O-017 Swim-up versus density gradients for sperm preparation in intrauterine insemination: a multi-centre randomised clinical trial
Authors: Duong T , Le T K , Vu A TL , Nguyen D L , Pham T D , Nguyen M T , Nguyen P TM , Nguyen T M , Le A H , Tran C T , Dang V Q , Vuong L N , Mol B W , Norman R J , Ho T M 
Published: July 2024

Study question

What is the effectiveness of swim-up (SU) and density gradients (DG) for sperm preparation in infertile couples undergoing intrauterine insemination (IUI)?

Summary answer

In couples undergoing IUI, there is no significant difference in the treatment outcomes between SU and DG.

What is known already

Swim-up (SU) and density gradients (DG) are the most two commonly used techniques for sperm preparation in intrauterine insemination (IUI). The latest Cochrane review concluded that there is uncertainty about the effectiveness of SU versus DG and no studies reported on live birth.

Study design, size, duration

This open-label, multi-centre randomised clinical trial was conducted on 912 infertile couples at a tertiary IVF center, Ho Chi Minh City, Vietnam from August 2020 to June 2023. Couples were randomly asigned to two groups, SU and DG using computerized randomisation on the day of IUI with variable block size of 2, 4 or 6. Primary outcome was live birth rate.

Participants/materials, setting, methods

Infertile couples were eligible if aged ≥18, indicated for IUI with ≤2 IUI prior attempts and husbands’ sperm concentration ≥5x106/ml, progressive motility (PR) ≥32% and total PR sperm count &gt;5x106 before sperm preparation (WHO 2010 criteria). Couples using frozen semen, or high viscosity semen were not eligible. Women had ovulation induction using hMG. Sperm preparation was performed within one hour after ejaculation. IUI was performed once at 36 to 40 hours after hCG trigger.

Main results and the role of chance

Between August 2020 and June 2023, 912 couples were randomly assigned to SU (n = 456) or DG (n = 456). Baseline characteristics were comparable between the two groups (mean female age of 31.3 ± 0.4 years; total sperm count: 86.2 [52.9;137.6] million; sperm motility: 44.8 ± 8.2%).

Live birth occurred in 55 (12.1%) couples in the SU group and 71 (15.7%) couples in the DG group (RR 0.77; 95% CI 0.56-1.07). Ongoing pregnancy and multiple pregnancy were also comparable between the two groups. There were no statistically significant differences between the SU and DG groups with respect to the occurrence of pregnancy complications, obstetric and perinatal complications, preterm delivery, birth weight and neonatal complications.

Pre-planned subgroup analysis showed that the live birth rate was not materially affected by the IUI indications, total motile sperm after preparation (&lt;1, ≥1 and &lt;5, ≥5 and &lt;10 and ≥10 million).

Limitations, reasons for caution

The main limitation of the study was its open-label design, due to the nature of the interventions.

Wider implications of the findings

Our study suggests that in couples undergoing IUI with progressive motility (PR) ≥32% and total PR sperm count &gt;5x106 before sperm preparation, SU or DG can both be used for sperm preparation, with a preference for density gradients.

Trial registration number

NCT04477356