The Association for Dietetics in South Africa (Adsa) says the composition of a woman's diet before, during and after pregnancy might influence the pregnancy, the delivery and the health of the mother and child.
The association advises women who plan to fall pregnant or who are pregnant to consult a registered dietitian to assess their nutrient needs and identify eating plans to meet these needs.
"The key components of a healthy lifestyle during pregnancy include appropriate weight gain, appropriate physical activity and enjoying a variety of foods," Berna Harmse, president of Adsa, says.
"When women choose to eat all kinds of junk foods then they run the risk of starving their unborn babies of the nutrients they need to grow healthily," dietician Carol Browne says.
On the one hand, not gaining enough weight during pregnancy means the unborn baby will not grow to its fullest potential and might have developmental problems after birth, Browne says.