Background: Malaria parasitemia during pregnancy is a most important public health problem to governments and to individuals in malaria endemic regions of the world. Moderate or severe anemia during pregnancy may be associated with heavy parasitic infestation. However, malaria may not be the only cause of anemia in pregnant women in developing countries.

Objective: To determine the prevalence of malaria and anemia in different trimester, gravida and age group
Study design: A cross-sectional study that recruited 113 pregnant women who were screened for the malaria parasites and anemia.

Setting: The study was conducted in the antenatal clinic of two general hospitals in Ikorodu Local Government Area (LGA) in Lagos, Southwest Nigeria.
Participants: The pregnant women recruited for this study were living in communities on the coasts of the Lagos Lagoon.

Measurements: Socio-demographic profile, obstetrics and gynecologic history and other relevant data of the pregnant women were collected using a semi-structured questionnaire instrument in an interview. Blood samples were analyzed for Packed Cell Volume (PCV) level and malaria parasites

Results: Malaria prevalence was 19.5% and the prevalence of anemia was 81.4%. The highest prevalence of malaria (27.5%) occurred in the 3rd trimester and among primigravida. The highest prevalence of anemia was in the 2nd trimester and among the multigravida. Those with severe anemia were approximately five times more likely to have malaria parasitemia (χ²=8.16, P-value=0.004, OR=4.84, 95% CI: 1.53, 15.35) compared to all other pregnant women. Women in the third trimester were 1.25 as likely to develop severe anemia than those in first or second trimester (χ²=0.18, P-value=0.69, OR=1.25, 95% CI=0.41, 3.82). Secundigravida were 1.60 times more likely to develop moderate anemia (χ²=1.20, P-value=0.27, OR=1.60, 95% CI=0.69, 3.76) and multipara were 1.35 times more likely to develop mild anemia (χ²=024, P-value=0.62, OR=1.35, 95% CI=0.41, 4.47). Regardless of whether the pregnant woman was parasitized or not, the mean PCV of those who consumed herbal tea (28.2±5.2) was significantly lower (t=-2.24, P-value=0.01) than those who did not consume herbal tea (30.8±6.5) in pregnancy.

Conclusion: The prevalence of anemia in pregnancy was very high while the prevalence of malaria was very low. Anemia was commoner in the 2nd trimester and among multigravida while malaria was more prevalent in the 3rd trimester and among primigravida. Consumption of herbal tea was associated with low Packed Cell Volume.

Keywords: pregnancy, malaria, anemia, maternal age, trimester, gravidity, South-west Nigeria

It is estimated that, annually, about 30 million pregnant African women are exposed to the risk of malaria infection¹ and 56 million suffer anemia. In regions of intense transmission, infection with Plasmodium falciparum is usually asymptomatic and therefore undetected and untreated although the malaria parasites are incubated in the placenta.² Various studies have reported main adverse effects of malaria in pregnancy such as maternal anemia and low birth weight babies.^3–5 Individuals in endemic areas build up immunity against malaria by acquiring specific antibodies capable of hindering parasite sequestration.⁶ However, pregnant women are susceptible to infection, despite previously acquired immunity probably because of her lowered immune response and reduced ability to effectively clear malaria parasites from her system.^7,8 Furthermore, probably because of its high nutrient and oxygen content, malaria parasites sequester in the placenta, more than in the peripheral blood, though Pereira et al.⁹ stated that the specific adherence of malaria parasites to placenta tissues is mediated by a certain protein, the VAR2CSA protein, which binds to placental chondroitin sulfate (CS) on chondroitin sulfate proteoglycans (CSPGs) in the placental syncytium.⁹ Clinical complications such as anemia, pulmonary edema, hypoglycemia, cerebral malaria, puerperal sepsis, miscarriage, premature delivery, low birth weight, congenital infection, and/or perinatal death are possible outcomes of malaria infection during pregnancy.^10–16 It is pertinent to note however that anemia is especially problematic because hemoglobin level falls due to greater expansion of plasma volume relative to increase in red RBC volume, especially so in the second trimester of cases. It has been shown that anemia increase when there is elevated number of malaria cases¹⁷ and the incidence of anemia during pregnancy is aggravated in malaria high-transmission settings. These adverse effects of P. falciparum infection in pregnancy are most pronounced for women in their first pregnancy.^18,19 In addition to malaria parasite-induced hemolysis during infection, iron deficiency heightened by nutritional deficiencies can result in iron-deficiency anemia; folate-deficiency anemia or Vitamin B12-deficiency anemia and worm infestation worsen the anemia situation in the general populace and in pregnancy, foretells poor maternal outcomes.^20–22 Interventions are therefore targeted at this group of people to abate the problems and surveillance of the affected population becomes necessary to monitor the impact periodically. The objective of this study was to examine the pattern of anemia among pregnant women in Lagos Nigeria and describe the proportion of the anemia due associated with malaria parasitemia. Intervention can therefore be better targeted. Furthermore, proportion of anemic pregnant women due from malaria infection can be deduced separate from anemia due to other causes.

This cross-sectional study, implemented from January to April of 2009, at the antenatal clinics of Ijede General Hospital and Ikorodu General Hospital in Ikorodu Local Government Area (LGA), two government operated facilities in Lagos, Southwest Nigeria, has been reported elsewhere.²³ Ikorodu General Hospital is located in the urban center of the LGA whereas Ijede General Hospital is located in its rural parts, approximately 8 km further eastwards. Both Health facilities are located within communities adjacent to the northern fringe of the Lagos lagoon. Ikorodu, a semi-urban town, is the headquarters of Ikorodu LGA which lies between latitude 6037’N- 6045’N and longitude 303’East-305’East. Population migration from metropolitan Lagos and other parts of Nigeria has increased the population of this LGA from about 400,000 in 2000 to over 700,000 in 2009, though Ijede residents were still mainly a homogenous population of approximately 10-15,000, made up of farmers, fishermen and petty traders. There were three primary schools and one secondary school in Ijede. Due to its proximity to Lagos, the community still has good access road, pipe borne water and relatively stable electric supply. By contrast, Ikorodu, because of its size and semi-urban features, has a network of tarred roads, more public and private health and educational facilities and is supplies with large markets where entrepreneurs ply their trade. Some of the residents at Ikorodu and Ijede work in offices in metropolitan Lagos, commuting either by road or by water transportation over the lagoon of Lagos.

Sample size calculation for each health facility

Sample size was calculated assuming a prevalence of 20% for malaria in pregnancy, for an error rate of 10% and a confidence interval of 95%, the sample size needed is

$\frac{Z^{2}pq}{d^2} = \frac{{1.96}^{2}X0.2X0.8}{{0.1}^2} =62$

where

Z =z-score at 95% confidence interval = 1.96

P = prevalence rate (20%)

q = Failure rate (80%)

d= error rate (10%)

Sixty-two participants were required in each facility of study.

The study population

Briefly, participants included consenting pregnant women who had come to attend their antenatal clinic but who were feeling unwell. Pregnant women that had other symptoms than self-reported fever were excluded. These participants attending antenatal clinics (ANC) were interviewed by researchers trained, to administer the semi-structured questionnaire. Socio-demographic characteristics, obstetrics and gynecology history, history of illness - especially febrile episodes, medication they were using during current pregnancy and their health-behavioral pattern such as possession and utilization of LLIN and use of Intermittent Preventive Treatment of malaria in pregnancy (IPT). 0.5ml venous blood sample was collected into labeled EDTA microtainer bottles. Malaria microscopy was performed as earlier described²⁴ and hematocrit was determined by measuring Packed Cell Volume (PCV) in microhematocrit tubes spun in hematocrit centrifuge at 12,000 – 15,000 rpm (xG) for 5 minutes and read using a hematocrit reader (Hawksley, England). Thick and thin blood films were made according to WHO specification¹⁴ and the thin smears fixed with methanol. The slides were allowed to air dry until the next day when they were stained for 30 minutes using 3% Giemsa stain. The slides were examined under 100X oil immersion lenses and parasite density per µl was calculated by multiplying the number of parasites per high power field (HPF) by 500, based on the assumptions that 5-8µl of blood is used in making a thick blood films and that 0.002µl of blood is in a HPF.²⁵ To declare a slide negative, at least 200 high powered fields were read. Anemia was classified as mild (PCV <36%), moderate (PCV 23.3 - 33.2%) or severe (PCV < 23.3%).²⁶

Inclusion/exclusion criteria

Women who lived in the communities where the health facilities were located and who were consulting only for ante-natal care at these facilities were included in the study. Those who were brought in as emergency obstetric cases or women consulting for casual gynecological cases were excluded from the study. Also excluded were non-indigenes and those on admission for chronic systemic illnesses.

Data analysis

Data were analyzed using Stata-13. The mean, median, mode and various rates were determined for continuous variables such as age, and PCV. Geometric mean parasite densities were calculated, and Students t-test and chi squared analysis were used to compare differences. Differences of means were considered significant at a 95% confidence limit i.e. when P values are below 0.05. Association was determined by computing logistic regression analysis of positive participants with other exposure variables at 95% confidence interval

Consent and ethical approval

The purpose of the study was explained to the pregnant women and the researcher requested for their consent to include them as participants in the study. The study was conducted as a sub-study of another study “Characterization of molecular markers associated with Plasmodium falciparum resistance to antimalarial drugs and evaluation of PCR methods for parasite density estimation in rural and semi-urban site in southwest Nigeria” for which ethical approval was obtained from the Nigerian Institute of Medical Research Institutional Review Board. All work was performed according to the guidelines for human experimentation in clinical research and Helsinki declaration

Malaria in pregnancy

Table 1 & Figure 1 of the 113 pregnant women enrolled in the study, only 22 (19.5%) were positive for malaria parasites with a geometric mean parasite density of 7,500 and a mean PCV of 26.8±6.6%. In all, 19 (16.8%) of the study subjects were in the first trimester of whom 3 (15.8%) were parasite-positive with a GMPD of 339.7, 54 (47.8%) were in the second trimester among whom 8 (14.8%) were positive for malaria parasites with a GMPD of 1077.4 and 40 (35.4%) were in their third trimester among whom 11 (27.5%) had malaria parasitemia with a GMPD of 715.3. Malaria parasites were observed more among women in their first pregnancy (8/32, 25.0%; GMPD = 390.3) than among those in the second (4/32, 12.5%, GMPD = 5040.4) or more than two (10/49, 20.4%, GMPD = 590.3) pregnancies. Figure 1 illustrates the status of malaria parasitemia among the study subjects showing that malaria was most prevalent among pregnant women aged 26-30 years and least among those aged 20 years or less. Women in the third trimester of pregnancy were more than twice likely to be positive for malaria parasite (OR=2.14, 95% CI: 0.83, 5.50) than those in other trimesters. Those in their first pregnancy were 1.60 times as likely to be positive for malaria parasites than secundigravida or multipara women. Overall, malaria parasitemia was observed more in the 3^rd trimester (11, 27.5%) and among those pregnant for the first time (8, 25.0%).