The Relationship between Maternal Haemoglobin and Haematocrit with Low Birth Weight and Preterm Labour

Neonatal mortality rate is among the most important health indicators in every country, which is linked to the adequacy of maternal health care and social and economic factors (1). One of the determinants of neonatal mortality is low birth weight (LBW) (1, 2). The LBW is defined as birth weight of a newborn between 1500 and 2500 g (1). Mortality rate in the neonates with LBW  is reported as 40 times and in newborns with very low birth weight (VLBW), between 1000 and 1500 g, is announced as 200 times higher than that in neonates with normal birth weight (2). According to statistics, 90% of the newborns with LBW are annually born in developing countries (3). In some areas of Asia, one out of two live births is considered to be a neonate with LBW (3).

In Iran, 289 children below 5 years old daily die among which 48% are neonates mostly with LBW (3). Maternal age, occupation, and weight, as well as a history of LBW in previous pregnancies, the number of pregnancies along with addiction and pregnancy duration have been identified as predicting factors for the LBW (4-6). On the other hand, poor socio-economic condition, malnutrition, hypertension, multiple pregnancies, and low maternal haemoglobin (Hb) and haematocrit (HCT) levels, as well as illiteracy, maternal chronic diseases, and alcohol use were reported to be related with the LBW (7-9). It is believed that the LBW is associated with mental retardation, learning disorders, and cognitive growth retardation, as well as visual-motor disorders, and cerebral palsy (CP) (10).

Preterm labour (PTL) is defined as giving birth earlier than 37 weeks of gestation (11). Based on the differences observed in mortality and morbidity, the PTL was divided into the following categories based on the gestational age (GA), which were mild preterm (between 32 and 36 weeks of gestation), very preterm (between 28 and 31 weeks of gestation), and extremely preterm (earlier than 28 weeks of gestation) (12). The PTL may be related to cardiopulmonary disorders, brain growth retardation, and various anomalies (13). Morbidity and mortalities due to the PTL are mainly attributed to prematurity of the organs and include respiratory distress syndrome, bronchopulmonary dysplasia, pneumothorax, pneumonia, patent ductus arteriosus, intraventricular haemorrhage, periventricular leukomalacia, and the CP (13). The neonates with both LBW and PTL are at extremely high risks regarding morbidity and mortality (2, 13, 14).

Anaemia in pregnancy is defined as the HCT level below 33% or the Hb level below 11g/dl in the first and third trimester and the Hb below 10.5 g/dl in the second trimester (15, 16). Anaemia in pregnancy can lead to the PTL, intrauterine growth retardation, reduced physical activity capacity, immune response disorders, and heart failure in mother; however, it can result in the LBW, PTL, low Apgar score, and perinatal mortality in newborns (17, 18). It was previously reported that anaemia in the first half of pregnancy is related to increased risk of the PTL (19). Therefore, maternal anaemia is among the preventable causes of the PTL and LBW. On the other hand, the higher values of the HCT are related to maternal and neonatal adverse outcomes (19). The present study was carried out in order to evaluate the maternal factors, which contribute to the neonatal LBW and PTL in women that gave birth to live neonates and were admitted in the obstetric ward of Mobini Hospital, Sabzevar, Iran.

Materials and Methods

This cross-sectional study was conducted on women that gave birth to live newborns in Mobini Hospital, Sabzevar, Iran in 2016. The inclusion criteria were giving birth to live infant and having complete medical records. The exclusion criteria were multiple pregnancies, history of diabetes, thalassemia or sickle cell anaemia in mother, and infants with gross congenital abnormalities, as well as pre-eclampsia and the obstetric causes of the PTL, including placenta abruption or premature rupture of membranes.

All the participants were interviewed by the author and asked to provide information regarding their age, infant gender, place of residence, educational level, the number of pregnancies, number of health care visits during pregnancy, and neonatal outcomes. Birth weight was obtained from medical records of the newborns and GA was obtained from the medical records based on ultrasounds. The Hb and HCT levels in the first, second, and third trimester were obtained from medical records of the subjects. The HB and HCT were measured by Technicon H-1 blood counter after taking peripheral venous blood in Ethylenediaminetetraacetic acid tubes. The HCT was divided into three groups, which were low (<34%), normal (34%-40%), and high (>40%), while the Hb was grouped into low (<10.5g/dl), normal (10.5-13g/dl), and high (>13 g/dl) based on the WHO criteria.

The data were analysed using SPSS (version 19). The Continuous data were checked for normality by Kolmogorov-Smirnov test. The mean and standard deviation were utilized to describe quantitative variables. The Qualitative variables were presented as frequency and percentage. The Chi-square test was used to evaluate the relation between categorical variables. P-values lower than 0.05 were statistically considered significant.

Results

A total of 383 pregnant women were recruited in this study. The mean age of the subjects was 25.5 years. The body mass index mean of the subjects was 22.6 kg/m². Table 1 tabulates the demographic characteristics of the women. The mean birth weight of the newborns was 3180 g (birth weight range: 2100-4700g). The LBW was observed in 21 (5.5%) of the neonates, while the birth weight was reported between 2500-4000 g in 353 (92.2%) newborns; furthermore, 9 (2.3%) cases had the birth weight of more than 4000 g.

The mean GA of the subjects was 38 weeks (minimum GA: 33 weeks, maximum GA:
42 weeks). The PTL, term, and post-term pregnancies were observed in 38 (9.9%), 296 (77.3%), and 49 (12.8%) subjects, respectively. The HCT of the subjects in the first trimester was reported as 38% (minimum HCT: 30%, maximum HCT: 47%), while the HCT in the second and third trimesters were 35.5% (minimum HCT: 26%, maximum HCT: 45.5%) and 34.5% (minimum HCT: 28%, maximum HCT: 41.8%). The HCT categories of the subjects are shown in Table 2. The Mean Hb of the subjects in the first trimester was 12.8 g/dl (minimum Hb: 9 g/dl, maximum Hb: 16 g/dl), while the mean Hb in the second and third trimesters were 12.07 g/dl (minimum Hb: 9.5 g/dl, maximum Hb: 14.2 g/dl) and 11.5 g/dl (minimum Hb: 8.6 g/dl, maximum Hb: 14 g/dl). Table 2 presents the HCT categories of the cases.

 

 

The results of the chi-square test revealed a significant relation between birth weight with the HCT and Hb levels in the first, second, and third trimesters (P<0.001). The association between the GA at birth with the HCT and Hb levels in pregnancy were significant based on the results of chi-square test (P<0.01) (Table 4). The relationship between birth weight and gestational age, along with other study parameters, including maternal age, maternal height, the number of pregnancies, maternal education level, and neonate gender, as well as place of residence, and economic status are shown in Table 5. There was a significant relationship between the number of pregnancies and maternal educational level (P<0.05) based on the results of chi-squared test (Table 5).