Association of Maternal Total Cholesterol With SGA or LGA Birth at Term: the Japan Environment and Children's Study.

CONTEXT: Maternal cholesterol is important for fetal development. Whether maternal serum total cholesterol (maternal TC) levels in midpregnancy are associated with small (SGA) or large (LGA) for gestational age independent of prepregnancy body mass index (BMI) and weight gain during pregnancy is inconclusive.
OBJECTIVE: This work aimed to prospectively investigate the association between maternal TC in midpregnancy and SGA or LGA.
METHODS: The Japan Environment and Children's Study is a nationwide prospective birth cohort study in Japan. Participants in this study included 37 449 nondiabetic, nonhypertensive mothers with singleton birth at term without congenital abnormalities. Birth weight for gestational age less than the 10th percentile and greater than or equal to the 90th percentile were respectively defined as SGA and LGA by the Japanese neonatal anthropometric charts.
RESULTS: The mean gestational age at blood sampling was 22.7 ± 4.0 weeks. After adjustment for maternal age, sex of child, parity, weight gain during pregnancy, prepregnancy BMI, smoking, alcohol drinking, blood glucose levels, household income, and study areas, 1-SD decrement of maternal TC was linearly associated with SGA (odds ratio [OR]: 1.20; 95% CI, 1.15-1.25). In contrast, 1-SD increment of maternal TC was linearly associated with LGA (OR: 1.13; 95% CI, 1.09-1.16). Associations did not differ according to prepregnancy BMI and gestational weight gain (P for interaction > .20).
CONCLUSION: Maternal TC levels in midpregnancy were associated with SGA or LGA in a Japanese cohort. It may help to predict SGA and LGA. Favorable maternal lipid profiles for fetal development must be explored.

Small for gestational age (SGA) and large for gestational age (LGA) increase the long-term risk of hypertension, type 2 diabetes mellitus, cardiovascular diseases, and stroke in later life, leading to premature death worldwide (1-7). Additionally, undiagnosed SGA and LGA before delivery are related to adverse birth outcomes such as fetal asphyxia, still birth, and neonatal cerebral hemorrhage (8-11). Elucidating pathophysiological mechanisms underlying SGA and LGA can help explore potential prevention strategies.

Maternal cholesterol is important for membrane function and the development of the nervous and aortic systems of the fetus (12-14). Progressive elevation of maternal lipid levels according to gestational age is observed during normal pregnancy (15-17), and maternal total cholesterol (TC) level is considered one of the predictive markers for abnormal fetal development (18, 19). Lower maternal TC levels in midpregnancy reportedly increase the risk of SGA (20-22), whereas no associations have been observed in early (19, 23, 24) and late (25) pregnancy. In contrast, associations between higher maternal TC levels and adverse outcomes, including LGA, have been reported in early and midpregnancy (18, 19). However, whether maternal TC levels in midpregnancy are associated with SGA or LGA, independent of potential confounding factors such as weight gain during pregnancy (26), prepregnancy body mass index (BMI) (27, 28), and maternal blood glucose levels is still unclear (29). In addition, to our knowledge, no previous studies have examined the association between maternal TC in midpregnancy and adverse outcomes, such as SGA or LGA, among the same study population.

Thus, this study aimed to investigate the associations between maternal TC levels in midpregnancy (14th-27th gestational week) and SGA or LGA. We statistically controlled for potential confounding factors and conducted stratified analyses by important confounding factors, including prepregnancy BMI and weight gain during pregnancy.

Materials and Methods

The Japan Environment and Children’s Study (JECS) is an ongoing nationwide prospective birth cohort study that examines the effect of environmental factors, lifestyle, medical, and psychosocial conditions during pregnancy and early childhood on the offspring’s health and development at birth and in later life. Details of the JECS design have been described in a previous study (30). The JECS protocol was reviewed and approved by the Ministry of the Environment’s Institutional Review Board on Epidemiological Studies and the ethics committees of all participating institutions. All participants in the present study provided written informed consent. Data for the present analyses were extracted from the data set released in October 2019 (data set jecs-ta-20190930-qsn).

Study Population

A total of 104 062 fetuses were registered in the JECS. Between January 2011 and March 2014, cooperating health care providers in 15 regional centers across Japan recruited pregnant women in the first trimester in principle and/or at local government offices issuing home-based records for a pair of mother and child, namely maternal and child health handbooks (an official booklet issued to all expecting mothers in Japan to receive municipal services for pregnancy, delivery, and child care and keep related medical records at home). The eligibility criteria for participants were the following: (i) living in the study area at the time of recruitment (ie, any of the 15 regional centers located throughout Japan) and expected to continue to reside in Japan for the foreseeable future; (ii) an expected delivery between August 1, 2011, and mid-2014; and (iii) an understanding of the Japanese language to complete the self-administered questionnaire (30).

The present study was first restricted to 88 086 mother and infant pairs with singleton live births at term. Eligibility criteria aimed to exclude those who were at elevated risk of SGA and/or LGA and with missing values. In particular, the exclusion criteria were the following: 1) missing values for maternal TC in midpregnancy (14th-27th gestational week), blood glucose at pregnancy and/or fasting status, smoking status during pregnancy, alcohol drinking status during pregnancy, and household income; 2) gestational diabetes mellitus defined by medical records and/or glycated hemoglobin A1c (HbA1c) greater than or equal to 6.5% and/or fasting blood glucose greater than or equal to 92 mg/dL during pregnancy; 3) higher blood glucose level at pregnancy (nonfasting blood glucose during pregnancy ≥ 100 mg/dL, which is the first criterion to identify women with gestational diabetes mellitus) (31); 4) history of diabetes; 5) anemia, heart disease, hypertensive disorder of pregnancy, history of hypertension, polycystic ovary syndrome, thyroid or kidney disorders, and cancer during pregnancy; and 6) infants with congenital cerebral and/or heart abnormalities; and chromosomal abnormalities (32). Finally, a total of 37 449 mother and infant pairs of singleton births at term were eligible for the present analysis (Fig. 1).

Figure 1.

Study enrollment flowchart.

We performed a sensitivity analysis of the exclusion procedure and found no significant difference in the participants’ characteristics on all items of Table 1 except for blood glucose levels during pregnancy between the overall JECS participants (33) and eligible participants of the present study (results not shown). In addition, we previously reported that the characteristics of overall JECS participants were similar to those obtained from the Japanese Vital Statistics Survey in 2013 (33).

Table 1.

Characteristics of participants according to maternal total cholesterol level in midpregnancy (n = 37 449)

	No.	(%)	Maternal total cholesterol valuea in midpregnancy		P
Sex of child
Male	19 024	(50.8)	229.9	(229.4-230.4)	< .01
Female	18 425	(49.2)	231.2	(230.7-231.7)
Age of mother at delivery, y
< 35	27 600	(73.7)	229.5	(229.1-230.0)	< .01
≥ 35	9849	(26.3)	233.3	(232.6-234.0)
Parity
0	15 343	(41.0)	228.4	(227.9-229.0)	< .01
≥ 1	22 106	(59.0)	232.0	(231.5-232.5)
Maternal weight gain during pregnancy, kg
< 7.0	5600	(15.0)	228.0	(227.1-228.9)	< .05
7.0-11.9	19 590	(52.3)	230.2	(229.7-230.7)
≥ 12.0	12 259	(32.7)	232.2	(231.6-232.8)
Maternal body mass index before pregnancy
< 18.5	6073	(16.2)	229.4	(228.6-230.3)	< .05
18.5-24.9	28 068	(74.9)	230.8	(230.4-231.3)
≥ 25.0	3308	(8.8)	229.9	(228.7-231.2)
Smoking status during pregnancy
None	21 888	(58.4)	231.4	(230.9-231.9)	< .05
Former (quit smoking before pregnancy)	8885	(23.7)	230.6	(229.8-231.3)
Former (quit smoking during early pregnancy)	5084	(13.6)	228.6	(227.6-229.5)
Current smokers	1592	(4.3)	224.7	(223.0-226.5)
Alcohol drinking status during pregnancy
None	12 380	(33.1)	231.8	(231.2-232.5)	< .05
Former	24 020	(64.1)	230.1	(229.7-230.6)
Current	1049	(2.8)	224.8	(222.7-226.9)
Blood glucose levelsb during pregnancy, mg/dL, tertile
1	12 415	(33.2)	230.4	(229.8-231.0)	.29
2	11 501	(30.7)	231.1	(230.5-231.7)
3	13 533	(36.1)	230.2	(229.6-230.8)
Household income, million Japanese yen
< 2	2066	(5.5)	227.2	(225.7-228.7)	< .05
2-5	25 456	(68.0)	230.9	(230.5-231.3)
6-9	8359	(22.3)	230.2	(229.4-230.9)
≥ 10	1568	(4.2)	230.5	(228.8-232.2)

Maternal total cholesterol levels are reported in geometric mean and 95% CI. P values are from t test or analysis of variance for multiple measurements with Bonferroni correction.

Maternal total cholesterol values were adjusted for gestational age (day) at blood sampling by the residual method.

Blood glucose levels during pregnancy were categorized as < 78, 78-84, ≥ 85 mg/dL for a nonfasting blood sample and < 76, 76-81, ≥ 82 mg/dL for a fasting blood sample according to each tertile range.

Measurement of Bioassay

Nonfasting blood samples were collected from pregnant women in early and midpregnancy. The blood samples were assayed by a contract clinical laboratory (SRL Inc, a commercial laboratory in Tokyo, Japan). Serum blood TC at midpregnancy was analyzed enzymatically using a 7700 clinical chemistry/immunoassay hybrid analyzer (Hitachi High-Technologies Co Ltd). HbA1c at early pregnancy was measured using a high-performance liquid chromatographic method, with reference to the National Glycohemoglobin Standardization Program or Japan Diabetes Society. HbA1c values identified in reference to the Japan Diabetes Society were adjusted by the following formula (34):

Calculated HbA1c = 1.02 × HbA1c (Japan Diabetes Society) + 0.25

Explanatory Variable

Raw maternal TC values had a significant positive correlation with gestational age (days) at the time of blood sampling. Therefore, we performed residual procedures (35) to adjust the maternal TC value to the gestational age at the time of blood sampling. Because of the normal distribution, gestational age-adjusted maternal TC was used as a continuous variable.

Ascertainment of Small for Gestational Age and Large for Gestational Age

Gestational age at birth and neonatal anthropometric measurements were transcribed from the medical records. Ultrasonography during early pregnancy and/or estimation from the last menstrual period were used to determine the gestational age in weeks and days in each facility. The Z score of the birth weight for gestational age was calculated based on the Japanese neonatal anthropometric charts. Then, Z scores of the birth weight for the gestational age less than –1.28 155 (< 10th percentile) and greater than or equal to 1.28 155 (≥ 90th percentile) were defined as SGA and LGA, respectively (36).

Covariates

Lifestyle-related data and socioeconomic status were self-reported during the early period of participants’ pregnancies (37). Anthropometric measurements, medical history, and medical information during pregnancy and at delivery were transcribed from the medical records by cooperating health care providers. Because the Japan Society of Obstetrics and Gynecology recommends examination of random glucose levels in all pregnant women to screen for gestational diabetes mellitus (38), random and fasting blood glucose data during pregnancy are normally available in the medical records.

The age of the mother at delivery was used as a continuous variable. Parity (0, ≥ 1) and sex of the child (male, female) were dichotomized. Prepregnancy BMI was computed as prepregnancy body weight (in kilograms) divided by the square of height (in meters) and used as a categorical variable (< 18.5, 18.5-24.9, ≥ 25.0) since its distribution was skewed. Smoking status was classified as “nonsmokers,” “former smokers (quit before pregnancy),” “former smokers (quit during early pregnancy),” and “current smokers.” Alcohol drinking status during pregnancy was categorized as “nondrinkers,” “former drinkers,” and “current drinkers” (39). Household income levels (million Japanese yen) were divided into less than 2, 2 to 5, 6 to 9, and 10 or greater. Blood glucose levels (in milligrams per deciliter; mg/dL) during pregnancy were categorized as less than 78, 78 to 84, 85 or greater for a nonfasting blood sample, and less than 76, 76 to 81, and 82 or greater for fasting blood samples according to the tertile of each distribution. Notably, we applied HbA1c as an exclusion criterion but not as a covariate because HbA1c at early pregnancy did not show any significant association with SGA, whereas blood glucose levels during pregnancy reported in medical records showed significant associations both with SGA and LGA. Study areas were divided into the location of the 15 regional centers such as “Hokkaido”, “Miyagi”, “Fukushima”, “Chiba”, “Kanagawa”, “Koshin”, “Toyama”, “Aichi”, “Kyoto”, “Osaka”, “Hyogo”, “Tottori”, “Kochi”, “Fukuoka”, and “South Kyushu/Okinawa.”

Statistical Analysis

The characteristics of participants were reported according to the geometric mean and 95% CI of the maternal TC levels. The differences in the geometric mean of the maternal TC were tested by t test or analysis of variance for multiple measurements with Bonferroni correction.

Multiple logistic regression models were used to estimate the adjusted odds ratios (ORs) and 95% CI of SGA or LGA by 1 SD (=35.33) of maternal TC. In addition, tests for linear and quadratic trends were performed.

The dose-response relationships between maternal TC and SGA or LGA were examined by restricted cubic spline models. In the models, maternal TC in midpregnancy was included as a restricted cubic spline using 6 knots at prespecified locations according to the percentiles of the distribution, the 5th, 10th, 25th, 75th, 90th and 95th percentiles, and was adjusted for all covariates. Curves showed ORs compared with the median value of the maternal TC (231 mg/dL). The aforementioned dose-response analyses were carried out using R with package of “rms.”

Additional sensitivity analyses included stratified analyses by prepregnancy BMI (< 18.5, 18.5-24.9, ≥ 25.0), maternal weight gain (< 7, 7-11.9, ≥ 12 kg), and multiplicative interactions test. We then analyzed the relationship between maternal TC and incidence of SGA or LGA in participants with normal prepregnancy BMI (18.5-24.9) and maternal weight gain during prepregnancy (7-11.9 kg) (40, 41).

All statistical analyses were performed using IBM SPSS Statistics for Windows software (version 27.0; IBM) and R (version 3.4.3) for Windows (http://cran.r-project.org/). Statistical significance was set at P less than .05.

Results

The study participants had a mean (SD) age of 31.2 (4.9) years, 41.0% were nulliparous, and 16.2% had low BMI (< 18.5). The mean gestational age at the blood sampling of maternal TC was 22.7 ± 4.0 weeks.

Maternal TC levels were significantly lower in participants who had a male child or younger age (< 35 years) and who had a lower weight gain during pregnancy (< 7.0 kg) or a lower prepregnancy BMI (<18.5). Similarly, participants who were nulliparous, current smokers during pregnancy, current drinkers during pregnancy, and women from low-income households had significantly lower maternal TC levels. In contrast, maternal TC levels did not significantly differ according to the blood glucose levels during pregnancy (see Table 1).

Association Between Adjusted Maternal Total Cholesterol Levels and Small for Gestational Age or Large for Gestational Age

Among 37 499 mothers with a singleton birth, 2638 (7.0%) cases of SGA and 3709 (9.9%) of LGA were observed. After adjustment for all potential confounding variables, 1-SD decrement of maternal TC was linearly associated with SGA (OR = 1.20); 95% CI, 1.15-1.25) (P for linear trend < .01; P for quadratic trend = .48). In contrast, 1-SD increment of maternal TC was linearly associated with LGA (OR = 1.13; 95% CI, 1.09-1.16) (P for linear trend < .01; P for quadratic trend = .22) (Table 2). Furthermore, the restricted cubic spline models with multiple adjustment indicated the dose-response relationships between maternal TC and both SGA and LGA (Fig. 2).

Table 2.

Odds ratios of small or large for gestational age by 1 SD of maternal total cholesterol in midpregnancy (n = 37 449)

Outcome	n	(%)	Crude model	Multivariable-adjusted modelb	P for linear trend	P for quadratic trend
Small for gestational age	2638	(7.0)	1.22 (1.18-1.28)	1.20 (1.15-1.25)	< .01	.48
Large for gestational age	3709	(9.9)	1.14 (1.10-1.18)	1.13 (1.09-1.16)	< .01	.22

Odds ratios of small for gestational age were reported by 1-SD decrement of maternal total cholesterol in midpregnancy. Odds ratios of large for gestational age were reported by 1-SD increment of maternal total cholesterol in midpregnancy. SD of maternal total cholesterol = 35.33 mg/dL.

Maternal total cholesterol values were adjusted for gestational age (day) at blood sampling by the residual method.

Adjustment for maternal age at delivery (year), sex of child (male, female), parity (0, ≥ 1), maternal weight gain during pregnancy (kg), maternal body mass index before pregnancy (< 18.5, 18.5-24.9, ≥ 25.0), smoking status during pregnancy (nonsmokers, quit smoking before pregnancy, quit smoking during early pregnancy, current smokers), alcohol drinking status during pregnancy (nondrinkers, former drinkers, current drinkers), blood glucose levels during pregnancy (< 78, 78-84, ≥ 85 mg/dL for a nonfasting blood sample and < 76, 76-81, ≥ 82 mg/dL for a fasting blood sample as each tertile value), household income (< 2, 2-5, 6-9, ≥ 10 million Japanese yen), and study areas (Hokkaido, Miyagi, Fukushima, Chiba, Kanagawa, Koshin, Toyama, Aichi, Kyoto, Osaka, Hyogo, Tottori, Kochi, Fukuoka, and South Kyushu/Okinawa).

Figure 2.

Multivariable-adjusted associations of maternal total cholesterol in midpregnancy with A, small for gestational age, and B, large for gestational age (n = 37 449). In the models, maternal total cholesterol in midpregnancy was included as a restricted cubic spline using 6 knots at prespecified locations according to the percentiles of the distribution, the 5th, 10th, 25th, 75th, 90th, and 95th percentiles, and was adjusted for maternal age at delivery (year), sex of child (male, female), parity (0, ≥ 1), maternal weight gain during pregnancy (kg), maternal body mass index before pregnancy (< 18.5, 18.5-24.9, ≥ 25.0), smoking status during pregnancy (nonsmokers, quit smoking before pregnancy, quit smoking during early pregnancy, current smokers), alcohol drinking status during pregnancy (nondrinkers, former drinkers, current drinkers), blood glucose levels during pregnancy (< 78, 78-84, ≥ 85 mg/dL for nonfasting blood sample and < 76, 76-81, ≥ 82 mg/dL for fasting blood sample as each tertile values), household income (< 2, 2-5, 6-9, ≥ 10 million Japanese yen), and study areas (Hokkaido, Miyagi, Fukushima, Chiba, Kanagawa, Koshin, Toyama, Aichi, Kyoto, Osaka, Hyogo, Tottori, Kochi, Fukuoka, and South Kyushu/Okinawa). The reference of maternal total cholesterol in midpregnancy (odds ratio fixed as 1.0) was 231 mg/dL.

Stratified Analyses By Prepregnancy Body Mass Index and Weight Gain During Pregnancy

Analysis that included only participants with normal BMI (18.5-24.9) in prepregnancy and appropriate weight gain during pregnancy (7-11.9 kg) did not materially change the results. This means that completely excluding the effect both of prepregnancy BMI and weight gain during pregnancy did not alter the significant association between maternal TC and both SGA and LGA (Table 3 and Fig. 3).

Table 3.

Odds ratios of small or large for gestational age by 1 SD of maternal total cholesterol in midpregnancy among mothers with normal body mass index (18.5-24.9) and weight gain (7-11.9 kg) (n = 14 917)

Outcome	n	(%)	Crude model	Multivariable-adjusted modelb	P for linear trend	P for quadratic trend
Small for gestational age	1051	(7.0)	1.21 (1.13-1.29)	1.19 (1.12-1.27)	< .01	.38
Large for gestational age	1162	(7.8)	1.11 (1.05-1.18)	1.09 (1.03-1.16)	< .01	.99

Odds ratios of small for gestational age were reported by 1-SD decrement of maternal total cholesterol in midpregnancy. Odds ratios of large for gestational age were reported by 1-SD increment of maternal total cholesterol in midpregnancy. SD of maternal total cholesterol = 35.33 mg/dL.

Maternal total cholesterol values were adjusted for gestational age (day) at blood sampling by the residual method.

Adjustment for maternal age at delivery (year), sex of child (male, female), parity (0, ≥ 1), maternal weight gain during pregnancy (kg), maternal body mass index before pregnancy (< 18.5, 18.5-24.9, ≥ 25.0), smoking status during pregnancy (nonsmokers, quit smoking before pregnancy, quit smoking during early pregnancy, current smokers), alcohol drinking status during pregnancy (nondrinkers, former drinkers, current drinkers), blood glucose levels during pregnancy (< 78, 78-84, ≥ 85 mg/dL for a nonfasting blood sample and < 76, 76-81, ≥ 82 mg/dL for a fasting blood sample as each tertile value), household income (< 2, 2-5, 6-9, ≥ 10 million Japanese yen), and study areas (Hokkaido, Miyagi, Fukushima, Chiba, Kanagawa, Koshin, Toyama, Aichi, Kyoto, Osaka, Hyogo, Tottori, Kochi, Fukuoka, and South Kyushu/Okinawa).

Figure 3.

Multivariable-adjusted associations of maternal total cholesterol in midpregnancy with A, small for gestational age, and B, large for gestational age among mothers with normal body mass index (18.5-24.9) and weight gain (7-11.9 kg) (n = 14 917). In the models, maternal total cholesterol in midpregnancy was included as a restricted cubic spline using 6 knots at prespecified locations according to the percentiles of the distribution, the 5th, 10th, 25th, 75th, 90th and 95th percentiles, and was adjusted for maternal age at delivery (year), sex of child (male, female), parity (0, ≥ 1), maternal weight gain during pregnancy (kg), maternal body mass index before pregnancy, smoking status during pregnancy (nonsmokers, quit smoking before pregnancy, quit smoking during early pregnancy, current smokers), alcohol drinking status during pregnancy (nondrinkers, former drinkers, current drinkers), blood glucose levels during pregnancy (< 78, 78-84, ≥ 85 mg/dL for nonfasting blood sample and < 76, 76-81, ≥ 82 mg/dL for fasting blood sample as each tertile values), household income (< 2, 2-5, 6-9, ≥ 10 million Japanese yen), and study areas (Hokkaido, Miyagi, Fukushima, Chiba, Kanagawa, Koshin, Toyama, Aichi, Kyoto, Osaka, Hyogo, Tottori, Kochi, Fukuoka, and South Kyushu/Okinawa). The reference of maternal total cholesterol in midpregnancy (odds ratio fixed as 1.0) was 231 mg/dL.

In addition, stratified analysis by prepregnancy BMI or weight gain during pregnancy showed an independent association between maternal TC and both SGA and LGA. The multiplicative interaction analysis confirmed that the associations between maternal TC and both SGA and LGA were not statistically affected by prepregnancy BMI levels and weight gain during pregnancy (P for interaction > .2) (Tables 4 and 5).

Table 4.

Odds ratios of small for gestational age (SGA) by 1 SD of maternal total cholesterol in midpregnancy by stratified analyses (n = 37 449)

		SGA	(%)	Crude model	Multivariable- adjusted modelb	P for linear trend	P for quadratic trend	P for interaction
Stratified by prepregnancy body mass index, kg/m2
< 18.5	(n = 6073)	649	(10.7)	1.15 (1.05-1.25)	1.12 (1.03-1.22)	< .01	.66	.20
18.5-24.9	(n = 28 068)	1850	(6.6)	1.25 (1.19-1.31)	1.22 (1.16-1.28)	< .01	.26
≥ 25.0	(n = 3308)	139	(4.2)	1.28 (1.07-1.52)	1.26 (1.05-1.51)	< .05	.47
Stratified by weight gain during pregnancy, kg
< 7.0	(n = 5600)	615	(11.0)	1.22 (1.12-1.33)	1.21 (1.11-1.33)	< .01	.19	.99
7.0-11.9	(n = 19 590)	1473	(7.5)	1.19 (1.13-1.26)	1.18 (1.11-1.24)	< .01	.78
≥ 12.0	(n = 12 259)	550	(4.5)	1.24 (1.14-1.36)	1.23 (1.12-1.35)	< .01	.95

Odds ratios of small for gestational age were reported by 1-SD decrement of maternal total cholesterol in midpregnancy. Odds ratios of large for gestational age were reported by 1-SD increment of maternal total cholesterol in midpregnancy. SD of maternal total cholesterol = 35.33 mg/dL.

Maternal total cholesterol values were adjusted for gestational age (day) at blood sampling by the residual method.

Adjustment for maternal age at delivery (year), sex of child (male, female), parity (0, ≥ 1), maternal weight gain during pregnancy (kg), maternal body mass index before pregnancy (< 18.5, 18.5-24.9, ≥ 25.0), smoking status during pregnancy (nonsmokers, quit smoking before pregnancy, quit smoking during early pregnancy, current smokers), alcohol drinking status during pregnancy (nondrinkers, former drinkers, current drinkers), blood glucose levels during pregnancy (< 78, 78-84, ≥ 85 mg/dL for a nonfasting blood sample and < 76, 76-81, ≥ 82 mg/dL for a fasting blood sample as each tertile value), household income (< 2, 2-5, 6-9, ≥ 10 million Japanese yen), and study areas (Hokkaido, Miyagi, Fukushima, Chiba, Kanagawa, Koshin, Toyama, Aichi, Kyoto, Osaka, Hyogo, Tottori, Kochi, Fukuoka, and South Kyushu/Okinawa).

Table 5.

Odds ratios of large for gestational age by 1 SD of maternal total cholesterol in midpregnancy by stratified analyses (n = 37 449)

		LGA (%)	Crude model	Multivariable- adjusted modelb	P for linear trend	P for quadratic trend	P for interaction
Stratified by prepregnancy body mass index, kg/m2
< 18.5	(n = 6073)	340 (5.6)	1.20 (1.07-1.33)	1.17 (1.05-1.31)	< .01	.14	.29
18.5-24.9	(n = 28 068)	2772 (9.9)	1.14 (1.10-1.19)	1.14 (1.08-1.17)	< .01	.41
≥ 25.0	(n = 3308)	597 (18.0)	1.10 (1.01-1.20)	1.09 (0.99-1.04)	.06	.61
Stratified by weight gain during pregnancy, kg
< 7.0	(n = 5600)	332 (5.9)	1.19 (1.07-1.33)	1.20 (1.07-1.34)	< .01	.45	.95
7.0-11.9	(n = 19 590)	1561 (8.0)	1.11 (1.05-1.16)	1.09 (1.03-1.15)	< .01	.98
≥ 12.0	(n = 12 259)	1816 (14.8)	1.14 (1.09-1.20)	1.13 (1.08-1.19)	< .01	.13

Odds ratios of small for gestational age were reported by 1-SD decrement of maternal total cholesterol in midpregnancy. Odds ratios of large for gestational age were reported by 1-SD increment of maternal total cholesterol in midpregnancy. SD of maternal total cholesterol = 35.33 mg/dL.

Maternal total cholesterol values were adjusted for gestational age (day) at blood sampling by the residual method.

Adjustment for maternal age at delivery (year), sex of child (male, female), parity (0, ≥ 1), maternal weight gain during pregnancy (kg), maternal body mass index before pregnancy (< 18.5, 18.5-24.9, ≥ 25.0), smoking status during pregnancy (nonsmokers, quit smoking before pregnancy, quit smoking during early pregnancy, current smokers), alcohol drinking status during pregnancy (nondrinkers, former drinkers, current drinkers), blood glucose levels during pregnancy (< 78, 78-84, ≥ 85 mg/dL for a nonfasting blood sample and < 76, 76-81, ≥ 82 mg/dL for a fasting blood sample as each tertile value), household income (< 2, 2-5, 6-9, ≥ 10 million Japanese yen), and study areas (Hokkaido, Miyagi, Fukushima, Chiba, Kanagawa, Koshin, Toyama, Aichi, Kyoto, Osaka, Hyogo, Tottori, Kochi, Fukuoka, and South Kyushu/Okinawa).

Discussion

This large-scale birth cohort study has shown that lower and higher maternal TC in midpregnancy is significantly associated with the development of SGA or LGA among Japanese mothers with singleton birth at term, independent of potential confounding factors, including prepregnancy BMI and weight gain during pregnancy. To our knowledge, this is the first study to show an association between maternal TC in midpregnancy and SGA and LGA in participants with normal prepregnancy BMI and normal weight gain during pregnancy.

The implications of the present findings are 3-fold. First, participants with low and high maternal TC levels in midpregnancy may have a higher risk of SGA and LGA, respectively. These results are consistent with and extend the findings of previous studies. Among Indian mother and child pairs, maternal TC in midpregnancy (at a gestational age of 18 weeks) was linearly associated with birth size (21). Similarly, our study showed a significant continuous OR by 1 SD of maternal TC for SGA and LGA, indicating a dose-response relationship between maternal TC and adverse weight for gestational age. Furthermore, a previous study in the United States reported that maternal TC less than the third percentile (< 138 mg/dL, mean gestational age of 17.6 weeks) in midpregnancy was associated with SGA among Black and White Americans (20). The present study indicated that lower maternal TC compared with the median value of the maternal TC (231 mg/dL, mean gestational age of 22.2 weeks) showed a significantly higher OR of SGA among Japanese, even in women with normal prepregnancy BMI and weight gain during pregnancy. Conversely, compared with the median value, 1-SD increment of maternal TC indicated a significantly higher OR of LGA. These findings are consistent with those of a previous study in China, which indicated that maternal TC greater than or equal to the 95th percentile (≥ 290 mg/dL, at a gestational age of 14-27 weeks) was associated with LGA in midpregnancy (18).

Excessive maternal cholesterol may have adverse outcomes, even though an appropriate level of maternal cholesterol contributes to fetal development (42, 43). Low serum cholesterol level indicates undernutrition and may reflect several micronutrient deficiencies, such as high-density lipoprotein cholesterol (44, 45) and essential fatty acids (46), necessary for fetal development. Although the present study did not examine the effect of energy intake on maternal TC levels, our results suggest that low energy intake or undernutrition during pregnancy implied by extremely low maternal TC in midpregnancy should be avoided to prevent SGA, even in mothers with normal prepregnancy BMI and weight gain during pregnancy. In contrast, previous animal studies have shown that maternal high-fat feeding during pregnancy might affect adipocyte differentiation, adipose tissue development, and hepatic steatosis in offspring, which leads to a lifelong risk of adiposity and atherosclerosis (47, 48). Future studies should evaluate the effect of maternal TC concentration on adiposity and development of offspring and the incidence of noncommunicable diseases in adulthood.

Second, maternal TC may help identify high-risk pregnancies for SGA and LGA in Japanese women. Since total cholesterol is not greatly influenced by fasting states at blood sampling, it is often measured concurrently with other blood examination components during pregnancy. It would be worth carefully observing lower and higher maternal TC in clinical settings.

However, we must also focus on the inconsistent findings regarding the association between maternal TC and offspring’s birth size in previous studies as no significant associations in early pregnancy were reported (23-25). This might be explained by different timing of maternal blood sampling, such as early or midpregnancy, or differences in the adjusted confounders. As our present study strictly excluded and controlled major potential confounding factors, the present findings may be meaningful in demonstrating the risk of abnormal birth size in Japanese women. In addition, recent studies reported that ethnic differences in genetic factors related to lipid metabolism regulation may affect the associations between maternal TC and birth size and risk of cardiovascular diseases in adulthood (49). Inconsistent findings between studies from European countries (23, 24) and ours might be due to the different ethnic background. Future multiple-ethnic studies must investigate the genetic differences that may influence maternal lipid metabolism and its relationship with fetal and child development.

Finally, the molecular pathway underlying the disturbance in lipid metabolism during pregnancy must be elucidated. Although the association between maternal TC in midpregnancy and SGA or LGA may be partially explained by maternal fat or energy intake, our study showed that the associations were independent of prepregnancy BMI and weight gain during pregnancy. This implies that the alteration of maternal TC biosynthesis or degradation would be a consequence of factors other than maternal food intake, and maternal TC might be a mediator of other causal factors and background diseases. We previously reported that exposure to environmental chemicals such as di (2-ethylhexyl) phthalate induces stunting of fetal development mediated by maternal lipid malnutrition in animals (50-52). Further studies must investigate the effect of environmental chemicals on fetal development, which is mediated by a disturbance in lipid metabolism during pregnancy.

The strengths of the present study are the diverse sample from a nationwide, large-scale birth cohort and the availability of important covariates such as prepregnancy BMI and weight gain during pregnancy. In addition, stratified analyses by important variables were performed while conducting multiplicative interaction analysis. In addition, we applied the residual method to control the influence of blood sampling timing on the maternal TC. However, there are several limitations in the present study. First, we did not measure sexual hormone levels, which can influence the offspring’s birth size via maternal lipid metabolism perturbation (53). Second, we did not investigate maternal triglyceride and lipid profiles such as low- and high-density lipoprotein cholesterol and fatty acids. Further studies exploring favorable lipid profiles during pregnancy for appropriate fetal development are warranted.

In conclusion, lower and higher maternal TC in midpregnancy were associated with the development of SGA and LGA, respectively, in Japanese mothers with a singleton birth at term, independent of potential confounding factors, including prepregnancy BMI and weight gain during pregnancy. Maternal TC in midpregnancy may help predict SGA and LGA before delivery, which can prevent adverse birth outcomes among SGA and LGA infants. Further studies must explore favorable lipid profiles during pregnancy for fetal development.