Annals of Tropical Medicine & Parasitology, Vol. 94, No. 1, 7± 13 (2000)
Low birthweight associated with maternal anaemia and Plasmodium falciparum infection during pregnancy, in a peri-urban/urban area of low endemicity in Uganda BY I. N. KASUMBA, A. J. NALUNKUMA, G. MUJUZI, F. S. KITAKA Med Biotech Laboratories, P.O. Box 9364, Kampala, Uganda R. BYARUHANGA, P. OKONG St Francis Nsambya Hospital, Kampala, Uganda T. G. EGWANG* Med Biotech Laboratories, P.O. Box 9364, Kampala, Uganda AND
Received 2 August 1999, Revised 5 October 1999, Accepted 6 October 1999 A cross-sectional study of pregnant women was conducted at Nsambya Hospital in Kampala, to investigate the prevalence and effect of Plasmodium falciparum infections during pregnancy, in a peri-urban/urban location. Overall, 544 pregnant women were recruited when they presented at the labour ward for delivery. After giving informed consent, each subject answered a questionnaire and underwent a physical examination, and peripheral-blood samples were obtained. After each uncomplicated delivery, samples of placental and cord blood were obtained from the placenta and infant, respectively, and infant birthweights were recorded. Smears were prepared from the blood samples and checked for parasites. Only 46 and 36 of the 537 women investigated were positive for P. falciparum infection in their peripheral and placental blood, respectively. Plasmodium falciparum was the only parasite encountered. The prevalences of low birthweight and maternal parasitaemia and the intensities of maternal infection were each greater in primigravidae than secundi- or multi-gravidae. Despite the low prevalence of parasitaemia in this population, P. falciparum infection in the primigravidae was a signi® cant contributor to their ill health, leading to low birthweights in their infants.
Malaria accounts for 10% of Africa’s total disease burden (WHO, 1999). Primigravidae bear much of the malaria-attributable burden, since they are the individuals at highest risk both of malarial infection and of severe malaria. In endemic areas, the prevalence of malarial infection among primigravidae peaks before 20 weeks’ gestation (Brabin, 1991). In sub-Saharan Africa, maternal malaria appears to be one of the principal causes of low birthweight (LBW) among the infants produced * Author to whom correspondence should be addressed. E-mail:
[email protected]; fax: 1 256 41 268251.
during ® rst and second pregnancies. LBW is the most important risk factor for infant mortality, although premature neonates are at greater risk than full-term babies who have suffered intra-uterine growth retardation. Maternal malaria has most impact during ® rst pregnancies, becoming less severe during the second and subsequent ones (McGregor et al., 1983; Fleming, 1989; Jackson et al., 1991; Brabin, 1993; Steketee et al., 1994). The increased susceptibility of primigravid women to malaria has been attributed to immunosuppression (Rasheed et al., 1993), or to sequestration of infected red blood cells in
ISSN 0003-4983 (print) ISSN 1364-8594 (online)/00/010007-07 Carfax Publishing
Ó 2000 Liverpool School of Tropical Medicine
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KASUMBA ET AL.
the placenta, through binding to chondroitin sulphate A (CSA) in the placental syncytiotrophoblast (Fried and Duffy, 1996; Rogerson and Brown, 1997). Conversely, several mechanisms underlying increased resistance of multigravid women to the severe effects of malaria have been proposed. These include the presence of a repertoire of agglutinating antibodies against a wide range of placental parasite isolates in sera of multigravid women (Beeson et al., 1999), and the existence of a sub-population of P. falciparum parasites that speci® cally bind placental CSA, with development of antibodies against the CSA-binding parasites in multigravid women (Fried et al., 1998). The preliminary, baseline ® ndings from a cross-sectional study to investigate the prevalence and effect of P. falciparum infections during pregnancy, in a peri-urban/urban population of Ugandan women, are described below. SUBJECTS AND METHODS Study Site and Subject Recruitment During a 3-month dry spell from July to October 1998, a cross-sectional study of malaria in pregnant women at delivery was undertaken at St Francis Nsambya Hospital. This missionary hospital is located on Nsambya Hill in Makindye division, about 1 km from the centre of the Ugandan capital, Kampala. The hospital has private and public labour and delivery wards but only the public ward was selected for the cross-sectional study, because pregnant women in this ward are more representative of the general, middle-class, urban population in Kampala. The study was approved by the Ugandan National Council for Science and Technology and the hospital ethical committee. Informed consent to participate was sought consecutively as the women presented at the hospital and booked for delivery in the labour ward. Study objectives and expected outcomes were explained to the women in their native language (Luganda) by a project midwife, who enrolled consenting women into the study. Gestational age was
determined manually, axillary body temperature was taken, and a standard questionnaire ® lled out for each study subject, by the midwife. The weights of live newborns were measured, low birthweight (LBW) being de® ned as a birthweight of , 2500 g. Other pregnancy outcomes, such as stillbirths, were recorded. Study subjects were grouped into primigravidae, secundigravidae or multigravidae. Subjects with positive blood smears were treated, before discharge, with a standard dose of chloroquine phosphate or a one-dose regimen of FansidarÒ (sulfadoxine± pyrimethamine). Sample Collection and Laboratory Analyses Each participant donated three blood samples: peripheral blood (collected by venepuncture on admission to the labour ward) and placental and cord blood (both collected immediately upon uncomplicated delivery). At each delivery, an incision was made on the maternal side of the placenta and another on the foetal side of the cord, so that blood samples could be collected into 20-ml syringes containing EDTA and transferred into 50-ml Falcon tubes. For malaria diagnosis, thick and thin blood smears were prepared from all blood samples, Giemsa-stained and examined under high-power objectives by the same microscopist throughout the project period. Parasitaemia (parasites/l l) was estimated by counting infected red blood cells against 200 white blood cells and assuming each subject had 8000 white blood cells/l l blood (Warhurst and Williams, 1996). Haematocrit or packed-cell volume (PCV) was measured using a microhaematocrit centrifuge. Maternal anaemia was indicated by a PCV of , 30% (Verhoeff et al., 1999). Data Analysis Statistical analysis was carried out using version 6.02 of the Epi-Info software (Centers for Disease Control and Prevention, Atlanta, GA). Geometric means were calculated for parasite densities. Student’s t-tests and Pearson’s v 2 test were used to analyse continuous and categorical variables, respectively.
LOW BIRTHWEIGHT IN MALARIA IN PREGNANCY
RESULTS Characteristics of the Subjects Although 544 women were recruited, only data for the 537 (98%) who each provided a complete set of blood samples were included in the analysis. There were no maternal deaths. Most of the subjects (81%) resided in Kampala: 62% in Makindye division and 19% in the other four surrounding divisions of Rubaga, Kawempe, Nakawa and Central. As each patient at the study hospital is charged a small fee, its patients are more representative of the relatively privileged, lower-middle-class population of Kampala than of poorer groups. Among the present subjects, this is re¯ ected in the high attendance at antenatal clinics ( . 90% of all subjects) and the fairly common use of antimalarial drugs during pregnancy (37%± 43%). Of the subjects who reported taking antimalarial drugs during their current pregnancy, 65.8% had used chloroquine, 15.1% quinine, 6.9% sulfadoxine± pyrimethamine and 1.4% amodiaquine. Because of the cross-sectional nature of the study, it was not possible to get clear information about the dose regimens of the drugs taken. The primi-, secundi- and multi-gravidae investigated were generally comparable, although, as would be expected, the multigravidae were signi® cantly older than primigravidae (P , 0.05; Table 1). The frequency of stillbirths was low (2.6%± 6.5%). Out of the 23 stillbirths documented, only ® ve corresponded to mothers with positive smears of placental blood (data not shown). Plasmodium falciparum Parasitaemia All the malarial infections observed in the study were exclusively of P. falciparum. The prevalences of maternal and placental infection and parasitaemias are shown in Table 1, by parity. The overall prevalence of parasitaemia in the study population was low, being 8.6% (range 5 7%± 10%) in the peripheral blood samples and 6.7% (range 5 5%± 10%) in the placental. There were no congenital malarial infections (indicated by positive cord-blood smears) detected in the
9
study. Thirty± six (78.2%) of the 46 subjects with positive peripheral-blood smears also had positive placental-blood smears. The prevalence of peripheral-blood parasitaemia did not signi® cantly differ with parity (v 2 for trend 5 1.65). In contrast, however, the prevalence of placental parasitaemia decreased signi® cantly with increasing parity (P , 0.05; Table 1). The geometric mean intensities of peripheral and placental parasitaemia were 2± 3-fold higher in primigravid mothers than in the multigravid (P , 0.05). Although the geometric mean intensities of peripheral parasitaemia in secundigravidae and multigravidae were similar, the geometric mean intensity of placental parasitaemia in the secundigravidae was 4.5-fold less than in the multigravidae. The reason for this difference is still unclear. Parity and Birthweight The mean birthweights of babies born to multigravidae were greater than those of babies born to primigravidae, irrespective of the level of parasitaemia or anaemia status. The prevalence of LBW deliveries was higher among the primigravidae than in the other two groups (Table 1). Birthweight and Maternal Parasitaemia (Table 2) Although babies born to primigravidae and secundigravidae with placental parasitaemia had lower mean birthweights than those born to aparasitaemic subjects of the same parity, these differences were not statistically signi® cant. However, when the study subjects were considered together, irrespective of parity, there was a signi® cant difference in mean birthweights between the babies of parasitaemic and aparasitaemic subjects (P , 0.05; Table 2). Birthweight and Maternal Anaemia When the subjects were considered together, the mean PCV in those with placental parasitaemia was found to be lower than that in the aparasitaemic, but this difference was not statistically signi® cant (data not presented). The prevalence of anaemia (i.e. PCV , 30%) was 6.6%, 8.8% and 7.5% in primigravid,
10
KASUMBA ET AL. TABLE 1 Characteristics of the study subjects
Characteristic No. of subjects Mean (S.D.) age (years) Mean (S.D.) gestational age (weeks) BIRTHWEIGHT OF INFANT Mean (S.D.)
Secundigravidae
Multigravidae
P
154 20.7 (4.2)* 38.1 (2.5)
116 21.0 (2.8) 38.3 (1.9)
267 27.0 (4.7) 38.5 (2.2)
, 0.05 NS
2917 (580)* 2825.2± 3009.7
3015 (502) 2924.1± 3107.7
3160 (564) 3091.8± 3228.4
, 0.05
36.9 94.0
36.4 94.0
36.3 97.4
NS NS
42.2
37.1
43.1
NS
93.4 6.5 15.5*
97.4 2.6 7.0
96.2 3.7 6.9
NS NS , 0.05
11.0
8.6
7.1
NS
6.0
5.2
, 0.05
1155.7* 832± 1606
457.6 276± 760
557.3 423± 734
, 0.05
1099.0* 745± 1621
77.8 53± 113
346.8 239± 504
, 0.05
(g)
95% con® dence interval Mean packed-cell volume (%) %who attended antenatal clinic during current pregnancy % who used an antimalarial drug during current pregnancy %
Primigravidae
OF BIRTHS
Live Still Low birthweight, live % with peripheral parasitaemia at delivery % with placental parasitaemia at delivery
9.7*
PERIPHERAL PARASITAEMIA
(parasites/l l blood) Geometric mean 95% con® dence interval PLACENTAL PARASITAEMIA
(parasites/l l blood) Geometric mean 95% con® dence interval
* Signi® cantly different from corresponding result for multigravidae (P , 0.05). NS, Not signi® cant.
secundigravid and multigravid subjects, respectively; again, these differences were not statistically signi® cant (P . 0.05). Despite the low prevalence of anaemia, children born to anaemic primigravidae and secundigravidae had mean birthweights that were 437 and 431 g lower, respectively, than those of the babies born to the non-anaemic subjects of the same parity (P , 0.02 for each; Table 2). No signi® cant difference was observed in the mean birthweights of babies born to anaemic and non-anaemic multigravidae.
Birthweights, Visits to Antenatal Clinics (ANC), and Use of Antimalarial Drugs during Pregnancy On admission, almost all of the subjects (95.7%) reported that they had attended an ANC at least once during their current pregnancy. Only 10% of the babies born to the 514 ANC attendees but 44% of those born to the 23 non-attendees were LBW. Reported use of an antimalarial drug, either at any time during the pregnancy or in the week preceding delivery, did not appear to affect birth
10 9 20
39
Primigravidae Secundigravidae Multigravidae
All
2951 (717)
2500 (697)* 2633 (707)* 3310 (553)
BWOI
30%
484
140 104 236
No.
BWOI
30%
3074 (551)
2957 (553) 3064 (445) 3150 (565)
A PCV $
36
15 7 14
No.
2920 (554)²
2750 (660) 2771 (660) 3200 (429)
BWOI
Placental infection
*Signi® cantly lower than corresponding value for infants born to mothers with higher PCV (P , 0.02). ² Signi® cantly lower than corresponding value for infants born to mothers without placental infection (P , 0.05).
No.
Parity
A PCV ,
Mothers with:
490
136 107 247
No.
3158 (566)
2936 (572) 3043 (494) 3158 (572)
BWOI
No placental infection
TABLE 2 Relationship between maternal packed-cell volume (PCV), placental malaria and parity, and mean (S.D.) birthweight of the infants (BWOI), in g LOW BIRTHWEIGHT IN MALARIA IN PREGNANCY 11
12
KASUMBA ET AL.
weights; the prevalence of LBW among the babies born to the women who did not use antimalarial drugs (31/277; 11%) was comparable with that of babies born to the users (23/231; 10%). DISCUSSION During a cross-sectional study of P. falciparum infection during pregnancy in a peri-urban/ urban population in Kampala, 537 women who delivered were subject to complete clinical and laboratory analyses for maternal and placental parasitaemia and anaemia. The prevalences of parasitaemia and anaemia were surprisingly low in this population. There seem to be two explanations for the low prevalence of parasitaemia. Firstly, the study took place during a 3-month period when Kampala was unusually dry and therefore malaria transmission was probably less intense than normal. Secondly, the vast majority of the women investigated had attended ANC prior to admission and some had taken antimalarial drugs during pregnancy. Attendance at ANC appeared to be of signi® cant bene® t in terms of the birthweight of the baby, with 90% of ANC attendees producing infants of normal birthweight. The importance of improving antenatal care was demonstrated by Brabin et al. (1998), who reported that poor antenatal care increased the risk of low birthweight in pregnant adolescent Malawians. In the present study, use of an antimalarial drug (mostly chloroquine) during pregnancy appeared to offer no protection against the delivery of an LBW baby, possibly because of chloroquine resistance in local strains of P. falciparum. The ef® cacy of chloroquine and other antimalarial drugs in pregnant women needs to be urgently evaluated in peri-urban/urban centres such as Kampala. That there was a signi® cant difference in mean birthweights between the babies of para-
sitaemic and aparasitaemic subjects (when parity was ignored) indicates that maternal P. falciparum infection per se may indeed have an adverse effect on birthweight. Placental anaemia, which tended to be more frequent in the parasitaemic women than in the aparasitaemic, probably causes intra-uterine growth retardation. In the present work, the true prevalence of placental infection remained unclear, since studies of placental pathology were not undertaken. Such studies would have provided useful insights about the effect of placental parasitaemia on the placental microenvironment. This gap in our knowledge will be ® lled by the results of future studies. This report represents the results of the ® rst detailed study of malaria during pregnancy in Kampala in 27 years, since the work of Hamilton et al. (1972). It has identi® ed primigravidae from a peri-urban/urban population in an area of low endemicity as being at increased risk of having LBW infants. The present results con® rm the earlier observation that maternal malaria contributes signi® cantly to the low birthweight of infants born to primigravid women (McGregor et al., 1983). A policy of antimalarial prophylaxis and a study of drug ef® cacy should be implemented among the primigravidae of Kampala.
ACKNOWLEDGMENTS.
We are indebted to Dr P. Kiiza, the Medical Superintendent, the nurses and the pregnant women of Nsambya Mission Hospital, who made this study possible. We are very thankful to Professors E. Riley and C. Curtis and Dr U. d’Alessandro for helpful criticisms and comments. This investigation received ® nancial support from World Bank/WHO Special Programme for Research and Training in Tropical Diseases (TDR), via a re-entry grant (980008) to I.N.K. and a career development award (940849) to T.G.E.
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