventive treatment (IPT) with sulfadoxine-pyrimethamine (SP) is more efficacious than weekly chloroquine (CQ) chemoprophylaxis in preventing these adverse consequences. To our knowledge, there are no published trials evaluating IPT in West Africa.
Methods.
We undertook a randomized controlled trial of weekly CQ chemoprophylaxis, 2-dose IPT with CQ, and 2-dose IPT with SP; 1163 women were enrolled.
Results.
In multivariate analyses, when compared with weekly CQ, IPT/SP was associated with a reduction in third-trimester anemia (adjusted odds ratio , 0.49; P < .001), placental parasitemia (AOR, 0.69; P = .04), and low birth weight (<2500 g) (AOR, 0.69; P = .04). The prevalence of placental infection remained unexpectedly high, even in the IPT/SP group (24.5%), possibly because of the intensity of seasonal transmission. There were no significant differences in stillbirths, spontaneous abortions, or neonatal deaths among the 3 groups.
Conclusions.
In Mali, IPT with SP appears more efficacious than weekly chloroquine chemoprophylaxis in preventing malaria during pregnancy. These data support World Health Organization recommendations to administer at least 2 doses of IPT during pregnancy. In intensely seasonal transmission settings in Mali, >2 doses may be required to prevent placental reinfection prior to delivery.
An estimated 25 million pregnancies occur annually in malarious areas of sub-Saharan Africa [1]. In areas of stable malaria transmission, pregnant women with Plasmodium falciparum are often asymptomatic, but the parasite sequesters in the placenta; these infections are associated with maternal anemia, premature delivery, and low birth weight (LBW; <2500 g) [16]. Primigravid and secundigravid women have the highest prevalence of placental parasitemia and malaria-associated LBW [711]. LBW is the greatest risk factor for neonatal mortality and is a major contributor to infant mortality [12]
In the past, antimalarial chemoprophylaxis (generally with chloroquine [CQ]) has been recommended for pregnant women in malaria-endemic areas. However, the usefulness of such an approach has been limited in many settings because of poor adherence by pregnant women to a weekly or more frequent drug regimen and increasing levels of P. falciparum resistance to CQ [1315]. Intermittent preventive treatment (IPT) with 2 doses of sulfadoxine-pyrimethamine (SP) given during the second and the third trimesters of gestation represents an alternative prevention strategy that has been shown, in several studies in East Africa, to be efficacious in reducing rates of placental malaria [4, 16], LBW [17], and severe maternal anemia during pregnancy [18]. To our knowledge, there are no published trials evaluating IPT with CQ in areas with CQ-sensitive P. falciparum.
In Mali, levels of CQ resistance are lower than in East Africa; consequently, CQ has remained the first-line antimalarial drug for treatment, and weekly CQ chemoprophylaxis has been the standard of care for the prevention of malaria during pregnancy. However, correct utilization of CQ chemoprophylaxis by pregnant women is thought to be limited in Mali, as it is in neighboring Burkina Faso [15]. If IPT with either CQ or SP were shown to be efficacious in reducing adverse effects of malaria during pregnancy, it would be an attractive alternative to weekly CQ, since it is easier to deliver. Therefore, we evaluated the efficacy and safety of 2 IPT regimens (2 treatment courses of CQ and 2 treatment doses of SP), compared with the standard of care (CQ treatment followed by weekly CQ chemoprophylaxis), in preventing the adverse effects of malaria in primigravid and secundigravid women.
STUDY SUBJECTS AND METHODS
Study site.
The study was conducted from March 1998 to March 2001 in the community health centers (CSCOM) of Bandiagara and Koro, 2 medium-sized semirural towns with 11,000 inhabitants each. Koro is located 735 km northeast of Bamako, in the Mopti region of Mali, near the border with Burkina Faso; Bandiagara is 60 km west of Koro. Persons living in both towns are of relatively similar socioeconomic status and are mainly from the Dogon ethnic group. Malaria transmission is highest during the rainy season (JuneOctober). In vivo CQ resistance measured in children <5 years old is moderate (85% adequate clinical response) (K. Kayentao, personal communication). SP retains very high efficacy, with 100% adequate clinical response (K. Kayentao, personal communication). The seroprevalence of HIV in this region is 1.4% (K. Kayentao, personal communication).
Study subjects.
Women were enrolled in the antenatal care (ANC) clinics in Koro and Bandiagara. All attendees in their first or second pregnancy and between 16 and 26 weeks of gestation were eligible, if they provided written informed consent after receiving explanation of the study protocol in their local language (Dogon). Women who reported living >15 km from the CSCOM, who were severely ill, or who reported prior adverse drug reaction (ADR) to CQ, sulfa-containing medications, or any other antimalarial medication were excluded from the study. Human-subjects committees at the Faculty of Medicine, Pharmacy and Dentistry of Mali and at the Centers for Disease Control and Prevention approved the study protocol.
A questionnaire was administered to enrolled women, to collect information on sociodemographic factors, malaria symptoms, and antimalarial drug use during the current pregnancy. Height, weight, and temperature were measured. Gestational age was estimated by measuring uterine fundal height. A finger-stick blood sample was drawn for hemoglobin testing and a malaria thick blood film. Urine was collected for qualitative analysis of 4-aminoquinolones and sulfa compounds. Through block randomization, women were assigned to receive 1 of 3 regimens: (1) weekly CQ chemoprophylaxis (weekly CQ): a treatment dose (25 mg/kg CQ base over 3 days) at first ANC visit, followed by weekly prophylaxis (300 mg CQ base per week); (2) 2-dose IPT with CQ (IPT/CQ): treatment doses of 25 mg/kg of CQ base over 3 days, at enrollment and again early in the third trimester (2830 weeks gestation); and (3) 2-dose IPT with SP (IPT/SP): treatment doses (1500 mg of sulfadoxine and 75 mg of pyrimethamine), with the same timing as IPT/CQ. All participating women were asked not to self-administer antimalarials other than the study medication but to return for evaluation of any malaria symptoms that were experienced between scheduled monthly visits. All study drug administration was observed. Women received ferrous sulfate (120 mg) and folic acid (0.8 mg) daily for the duration of pregnancy, as recommended by the Ministry of Health.
Follow-up.
At follow-up visits (2 weeks after enrollment and then monthly), women were questioned about malaria symptoms and potential adverse effects of antimalarial drug treatment, and a temperature and blood film were taken if a woman reported symptoms of malaria. Women in the CQ groups who developed malaria received a treatment dose of CQ (25 mg/kg base) over 3 days. Women in the IPT/SP group who developed malaria were treated with SP. Women in either CQ arm for whom treatment with CQ for symptomatic malaria failed were subsequently treated with SP. CQ or SP treatment was not given at intervals <1 month apart, and SP was not given in the last month of pregnancy. Hemoglobin was remeasured between 30 and 34 weeks gestation. Women with other illnesses or severe anemia detected at any time were referred to the hospital staff for medical care. All participants were encouraged to give birth in the hospital.
Delivery.
Capillary blood was collected for a thick blood film prior to delivery. At delivery, women received standard clinical care through the attending nurse midwives or physicians. After delivery of the neonate and placenta, blood was collected from the maternal side of the placenta and the umbilical cord, for thick blood films. Neonates were weighed on a digital scale within 24 h of birth. Gestational age was estimated using a Ballard examination [19].
Neonatal and infant follow-up.
Between 3 and 7 days of age and again at age 6 weeks, all neonates/infants (including those who were delivered at home) were assessed for general health status and the presence of scleral or cutaneous icterus. Any neonate/infant showing signs of illness was referred to the hospital or clinic, and the study team assisted with transportation if needed. The primary caretaker was interviewed in all cases of neonatal/infant deaths, to try to determine the suspected cause of death by use of a verbal autopsy form.
Laboratory investigations.
Thick blood films were stained with Giemsa and examined for malaria parasites. Parasites and leukocytes were counted. Parasite densities were estimated using an assumed leukocyte count of 7500 leukocytes/L of blood. A film was determined to be negative if no parasites were identified in the course of examining fields in which 300 total leukocytes had been counted. Hemoglobin was measured using a HemoCue hemoglobin detection system (HemoCue AB). A modified Saker-Solomons test [20] and the method of Mount et al. [21] were used for the measurement of 4-aminoquinolones and sulfa compounds, respectively, in urine.
Definitions.
Parasitemia (in peripheral, placental, or cord blood) was defined as the presence of asexual-stage parasites in thick blood films. LBW was defined as birth weight <2500 g. Neonates were classified as premature if they were <37 weeks gestation (evaluated by Ballard examination) at birth. Women with hemoglobin levels <11 g/dL and <8 g/dL were considered to have anemia and moderate-to-severe anemia, respectively.
Statistical analysis.
Data entry, validation, and cleaning were performed with Epi Info (version 6.04b; CDC); primary analysis was performed on an intention-to-treat basis. Results from all women who delivered singleton newborns were included in birth outcome and neonatal analyses. Differences between means of normally distributed continuous variables were compared using 1-way analysis of variance, distribution of nonnormal continuous variables were compared using the Kruskal-Wallis test, and differences between proportions were tested using the 2 or Fisher's exact test (for tables with an expected value, in any cell, of <5). In univariate analyses comparing outcome measures for the 3 treatment groups, initial evaluation of significance was based on the results of a 2 × 3 2 test. For any measures with P < .05, further comparisons were made: IPT/SP versus weekly CQ, IPT/SP versus IPT/CQ, IPT/CQ versus weekly CQ, and IPT/SP versus IPT/CQ combined with weekly CQ. To account for multiple comparisons, the results of these tests were considered to be statistically significant only when P < .0125 (.05 divided by 4). To evaluate the relationship between treatment group and primary outcome measures of malaria during pregnancy (anemia, placental malaria, LBW, and prematurity), logistic regression models were constructed through backward elimination. The analysis of LBW and premature delivery was restricted to live-born singletons. Variables that were significant in univariate analysis or were known to be confounding variables or independent predictors in other studies were included in the initial models. Treatment group was maintained as a variable in each of the models, regardless of statistical significance. Other variables were retained if the P value of the adjusted odds ratio (AOR) was <.05. STATA software (release 7.0; StataCorp) and SPSS (version 11.0; SPSS) were used for statistical analyses.
RESULTS
Study population.
A total of 1163 women were enrolled in the study: 394 in the weekly CQ group, 380 in the IPT/CQ group, and 389 in the IPT/SP group. There were no significant differences in characteristics among women enrolled in the 3 treatment groups. At enrollment, 58.8% of women were parasitemic, with similar rates across the 3 groups (table 1).
Forty-two women (3.6%) were lost to follow-up during the intervention phase of the study. Of these, 5 elected to withdraw from the study (for unknown reasons), and 37 moved out of the study area. An additional 9 women (0.8%) were lost to follow-up near the time of delivery, and no delivery information was available for these women. Two women (0.2%) died during the follow-up period, despite hospitalization and intensive medical care (1 from severe anemia during the third trimester; and the other during delivery, as a result of a peripartum hemorrhage). A total of 1110 women were followed to the point of having a delivery outcome. There were no significant differences among the study groups in the proportion of women lost to follow-up.
Efficacy of regimens: malaria and anemia.
The proportion of women with parasitemia at enrollment who had not cleared their parasitemia by the 2-week follow-up visit was significantly lower in the IPT/SP group (1.8%), compared with the CQ groups (weekly CQ, 19.5%; IPT/CQ, 17.3%; 2 2 × 3 table, P < .001; IPT/SP vs. weekly CQ, P < .001; IPT/SP vs. IPT/CQ, P < .001); the difference between the 2 CQ groups was not significant.
During follow-up, the proportions of women who visited clinics for malaria clinical symptoms (fever or history of fever) were 22.5% in the weekly CQ group, 21.7% in the IPT/CQ group, and 14.13% in the IPT/SP group (P = .006). The proportion of women treated for 1 episodes of blood filmconfirmed malaria during the follow-up period was higher in the weekly CQ and IPT/CQ groups (24.1% and 24.7%, respectively) than in the IPT/SP group (17.2%) (P = .02). The proportion of women with third-trimester anemia was higher in the weekly CQ group (58.4%) and IPT/CQ group (58.3%) than in the IPT/SP group (40.4%) (P < .001) (table 2). The mean hemoglobin level was significantly higher in the 2-dose IPT/SP group (11.1 g/dL) than in the IPT/CQ and weekly CQ groups (10.6 g/dL for each group) (P < .001).
Outcome measures at delivery.
Compared with women who gave birth in the IPT/SP group, women who gave birth in the IPT/CQ and weekly CQ groups were more likely to have peripheral and placental malaria, although these differences were not statistically significant (table 2). Neonates born to women in the IPT/SP group had significantly higher mean birth weights (2709 g), compared with neonates born to women in the IPT/CQ group (2613 g) (P = .005 by Kruskal-Wallis test) but not compared with the weekly CQ group (2676 g) (P = .18) (table 2). The incidence of LBW among neonates born to women in the IPT/CQ group (33.2%) was significantly higher than among those born to women in the IPT/SP group (23.3%) (P = .006).
Compared with women in the weekly CQ (2.3%) and IPT/SP (2.7%) groups, women in the IPT/CQ group (8.4%) were significantly more likely to have singleton premature neonates (IPT/CQ vs. weekly CQ, P < .001; IPT/CQ vs. IPT/SP, P = .001) (table 2). The rates of spontaneous abortion were 2.6% in the weekly CQ group, 1.4% in the IPT/CQ group, and 2.7% in the IPT/SP group (P = .40). The proportions of stillbirths were 2.4% in the weekly CQ group, 3.1% in the IPT/CQ group, and 4.8% in IPT/SP group (P = .15). The proportions of neonatal deaths among singleton live births were 3.1% in the weekly CQ group, 5.9% in the IPT/CQ group, and 2.9% in the IPT/SP group (P = .09).
Adverse events: mother.
During the 2 weeks after administration of CQ or SP to women, there were no significant differences in the incidence of reported ADRs among women in the weekly CQ, IPT/CQ, and IPT/SP groups (4.4%, 3.7%, and 2.8%, respectively; P = .50). The most common complaints were vomiting (1.7%), fever (1.4%), nausea (0.3%), itching (0.3%), and dizziness (0.2%). There was 1 severe ADR (urticaria) reported in the weekly CQ group, which resolved without sequelae.
Adverse events: neonates and infants.
Icterus was observed during the first week of life among 1.8% of neonates in the weekly CQ group, 1.9% of neonates in IPT/CQ group, and 0.6% of neonates in IPT/SP group (P = .26). The most frequent adverse effects reported in neonates and infants <6 weeks of age were cough (21.0%), fever (13.2%), conjunctivitis (4.8%), and skin infection (3.4%), but no statistically significant differences were observed between groups. Overall, the rates of adverse effects were 33.9% in the weekly CQ group, 33.3% in the IPT/CQ group, and 32.9% in the IPT/SP group (P = .64). Among 1037 live-born singleton neonates born to 1110 women, a total of 41 (4.0%) of neonates/infants died within 6 weeks of life11 in the weekly CQ group (3.1%), 20 in the IPT/CQ group (6.2%), and 10 in the IPT/SP group (2.9%) (P = .09). Of these deaths, 24 occurred within the first week of life5 in the weekly CQ group (1.4%), 12 in the IPT/CQ group (3.5%), and 5 in the IPT/SP group (1.5%) (P = .09). One neonate in the weekly CQ group died at age 3 days, with icterus and a diagnosis of neonatal sepsis. The most frequent reported causes of neonatal/infant death were infant refusal to breast-feed (10/41; 24.4%), complications of prematurity (7/41; 17.1%), respiratory diseases (5/41; 12.2%), congenital anomalies (2/41; 4.9%), fever (2/41; 4.9%), and other causes (15/41; 36.6%). The congenital anomalies included 1 neonate in the IPT/CQ group who had 6 fingers and 1 neonate in the IPT/SP group who had anal atresia. One additional neonate who died in the IPT/CQ group was born with 6 fingers, but the primary cause of death was listed as "prematurity."
Multivariate analysis.
Maternal characteristics associated with third-trimester anemia included anemia at enrollment, placental malaria, and delivery during the rainy season (table 3). Women in the IPT/SP group were less likely to have third-trimester anemia (AOR, 0.49; P < .001) than were women in the weekly CQ group. Delivery during the rainy season, fever within the 2 weeks prior to delivery, and maternal age <20 years were all associated with an increased risk of placental malaria infection (table 3). Having received ANC before study enrollment and being enrolled at a gestational age 24 weeks were associated with a reduction in placental malaria. Women in the IPT/SP group were less likely than women in the weekly CQ group to have placental malaria (AOR, 0.69; P = .40). IPT/SP was also associated with a similar reduction in the risk of LBW (AOR, 0.69; P = .04) (table 3). Neonates who were female or were born to primigravid women, to women who were <150 cm in height, to women who had a fever in the 2 weeks before delivery, or to women who had placental malaria infection were at an increased risk for LBW. IPT/CQ was associated with an increased risk of premature delivery (AOR, 4.09; P = .001), compared with weekly CQ chemoprophylaxis (table 3); IPT/SP appeared statistically equivalent to IPT/CQ (AOR, 1.15; P = .78). Other independent risk factors for premature delivery were fever within 2 weeks of delivery and gestational age 24 weeks at enrollment.
DISCUSSION
In a randomized trial comparing 3 regimens for the prevention of malaria during pregnancy, we observed that, among primigravid and secundigravid women, IPT with 2 doses of SP was more efficacious than weekly chemoprophylaxis with CQ in preventing placental malaria infection, after adjusting for other risk factors. IPT with 2 doses of CQ performed similarly to weekly CQ chemoprophylaxis. IPT with SP was also more efficacious than weekly CQ chemoprophylaxis in preventing the 2 major adverse consequences of malaria during pregnancy: maternal anemia and LBW. Although mean birth weight was greater in the IPT/SP group than in the weekly CQ group, this difference was not statistically significant. The risk of premature delivery was similar between the IPT/SP and CQ chemoprophylaxis groups; however, women in the IPT/CQ group were >4 times more likely to have a premature delivery, after adjusting for other factors. There were no significant differences in rates of adverse events among women in the 3 groups nor among neonates/infants born to enrolled women. Only 1 severe adverse event (urticaria) was reported in 1 woman in the CQ chemoprophylaxis group; no severe cutaneous reactions were reported. There were no statistically significant differences in the rates of stillbirth or spontaneous abortion among the 3 groups and no reported cases of kernicterus.
These results are consistent with those of other randomized trials that have demonstrated that IPT is more efficacious than chemoprophylaxis with CQ in preventing maternal anemia [4, 18, 22] and placental parasitemia [4, 16, 22]. The results are also consistent with the few published observational studies that have shown that women who give birth and have received IPT during pregnancy have higher mean hemoglobin levels [17, 23] and are less likely to be anemic [23], less likely to have placental parasitemia [23, 24], and less likely to have a neonate with LBW [17, 23, 24]. The lack of adverse effects associated with SP and the lack of association with adverse maternal or fetal outcomes are also consistent with findings from other published trials [4, 16, 18].
In multivariate analysis, placental malaria infection appeared to be a strong risk factor for maternal anemia; anemia at enrollment and delivery during the rainy season were less-strong risk factors. Placental malaria was also strongly associated with LBW. This association (and its strength) was consistent with results of other published studies [8, 15, 25]. Other risk factors for LBW, including being primigravid, having short stature, and female sex of the neonate, are also consistent with those found in other settings [15].
The finding that late study enrollment (gestational age 24 weeks)and, therefore, later delivery of preventive drugs (IPT or chemoprophylaxis)was associated with a reduced risk of placental parasitemia but an increased risk for premature delivery demonstrated the importance of early prenatal care. Although women who receive a later first dose of IPT appear to clear parasites from their placenta, this clearance may not be as effective at preventing some of the potential adverse consequences associated with malaria during pregnancy. Although the presence of parasites in the placenta may be a useful marker, these results are a reminder that measurement of impact indicators gives the best picture of efficacy and effectiveness.
In the prevention of premature delivery, IPT/SP and CQ chemoprophylaxis appeared to perform equivalently. This may reflect the balance between the potential antipyretic effect of weekly CQ (which is likely mediated by inhibition of tumor necrosis factor) [26], which would not be expected with IPT/SP, and the superior efficacy of IPT/SP in preventing placental malaria infection. IPT/CQ, which provides neither a weekly dose of a potentially antipyretic drug nor the efficacy in preventing placental parasitemia, therefore appears to be a significant risk factor for premature delivery.
Although, in multivariate analysis, IPT with SP was more efficacious in clearing placental parasitemia when compared with weekly chemoprophylaxis, our findings showed unexpectedly higher rates of placental malaria in the IPT/SP group than has been observed in previous trials in Malawi and Kenya [4, 16]. The most likely explanation for this finding is high rates of reinfection after the second dose of SP in this area with intensely seasonal transmission. Another possibility is that the coadministration of folic acid and SP resulted in a functional reduction of SP efficacy. There is in vitro evidence that P. falciparum parasites may use exogenous sources of folic acid, thus overcoming SP inhibition of folate metabolism [27, 28], and in vivo evidence from the Gambia that SP efficacy in treatment of children with malaria was reduced when coadministered with folic acid, compared with coadministration with iron and placebo [29]. Since rates of resistance of P. falciparum to SP are very low in the study area (<5% parasitological failure rate; K. Kayentao, personal communication) drug resistance is unlikely to be a factor in the persistently high prevalence of placental parasitemia that was observed in this study.
In summary, IPT with SP was more efficacious than weekly CQ chemoprophylaxis in preventing malaria during pregnancy and its associated adverse outcomes among primigravid and secundigravid women. In addition, IPT with SP appeared to be as safe and as well tolerated as CQ chemoprophylaxis. These resultsto our knowledge, the first in West Africa to confirm the superior efficacy of IPT with SP when compared with CQ chemoprophylaxisshould encourage West African decision makers to follow World Health Organization recommendations for the adoption of IPT with SP as policy for pregnant women, as part of a package that should include insecticide-treated nets [1]. Mali and other West African countries should seek resources from the Global Fund for AIDS, Tuberculosis, and Malaria and from other sources, for the implementation and scale-up of these important malaria-control interventions to protect this vulnerable population.
Acknowledgments
We wish to thank the study staff who provided follow-up for antimalarial drug administration: Bourema Ouologem, Joseph Tembely, Aissata Togo, Mamoudou Djimde, Moise Guindo, and Boubacar Kansaye. We also thank the staff at the Koro Health Center (Guindo Souhaibou, Haidara Fousseyni, and Dicko Modibo), at the Bandiagara Health Center (Cissé Mahamadou, Siaka Sidibé, and Pierre Mounkoro), and in the laboratory (Issa Cissé). We also extend many thanks to the staff of the maternity units, the local women's associations, and the community leaders in Koro and Bandiagara, for their encouragement of pregnant women to take part in the study, as well as the pregnant women and their newborns who participated in the study.
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