Data source and study population
Births were identified from the records collected by the information
system of Guangdong Women and Children Hospital from September 2014 to
March 2018 (N = 37,193). We extracted maternal information including age
at delivery, delivery mode, pre-pregnancy weight and height, parity, the
date of last menstrual period, delivery date as well as smoking status
during pregnancy. We also extracted the information of the newborns
including birth weight and infant sex. The test results of maternal
mid-pregnancy ApoA-1, ApoB and oral glucose tolerance test (OGTT) were
obtained from laboratory information system of the study hospital.
Maternal mid-pregnancy ApoA-1 and ApoB values were determined based on
fasting blood samples tested during their routine pregnancy tests at a
median of 18 weeks of gestation (IQR : 16 - 22 weeks) and were measured
by immunoturbidimetric assays.
The women satisfying the follow criteria were included in the analysis:
1) who had the data of mid-pregnancy ApoA-1 and ApoB, OGTT, the date of
last menstrual period, pre-pregnancy weight and height; 2) gave a single
live birth. We excluded post-term births (gestational
age>42 weeks), babies with birth defects or the recorded
birthweight out of the range 500-5000 g. We further excluded the outlier
value (< 25th -1.5 IQR or > 75th +1.5 IQR) of
ApoA-1 and ApoB. Finally, a total of 5,986 mother-newborn pairs were
included in the present study (Fig. 1) . We compared
characteristics between included women (n= 5,986) and those who were
excluded due to mid-pregnancy apolipoprotein measurements were not
available (n= 7,917). Mothers in the included group were slightly
younger (32.2 vs 32.4; p = 0.021) than women who were excluded but there
was no significant difference in pre-pregnancy BMI or the incidence of
preterm birth between this two groups (see supplementary Table
S1 ).
As all data used in the present study was de-identified, no written
informed consents were obtained from the participants. The study
protocol has been approved by the ethics committee of Guangdong Women
and Children Hospital.