Research
Energy balance
Pre-pregnancy underweight (BMI <18.5) significantly increases the risk of preterm birth by 32% and small-for-gestational age babies by 64%.
If you are underweight before pregnancy, you are at higher risk for having a preterm or small baby. Focus on achieving a healthy weight through balanced nutrition before conceiving to reduce these risks.
GoodSupportsHIGH confidence
This review found that pre-pregnancy underweight significantly increases the risk of preterm birth by 32% (RR 1.32, 95% CI 1.22-1.43)... Pre-pregnancy underweight was also found to significantly increase the risk of small-for-gestational age babies (RR 1.64, 95% CI 1.22-2.21).
Why this rating
Based on 34 observational studies.
Source
Preconception care: nutritional risks and interventions
Sohni V Dean et al. · Reproductive Health · 2014
DOI 10.1186/1742-4755-11-s3-s3
Meta-analysis · 146 studiesCited 282×
Read the paper DOI resolved against Crossref · corpus check 2026-06-10
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