Birth weight and child development are influenced multifactorial [21–23], among others by the lipid concentrations of the mother during pregnancy.
The relation between LDL- as well as total cholesterol on birth weight, described by Okala et al., could not be found here [22]. The determination of Okala's maternal lipids was carried out in the 20th and 30th week of pregnancy. This lack of relation may be attributed to the much earlier determination time compared to the LIFE-Child study, since the knowledge that the serum lipids show strong physiological concentration changes in the course of pregnancy [1]. Thus, comparability is difficult. Likewise, Wang et al., who also carried out the determination of the lipids in the 24th and 36th week of pregnancy, we were able to show that the HDL concentration of the mothers is inversely correlated with the birth weight of the newborns [21], whereby we were able to show that the HDL concentration also seems to influence growth and weight in the longer term up to the first year of life. The influence of maternal BMI on birth weight [24] and the correlation to SES [25] has already been shown in other studies. However, no study could be found that examined the influence of maternal BMI or serum lipid levels on anthropometric markers other than birth height or weight, as shown here.
Just like infant anthropometry, the serum lipid concentrations of newborns are influenced multifactorial [26–29]. Among other things, the lipid concentrations of the mothers seem to be related to the lipid concentrations of the children (Table 4), although this connection could no longer be demonstrated after adjusting for maternal BMI and/or socioeconomic status. The lipid concentrations of the children shown in Table 5, divided by maternal normo- and dyslipidemia, showed no statistical significance, but there is a trend: children of dyslipidemic mothers showed a clearly disadvantageous lipid profile with regard to cardiovascular risk. „Cardiometabolic dysfunction during pregnancy may not only contribute to long-term effects of the mother and child's vascular health but also potentially create cardiovascular risk for generational offspring.” [30]. In addition, non-HDL cholesterol is considered a cardiovascular risk factor. Higher non-HDL levels in childhood correlate with an increased carotid intima media thickness in adulthood [31]. Our results show, that maternal non-HDL cholesterol levels in the third trimester correlate with maternal BMI as well as birth weight and neonatal BMI. A correlation to the SES could not be found. All these results illustrate the importance of a healthy lifestyle with normal lipid levels during pregnancy.
Of course, a large number of additional factors not examined here also influence the lipid concentrations of children within the first few months of life, such as the influence of breastfeeding [27] or nicotine consumption during pregnancy [32]. The latter was deliberately neglected in this study, since the smoking status of the mother during pregnancy was not recorded when the LIFE-Child Study started recruiting, and the number of complete mother-child pairs would have been even lower. The influence of breast-feeding and nutritional habits of the mothers on the lipid concentrations of newborns and the relation to their SES is currently being carried out in another sub-analysis of the LIFE-Child study.
The considerable number of 982 mother-child pairs with regular follow-up examinations is a major advantage of this study. In addition, this is the first study ever to investigate the relation between maternal lipid concentrations during pregnancy and the various parameters of child anthropometry as well as the socioeconomic status in a German cohort.
It is critical to note that the LIFE Child study design includes a single blood measurement per visit. Thus, short-term intra-individual variation of blood lipids due to biological variation and preanalytical and analytical errors may have influenced our results. The use of standardized procedures (fasting subjects, standardized time of taking blood, standardized analysis protocols) carried out by trained professionals should minimize those effects as far as possible within the framework of the LIFE Child study. Due to the invasive blood sampling to determine serum lipids, many parents also refuse the blood test in the first year of life, so that the subgroup analyzed comprised a significantly small number of complete mother-child pairs. Due to the small number of cases, it is much more difficult to show statically significant differences. Nevertheless, the results identified at least clinically relevant trends. In addition, it must be critically noted that the study population of LIFE-Child is not (completely) representative of a Caucasian cohort. Families with a low SES are clearly underrepresented at 3.6% compared to the middle and upper classes. Moreover, pregnancy related pathologies are underrepresented. The analysis of the pregnancy cohort of the LIFE Child Study showed a prevalence of gestational diabetes of 2.7%, pregnancy-associated hypertension of 0.7% and a rate of premature birth of 6.4% [1]. The rate of preterm birth (≤ 37.0 weeks of gestation) in the current mother-child cohort was only 5.7% versus around 8% in Saxony/Germany [33] and 13% in the perinatal center of the University Hospital Leipzig (UKL). The relation, found in other studies, between maternal dyslipidemia and preterm birth [34] could not be shown in our results, which may be due to the low prevalence. Interestingly, the generally well-documented positive correlation between maternal BMI and frequency of cesarean section could not be shown in this mother-child cohort [35, 36]. However, it is questionable whether this is only due to the low prevalence of 17.5%. There are a few studies that were also not able to show this connection [37]. Since the LIFE-Child cohort is a primarily healthy collective with few pathologies and since the majority of the probands were delivered at the perinatal center University Hospital Leipzig, which already has a lower caesarean section rate of around 25% (including high-grade multiple pregnancies, extreme premature births (≤ 28.0 wog), preeclampsia, HELLP syndrome, placenta previa or abnormal invasive placentas), compared to the national average of around 30% [38], it can be assumed that there is indeed no relation between the maternal BMI and the C-section rate in this cohort. The positive preselection of the LIFE Child cohort and the resulting low rate of preterm birth, although participation in the study does not provide for any exclusion criteria, may result from the greater health awareness in families with middle and higher socioeconomic status [25] and therefore the greater willingness to participate in studies.
Nevertheless, this does not diminish the results of this study. Rather, it can be assumed that if more families with a lower SES participated, the effects would be even more pronounced. The results of this mother-child analysis show an inverse relation between maternal BMI and the Winkler Index. A similar association has also been described for childhood [25, 39]. Likewise, a high SES was associated with higher maternal serum lipid concentrations of HDL cholesterol and ApoA1, which are considered cardioprotective. As already shown in preliminary studies, a higher SES in childhood also correlates with a cardioprotective lipid profile [3], although this connection could not be shown in the present study collective, due to the small number of lipid determinations in the first year of life. Therefore, it can be assumed that the differences would even more pronounced if the SES would uniformly distribute over the study collective. It is important to recognize that children with low SES are at disadvantage in terms of cardiovascular health and the mother's social background during pregnancy effect this consistently. Therefore, preferably pregnant women and children with a low SES should be given priority in prevention programs in order to compensate health disadvantages.