Introduction

Peak expiratory flow rate (PEFR) was designated as the maximal air flow rate achieved while forcefully expelling from the lungs following maximal inspiration (Pocock and Christopher, 1999). The use of PEFR as a parameter for assessing respiratory function was first introduced by Hadon in 1942. From a position of maximum inspiration, the PEFR represents the largest expiratory flow rate expressed in litres per minute and has remained a simple effective tool for the assessment of ventilatory function (Wright and McKerrow, 1959;Pocock and Christopher, 1999;Dikshit et al., 2005). The inexpensive nature of the peak expiratory flow rate makes it a suitable test of ventilatory function for use in many parts of Africa where medical facilities are still poor and hence represents a simple, easy and portable test for lung function (Cotes, 1993; Quanjer et al., 1995; Radoes and Camargo, 2004). PEFR can be affected by a number of factors including age, sex, body mass index (BMI), daily activities, nutrition, pregnancy, and smoking. Thus, the PEFRmainly depends on the voluntary and muscular effort of the subject (Daniel et al., 2011).

Hematology is the branch of internal medicine and allied fields concerned with the study of blood, including the blood forming organs and diseases. Hematological parameters are those related to blood and the blood forming organs. The values of these parameters, some of which includes Packed Cells Volume (Hematocrit), Red and White Blood Cells counts, Platelet count, Erythrocyte Sedimentation Rate, Differential Leukocytes count, etc., enables the health worker to reach one of several diagnosis anddecisions.The fact remains that some hematological parameters are bound to show alterations in certain conditions, including pregnancy. For example, it is known that hematocrit value may be employed to evaluate anemic condition; erythrocyte sedimentation rate (ESR) value maybe employed as a non-specific measure of inflammation, sickle cell anemia or rheumatoid arthritis, hereditary spherocytosis and congestive heart failure (Pisetsky, 2007), platelet count value have been employed to monitor the cause of excess bleeding (Campbell and Neil, 2008; Schmaier, 2008), white blood cells count (which are the cells of the immune system) is areliable indicator that can be used to track several disease conditions, etc. Pregnancy, the state of retaining the developing embryo within the uterus of the female, is typically conveniently broken down into three periods or trimesters of the average duration of about 42 weeks (Cunningham et al., 2010). Maternal physiology undergoes considerable changes during pregnancy, and these are even secondary to the effects of progesterone and estrogen which are products of the ovary in the first 12 weeks of pregnancy, and thereafter are produced by the placenta. These changes enable both the fetus and placenta to develop and prepare the mother and baby for delivery (Bernhard and John, 2003). All the aforementioned changes are known as adaptations to the pregnant state which begins after conception. For example, maternal endocrine system adaptation to pregnancy state involves the hypothalamus, pituitary, parathyroid, thyroid, adrenal glands and the ovary, and all these are linked to varying degrees of interactions with fetal-placental-maternal units. Thus, there is no doubt that changes in hematological parameters are bound to occur in parallel with the adaptations to the pregnant state. It was the aim of this study to assess possible alterations in some of the vital hematological parameters in pregnancy state and compare these with those of non-pregnant state.

Materials and Method

Eighty-four (84) pregnant women between the ages of 20-40 years were enrolled in the Antenatal Clinic of the University of Benin Teaching Hospital (UBTH) and St. Philomena’s Catholic Hospital, Benin City, Nigeria, were engaged for this study. The studygroupings of the pregnant women were: ten (10) in the first trimester, forty (40) in the second trimester and thirty-four (34) in the third trimester. There was another group of thirty-four (34) non-pregnant age-matched women who also served as control subjects. Ethical approval was obtained from the Research and Ethics Committee of both Hospitals for the study. The women were screened with some exclusion criteria including those involving some types previous medical history and treatments, smokers, cases involving heavy regular consumption of alcohol, etc., all of which served as exclusion criteria for the study. Height and weight of each participating woman wasdetermined using standard anthropometric protocol (International Society for the Advancement of Anthropometry, 2001). The blood pressure of each subject wasalso measured.The BMI was calculated from the formula: weight (kg)/height (meters2).The peak flow rate was determined using the Wright’s mini peak flow meter while subject was in sitting position. Informed consentthat also met the inclusion criteria was obtained from each subject, and the purpose of the research and details of the procedures were explained to each subject.

Subjects were required to make maximal expiratory effort into the peak flow meter after an initial maximum inspiration. Three readings were taken with the highest value recorded.With the use of syringes and needle, hand gloves and methylated spirit, some hematological values were measured from the blood sample of each subject. The blood specimen bottles containing k EDTA (anticoagulant), cotton wool and tourniquet of about three milliliters of venous blood was collected from the median cubital vein with minimum stasis, while subject was seated. The blood samples were immediately transferred into the k EDTA containing tubes and properly mixed before they were transferred to a valid clinical laboratory whereupon, each was analyzed for Packed Cell Volume(PCV), Total White Cells Count, Platelets Count, Erythrocyte Sedimentation Rate (ESR), using automated haematological analyzer (Sysmex-k 10001VB=15.20, Japan). The results of the analysis of each of the blood samples were generated by the analyzer, and displayed by a paper speed on thermal printing copy. All statistical analysis were performed by the statistical package for the social science (SPSS), using the paired simple t-test with probability level p< 0.05 regarded as statistically significant.

Results

As presented in Table 1 werethe mean ±SEM values of the anthropometric characteristics and hematological parameters of the subjects. The results show that the gestational age increased significantly across the three trimesters (p< 0.001), the increase in the maternal weight was significant only in the third trimester, while the mean values of the maternal age and height remained unchanged. The determined values of the packed cell volume as noted in Table 2 revealed a consistently significantlydecreased across the three trimesters (p<0.001). Similarly, the platelets count showed notable decrease (p<0.005) in the second and third trimesters compared to the control. Values of the ESR increased significantly across the three trimesters (p<0.001), while the observed significant increase in WBC (p<0.005) was noted only in the second and third trimesters compared tothose of the control subjects. However, it is noteworthy that a significant increase was recorded when the result of the WBC of the first and third trimesters were compared.

Table 1: Mean values of anthropometric, body mass index, systolic and diastolic blood pressures in non-pregnant and pregnant women across the trimesters.   Click here to View figure

*Significant values are Mean± SEM compared to the control (***, ** and * denotep<0.001, p<0.01and p<0.05 respectively). a represents the non-pregnant group, b represents women in first trimester, c  represents women insecond trimester,    drepresents women in third trimester.

Table 2: Peak expiratory flow rate (PEFR) and some haematological parameters as determined in the non-pregnant and pregnant women across  the three trimesters

*Significant values are Mean ± SEM compared with control (*** ,**and *denotep<0.001, p<0.01 and p<0.05 respectively).arepresents the non-pregnant group,b represents women in first trimester,c represents women in second trimester, drepresents women in third trimester.

Discussion

As was noted in some earlier report, pregnancy and advancing gestation were associated with physiological changes in ventilatory function (Pernoll et al, 1975). In this study, PEFR showed a fairly consistent decrease acrossthe three trimesters of pregnancy (Table 2). Furthermore, the result revealed that the decrease in mean PEFR value ofthe pregnant womenwas lowest in the third trimester (391.25±7.81/min). Thus, significant decrease in PEFR in the three trimesters of pregnancy with the highest decreaseoccurring in the third trimester havebeen confirmed in the present study.

Theobserved progressive decrease in PEFR values in the two trimesters of pregnancy in this study can be attributed to the mechanical effects of the enlarged uterus caused by upwards thrusts (pushing) applied to the diaphragm,and which obviously limits its movements. Thus, it can be argued that there was also the resultant airways obstruction translated into the reduced PEFR valuesespecially in the late pregnancy (third trimester)where thehighest decline in PEFRin this study (391.251/min) was observed (Table 2).

Amongst the hematological parameters examined in this study, thepacked cell volume (PCV) of the pregnant women showed a clear decrease across the three trimesterscompared to the non-pregnant subjects (Table 2). This result isconsistent with the reports of earlier workers who similarly noted a decline in PCV in women in various states of pregnancy (Osoagbaka et al., 2000; Imam and Yahaya, 2008; Osonoga et al., 2011). James et al. (2008)also reported a significance difference in PCV across the trimesters. However, Dapper et al.(2006) on the other hand made some contrary observation, in which case the PCV was found to be lowest in the second trimester.

It is note worthy that the observed decrease in the PCV value was not statistically significant in the first and second trimesters and there was a slight increase in the third trimester (Table 2). These findings appear to be largely in agreement with those of Akingbola et al.(2006) and the reports of Akinsegun et al.(2013). Decreases in the PCV may be due to the vasodilatation activities of progesterone which ultimately leads to a reduction in blood pressure, thereby triggering the release of rennin andaldosterone through the renin-angiotensin system (RAS). The RAS on the other hand go through the normal tendency forthe retention of renal sodium thereby resulting into an increase in plasma volume (45%). Since the increase in plasma volume does not normally affect red cell mass, a physiological anaemia in pregnancy is obviously bound to result (Bernard and John, 2003). In this study, there was a slight but significant rise in PCV in the third trimester (Table2) which might be as a result of the slower increase in plasma volume, characteristic of late pregnancies. Also, it is known that in late pregnancy, the turn-over rate of progesterone and oestrogen occur and which eventually lead to the decrease in plasma volume with resultantslight rise in PCV value.

The increase in erythrocyte sedimentation rate (ESR) observed in this study was largely consistent with thefindings of earlier workers (Osoagbaka et al., 2000; Sonuga et al., 2011). It is possible that this can also be attributed to increases in plasma volume anemia and marked increase in fibrinogen as known to normally occur in pregnancy (Manten et al., 2004).

Earlier reportshave noted increases in total white blood cells (WBC) count in the state of pregnancy as was similarlyobserved throughout the three trimesters in this study (Table 2). While Pitkin and Witte (1979) generally reported increases in WBC in the state of pregnancy,it was observed in one other report that such increases in WBC may have been as the result ofincreases in neutrophils(Akinsegun et al., 2013). On the other hand, pain, nausea and vomiting have been reported and attributed to leukocytosis in pregnancy without infection. In late pregnancy however, a gradual reduction was observed. This report is consistent with thework of Akingbola et al.(2006). It is believed that this may be as a result of gestational thrombocytopenia, although absolute WBC count tends to remain within the normal range for most women throughout the trimesters.

Conclusion

The results of this study have clearly demonstrated the possible effect of the gravid uterus on the peak expiratory flow rate which was noted to decrease progressively in the trimesters. Thus, it can be concludedthat decrease in packed cell volume and platelet count withconcomitant increase in erythrocyte sedimentation rate and total white cell count are tfeatures ofnormal pregnancy, andthis is alikelytenable hypothesis.

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