Low pre-pregnancy blood sugar linked with higher risk of preterm birth, other risks

An analysis of data from more than 4.7 million Chinese women showed that those who had low blood sugar levels prior to conception were more likely to have certain adverse pregnancy outcomes—such as their baby being born preterm or with low birth weight. Hanbin Wu of the Chinese University of Hong Kong, in collaboration with the National Research Institute for Family Planning, presents these findings on July 29^th in the open-access journal PLOS Medicine.

Glucose, a type of sugar, is the body’s main energy source. When blood levels of glucose are too high (known as hyperglycemia and found in prediabetes and type 2 diabetes) or too low (hypoglycemia), health risks may arise. Prior research has shown that women who are hyperglycemic before or during pregnancy are more likely to face adverse pregnancy outcomes, as are women who are hypoglycemic during pregnancy.

However, few studies have explored whether hypoglycemia detected before pregnancy is associated with adverse pregnancy outcomes for women without pre-existing diabetes. To help clarify, Wu and colleagues retrospectively analyzed data on 4,866,919 Chinese women from the National Free Preconception Checkup Project, a free health service for women planning to conceive. Using data from 2013 to 2016, they analyzed associations between preconception hypoglycemia and pregnancy outcomes.

A total of 239,128 of the women had preconception hypoglycemia. Compared to those with normal preconception blood sugar, they had a higher risk of certain adverse pregnancy outcomes, such as preterm birth, low birth weight, or birth defects. Women with hypoglycemia tended to be younger than those with normal blood sugar levels and were more likely to have BMIs in the “underweight” category.

However, the adverse pregnancy risks associated with preconception hypoglycemia varied for women with different BMIs. For instance, underweight women had a higher risk of miscarriage, while overweight women had a lower risk of their baby being large for their gestational age.

On the basis of these findings, the researchers suggest that screening for preconception hypoglycemia could be explored for its potential to improve pregnancy outcomes. Further research could also address some limitations of this study, such as by including women from other countries and more information on patients’ gestational complications.

The authors state, “In addition to paying attention to women with preconception hyperglycemia, our findings call for increased concern for women with hypoglycemia in preconception glycemic screening. These findings emphasize the importance of preconception examination in preventing and managing reproductive health risks for all women planning to conceive, and also highlight the necessity of comprehensive screening and coordinated interventions for abnormal FPG (fasting plasma glucose) prior to and during pregnancy, which is crucial for advancing the intervention window and mitigating the risk of adverse pregnancy outcomes.”

In your coverage, please use this URL to provide access to the freely available paper in PLOS Medicine: http://plos.io/4kBLtH7   

Citation: Wu H, Yang Y, Zhao C, Lyu X, Li J, Lei J, et al. (2025) Preconception hypoglycemia and adverse pregnancy outcomes in Chinese women aged 20–49 years: A retrospective cohort study in China. PLoS Med 22(7): e1004667. https://doi.org/10.1371/journal.pmed.1004667

Author countries: China

Funding: see manuscript