Some haematological parameters among pregnant women of African descent attending antenatal clinic in Sokoto North Western Nigeria

Abstract

Pregnancy is the fertilization and development of one or more offspring, known as an embryo or foetus in a woman’s uterus. Pregnancy is a critical stage of development during which maternal nutrition can strongly influence obstetric and neonatal outcomes. The aim of this study was to determine the effect of pregnancy on the full blood count parameters of pregnant women of African descent residing in Sokoto, North Western Nigeria. This case-control study investigated 74 pregnant subjects and 22 non-pregnant controls. The mean age and income of the subjects were 28.00 $\pm$ 8.295 and 2760.42 $\pm$ 7975.178 respectively. Haematological parameters were determined using a fully automated 5-part differential haematology analyzer (Model Mythic 22-CT, Orpheee, Switzerland). Results obtained of pregnant subjects were compared with that of non-pregnant controls. The prevalence of anaemia (Hb $<$ 11 g/dl) and thrombocytopenia (Platelet count $<$ 140 $\times$ 10 ${}^{9}$ /L) was 58.11% and 6.75% respectively among the pregnant subjects. The mean haemoglobin, PCV, platelet and red cell count were significantly lower among the pregnant subjects (10.7 $\pm$ 0.13 g/dl and 31.4 $\pm$ 0.38%, 252.7 $\pm$ 14.35 $\times$ 10 ${}^{9}$ /L and 3.7 $\pm$ 0.04) compared to the non-pregnant controls (12.2 $\pm$ 0.44 g/dl, 36.2 $\pm$ 1.17 %, 362.7 $\pm$ 36.51 $\times$ 10 ${}^{9}$ /L and 4.3 $\pm$ 0.11) ( $p=$ 0.004, 0.001, 0.009 and 0.000) respectively. There were no significant differences in the total white blood cell count between the pregnant subjects (5.3 $\pm$ 0.22) and non-pregnant controls (4.6 $\pm$ 0.59) ( $p=$ 0.267). The Neutrophils count was significantly higher among the pregnant subjects (42.6 $\pm$ 3.06) compared to the non-pregnant controls (20.0 $\pm$ 2.33) ( $p=$ 0.000). This study has shown that pregnancy has a significant effect on some haematological parameters of women of African descent. The results of this research work indicates the need to routinely monitor the full blood count, anaemia and thrombocytopenia among pregnant women of African descent.

Keywords

Haematological parameters pregnancy African descent antenatal clinic Sokoto Nigeria

1. Introduction

Pregnancy is a critical stage of development during which maternal nutrition can strongly influence obstetric and neonatal outcomes [1, 2]. Optimal nutrition is necessary to maintain the health of the mother, to help ensure a normal healthy delivery and also to reduce the risk of birth defects, sub-optimal foetal development and chronic health problems in childhood [3]. Poor nutritional status and sub-optimal pre- and antenatal care are common in developing countries, often resulting in pregnancy complications and poor obstetric outcomes [4]. Pregnant women in Sub-Saharan Africa (SSA) are at particular nutritional risk as a result of poverty, food insecurity, political and economic instabilities, frequent infections, and frequent pregnancies [5].

The main nutritional issues impacting these women include maternal under nutrition and deficiencies of key pregnancy micronutrients, such as iron, folate, calcium, vitamin D and vitamin A. Consequently, poor obstetric outcomes, such as anaemia, neural tube defects (NTDs), rickets, low birth weight (LBW) and maternal and neonatal mortality, are common in SSA. SSA is a region of intensive migration prompted by adverse economic, political and ecological conditions. Consequently, SSA immigrants represent a sizeable and growing immigrant population in many Western countries. Of the estimated 4.6 million recorded Africans living in the European Union, at least one-third are from SSA and approximately 250,000 of these immigrants are living in the UK [6]. Several studies have reported that pregnant women of African origin are more at highest risk of adverse birth outcomes, including preterm delivery, low birth weight infants, caesarean delivery and perinatal mortality [7, 8]. Although the exact causes of such outcomes have not yet been clearly identified, it is possible that poor nutritional status, high parity, closely-spaced pregnancies, pre-existing diseases and lower socioeconomic status in the host countries are contributing factors [9].

The major haematological changes during pregnancy are physiologic anaemia, neutrophilia, mild thrombocytopenia, increased procoagulant factors, and diminished fibrinolysis. Plasma volume increases by 10 to 15 percent at 6 to 12 weeks of gestation, and then expands rapidly until 30 to 34 weeks, after which there is only a modest rise. Red blood cell mass begins to increase at 8 to 10 weeks of gestation and steadily rises by 20 to 30 percent (250 to 450 mL) above non-pregnant levels by the end of pregnancy. A greater expansion of plasma volume relative to the increase in haemoglobin mass and erythrocyte volume is responsible for the modest fall in haemoglobin levels (physiological or dilutional anaemia of pregnancy) observed in healthy pregnant women. The Centers for Disease Control in the United States and Prevention has defined anaemia as haemoglobin levels of less than 11 g/dL in the first and third trimesters and less than 10.5 g/dL in the second trimester. Mean platelet counts of pregnant women may be slightly lower than in healthy non-pregnant women. The neutrophil count begins to increase in the second month of pregnancy and platelets in the second or third trimester, at which time the total white blood cell counts ranges from 9000 to 15,000 cells/microL. There is no change in the absolute lymphocyte count. The circulating levels of several coagulation factors change during pregnancy and contribute to the prothrombotic and anti-fibrinolytic changes associated with pregnancy [10].

During pregnancy, the total blood volume increases by about 1.5 litres, mainly to supply the demands of the new vascular bed and to compensate for blood loss occurring at delivery [11]. Of this, around one litre of blood is contained within the uterus and maternal blood spaces of the placenta. Increase in blood volume is, therefore, more marked in multiple pregnancies and in iron deficient states. Expansion of plasma volume occurs by 10–15% at 6–12 weeks of gestation [12]. During pregnancy, plasma renin activity tends to increase and atrial natriuretic peptide levels tend to reduce, though slightly. This suggests that, in pregnant state, the elevation in plasma volume is in response to an under filled vascular system resulting from systemic vasodilatation and increase in vascular capacitance, rather than actual blood volume expansion, which would produce the opposite hormonal profile instead [13, 14]. Red cell mass (driven by an increase in maternal erythropoietin production) also increases, but relatively less, compared with the increase in plasma volume, the net result being a dip in haemoglobin concentration. Thus, there is dilutional anaemia. The drop-in haemoglobin is typically by 1–2 g/dL by the late second trimester and stabilizes thereafter in the third trimester, when there is a reduction in maternal plasma volume (owing to an increase in levels of atrial natriuretic peptide). Women who take iron supplements have less pronounced changes in haemoglobin, as they increase their red cell mass in a more proportionate manner than those not on haematinic supplements.

The red blood cell indices change little in pregnancy. However, there is a small increase in mean corpuscular volume (MCV), of an average of 4 fl in an iron-replete woman, which reaches a maximum at 30–35 weeks gestation and does not suggest any deficiency of vitamins B12 and folate MCV does not change significantly during pregnancy and a haemoglobin concentration $<$ 9.5 g/dL in association with a mean corpuscular volume $<$ 84 fl probably indicates co-existent iron deficiency or some other pathology [15].

Post pregnancy, plasma volume decreases as a result of diuresis, and the blood volume returns to non-pregnant values. Haemoglobin and haematocrit increase consequently. Plasma volume increases again two to five days later, possibly because of a rise in aldosterone secretion. Later, it again decreases. Significant elevation has been documented between measurements of hemoglobin taken at 6–8 weeks postpartum and those taken at 4–6 months postpartum, indicating that it takes at least 4–6 months post pregnancy, to restore the physiological dip in haemoglobin to the non-pregnant values [16].

White blood cell count is increased in pregnancy with the lower limit of the reference range being typically 6,000/cumm. Leucocytosis, occurring during pregnancy is due to the physiologic stress induced by the pregnant state [17]. Neutrophils are the major type of leucocytes on differential counts [18, 19]. This is likely due to impaired neutrophilic apoptosis in pregnancy [20]. The neutrophil cytoplasm shows toxic granulation. Neutrophil chemotaxis and phagocytic activity are depressed, especially due to inhibitory factors present in the serum of a pregnant female [21]. There is also evidence of increased oxidative metabolism in neutrophils during pregnancy. Immature forms as myelocytes and metamyelocytes may be found in the peripheral blood film of healthy women during pregnancy and do not have any pathological significance [22]. They simply indicate adequate bone marrow response to an increased drive for erythropoiesis occurring during pregnancy.

Lymphocyte count decreases during pregnancy through the first and second trimesters and increases during the third trimester. There is an absolute monocytosis during pregnancy, especially in the first trimester, but decreases as gestation advances. Monocytes help in preventing foetal allograft rejection by infiltrating the decidual tissue possibly, through PGE2 mediated immunosuppression [23]. The monocyte to lymphocyte ratio is markedly increased in pregnancy. Eosinophil and basophil counts, however, do not change significantly during pregnancy [24].

Large cross-sectional studies done in pregnancy of healthy women (specifically excluding any with hypertension) have shown that the platelet count does decrease during pregnancy, particularly in the third trimester. This is termed as “gestational thrombocytopenia”. It is partly due to haemodilution and partly due to increased platelet activation and accelerated clearance [25]. There is paucity of data on the full blood count levels among pregnant women in Sokoto, North Western Nigeria. There is a need to investigate the full blood count parameters among pregnant women in the area to generate data that can help optimize the care offered pregnant women in the area. The aim of the study is to investigate the Full Blood Count Parameters, among pregnant women of African descent in Sokoto, North-West Nigeria.

2. Materials and methods

2.1 Study area

This study was conducted at the Specialist Hospital Sokoto (SHS), North-West Nigeria. The hospital is a secondary health institution located in Sokoto metropolis committed to the provision of quality healthcare services to people in Sokoto State and its environs. The state is located between longitudes 11 ${}^{\circ}$ 30’ to 13 ${}^{\circ}$ 50’ East and latitude 4 ${}^{\circ}$ to 6 ${}^{\circ}$ North. It has a land area of about 28,232.37 sq kilometer and stands at an altitude of 272 m above sea level near to the confluence of the Sokoto River and the Rima River. Sokoto state is at the extreme Northwest of Nigeria forming a border with Niger Republic. The state is in the dry Sahel surrounded by sandy terrain and isolated hills with an average annual temperature of 28.3 ${}^{\circ}$ C (82.9 ${}^{\circ}$ F). The weather is characterized by two seasons the wet and dry seasons. Rainfall (wet season) starts late around June and ends in September sometimes extending into October. The average annual rainfall is 550 mm with peak rainfall usually recorded in the month of August. The highest temperatures of 45 ${}^{\circ}$ C during the hot season are experienced in the months of March and April. Harmattan, a dry cold and dusty condition is experienced between the months of November and February. Sokoto state had a population of 4.2 million as at the 2006 census. The metropolis is estimated to have a population of 427,760 people 19 made up of Hausa and Fulani majority and a minority of Zabarmawa and Tuareg and other non-indigenous settlers. The two major languages in the state is Hausa and Fulfulde is spoken among the Fulani. The main occupation of the people is grain production and animal husbandry. Majority of the indigenous people practice agriculture. Crops produced include commercial crops like millet, sorghum, beans, rice and maize. Other occupations commonly practiced are dying, blacksmithing, weaving, carving, trading, and cobbling. Sokoto ranks second in livestock production in Nigeria. Modern Sokoto city is a major commercial center in leather crafts and agricultural products. Occupation of city inhabitants also include trading, commerce, with a reasonable proportion of the population working in private and public sectors.

2.2 Study design

The study population in this case-control study consist of 74 pregnant subjects and 22 non-pregnant controls. The subjects were recruited from among patients attending the antenatal clinic at Specialist Hospital Sokoto (SHS).

2.3 Inclusion criteria

All consenting legal adult ( $\geqslant$ 18 years) pregnant woman who are attending antenatal clinic without any history of hypertension and diabetes mellitus were consecutively recruited into the study.

2.4 Exclusion criteria

Non-consenting and non-legal adults ( $<$ 18 years) pregnant woman and those with history of hypertension and diabetes mellitus attending antenatal clinic will be excluded from participating in the study.

2.5 Sample size estimation

Using the formula $n=Z^{2}pq/d^{2}$ .

Where $n=$ minimum required sample size in a population $>$ 10,000, $Z=$ standard normal deviation, $P=$ proportion of success or prevalence, $q=$ proportion of failure ( $1-p$ ), $d=$ precision, tolerable margin of error, expected difference.

Consecutive recruitment of all consenting pregnant women was done to prevent bias. A structured questionnaire will be used to collect socio-demographics and obstetric-related data from subjects.

$\displaystyle n=Z^{2}pq/d^{2}$ $\displaystyle Z=95\%(1.96)$ $\displaystyle P=15\%(0.15)$ $\displaystyle Q=1-0.15=0.85$ $\displaystyle D=5\%(0.05)$

Therefore $n=(1.96)^{2}\times 0.15\times 0.85/(0.05)^{2}=195.9$ .

Sample size $=$ 196.

2.6 Study participation consent form

Written informed consent will be obtained from all participants in the study according to the Declaration of Helsinki.

2.7 Ethical clearance

Ethical clearance shall be sought for, from the Ethics and Research Committee of the Sokoto Specialist Hospital (SHS), Sokoto.

2.8 Statistical analysis

The data obtained will be analysed using SPSS version 20 (SPSS Inc., Chicago, IL, USA, 2011). The result will be expressed as percentage and Mean $+$ SD. Comparison will be made using analysis of variance (ANOVA), paired comparison will be carried out using the student $t$ -test and a $p$ -value of equal to or less than 0.05 ( $p<$ 0.05) will be considered as significant.

2.9 Sample collection and processing

About 3 mL of blood will be collected from each participant into ethylene diaminetetraacetic acid (K3DTA) bottle and used for full blood count testing using automated haematology analyser.

2.10 Methods of laboratory analysis

2.10.1 Analysis of full blood count

The full blood count parameters were analyzed using a fully automated 5-part differential haematology analyzer (Model Mythic 22-CT, Orpheee, Switzerland). The principle of the analyzer is based on the impedance and flow cytometry principle. The impedance principle is on the basis that red cell or white blood cells are poor conductors of electricity compared to the diluents such as saline.

Table 1
Distribution of subjects based on socio-demographic and obstetrics indices of subjects

Parameter	Frequency	%
Trimester
First	25	33.78
Second	25	33.78
Third	24	32.44
Parity
Prima	39	40.6
Para	14	14.6
Multi para	43	44.8
Ethnicity
Hausa	59	61.5
Fulani	11	11.5
Igbo	3	3.1
Yoruba	9	9.4
Others	14	14.6
Educational status
Non-formal	36	37.5
Primary	12	12.5
Secondary	38	39.6
Tertiary	10	10.4
Age (Years)
$<$ 24	31	41.89
25–34	34	45.95
35–44	9	12

Table 2

Mean haematological values of pregnant subjects and non-pregnant controls

Parameter	Mean values	Mean values	$t$ -value	$p$ -value
	of subjects	of controls
Haemoglobin	10.7 $\pm$ 0.13	12.2 $\pm$ 0.44	3.209	0.004*
(g/dl)
PCV (%)	31.4 $\pm$ 0.38	36.2 $\pm$ 1.17	3.902	0.001*
Total WBC	5.3 $\pm$ 0.22	4.6 $\pm$ 0.59	$-$ 1.133	0.267
( $\times$ 10 ${}^{9}$ /L)
Neutrophils (%)	42.6 $\pm$ 3.06	20.0 $\pm$ 2.33	$-$ 5.87	0.000*
Platelets	252.7 $\pm$ 14.35	362.7 $\pm$ 36.51	2.803	0.009*
( $\times$ 10 ${}^{9}$ /L)
MCV (fl)	82.4 $\pm$ 1.71	79.8 $\pm$ 2.94	$-$ 0.757	0.454
MCH (pg)	29.1 $\pm$ 0.37	28.7 $\pm$ 0.75	$-$ 0.474	0.639
MCHC (g/dL)	33.9 $\pm$ 0.15	35.5 $\pm$ 2.32	0.664	0.514
RBC (cells/ $\mu$ L)	3.7 $\pm$ 0.04	4.3 $\pm$ 0.11	4.811	0.000*

Table 3

Prevalence of anaemia and thrombocytopenia among subjects

Parameter	Number	%
Anaemia (HB $<$ 11 b/dl)	43	58.11
Thrombocytopenia (platelet count $<$ 140 $\times$ 10 ${}^{9}$ /l)	5	6.75

Table 4

Prevalence of Anaemia among subjects based on some socio-demographic and obstetric variables

Anaemia (Hb $<$ 11 g/dl)	Number	%
Educational status
Non-formal	16	21.62
Primary	18	24.32
Secondary	6	8.11
Tertiary	4	5.41
Parity (no of children alive)
Prima (0)	19	25.676
Para (1)	8	10.811
Multi para (2)	21	28.377
Ethnicity
Hausa	22	53.659
Fulani	7	17.073
Igbo	1	2.449
Yoruba	2	5.878
Others	9	21.951

Table 5

Prevalence of anaemia among subjects based on some socio-demographic and obstetric variables

Anaemia (Hb $<$ 11 g/dl)	Number	%
Educational status
Non-formal	16	21.62
Primary	18	24.32
Secondary	6	8.11
Tertiary	4	5.41
Parity (no of children alive)
Prima (0)	19	25.676
Para (1)	8	10.811
Multi para (2)	21	28.377
Ethnicity
Hausa	22	53.659
Fulani	7	17.073
Igbo	1	2.449
Yoruba	2	5.878
Others	9	21.951

Table 6

Effect of socio-demographic and obstetric variables on the leukocyte count of subjects

Factor	Mean $\pm$ SD	F	$p$ -value
Trimester
1st	3.71 $\pm$ 1.02	47.490	$<$ 0.001*
2nd	6.00 $\pm$ 2.05
3rd	6.25 $\pm$ 1.41
Parity
Prima	5.18 $\pm$ 1.53	0.871	0.459
Para	5.80 $\pm$ 2.06
Multi para	5.22 $\pm$ 1.99
Marital status
Single	6.07 $\pm$ 2.17	1.130	0.327
Married	5.28 $\pm$ 1.92
Type of marriage
Monogamous	5.21 $\pm$ 1.90	1.272	0.285
Polygamous	5.73 $\pm$ 2.02
Ethnicity
Hausa	5.12 $\pm$ 2.07	0.820	0.539
Fulani	5.41 $\pm$ 2.01
Igbo	7.00 $\pm$ 0.66
Yoruba	5.51 $\pm$ 1.79
Others	5.29 $\pm$ 1.59
Level of education
None	5.02 $\pm$ 2.00	0.772	0.546
Primary	5.77 $\pm$ 2.11
Secondary	5.22 $\pm$ 1.97
Tertiary	5.71 $\pm$ 1.31
Age (years)
$<$ 24	5.12 $\pm$ 2.14	0.751	0.521
25–34	5.47 $\pm$ 1.81
35–44	5.36 $\pm$ 1.61

Table 7

Effect of socio-demographic and obstetric variables of the neutrophil count of subjects

Factor	Mean $\pm$ SD	F	$p$ -value
Trimester
1st	14.20 $\pm$ 10.92	48.386	0.001*
2nd	50.69 $\pm$ 21.68
3rd	63.70 $\pm$ 7.43
Parity
Prima	52.21 $\pm$ 20.66	29.941	$<$ 0.001*
Para	49.08 $\pm$ 25.54
Multi para	38.43 $\pm$ 27.22
Marital status
Single	66.13 $\pm$ 9.73	6.341	$<$ 0.001*
Married	41.59 $\pm$ 26.32
Type of marriage
Monogamous	39.96 $\pm$ 26.28	33.341	$<$ 0.001*
Polygamous	53.81 $\pm$ 24.00
Ethnicity
Hausa	35.71 $\pm$ 26.54	17.449	0.001*
Fulani	50.37 $\pm$ 24.86
Igbo	68.03 $\pm$ 6.70
Yoruba	42.85 $\pm$ 26.09
Others	51.69 $\pm$ 24.17
Level of education
None	35.31 $\pm$ 28.18	29.353	$<$ 0.001*
Primary	50.48 $\pm$ 25.98
Secondary	41.62 $\pm$ 24.50
Tertiary	53.41 $\pm$ 26.68
Age (Years)
$<$ 24	35.58 $\pm$ 24.94	31.366	$<$ 0.001*
25–34	45.17 $\pm$ 27.50
35–44	56.92 $\pm$ 19.98

Table 8

Effect of socio-demographic and obstetric variables on platelets count of subjects

Factor	Mean $\pm$ SD	F	$p$ -value
Trimester
1st	297.48 $\pm$ 148.80	7.741	$<$ 0.001*
2nd	241.88 $\pm$ 57.32
3rd	204.46 $\pm$ 57.35
Parity
Prima	225.31 $\pm$ 61.10	5.026	0.003*
Para	256.08 $\pm$ 67.28
Multi para	252.84 $\pm$ 119.92
Marital status
Single	233.67 $\pm$ 51.39	7.317	0.001*
Married	249.16 $\pm$ 106.07
Type of marriage
Monogamous	253.22 $\pm$ 111.10	7.559	0.001*
Polygamous	228.43 $\pm$ 66.97
Ethnicity
Hausa	273.30 $\pm$ 126.32	3.665	0.005*
Fulani	218.90 $\pm$ 53.83
Igbo	213.00 $\pm$ 58.89
Yoruba	230.38 $\pm$ 73.30
Others	214.46 $\pm$ 61.76
Level of Education
None	253.51 $\pm$ 171.26	3.838	0.006*
Primary	235.09 $\pm$ 73.28
Secondary	258.27 $\pm$ 139.14
Tertiary	217.44 $\pm$ 63.06
Age (Years)
$<$ 24	249.13 $\pm$ 60.72	5.273	0.002*
25–34	258.68 $\pm$ 139.48
35–44	208.11 $\pm$ 53.98

3. Results

This case-control study investigated some haematological parameters among 74 consecutively-recruited pregnant women aged 18 to 44 years and mean age and mean income of 28.00 $\pm$ 8.295 years and 2760.42 $\pm$ 7975.178 naira respectively. Table 1 shows the mean values of some socio-demographic variables among the subjects. Haematological values were compared between pregnant subjects and non-pregnant controls. The haemoglobin, PCV, platelet and Red cell count was significantly lower among pregnant subjects (10.7 $\pm$ 0.13, 31.4 $\pm$ 0.38, 252.7 $\pm$ 14.35 and 3.7 $\pm$ 0.04) respectively compared to non-pregnant controls (12.2 $\pm$ 0.44, 36.2 $\pm$ 1.17, 362.7 $\pm$ 36.51 and 4.3 $\pm$ 0.11) ( $p=$ 0.004, 0.001, 0.009 and 0.000) respectively. Table 2 shows the Mean Haematological values of Pregnant Subjects and non-pregnant Controls. Table 3 show the prevalence of Anaemia and Thrombocytopenia among the pregnant Subjects. The prevalence of anaemia (HB $<$ 11 g/dl) and thrombocytopenia among the pregnant subjects was 58.10% and 6.76% respectively. The prevalence of anaemia was compared among subjects based on socio-demographic and obstetric variables. Table 4 shows the prevalence of anaemia among subjects based on some socio-demographic and obstetric variables. Table 5 shows the effects of socio-demographic and obstetric variables on the Haemoglobin level of subjects. Table 6 shows the effects of socio-demographic and obstetric variables on the leucocyte (Total White blood cell) count level of subjects. Table 7 shows the effects of socio-demographic and obstetric variables on the neutrophil level of subjects. Table 8 shows the effects of socio-demographic and obstetric variables on the platelets of level subjects.

4. Discussion

This study investigated the level of some Haematological indices among pregnant women and non-pregnant controls. Anaemia continues to be a major health problem in many developing countries and is associated with increased rates of maternal and perinatal mortality, premature delivery, low birth weight, and other adverse outcomes [26]. This study demonstrated that the prevalence of anaemia (Hb $<$ 11 g/dl) is 58.11% among the Sokoto pregnant women. Other studies have shown a higher degree of anaemia in pregnancy such as 87% in India [27]. 58.6% in China [27] while some others showed a lower prevalence; 50% in South Asia [28] and 43% in Turkey [29]. Our finding is also higher than the 40.4% [31] prevalence observed in Eastern Nigeria. In Abakiliki Nigeria, the prevalence of anaemia among pregnant at booking was 56% [32]. The prevalence of anaemia among pregnant women in Abeokuta, Nigeria was 76.5% [33]. The prevalence of anemia in developing countries is relatively high (33% to 75%) [34]. In Africa the prevalence of anaemia among pregnant women was 57.1% [35]. In Nigerian and other West African countries, the predisposing factors for anaemia in pregnancy include; iron and folate deficiency, grand multiparity, low socioeconomic status, malaria infestations, HIV infections, inadequate child spacing, hookworm infestation; HIV and haemoglobinopathies [36, 37].

We compared the prevalence of anaemia among the pregnant subjects based on socio-demographics and obstetric variables. We observed that the prevalence of anaemia was higher in less educated women with primary education and no no-formal education (24.32% and 21.62%) respectively. Our finding is consistent with previous reports [38, 39] which indicated that prevalence of severe anaemia was highest among women with an education level of primary school or below. Better educated women are more likely to have access to higher wages. They are also more likely to make better informed decision about nutrition, child spacing, adherence to iron and folic acid prescribed during pregnancy and more likely to use of insecticides- treated nets to prevent malaria infection.

Thrombocytopenia in pregnancy is typically characterized by a platelet count $<$ 140 $\times$ 10 ${}^{9}$ /L, commonly occurs in the mid-second to third trimester [40]. It is is a common haematologic abnormality during pregnancy associated with risk of bleeding during labour, after childbirth and during caesarean section. This study indicated a prevalence of thrombocytopenia (Platelet count $<$ 140 $\times$ 10 ${}^{9}$ /L) of 6.75% among the Sokoto pregnant women. Our finding is significantly higher than a prevalence of gestational thrombocytopenia of 13.5% observed among pregnant women in Lagos, Nigeria [41]. Similarly, a prevalence of 15.3% [42] was reported among pregnant women in Ghana. A prevalence of 11.6% [43] reported by Boehlen and Colleagues in 2006 while a 7.2% [44] prevalence was reported among Caucasian women. The cause of gestational thrombocytopenia is uncertain. However, it is thought to occur as a result of accelerated platelet consumption, increased plasma volume seen in pregnancy and the presence of anti-platelet antibodies may also play a role [45].

There were no significant differences in the WBC count of the pregnant subjects and the non-pregnant controls ( $p=$ 0.26). The neutrophil count was significantly higher among the pregnant subjects compared to controls ( $p=$ 0.000). There was a statistically significant difference in the total leucocyte and neutrophil count of the pregnant subjects-based on trimester ( $p\leqslant$ 0.001). Our finding is consistent with a previous report [46] which indicated a non-significant increase the levels of total WBC count among anemic pregnant women, compared to non-anemic women. Leucocytosis, occurring during pregnancy is due to the physiologic stress induced by the pregnant state. It is thought to be secondary to neutrophilia and attributed to increased inflammatory response, a consequence of selective immune tolerance, immunosuppression, immunomodulation of the foetus, impaired neutrophilic apoptosis in pregnancy as well as stress-induced redistribution of WBCs between the marginal and circulating pools [47]. Our finding is consistent with previous report which indicated that there is increase in total leucocyte count from the first trimester to the second trimester and dips during the third trimester [48]. Our finding is however at variance with previous reports which indicated a sustained increase of the WBC count across the three trimesters of pregnancy [40, 49].

5. Conclusions

This study has shown that pregnancy has a significant effect on some haematological parameters of women of African descent. The results of this research work indicate the need to routinely monitor the full blood count, anaemia and thrombocytopenia among pregnant women of African descent. Finding from this study indicates the importance of prenatal care and the need for micronutrient supplementation during pregnancy among women of African descent. There is need for authorities in African countries to encourage the fortification of food and beverages with various micronutrients to improve the wellbeing of pregnant women. There is need for public enlightenment program to educate pregnant women on the need to maintain a balanced diet containing sufficient number of micronutrients and vitamins.

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