THE RELATIONSHIP BETWEEN LOW MATERNAL SERUM CHOLESTEROL LEVELS IN EARLY PREGNANCY AND ADVERSE BIRTH OUTCOME

Abstract

Background: Prematurity and other adverse birth outcomes such as low birth weight and birth defects are major causes of perinatal morbidity and mortality. The majority of these perinatal losses occur in babies with birth weights of less than 2500-g. There is also an increase in long-term neurodevelopmental sequelae, and the risk of hypertension and diabetes in later life. The physiologic hypercholesterolaemia of later pregnancy suggests an adaptive function for pregnancy maintenance or fetal growth. Decreased levels of maternal total cholesterol and low-density lipoprotein cholesterol have been reported in association with adverse pregnancy outcome such as intrauterine growth restriction (IUGR) and preterm delivery. This study thus hypothesized a possible link between low maternal serum cholesterol level, a substrate essential for both the hormonal and physical changes of early pregnancy and adverse birth outcomes.
Objectives: The study was a prospective observational cohort study designed to determine the incidence of preterm delivery and impaired fetal growth (low birth weight in term delivery) in women without identified major risk factors for adverse pregnancy outcome and to assess whether low maternal serum cholesterol during early pregnancy is associated these adverse birth outcomes (preterm delivery and impaired fetal growth) in these women.
Methods: Participants were enrolled for the study by consecutive sampling method at gestational age of 14 to 20 weeks. They were enrolled over a period of 8 months. Excluded from the study were those women with serious non-obstetric problems, at gestational ages of less than 14 and more than 20 weeks. Additional patients were also excluded on review of clinical data at delivery when records indicate significant intercurrent infections or other illness, preeclampsia or other gestational disorders such as gestational diabetes.
A structured interviewer-administered questionnaire (proforma) was used to collect information on the demographic and socioeconomic data at entry to care. Gestational age was estimated by last menstrual period and ultrasound examination. Blood samples were obtained to measure total serum cholesterol concentrations and the sera were then analyzed enzymatically by the cholesterol oxidase: paminophenazone (CHOD PAP) method. Pregnancy outcomes were obtained by extraction from medical records and the labour ward register.
Data analysis: All quantitative data were entered in computer and analysed using SPSS version 17 for windows. The relationship between Low maternal serum cholesterol and adverse birth outcome (preterm delivery and low birth weight) was tested using chi-square. All significance were reported at P<0.05.
Results: The study showed incidences of 8.7% and 14.4% respectively for preterm delivery and delivery of low birth weight (LBW) babies in the low risk study patients. Preterm birth was 4.83-times more common with low total maternal cholesterol than with midrange total cholesterol (11.8% versus 2.2%, PL=0.024) while LBW was 2.02-times more common in mothers with low total maternal cholesterol than in control mothers with midrange cholesterol (13.4% versus 8.3%, PL=0.043). Term infants born to mothers with low total cholesterol had a 225.5-g lower average birth weight than those born to control mothers with mid-range cholesterol levels (2348.0 vs. 2573.5-g) and this difference was statistically significant (P=0.004).

Conclusion: We can suspect from the study that the low maternal serum cholesterol (hypocholesterolaemia) is associated with preterm delivery/low birth weight in term infants but this will require further validation with prospective and longitudinal characterization of
maternal serum cholesterol profiles in subsequent investigations of preterm birth and impaired fetal growth. Therefore, until such more studies are performed, pregnant women should be encouraged to follow a healthy, balanced diet and regular antenatal visit to their healthcare providers.