Does shipping embryos damage them?What the evidence actually says, including where it runs out
This is the question people ask before they ask about price. It deserves a real answer rather than a reassurance, so this page cites what exists, says how strong it is, and is explicit about what nobody can currently claim.
Short answer: does moving them hurt them?
No published evidence shows that correctly handled transport damages cryopreserved embryos. They stay frozen in nitrogen vapour the entire time, and the vessel is a passive device with nothing to fail mid-flight. The genuine risks sit in handling, custody and delay, not in the movement.
Do shipped embryos have lower success rates?
The available data does not show lower success rates for transported embryos. It also is not strong enough to prove the opposite. The most quoted comparison rests on 37 shipped embryos in a 2009 conference abstract, which is a signal, not a settled finding.
The study people are quoting without citing it
A 2009 abstract published in Fertility and Sterility compared outcomes for embryos that had been shipped against embryos that had not. The shipped group did not do worse. On the reported figures it did somewhat better.
| Measure | Shipped embryos | Not shipped |
|---|---|---|
| Survival after thaw | 85.2% | 78.2% |
| Implantation | 41.9% | 25.3% |
| Clinical pregnancy | 61.5% | 41.3% |
Read the limitation before you use these numbers. The shipped group was 37 embryos. That is a small enough sample that the differences could be noise, or could reflect which embryos got selected for shipping in the first place. It is a conference abstract from 2009, not a large modern cohort. The honest reading is narrow: this data gives no reason to believe transport harms embryos. It does not show transport improves anything.
Source: Fertility and Sterility, 2009 abstract. Read it yourself rather than taking our summary of it.
If your doctor has advised against moving them, that is not unreasonable
Plenty of reproductive endocrinologists prefer to transfer an embryo in the lab that froze it, on the argument that the freezing and thawing protocols are matched and the team knows its own material. That is a defensible clinical view. It is also a preference rather than a finding, and clinicians who hold it will often say so directly when asked whether the evidence supports it. Ask your own doctor that exact question: is this an evidence position or a lab-familiarity position? The answer tells you how much weight to give it.
What temperature do embryos travel at, and for how long?
They travel in nitrogen vapour at around minus 190 degrees Celsius. We rent the shipper to the route, and the unit we use for long-haul work, a Worthington CX100, is rated for a 17-day static hold at that temperature. That is the number worth comparing against your trip. A cross-country move takes hours. A Houston to Lagos move takes under two days.
Roughly -190°C in transit
The figure you will see quoted more often is -196°C. That is the boiling point of liquid nitrogen, not the vapour-phase temperature a dry shipper actually holds. Both sit far below the point where anything biological resumes.
17-day static hold
Seventeen days of static hold against a journey measured in hours is the margin, and the margin is the reassurance. It is not there because we expect to use it. It is there so a missed connection is an inconvenience rather than an incident.
No liquid, no power
Nitrogen is absorbed into the vessel lining, so there is no free liquid to spill and nothing to plug in. A passive vessel cannot suffer a compressor failure or a flat battery, which removes the failure modes people instinctively worry about.
We are deliberately not printing a precise threshold temperature at which cryopreserved material starts to degrade. Figures in the range of minus 130 to minus 150 get repeated widely online and we could not trace them to a primary source we would stand behind. If you find one, we would like to see it.
So what actually goes wrong when embryos are moved?
Almost never the cold. Things go wrong at the handoffs: time out of the tank at either end, a vessel that sat somewhere unrecorded, a cane that does not match the inventory sheet, or a shipper that was undercharged before pickup. All four are process failures, and all four are preventable.
Time out of the tank at each end
The two riskiest minutes of the whole trip are the transfer from storage tank to shipper and back again. That is lab work, done by embryologists, and it is the same work whether the specimens then travel five miles or five thousand.
Custody gaps
A vessel sitting on a warehouse floor overnight is not being harmed by the warehouse. It is being harmed by nobody knowing it is there. Gaps in the record are what turn a recoverable delay into an unrecoverable one.
Labelling and inventory errors
The failure mode nobody puts on a marketing page. A cane that does not match the inventory sheet is a bigger problem than a shipper that ran three degrees warmer than expected, and it is more common.
A vessel that was undercharged or knocked over
A vapour shipper holds temperature because nitrogen is absorbed into its lining. Short-charge it, or tip it hard enough to lose absorbed nitrogen, and its hold time drops. This is why charging protocol and physical handling matter more than the brand on the side.
Should you just move them yourself?
Across town, with a tank your clinic supplies and both labs expecting you, driving them yourself is a legitimate option and people do it. It stops working once a flight, a border, an overnight or a connection enters the picture, because those are the points where a private individual has no fallback.
Driving them yourself can make sense
- • Both clinics are in the same metro area
- • The releasing clinic supplies and charges the vessel
- • The receiving lab has a confirmed slot to receive on the same day
- • The whole thing is one car journey with no unattended stops
Where it stops being a good idea
- • Any commercial flight, domestic or international
- • Any overnight, because now the vessel is unattended in a hotel
- • Any border, where the paperwork is the actual job
- • Any situation where a delay leaves you with no second option
The objection people raise on forums is not really about safety. It is about handing something irreplaceable to a stranger who might be carrying several other tanks that day. That is a fair objection to a network courier model, and it is the reason we carry one consignment at a time, by hand, with the same person from pickup to delivery. If you want the mechanical comparison rather than the assurance, the provider comparison guide sets the two models side by side.
What we will not promise you
We will not tell you that moving your embryos will not affect your outcome, because nobody can know that. We will not quote a survival percentage for your specific specimens. What we will do is keep them cold, keep them accounted for, and hand you the record.
- The shipper charge record, the seal number applied at the sending lab, and a signed custody entry at every handover
- A chain-of-custody log naming every person who held the vessel
- One consignment at a time, hand-carried, no consolidation with other clients
