P–375 Intralipid supplementation in women with unexplained recurrent implantation failure and elevated uterine natural killer cell levels - A randomized placebo controlled trial

Study question Does intralipid supplementation in women with unexplained recurrent implantation failure (RIF) with elevated uterine natural killer cell (uNK) levels improve pregnancy outcomes during IVF? Summary answer Intralipid supplementation appears to improve clinical pregnancy rate in women with unexplained RIF with elevated uNK cell levels. What is known already The increased numbers of uNK cells in peri-implantation endometrium have been reported in women with recurrent miscarriage (RM) and RIF after IVF. However, reports are contradictory when it comes to correlation of increased numbers of uNK cells with pregnancy outcome. Current opinion suggests there is a potential for intralipid therapy in improving reproductive outcome, although data on live birth rate is very limited. No studies have assessed the effect of intralipid on IVF outcomes in RIF women based on elevated uNK cells. Identified studies have all used pNK cell testing as preferred diagnostic tool for analysis of NK cell levels. Study design, size, duration A randomized placebo controlled trial was conducted at Division of Reproductive Medicine at tertiary care institute. Thirty women with RIF and fifty fertile controls with age <35 years having regular menstrual cycles and no hormonal treatment in last 3 months were enrolled in the study from January 2019 to December 2020 for uNK cell testing. Randomization was done using random numbers and sealed envelopes. Only the subjects were masked and allocation concealment was done. Participants/materials, setting, methods Subjects included RIF 20–35 years, normal ovarian reserve, unexplained and tubal factors, normal karyotype and normal uterine cavity. Cut off for uNK cells was derived from fertile controls by immunohistochemical staining of CD56+ cells from midluteal endometrial biopsy sample. Subjects with elevated uNK cell levels were randomized during IVF to group A (Intralipid) or group B ( saline ). The infusion was repeated within one week of positive pregnancy test and then every 2 weeks. Main results and the role of chance The mean age and BMI were comparable between fertile control and study group(29.45±3.3 vs 31.17±3.3 years, 22.97±1.89 vs 23.21±2.2 kg/m2 ;p>0.05). The median uNK cell levels was 7%(used as cut off) in fertile controls and 13.5% in RIF. 18 women (60%, 18/30) with RIF who had elevated uNK cell level (>7%) were randomized. Four women were lost to follow up. The median age, BMI, number of previous failed cycles and duration of infertility were comparable between Group A(n = 7) and Group B(n = 7){30(IQR:27–31) vs 33(IQR:30–34)years, 22.7(IQR:21.08–24.4) vs 22.6(IQR:21.37–24.2)kg/m2, 2(IQR:2–3) vs 2(IQR:2–3), 8(IQR:7–8) vs 8(IQR:7–10)years}. The median FSH, AMH and AFC were 5.86(IQR:5.13–7.67)mIU/l, 2.4(IQR:2.16–6.12)ng/ml, 10(IQR:8–12) in Group A which were comparable with Group B {6.2(IQR:4.78–6.5)mIU/l, 4.8(IQR:2.67–6.25)ng/ml, 12(IQR:12–16) }. All patients underwent antagonist protocol. The clinical pregnancy rate was 57.14%(4/7) in group A which was significantly higher as compared to 28.6%(2/7) in group B(p < 0.05). None of the patients reported any side effects due to intralipid. Limitations, reasons for caution The limitation of present study is its small sample size. However, the study is currently recruiting more RIF patients, and these are the interim results of the same. More RCTs with larger sample size are required to assess the efficacy of intralipid in this specific subset of population. Wider implications of the findings: The present study suggests the beneficial effect of intralipid in women with unexplained RIF with elevated uNK cell levels in increasing the chemical and clinical pregnancy rate. However, ongoing pregnancy rate and live birth rate should be investigated further in this subset of population. Trial registration number CTRI/2019/01/017213