An Investigation of the Effect of Vitamin D Level During Frozen Embryo Transfer (FET) in IVF and Pregnancy Outcomes (VitD in FET)

July 13, 2026 updated by: Fakih IVF Fertility Center

Vitamin D Levels and Pregnancy Outcomes Following Frozen Embryo Transfer (FET) in the UAE

Vitamin D is best known for keeping our bones healthy, but growing research suggests it may also play a role in fertility. Many In vitro fertilization (IVF) clinics now routinely check vitamin D levels and prescribe supplements before treatment, but the science is still unclear on whether this actually improves the chances of pregnancy.

Our study, based in the United Arab Emirates (UAE), aims to find out whether a woman's vitamin D level on the day of her frozen embryo transfer (FET) makes a difference to whether she becomes pregnant and delivers a baby. The UAE is an ideal setting for this research, as vitamin D deficiency is particularly common in the region. The findings could shape how fertility clinics screen and treat women seeking fertility treatment in the future.

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Detailed Description

Serum vitamin D3 has attracted growing research interest for its potential role in female reproductive physiology. While some studies associate sufficient vitamin D3 levels with improved IVF outcomes, others have failed to confirm this, leaving the evidence base contested. Despite this uncertainty, pre-In vitro fertilization (IVF) vitamin D screening and supplementation of insufficient patients has become widespread clinical practice. Evidence specific to frozen embryo transfer (FET) cycles remains particularly limited. Recent prospective studies found no significant difference in ongoing pregnancy, live birth, or implantation rates between vitamin D3-insufficient women receiving supplementation and vitamin D3-replete women who did not, underscoring the need for higher-quality, targeted research. While emerging data support a role for vitamin D in endometrial receptivity, it remains unclear whether correcting insufficiency prior to FET meaningfully improves reproductive success.

To address these gaps, our study will evaluate the association between serum vitamin D3 levels on the day of FET and subsequent pregnancy and delivery outcomes at a UAE fertility center. Supplementation history and relevant clinical variables will be captured via patient questionnaire. Vitamin D status will be classified per International Society of Endocrinology guidance: deficient (<20 ng/mL), insufficient (20-29 ng/mL), and sufficient (≥30 ng/mL). Given the high regional prevalence of vitamin D deficiency, this study is well-positioned to determine whether vitamin D status represents a modifiable determinant of reproductive success, with direct implications for clinical screening and management protocols in this population.

Study Type

Observational

Enrollment (Estimated)

126

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact Backup

Study Locations

  • United Arab Emirates
      • Abu Dhabi, United Arab Emirates
        • Recruiting
        • Fakih IVF Fertility Centre LLC
        • Contact:
        • Contact:
        • Principal Investigator:
          • Michael Fakih, MD
        • Principal Investigator:
          • Lamiya Mohiyiddeen, MD, FRCOG

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult

Accepts Healthy Volunteers

No

Sampling Method

Non-Probability Sample

Study Population

Women undergoing FET cycle who do not suffer from conditions affecting implantation and have got vitamin D levels tested 3 - 6 months before FET cycle.

Description

Inclusion:

  • Women undergoing frozen embryo transfer (FET) at Fakih IVF.
  • Age between 18 and 40 years.
  • Body mass index (BMI) between 18 and 40 kg/m².
  • Patients who had serum vitamin D levels assessed within three months prior to FET
  • Supplementation with Vitamin D if deficient < 30 ng/mL (75 nmol/L).

Exclusion:

  • Age below 18 years or above 40 years.
  • BMI below 18 kg/m² or above 40 kg/m².
  • Patients who did not have vitamin D levels measured within three months prior to FET.
  • Patients who were found to have low vitamin D levels but did not receive supplementation.
  • Patients with recurrent implantation failure (RIF).
  • Patients with known uterine factors affecting implantation (e.g., congenital uterine anomalies, intrauterine adhesions, submucosal fibroids).
  • Patients with significant medical comorbidities that may affect pregnancy outcomes.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

Cohorts and Interventions

Group / Cohort
Intervention / Treatment
Women undergoing frozen embryo transfer (FET) at Fakih IVF

The study will enroll women aged 18-40 years with a BMI of 18-40 kg/m² undergoing FET at Fakih IVF, who had serum vitamin D assessed within three months prior to transfer. Women with deficient levels (<30 ng/mL) must have received supplementation prior to FET to be eligible.

Exclusions are designed to reduce confounding: women are excluded if vitamin D was not measured within the required window, if identified deficiency went untreated, or if they have a history of recurrent implantation failure (RIF). Women with uterine factors known to impair implantation including congenital anomalies, intrauterine adhesions, or submucosal fibroids are also excluded, as are those with significant medical comorbidities that may independently affect pregnancy outcomes.
Other: No Intervention: Observational Cohort
There are no interventions in this study. This is an observational cohort study.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Time Frame
Clinical pregnancy test
Time Frame: From enrollment on day of FET to 1 month post FET
From enrollment on day of FET to 1 month post FET
Concentration of serum 25-hydroxyvitamin D levels measured on the day of FET
Time Frame: Vitamin D level tested on the day of FET.
Vitamin D level tested on the day of FET.

Secondary Outcome Measures

Outcome Measure
Time Frame
Live birth rate, miscarriage rate, and preterm birth rate.
Time Frame: From enrollment to six weeks post partum
From enrollment to six weeks post partum

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Fakih IVF Fertility Center

Investigators

  • Principal Investigator: Michael Fakih, MD, Fakih IVF Abu Dhabi
  • Principal Investigator: Lamiya Mohiyiddeen, MD, FRCOG, Fakih IVF Abu Dhabi

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

June 1, 2026

Primary Completion (Estimated)

June 1, 2027

Study Completion (Estimated)

August 1, 2027

Study Registration Dates

First Submitted

June 26, 2026

First Submitted That Met QC Criteria

June 26, 2026

First Posted (Actual)

July 2, 2026

Study Record Updates

Last Update Posted (Actual)

July 15, 2026

Last Update Submitted That Met QC Criteria

July 13, 2026

Last Verified

July 1, 2026

More Information

Terms related to this study

Keywords

Other Study ID Numbers

  • FAKIHIVF-2025-5
  • DOH/ADHRTC/2025/1884 (Other Identifier: Department of Health Abu Dhabi)

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

IPD Plan Description

Not an NIH project

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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