Background: The association between maternal hemoglobin concentration and pregnancy outcome has been a source of ongoing controversy. Objectives: To assess the association between maternal hemoglobin concentration and preeclampsia, preterm birth and low birth weight. Methods: Retrospective analysis of 191 patients who gave birth at New Somerset Hospital between 1 and 22 May 2017 at 28 weeks' gestation or more, with a documented maternal hemoglobin concentration at 22–33 weeks' gestation.
Results: The distribution of pre-eclampsia, low birth weight and preterm birth were skewed towards the higher side of maternal hemoglobin concentration. There were statistically significant differences in the development of pre-eclampsia, low birth weight and preterm birth between maternal hemoglobin concentrations =>13g/dl and those <13g/dl. Conclusion: High maternal hemoglobin concentration at 22 – 33 weeks of pregnancy is associated with an increased prevalence of pre-eclampsia, low birth weight and preterm birth.
INTRODUCTION Background
Birth weight can reflect the mother's overall health just before conception and during pregnancy. Anemia during pregnancy is defined by the World Health Organization as a hemoglobin concentration below 11 g/dL (45). Anemia during pregnancy is associated with an increase in fetal and maternal morbidity and mortality and remains a major public health concern (46).
There is a correlation between maternal hemoglobin concentration in pregnancy and pregnancy outcome in terms of preterm birth, low birth weight, perinatal mortality and morbidity. Hemodilution occurs during pregnancy to increase perfusion of the placenta through a reduction in blood viscosity. The results of the association between maternal hemoglobin concentration and pregnancy outcome will guide clinicians to identify mothers who are at risk.
LITERATURE REVIEW The Placenta
According to Sandra et al. (59) high maternal hemoglobin concentration is associated with a decrease in placental weight. The outcome of the pregnancy is poor when the mother's hemoglobin concentration does not decrease during pregnancy (54). Huisman and Aarnoudse (4) reported that a high maternal hemoglobin concentration in the middle of the trimester is associated with low birth weight.
Yip (90) reported in his study that high maternal hemoglobin concentration is associated with poor pregnancy outcome. The relationship between maternal hemoglobin concentration and pregnancy outcome has been a source of constant controversy. There is no correlation between the mother's hemoglobin concentration during pregnancy and the outcome of the pregnancy.
METHODOLOGY Study Population
The aim of the study was to assess whether changes in maternal hemoglobin concentration in early to mid or late pregnancy are associated with adverse pregnancy outcomes related to low birth weight, preterm delivery and preeclampsia. The study is being conducted in part to fulfill the requirements for the award of the MMed Degree in Obstetrics and Gynecology by the University of Cape Town. All women who delivered a child within the study period at New Somerset Hospital with a gestational age of 28 weeks or more, with a documented maternal hemoglobin concentration at a gestational age of 22 – 33 weeks.
Consecutive recruitment of women who delivered an infant of 28 or more weeks' gestation with documented hemoglobin concentration at 22 – 33 weeks' gestation from 1 May 2017 until the sample size of 191 was reached (on 22 May 2017) at which point recruitment was stopped. The lowest maternal hemoglobin concentration documented at 22 – 33 weeks gestation was recorded on the data collection sheet. The highest blood pressure documented with proteinuria after 20 weeks' gestation was recorded on the data collection sheet.
Women who delivered at New Somerset Hospital with documented maternal hemoglobin concentration at 22–33 weeks' gestation. The measurements for evaluation were those that had already been made and were in the hospital archive, so there was no additional risk to the study patients. No patient names were used in the study or during the preparation of the final study report.
Paper-based data were kept in a secure location and were only accessible to those involved in the study. All data reviewed in the study were those previously obtained as part of the routine care of pregnant women in the antenatal period or during hospital delivery. The aim of the study was to recruit 191 patients to meet the minimum sample size requirements.
In addition, the study patients were divided into two categories: those with maternal hemoglobin =>13.0g/dl at week 22 – 33 of pregnancy considered as the group with failed physiological hemodilution in pregnancy and those with maternal hemoglobin <13.0g/dl in Pregnancy 22 - 33 weeks is considered as the group that has achieved physiological hemodilation in pregnancy.
RESULTS
The failed hemodilution group (Hb =>13) was associated with a relatively lower birth weight, higher preterm birth and pre-eclampsia rate, and low placental weight compared to the physiologic hemodilution group (Hb <13). However, there were no statistically significant differences in maternal age, parity, body mass index, smoking status, HIV status, alcohol consumption, rhesus status, syphilis status, stillbirth and Apgar score after 1 and 5 minutes between the two groups. There were no cases of low birth weight in maternal hemoglobin concentrations of <9.6 g/dl.
The highest proportion of low birth weight (72.73%) occurred with maternal hemoglobin concentration >15.5 g/dl. The distribution of low birth weight and birth weight => 2500 g for each category of maternal hemoglobin is shown below in Figure 2. The distribution of preterm birth and full-term birth for each category of maternal hemoglobin concentration is shown below in Figure 3.
The distribution of the development of preeclampsia for each of the maternal hemoglobin concentration categories is illustrated below in Figure 4. The lowest mean birth weight of 2360 g occurred with a maternal hemoglobin concentration of >15.5 g/dL. However, there were statistically significant differences in birth weight (p=0.002), pregnancy at birth (p=0.016) and placenta weight (p=0.01) between the two groups: with and without preeclampsia.
Pre-eclampsia was associated with relatively lower birth weight, preterm birth and low placental weight.
DISCUSSION
This association was independent of hemoglobin status. hemoglobin concentration in nulliparous women with fetal growth retardation. Also, Murphy et al reported a higher rate of preterm birth, low birth weight, and the development of hypertension in women with high maternal hemoglobin in the first and second trimesters. The resulting noticeable decrease in blood flow through the utero-placental unit and thus poor oxygen supply leads to tissue hypoxia with subsequent release of vasoactive substances from placental tissues into the circulation, causing generalized vasoconstrictive disorder and endothelial cell dysfunction affecting all organs of the body. affect. in high blood pressure, proteinuria and thrombocytopenia.
An increase in the permeability of the capillary endothelium occurs with a significant loss of serum proteins, resulting in a decrease in intravascular volume and an increased concentration of maternal hemoglobin. The body achieves this by increasing cardiac output and hemodilution, which results from a 50–60% increase in plasma volume and an increase in red blood cell mass, called physiological hemodilution (63). There is an interplay between viscous forces and kinetic forces regarding circulation in blood vessels, with viscous forces playing an important role in smaller blood vessels, such as the placenta, where flow velocity is low (98).
High viscosity with accompanying higher viscous forces and the resulting poor blood flow in the placenta lead to a poor supply of oxygen and nutrients to the developing fetus and therefore limitation in its growth. A low hemoglobin concentration can lead to a reduction in the supply of oxygen to tissues and therefore low hemoglobin in the utero-placental circulation with accompanying reduced oxygen supply to the placenta can lead to poor growth and development of the fetus (105). One such body's adaptation is the increase in the development of new blood vessels in the placenta (106).
This form of adaptation has been observed in the placenta of pregnancy where the concentration of maternal hemoglobin is low (107). In pregnancies where the mother's hemoglobin concentration is low, the increase in placental size can be explained by the development of many new blood vessels in the placenta, which occurs through adaptation. A possible explanation for the association between high maternal hemoglobin concentration and preterm birth may be the effect of hyperviscosity.
A decrease in maternal hemoglobin concentration in the second trimester, which probably reflects an adequate expansion of plasma volume, appears to be essential in relation to pregnancy outcomes, both in the fetus and in the mother.
CONCLUSION AND RECOMMENDATIONS
National, regional and worldwide estimates of preterm birth rates in the year 2010 with time trends since 1990 for selected countries: a systematic analysis and implications. Costs and health utilities associated with extremely preterm birth: evidence from the EPICure study Value Health. The relationship between the different low birth weight strata of newborns with infant mortality and the influence of the main health determinants in the extreme south of Brazil.
Low Birth Weight Infants: Morbidity and Mortality Pattern in a Tertiary Health Care Facility in Southeast Nigeria. Relationship between placental weight and birth weight of newborn in a Nigerian hospital. Maternal hemoglobin concentration and its relation to birth weight in newborns of mothers with preeclampsia.
High maternal hemoglobin concentration in the first trimester as a risk factor for pregnancy-induced hypertension. Hemoglobin levels during the first trimester of pregnancy are associated with the risk of gestational diabetes mellitus, pre-eclampsia and preterm birth in Chinese women: a retrospective study. The significance of an abnormally low or high hemoglobin concentration during pregnancy: A special consideration of iron nutrition.
High and low hemoglobin levels in pregnancy: different risks for preterm birth and small for gestational age.
