The blood is an important tissue in man. Haematological parameters are useful in making diagnosis of diseases and also help in the antenatal assessment of women in pregnancy. The physiological changes of pregnancy, due to the influence of hormones such as oestrogen, progesterone also affect haematological indices when compared with the non-pregnant state. The picture is further influenced by race, geographical location, age, environmental factors and the prevalence of infectious diseases such as malaria.
Studies have reported on the prevalence of peripheral and placental parasitaemia in areas of stable endemic malaria transmission in Africa. A review of studies from countries in Africa, gave a median prevalence of malaria infection in pregnancy as 27.8% (Steketee et al., 2001). On average, one in four pregnant women in areas of stable transmission in Africa has evidence of malaria infection at the time of delivery (Desai et al., 2007). This is based on the estimated prevalence of 26% of placental malaria (Guyatt and Snow, 2004).
In Sub-Saharan Africa, Plasmodium falciparum infection of the placenta remains a major challenge among pregnant women (Uneke, 2008) and its prevalence is influenced by maternal age, gravidity, use of malarial prophylaxis, nutrition, host genetics, level of hosts immunity, parasite genetics and transmission rates (Tako et al., 2005). The maternal and fetal effects of malaria are enormous in the tropics. These include miscarriages, stillbirths, preterm labour and deliveries, anaemia and severe malaria among others (Steketee et al., 2001).
Maternal anaemia is the commonest consequence of Plasmodium falciparum malarial infection (Uneke, 2008). In Sub-Saharan Africa, it is estimated that between 200,000 and 500,000 pregnant women develop severe anaemia as a result of malaria (Steketee et al., 2001). Anaemia is usually multifactorial in origin and although, malaria is an important contributor; nutritional deficiencies, hookworm, HIV infections and genetic red blood cell disorders (Sickle cell and thalassemias) are other important contributing factors (Shankar, 2000).
Excessive removal of non-parasitized erythrocytes, immune destruction of parasitized red cells and impaired erythropoiesis as a result of bone marrow dysfunction are few of the different mechanisms through which malaria may cause anaemia (Ekvall, 2003). The hypersplenism in malaria infection is associated with a reduction in all three blood series that is, causing not only anaemia, but also thrombocytopaenia and leucopaenia (Fleming, 1989a, b).
The severity and type of anaemia can be determined by the levels of haematological indices such as haemoglobin concentration, Packed Cell Volume (PCV), Mean Corpuscular Volume (MCV), Mean Corpuscular Haemoglobin Concentration (MCHC) and Mean Corpuscular Haemoglobin (MCH). Although, many studies have reported on anaemia as a complication of malarial infection in pregnancy, the pattern of these blood indices has not been documented. There is also dearth of information on the effect of pregnancy on other blood cells in the presence of plasmodium falciparum in Nigeria. Given the known complications of malaria in pregnancy even in the asymptomatic state there is need to determine the effect of malaria parasitaemia on various blood indices on pregnancy. Hence, this study examines the effect of malaria parasitaemia on haematological parameters in pregnancy.
MATERIALS AND METHODS
The study was conducted at the antenatal clinic of the University of Ilorin Teaching Hospital, Ilorin, Nigeria between March and June 2006. It attends to the population in the metropolis, surrounding towns and communities. It also serves as a referral centre for health facilities in the middle belt and parts of South-Western Nigeria. It is located in the North-Central geopolitical zone, an area of stable transmission of malaria all year round.
The Climate and Vegetation
The climate is tropical with guinea savanna vegetation. It has two distinct
seasons, a characteristic rainy season between May and October with high rainfalls
in June and August. The dry season is from December to February; completely
devoid of rains.
The Study Population
Pregnant women who presented for booking for antenatal care were studied.
Those who provided informed consent after counseling were enrolled into the
study. Five hundred women were randomly recruited. Information on socio-demographic
characteristics, obstetric and medical history and drug use were obtained by
resident doctors in obstetrics and gynecology, alongside one of the investigators.
The height, weight and vital signs of the participants were measured and their
complete medical and obstetric examinations were also done.
Sample Collection and Evaluation
Five milliliter of blood was collected by venepuncture using aseptic technique
from each participant into two EDTA bottles. One part was used for the determination
of haematological parameters while the other was used for the diagnosis of malaria.
Determination of Haematological Indices
Mean Corpuscular Volume (MCV), Mean Corpuscular Hemoglobin (MCHC), Mean
Corpuscular Haemoglobin Concentration (MCHC), White Blood Cell Count (WBC),
absolute RBC count, platelet count, haemoglobin level and Packed Cell Volume
(PCV) were determined using Sysmex KX 21 automated cell counter.
Diagnosis of Malaria
Thick and thin films were prepared and stained with Giemsa stain for parasite
identification and quantification as described by Warhurst and Williams (1996).
Parasite density was determined by counting the number of asexual parasites
relative to at least 200 leucocytes in each thick blood film and assuming a
mean leucocytes count of 800 μL-1 of blood (Trape, 1985). Parasitaemia
was graded as low (parasite <1000 μ L-1), moderate (>1000-9,999
μ L-1) and high (>10,000 μ L-1). This was
done by a trained and experienced microscopist.
Data were entered into Microsoft excel data sheet. Statistical analysis were done using the Epi-info statistical software version 2005. Associations between variables were tested using Chi-square for discrete variables and the student t-test for continuous variable. Analysis of variance tests were used to compare means of the haematological parameters. Level of statistical significance was designated at p-values less than or equal to 0.05 (p<0.05).
A total of five hundred respondents were recruited into the study and their blood samples were analyzed. The mean age (SD) of the women was 28.5 (±5.19) years while 45.6% were 26-30 years old; pimiparous women constituted 59%.
Three hundred and thirty six respondents had tertiary education and 2.4% (12) had no formal education. A majority of the respondents (97%) were married, 293 women (58.6%) booked in the second trimester, while 56 (11.2%) and 151 (30.2%) booked in the first and third trimesters, respectively. The socio-demographic characteristics of these women are shown in Table 1.
One hundred and sixty two (32.4%) women had malaria parasitaemia, out of which 96.3% were not febrile. Plasmodium falciparum was the only malaria species found in this study. The levels of the malaria parasite density were categorized into low, moderate and high densities as shown in the methodology. Among the infected women, none had low parasite density, while 46.9 and 53.1% had moderate and high parasite densities, respectively. Table 2 shows the values of the haematological parameters of the study population. The mean values of the haematological parameters were within reference levels expected in pregnancy, this is shown in Table 2.
demographic characteristics of the participants
of the mean values of parameters with malaria parasitaemia
Table 3 shows the comparisons between the means of the haematological
parameters and peripheral malarial parasitaemia in the pregnant women. The MCHC
was higher in the parasitaemic group than the non- parasitaemic group and the
difference was statistically significant (p = 0.0452).
relationship between degree of parasite density and the mean values of
There was also a significant correlation between RBC and parasitaemia (p =
0.01). The mean values of other hemoglobin and red cell indices were higher
in the parasitaemic group than the non- parasitaemic group. Conversely, platelet
and WBC counts were higher in those without malaria parasites than the infected
The levels of parasite density and its effects on the haematological parameters are shown in Table 4.
The mean value of WBC of 7.02x109 L-1 in women with high parasite density was higher than the value of 6.26x109 L-1 in the moderate and the difference was statistically significant (p = 0.03).
The pattern of peripheral malaria infection in this study agrees with findings from other studies on malaria in the Sub-Saharan region, where Plasmodium falciparum is the commonest species of the parasite (Uneke, 2008). Also, Plasmodium falciparum infection during pregnancy is usually asymptomatic and remains undetected and untreated despite the presence of the parasite in the placenta (Steketee et al., 2001). In this study, 3.7% of the women were symptomatic. The MCHC was significantly lower in pregnant women without peripheral parasitaemia than those with the parasite even though both groups had mean values within normal limits. The MCHC is an index of haemoglobin concentration per red cell, indicating the oxygen carrying capacity of each red cell. The inverse relationship between MCHC and malaria parasitaemia is unexpected knowing that anemia is the commonest complication of Plasmodium falciparum infection, nevertheless, the significant lower absolute count of RBC in the infected women was in consonance (Uneke, 2008). Probably, the higher MCHC in the parasitaemic women is compensatory for the presence of the parasite at the red cell level and seemingly lower value in the non-infected women was the expected norm from the haemodilutional effect of pregnancy. Both groups had mean values that demonstrated normochromia. Thus, a rise in MCHC in pregnancy may be indicative of malaria infection. More studies are needed on the effect of Plasmodium falciparum on MCHC to generate a definite conclusion on this finding.
The mean values of WBC count in both infected and non infected women were within normal reference range probably because the participants were evaluated at booking. Whereas during labour and puerperium, WBC may be more markedly elevated (Onwukeme, 1992). Nevertheless, this compared favorably well with the findings of other workers in Jos and Ibadan, Nigeria (Onwukeme and Uguru, 1990; Akingbola et al., 2006) although, they did not control for malarial infection but rather compared findings in pregnant and non pregnant women.
We found a significant increase in the mean values of WBC as the level of peripheral malaria parasitaemia increased. This was at variance with an expected decrease in the WBC count and possibly leucopaenia, as a result of depressed cellular immunity from the combined effect of malaria and pregnancy. In addition, Mckenzie et al. (2005) demonstrated that WBC count was lower in Plasmodium falciparum infection than Plasmodium vivax infection and non-infected individuals. Without particular reference to pregnancy, wickramasinghe and others showed that abnormalities in the blood changes in malaria are dependent on immunity, age, chronicity and the type of plasmodium infection (Wickramasinghe and Abdalla, 2000). This may explain the finding in this study.
Severe malaria caused by Plasmodium falciparum can cause thrombocytopaenia and rarely DIC (Abdalla, 2004) pregnancy is also associated with profound alterations in the fibrinolytic and coagulation systems. Plasmodium falciparum caused a lower platelet count in pregnant women in this study, when compared with those without peripheral parasitaemia. The difference was not statistically significant and the mean values were within normal range. In area of unstable malaria, platelet counts were significantly lower in patients with an episode of falciparum or vivax malaria compared to healthy pregnant women and symptomatic women infected by P. falciparum also had thrombocytopaenia more commonly (Tan et al., 2008). The reduced platelet count in malaria is said to be due to platelet activation, splenic pooling and a decreased platelet life span (Abdalla, 2004; Beale et al., 1972).
In conclusion, this study describes the pattern of blood parameters in asymptomatic plasmodium falciparum infection of the peripheral blood in pregnancy. There was normochromia with or without the infection but MCHC increased with peripheral parasitaemia. Similarly, asymptomatic P. falciparum was associated with normal WBC count in pregnant women at booking and total white cell count increased with parasite density.