A recent study published by BMJ Open discovered a 1.58 increased chance of birthing a small for gestational age (SGA) infant in pregnant women who are vitamin D deficient.
Infants that are SGA are typically below the 10th percentile in weight and length. However, this measurement can vary, as some babies may be proportionately small (equally low birth weight, body mass, length, etc.) and others may be disproportionately small (low birth weight with normal length measurements, etc.). Additionally, SGA babies may be born preterm, full term or postterm.
SGA occurs when a fetus does not receive adequate nutrients, usually due to a condition called intrauterine growth restriction (IUGR). IUGR can be caused by a number of factors, including genetics, maternal disease and/or modifiable behaviors, such as cigarette smoking.
Approximately 9.7% of newborns worldwide are born SGA. This percentage of SGA infants continues to increase each year. Additionally, SGA infants have much higher morbidity and mortality rates than infants of normal size.
Researchers have found associations between vitamin D and some pregnancy complications, such as preeclampsia, preterm birth, depression and miscarriage. However, the findings from research exploring the relationship between vitamin D and SGA infants have been conflicting. Therefore researchers conducted a meta-analysis that evaluated the effect of vitamin D deficiency in pregnant women on birth size.
A total of 13 studies with 28,285 participants were included in this meta-analysis. Studies were included if they met the following criteria:
- No history of chronic disease
- Single-child pregnancies
- Outcome group (women gave birth to a SGA infant) and control group (women who did not give birth to an SGA infant)
- Patients had available vitamin D levels
The researchers discovered that individuals with vitamin D levels below 20 ng/ml had a 1.58 increased risk of giving birth to a SGA infant compared to those with higher levels (p<0.01).
“The present study indicates that low vitamin D levels in pregnant women are associated with an increased risk of infants who are SGA. Further confirmation of these findings in larger-sample studies is required.”