Conversely, the research indicated that women who remained in a deficient or insufficient state, or whose levels declined, actually had lower odds of experiencing severe nausea and vomiting, also known as emesis.
“This study is suggestive of the importance of sufficient maternal vitamin D stores prior to conception,” the authors wrote in the journal Nutrients.“Sufficient 25(OH)D nutrient stores during the preconception and early gestation period are important and may be an indicator of a more robust implantation/placentation and therefore a healthy pregnancy.”
The findings highlight this link between successful embryo implantation and nausea and suggest that vitamin D status may be associated with nausea and vomiting as a result of important hormonal or placental signaling mechanisms in early gestation.
The study was conducted by researchers affiliated with the University of Maryland, National Institutes of Health, University of Pennsylvania and University of Utah and supported in by the Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development at the National Institutes of Health.
Insights from EAGeR trial
For their study, the research team conducted a secondary analysis of data from the Effects of Aspirin in Gestation and Reproduction (EAGeR) trial, a multisite, prospective, double-blind, block-randomized, placebo-controlled clinical trial designed to evaluate the effect of low-dose aspirin (LDA) on live birth in healthy women with regular menstrual cycles and one to two prior pregnancy losses.
The data provided the 25(OH)D status of mothers at preconception (n = 774) and eight weeks’ gestation (N = 641). Nausea and vomiting were captured via medical records and daily symptom diaries. Researchers used logistic regression and generalized estimating equations (GEE) to estimate associations.
As expected, data suggested higher levels of 25(OH)D were associated with symptoms of nausea and vomiting, represented by both clinically documented and self-reported symptoms.
Further, women who improved their vitamin D status from deficient (≤20 ng/mL) or insufficient (21–29 ng/mL) at preconception to sufficient (≥30 ng/mL) at eight weeks’ gestation had higher odds of experiencing medically documented nausea or emesis symptoms compared to those who remained sufficient at both time points.
Mechanism of action
Successful implantation and healthy placental function result in higher secretion of human chorionic gonadotropin (hCG) and it has been suggested these may manifest clinically as a more heightened nausea response.
Vitamin D, which is a secosteroid hormone, has been postulated to have an impact on early critical periods of implantation, with deficiency potentially leading to placental dysfunction due to the disruption of hormones (estrogen and progesterone) that help maintain a pregnancy and support endometrial receptivity and implantation of the uterus.
Specifically, trophoblasts are located in the outer layers of endometrial cells and help the embryo implant successfully and then form the placenta. These trophoblasts then support endometrial receptivity via vitamin D receptors in the uterus by providing an anti-inflammatory environment for successful implantation and placentation.
If sufficient levels of vitamin D are present in trophoblast cells and help form the placenta successfully, this may lead to a robust implantation process, increasing levels of hCG, which is associated with a higher likelihood of nausea in pregnancy, the report said.
In addition to the placentation processes, sufficient vitamin D in early pregnancy modulates inflammation, regulates hormone production and supports nutrient transfer to the placenta.
“If any disruptions occur during the preconception and early pregnancy period, placental dysfunction may occur, and a robust nausea response may be diminished and/or result in adverse pregnancy outcomes,” the researchers noted. “Therefore, like folic acid, achieving sufficient vitamin D levels prior to or during the periconceptual period may be essential for optimal placental development.”
In recognition of its importance in the early pregnancy period, the Endocrine Society has updated its vitamin D and pregnancy guidelines by recommending universal vitamin D supplementation to pregnant women of 2500 IU per day to ensure sufficient levels are achieved and maintained during pregnancy.
“Sufficient preconception vitamin D may promote robust implantation and higher human chorionic gonadotropin (hCG) levels, potentially increasing nausea and vomiting in pregnancy,” the researchers wrote.
They noted that future studies are needed to assess the association between 25(OH)D and nausea in preconception and early gestation in larger sample sizes and more diverse populations.
Source: Nutrients 2026, 18(4), 692. doi: 10.3390/nu18040692. “Periconception Maternal Vitamin D Status on Nausea and Vomiting Symptoms in Early Pregnancy Among Women with a History of Pregnancy Loss”. Alkhalaf, Z.M. et al.
