Written and maintained by CASRAI Editorial Board
Published · Last updated
This page describes products and general use; it is not medical advice.
On this page
Laminaria is a hygroscopic cervical dilator: a conical, expansible device made from the root of a seaweed that swells as it absorbs moisture. Synthetic osmotic dilators such as Dilapan-S are a separate product type that FDA files under the same regulation. This reference is for clinic staff, buyers and students who need to tell the product types apart and read their FDA classification correctly.
What laminaria is
Under 21 CFR 884.4260, FDA defines a hygroscopic laminaria cervical dilator as a device designed to dilate (stretch open) the cervical os by cervical insertion of a conical and expansible material made from the root of a seaweed (Laminaria digitata or Laminaria japonica). “Hygroscopic” means the material takes up water and expands. The regulation is titled “Hygroscopic Laminaria cervical dilator” and classifies the device as Class II (performance standards). The same section states the device is used to induce abortion. Source: eCFR, checked 2026-10-30.
Who uses it: the device is a clinician-applied obstetric and gynecologic product, so its users are licensed clinicians; buyers and supply staff in those settings handle the purchasing and storage side.
How it is built
Natural laminaria is the processed seaweed root itself. Synthetic osmotic dilators are manufactured to mimic that shape. In the NLM AccessGUDID record for Dilapan-S (MEDICEM Technology s.r.o.), the device is described as a hygroscopic cervical dilator similar in shape to natural laminaria tents, with a hydrophilic active part, a polypropylene handle and a polyamide string, and it swells as it absorbs moisture. Source: AccessGUDID, checked 2026-10-30.
Types and variants
| Type | FDA product code and name | Material / key difference | Source |
|---|---|---|---|
| Natural laminaria | HDY, “Dilator, Cervical, Hygroscopic-Laminaria”; 21 CFR 884.4260; Class 2 | Made from the root of Laminaria digitata or Laminaria japonica seaweed | eCFR 884.4260; openFDA classification database |
| Synthetic osmotic dilator (for example Dilapan-S) | PKN, “Dilator, Cervical, Synthetic, Osmotic”; regulation 884.4260; Class 2; definition “Cervical softening and dilation” | Hydrophilic active part with a polypropylene handle and polyamide string (Dilapan-S listing) | FDA product classification database; AccessGUDID |
Laminaria, Dilapan and “osmotic dilators”
“Osmotic dilator” is the umbrella phrase for devices that open by absorbing fluid. Laminaria is the natural-seaweed version. Dilapan is a brand name of a synthetic product, listed in AccessGUDID as Dilapan-S. FDA’s synthetic code is literally named “Dilator, Cervical, Synthetic, Osmotic”.
FDA classification
Both product codes sit under regulation number 884.4260 and are Class 2. The regulation text itself describes the seaweed-root device; FDA’s product code database is where the synthetic category appears, with no special controls listed on the PKN page. Sources: eCFR; FDA Product Classification database (code PKN) and openFDA (code HDY), checked 2026-10-30. For how classes and premarket routes work in general, see FDA medical device regulations: classification, 510(k) and PMA and FDA 510(k) premarket notification.
Sizes and specifications
One published listing: the AccessGUDID record for Dilapan-S (device identifier 08595231703551) gives an outer diameter of 3 mm and a length of 55 mm, supplied sterile and labelled single use; the record states the labeling does not contain MRI safety information. This is one product listing, not a size range for the category; other records carry other identifiers and dimensions.
Safe use and handling basics
Dilators are applied by clinicians following the manufacturer’s instructions for use. The Dilapan-S listing identifies the device as sterile and single use. Product identification data for these devices is published through FDA’s unique device identifier system; see UDI for medical devices.
Common mix-ups
- Laminaria is not a drug. FDA regulates it as a device under 21 CFR 884.4260, Class II.
- Synthetic does not mean a different regulation number. The PKN code shares 884.4260 with the seaweed device.
- Record labels can differ. AccessGUDID entries for Dilapan-S do not all show the same product code (PKN in some, LOB in others), so check the FDA product classification page for the code.
- A dilator is not a scoring tool. Clinicians assess cervical readiness separately; see the Bishop score, and for another obstetric and gynecologic instrument class, the uterine curette.
Frequently asked questions
What is laminaria?
A hygroscopic cervical dilator made from the root of the seaweed Laminaria digitata or Laminaria japonica, classified by FDA as Class II under 21 CFR 884.4260.
What is Dilapan?
A brand of synthetic hygroscopic cervical dilator; the Dilapan-S record in AccessGUDID (MEDICEM Technology s.r.o.) describes a hydrophilic active part, a polypropylene handle and a polyamide string.
What are osmotic dilators?
Devices that dilate by absorbing moisture and swelling. FDA lists synthetic ones under product code PKN and laminaria under HDY.
Sources
- eCFR, 21 CFR 884.4260, Hygroscopic Laminaria cervical dilator, checked 2026-10-30: ecfr.gov
- FDA Product Classification, code PKN, checked 2026-10-30: accessdata.fda.gov
- openFDA device classification API, code HDY, checked 2026-10-30: api.fda.gov
- NLM AccessGUDID, Dilapan-S, checked 2026-10-30: accessgudid.nlm.nih.gov
Related supplies: gynecology and urology supplies.
