Jian-meng Liu

Title: Professor, Doctoral Supervisor

Duty: Director of the National Health Commission Key Laboratory of Reproductive Health

Email: liujm@pku.edu.cn

Address: 38 Xueyuan Rd , Haidian District,Beijing,China

Personal profile

03/2024-Present Professor, Institute of Reproductive and Child Health of Peking University, Beijing, P. R. China

06/2016~03/2024 Professor and Dean, Institute of Reproductive and Child Health of Peking University, Beijing, P. R. China

05/2008~05/2016 Professor and Deputy Dean, Institute of Reproductive and Child Health of Peking University, Beijing, P. R. China

08/2006~04/2008 Professor, Institute of Reproductive and Child Health of Peking University, Beijing, P. R. China

11/2001~12/2003 Visiting Scholar at Harvard University

08/1999~07/2006 Associate Professor, Institute of Reproductive and Child Health of Peking University, Beijing, P. R. China

08/1998~07/1999 Assistant Professor, Institute of Reproductive and Child Health of Peking University, Beijing, P. R. China

08/1995~07/1998 PhD, Department of Epidemiology and Health Statistics, School of Public Health, Beijing Medical University, Beijing, P. R. China

10/1991~07/1995 Visiting staff & scholar and program officer at Ministry of Health, Sydney University, and Inner Mongolia Department of Health

08/1988~09/1991 Dean of the Computer Room, Inner Mongolia Maternal and Child Health Hospital

08/1985~07/1988 MPH, Department of Health Statistics, School of Public Health, Tongji Medical University, Wuhan, P. R. China

09/1980~07/1985 MD, Department of Preventive Medicine, Baotou Medical College, Baotou, P.R. China

My team's main research areas are reproductive and perinatal epidemiology, as well as the development and utilization of maternal and child health big data. I have hosted multiple projects from the Ministry of Science and Technology, the National Natural Science Foundation of China, the National Health Commission of China, and international organizations. I have published more than 200 papers in domestic and international core journals, such as JAMA, BMJ, JAMA Internal Medicine, CMAJ, and Chinese Medical Journal. I have also taught graduate courses on "Epidemiological Field Experiments (Randomized Controlled Clinical Trials)" and undergraduate courses on "Epidemiology". Additionally, I serve as the editor-in-chief of the Chinese Journal of Reproductive Health, the chairperson of the Committee on Environment and Reproductive Health of the Chinese Society for Environmental Mutagens, the deputy chairperson of the Fertility Protection Branch of the Chinese Preventive Medicine Association, and a member of the Expert Committee of the National Obstetrics Quality Control Center.

Main research directions

Reproductive and perinatal epidemiology

Representative research projects

(1) National Natural Science Foundation of China, Research on the Impact of Clamping Time of Umbilical Cord during Cesarean Section on Health Outcomes such as Offspring Hemoglobin and Maternal Blood Loss, 2022-2025, PI.

(2) United Nations Children's Fund, Survey on Nutrition Status of Women and Children in Developing Countries, including Folic Acid, 2020-2022, PI.

(3) National Natural Science Foundation of China, Randomized Controlled Study on the Correlation between Stripping of Umbilical Cord Blood during Cesarean Section and Infant Iron Deficiency-related Health Outcomes, 2016-2020, PI.

(4) Ministry of Science and Technology, Research on Prevention and Treatment Strategies for Complications during Pregnancy among Elderly Women, 2016-2021, Co-PI (not the Chief Investigator).

(5) National Health Commission of China, Research on Indicators of the Outlines of Women's and Children’s Development in China, 2019, PI.

(6) National Health Commission of China, Research on the Correlation between Adjustments in Fertility Policies and Related Outcomes of Pregnant Women and Newborns, 2017-2018, PI.

(7) National Natural Science Foundation of China, Cohort Study on the Association between Maternal Request for Cesarean Section and Childhood Metabolic Syndrome, 2013-2016, PI.

(8) National Natural Science Foundation of China, Follow-up Observation and Mechanism Study of Kidney Damage among Children with Kidney Stones Caused by Melamine-contaminated Milk Powder, 2011-2013, PI.

(9) Centers for Disease Control and Prevention (CDC) of the United States, Randomized Controlled Study on the Prevention of Adverse Outcomes during Pregnancy, Labor, Postpartum, and Infancy through Folic Acid, Iron, and Multivitamin Supplementation during Pregnancy, 2006-2012, Project Leader (not the Chief Investigator).

Representative papers (Note：*Corresponding author, #Co-first author)

(1) Li HT, Hellerstein S, Zhou YB, Liu JM*, Blustein J. Trends in Cesarean Delivery Rates in China, 2008-2018. JAMA. 2020;323(1):89-91.

(2) Li HT#, Xue M#, Hellerstein S, Cai Y, Gao YQ, Zhang YL, Qiao J*, Blustein J, Liu JM*. Association of China’s universal two child policy with changes in births and birth related health factors: national, descriptive comparative study. BMJ. 2019;366: l4680.

(3) Liao Z, Zhou Y, Li H, Wang C, Chen D, Liu JM*. The Rates and Medical Necessity of Cesarean Delivery in the Era of the Two-Child Policy in Hubei and Gansu Provinces, China. Am J Public Health. 2019;109(3):476-82.

(4) Li HT, Hellerstein S, Kang C, Trasande L, Gao Y, Zhang Y, Luo S, Zhou YB, Qiao J*, Blustein J, Liu JM*. The number of births in China in 2015: policy meets superstition. Science Bulletin. 2018;63(19):1235-7.

(5) Li HT#, Luo SS#, Trasande L, Hellerstein S, Kang CY, Li JC, Zhang YL, Liu JM*, Blustein J. Geographic variation and temporal trends in cesarean delivery rates in China, 2008-2014. JAMA.2017;317(1):69-76.

(6) Blustein J, Liu JM*. Time to consider the risks of caesarean delivery for long term child health. BMJ. 2015;350:h2410.

(7) Li HT, Trasande L, Zhu LP, Ye RW, Zhou YB, Liu JM*. Association of cesarean delivery with anemia in infants and children in 2 large longitudinal Chinese birth cohorts. Am J Clin Nutr. 2015;101(3):523-9.

(8) Liu JM*, Mei ZG, Ye RW, et al. Micronutrient supplementation and pregnancy outcomes: double-blind randomized controlled trial in China. JAMA Internal Medicine. 2013;173:276-82.

(9) Liu JM*, Ren A, Yang L, et al. Urinary tract abnormalities in Chinese rural children who consumed melamine-contaminated dairy products: a population-based screening and follow-up study. CMAJ. 2010; 182:439-43.

(10) Zhang Yuan, Zhou Yubo, Li Hongtian, Gao Yanqiu, Zhang Yali, Luo Shusheng, Kang Chuyun*, Liu Jian-meng*. Secular trends of institutional delivery rate in China from 1996 to 2015. National Medical Journal of China. 2017; 97(17): 1337-42.

Main research progress

Over the past two decades, I have led my team to conduct research focusing on significant issues in the field of maternal and child health and reproductive health, primarily concentrating on three directions: the impact of prenatal nutrition on maternal and child health outcomes, the epidemiological characteristics of cesarean delivery and its impact on offspring health, and the monitoring and evaluation of the effects of fertility policies. Additionally, we have also conducted some work on public health issues such as melamine-contaminated milk powder and the COVID-19 pandemic. Some typical work is as follows:

(I) Nutrition During Pregnancy and Health Outcomes for Mothers and Infants

Nutritional factors are highly modifiable, and their impact on maternal and infant health has always been a hot research topic. In the early 2000s, it was unclear whether iron supplements or other micronutrients needed to be supplemented during pregnancy as prenatal preventive measures, apart from folic acid. To address this question, our team collaborated with the Centers for Disease Control and Prevention (CDC) in the United States to conduct the largest randomized controlled trial globally, studying the effect of prenatal supplementation of multiple micronutrients on preventing adverse pregnancy outcomes based on individual randomization. The study recruited 18,775 primiparous women without anemia or with mild anemia from five counties in northern China from May 2006 to April 2009. Participants were randomly assigned to receive daily folic acid (400 μg; control group), folic acid-iron (30 mg), or a combination of folic acid, iron, and 13 other vitamins and minerals, starting before 20 weeks of gestation and continuing until delivery. The primary outcome of the study was perinatal mortality, while secondary outcomes included neonatal and infant mortality, preterm birth, birth weight, birth length, gestational hemoglobin concentration, and anemia. The study found that compared to daily folic acid supplementation alone, the supplementation of iron-folic acid (with or without other micronutrients) did not affect perinatal mortality and had no significant impact on other adverse maternal and infant outcomes except for anemia in late pregnancy (JAMA Intern Med. 2013;173(4):276-82). The findings provide important reference for maternal and child health practices in China and have been cited by the World Health Organization's expert panel, contributing evidence to the development of global guidance. In addition, our team has also conducted population intervention trials focusing on partially hydrolyzed formula powders containing low lactose and probiotics, evaluating their effects on gastrointestinal function in infants and young children (Nutrients. 2023;15(6):1313; Nutrients. 2021;13(10):3371). A series of studies have been carried out to explore the impact of pre-pregnancy weight and weight gain during pregnancy on pregnancy outcomes, providing strong evidence for demonstrating the causal relationship between prenatal nutrition and pregnancy outcomes (Paediatr Perinat Epidemiol. 2015;29(3):232-40; Obesity. 2019;27(6):1030-1036; Br J Nutr. 2019;122(3):352-359; Lancet Reg Health West Pac. 2021;13:100207).

(II) The Epidemiological Characteristics of Cesarean Delivery and Its Impact on Offspring Health

Cesarean delivery is a crucial technique for saving the lives of mothers and infants. A low cesarean delivery rate cannot meet medical needs, but an excessively high rate is not only a medical issue but also a social concern. To address the long-standing lack of authoritative data on the epidemiological characteristics of cesarean delivery in China, our team conducted in-depth research using nationwide data on delivery methods from 2008 to 2014. We found that the average cesarean delivery rate in China was approximately 29% in 2008 and increased to 34.9% in 2014, providing significant insights into the current status of cesarean delivery in China. We also observed contrasting trends in cesarean delivery rates among different districts and counties. In economically underdeveloped areas with lower cesarean delivery rates in 2008, the rates showed a steady upward trend, reflecting the effectiveness of policies aimed at strengthening maternal and child health services and improving access to hospital deliveries in rural areas. Conversely, in economically developed areas with higher cesarean delivery rates in 2008, the rates exhibited a downward trend, indicating the success of measures to reduce cesarean deliveries. The decline in cesarean delivery rates in megacities was particularly pronounced, and this decrease did not lead to an increase in maternal and perinatal mortality, providing a basis for other countries and regions with high cesarean delivery rates to set reduction targets. Furthermore, we observed significant differences in cesarean delivery rates among different provinces and districts, with both severe underutilization and overutilization of cesarean deliveries. Based on these findings, we proposed the need for differentiated policies to reduce disparities in cesarean delivery rates, optimize resource allocation, and improve maternal and child health (JAMA 2017;317:69-76). Subsequently, our team reinvestigated the changing characteristics in cesarean delivery rates in China from 2008 to 2018 (JAMA 2020;323:89-91), providing further evidence for understanding the current status and forecasting future trends of cesarean delivery in China, which has high reference value for adjusting and improving relevant policies.

With the rapid increase in cesarean delivery rates, the impact of cesarean delivery on offspring health has become a research hotspot. Our team has conducted a series of studies focusing on the association between cesarean delivery and childhood overweight/obesity, metabolic syndrome, anemia, and other conditions. These studies include cohort studies, systematic reviews and meta-analyses, randomized controlled trials, animal experiments, and statistical simulation studies, providing robust evidence of the impact of cesarean delivery on offspring health. In 2012, our team wrote a Letter to the Editor (Am J Clin Nutr 2012;96:215-216), arguing that cesarean delivery increases the risk of obesity in offspring. Subsequently, we conducted a systematic review and meta-analysis, synthesizing nine studies and concluding that cesarean delivery increases the risk of childhood overweight/obesity (Int J Obes 2013;37:893-899). Given that previous studies did not distinguish between medically indicated cesarean deliveries and cesarean deliveries requested by mothers without medical indications, our team further examined the association between maternal request for cesarean delivery and childhood overweight, finding that maternal request for cesarean delivery also increases the risk of childhood overweight (Pediatr Obes 2014;9:10-16). Additionally, we found that cesarean delivery increases the risk of anemia in children (Am J Clin Nutr 2015;101:523-529) and the risk of abnormalities in some components of metabolic syndrome (Nutr Metab Cardiovasc Dis 2019;29:775-82). To address the significant differences in results obtained from different study designs regarding the causal relationship between cesarean delivery and offspring health, we recently conducted comparative meta-analyses and statistical simulation studies, finding that cohort studies are more reliable than sibling-control studies (BMC Med 2023;21:348). To exclude confounding factors, we also conducted a rat animal experiment, discovering that cesarean-delivered pups exhibited faster weight gain and higher levels of multiple metabolic syndrome indicators, such as triglycerides, compared to vaginally delivered pups. Furthermore, a high-sugar/high-fat diet exacerbated the differences in metabolic indicators between cesarean-delivered and vaginally delivered pups (Pediatr Res 2024. DOI: 10.1038/s41390-024-03079-6). Additionally, we conducted a randomized controlled trial on vaginal seeding, finding that vaginal microbiota transplantation had no significant impact on the overall structure of the intestinal microbiota, BMI, or allergy risk index in cesarean-delivered infants. However, compared with the non-transplantation group, infants in the transplantation group showed a significantly higher trend in intestinal Lactobacillus and Bacteroides levels at birth and 6 months of age, and a significantly lower risk of obesity at 6 months of age (Am J Obstet Gynecol MFM. 2023;5(1):100793). The aforementioned series of evidence suggests that there is likely a causal relationship between cesarean delivery and various diseases in offspring.

(III) Monitoring and Evaluation of the Effects of Fertility Policy

In recent years, China's fertility rate has declined rapidly, making fertility issues a focal point of concern for government departments, academic peers, and the general public. In 2015, the second year of implementing the selective two-child policy, it was predicted that the number of births would increase by approximately 2 million, but the actual number of births did not increase, causing concern about the policy's effectiveness. My team systematically analyzed the spatial and temporal distribution patterns of births over the past 20 years and proposed that the Chinese zodiac sign of the Sheep was the main reason for the decrease in birth rates despite the policy, which contradicted the prevailing view that there was no taboo against giving birth in the year of the Sheep. This conclusion provided support for assessing the effects of the selective two-child policy (Sci Bull 2018;63:1235-1237). In 2016, when the universal two-child policy was implemented, the increase in the number of births and changes in important maternal and child characteristics attracted significant attention. Further empirical research based on big data led by my team revealed that the effects of the policy began to emerge about nine months after its implementation, and by the end of 2017, the cumulative increase in births due to the policy was approximately 5.4 million. Compared with 2016, the number of first-child births in 2017 decreased significantly, explaining why the policy was effective but the total number of births did not increase year by year. It was also found that after the policy took effect, the proportion of multiparous women and older women began to rise, peaking around February 2017, with an increase of approximately 9 percentage points and 6 percentage points, respectively. However, by the end of 2017, there were signs of a decrease in the incremental number of births and the proportion of multiparous and older women. Based on this, We proposed the scientific argument that the concentrated release of cumulative fertility demand might have entered a declining phase after experiencing an ascending and plateau phase. This research, based on empirical analysis of big data, addressed the issue of population growth brought about by the universal two-child policy and provided evidence regarding maternal and child health outcomes (BMJ 2019;366:l4680).

Future Work

With the continued decline in the number of births, the issue of healthy fertility has received more attention than ever before. In the future, I will continue to lead my team in conducting research on reproductive and perinatal epidemiology to provide high-quality evidence for government decision-making and public health interventions.

Key research directions include:

(1) Monitoring fertility rates in the population and studying influencing factors and improvement strategies.

(2) Investigating the relationship between maternal nutrition, obstetric factors, and offspring health.

(3) Conducting translational research on women's and children's health and reproductive health.