By Eric Madrid MD 

The three trimesters of pregnancy set the stage for a baby's health. As the embryo becomes a fetus, and organs begin to fully develop, the nutrition a baby receives from its mother can affect everything from the heart strength to eyesight. Over the years, many have wondered what supplements, if any, should be taken beyond a prenatal vitamin.    

Three important studies, focusing on the intake of specific supplements, have been published in 2018 providing insight into these questions. 

In a February 2018 study, researchers from Johns Hopkins School of Public Health in Baltimore, Maryland conducted a meta-analysis evaluated the effect on a child’s future risk of developing allergies or an autoimmune disease based on three factors: maternal diet during pregnancy, breastfeeding status, and consumption certain supplements taken during pregnancy.  

In the study, researchers evaluated hundreds of studies from 1946 to 2017, which included over 1.5 million participants. Here is what they found: 

Probiotics may help reduce Eczema risk  

Nineteen of the studies evaluated the mother’s probiotic use during pregnancy and during the breastfeeding period. The results showed that children of mothers taking probiotics were 22 percent less likely to develop eczema when compared to the mothers who did not take probiotics. Worldwide, it is estimated that up to 20 percent of children have eczema, which can range from mild to severe for many.                   

Fish oil may help reduce Egg Allergy risk 

Six of the studies evaluated fish oil supplementation during pregnancy and breastfeeding. The results showed that these children were 31 percent less likely to develop egg allergies when compared to mothers who did not take fish oil. Up to 2.5 percent of children have egg allergies, which may or may not diminish as the child ages.  

The scientists concluded that breastfeeding may reduce the risk of developing type 1 diabetes, an autoimmune condition that often requires lifelong use of insulin and can have a long-term effect on organ health.  

Fish oil may help reduce Childhood Asthma risk 

Another study published in February, 2018 in the Journal of Family Practice showed that fish oil supplementation during the third trimester (last 13 weeks) of pregnancy could help prevent childhood asthma. The researchers stated the children of mothers who supplemented with fish oil had lower risk of asthma between the ages of three and five when compared to those children whose mothers took a placebo pill.   

Further, it was noted that doses of at least 2,700 mg per day need to be taken in order to see this benefit. Daily doses of 900 mg of fish oil were insufficient to prevent childhood asthma.   

If you think consumption of fish would be a suitable alternative, think again.  Pregnant women are advised to avoid fish that is high in mercury due to the risk of fetal harm. The Federal Drug Administration (FDA) recommends 2-3 servings of low mercury fish per week.    

Fish low in mercury and acceptable to consume during pregnancy include: 

  • Tilapia 
  • Salmon 
  • Cod 
  • Catfish 
  • Tuna (canned-light)  

Fish which should be avoided during pregnancy include: 

  • Swordfish 
  • Shark 
  • Tilefish 
  • King mackerel 

Vitamin D and postpartum depression   

A May 2018 study in the Journal of Affective Disorders showed that pregnant women with lower vitamin D levels in their blood were more likely to suffer from depression after giving birth.   Pregnant women should consider supplementing with 1,000-5,000 IU daily of vitamin D. 

Supplements during pregnancy 

Disclaimer: If you are pregnant, consult with your obstetrician before taking any supplements.   


  1. Garcia-Larsen V, Ierodiakonou D, Jarrold K, et al. Diet during pregnancy and infancy and risk of allergic or autoimmune disease: A systematic review and meta-analysis. Basu S, ed. PLoS Medicine. 2018;15(2):e1002507.  
  3. Neutze D, Evans KL, Koenig M, Castelli G, Mounsey A, Stevermer JJ. PURLs: Does fish oil during pregnancy help prevent asthma in kids? The Journal of Family Practice. 2018;67(2):100-102. 
  4. A systematic review of the associations between maternal nutritional biomarkers and depression and/or anxiety during pregnancy and postpartum Trujillo, Janet et al. Journal of Affective Disorders , Volume 232 , 185 - 203