INTRODUCTION
Preterm birth (PTB), defined as birth before 37 complete gestational weeks, accounts for about 18% of all deaths in under-five children and 35% of death among newborns1. Evidence have suggested that PTB was related to a serious of adverse health outcomes during childhood and adulthood, such as neurodevelopmental impairment, respiratory diseases, diabetes mellitus, hypertension and cardiovascular disease2-6. Precise etiology of PTB is still largely unknown. Emerging evidence has suggested that maternal dyslipidemia during pregnancy might be a risk factor for PTB7-13. A recent meta-analysis of these studies reported that a more atherogenic maternal lipid profile including elevated total cholesterol, triglycerides and low high-density lipoprotein (HDL) was positively related to the risk of PTB14.
Apolipoprotein (Apo) is a key component of lipid metabolism and transportation. ApoA-1 is the main structural protein component of HDL. ApoB represents the total amount of potentially atherogenic circulating lipoproteins, including low-density lipoprotein (LDL), very low-density lipoprotein (VLDL) and intermediate-density lipoproteins (IDL). The ApoB/ApoA-1 ratio reflects cholesterol balance between atherogenic and anti-atherogenic lipoprotein particles and were thought to be a reliable parameter to reflect lipid disturbance15. Abundant evidence have shown that apolipoprotein levels were associated with metabolic syndrome16, insulin resistance17 and cardiovascular disease15 among non-pregnant population. Epidemiological studies suggested that serum ApoB level and ApoB/ApoA-1 ratio during pregnancy were positively related to the risk of preeclampsia18-20, uteroplacental acute atherosis21 and intrauterine growth restriction22. However, evidence regarding the association between maternal apolipoprotein levels and PTB is limited. To our knowledge, only three previous studies have investigated the relationship between maternal ApoA-1 and PTB with conflicting results23-25. Furthermore, the effects of maternal ApoB and ApoB/ApoA-1 ratio on PTB have not been studied yet.
Thus, we aim to explore the relationship between serum ApoA-1, ApoB, ApoB/ApoA-1 ratio during pregnancy and PTB among Chinese pregnant women.