The one add-on with real evidence behind it
Hyaluronate in the transfer medium works. It also raises the twin rate.
This topic exists because a guide that says every add-on is worthless is not being honest, and would not deserve to be believed about the rest.
Adding hyaluronic acid to the fluid the embryo is transferred in, marketed as embryo glue, has been reviewed across 26 studies covering 6,704 participants. Each outcome below rests on a subset of those studies, given in the table:
| Outcome | Effect | In absolute terms |
|---|---|---|
| Live birth, 10 trials, 4,066 women | Relative risk 1.21 (95% CI 1.10 to 1.31), moderate quality | Baseline 33% becomes 37% to 44% |
| Clinical pregnancy, 17 studies, 5,247 women | Relative risk 1.16 (95% CI 1.09 to 1.23), moderate quality | Increased |
| Multiple pregnancy, 7 studies, 3,337 women | Relative risk 1.45 (95% CI 1.24 to 1.70), moderate quality | Increased by about 45% in relative terms |
| Miscarriage, 7 trials | Relative risk 0.96 (95% CI 0.75 to 1.23) in the studies at low risk of bias | No conclusive effect |
That live birth result is roughly eight extra live births per 100 women at a 33% baseline, at moderate certainty. It is the strongest positive finding for any add-on in this stage.
The UK regulator rates it yellow, meaning conflicting moderate to high quality evidence, which is more cautious than the Cochrane result alone would suggest and reflects exactly this uncertainty.
If a clinic offers you this one, the evidence supports having the conversation. That is more than can be said for most of the others in this stage, and saying so is the point of including it.