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Laminaria

Scientific Name(S): Laminaria digitata Lamour or L. japonica. Family: Laminariaceae

Common Name(S): Kelp, brown algae, laminaria, horsetail, Seaweed

Laminaria is an herbal medicine used to induce labor and abortion. The dried stem of Laminaria mechanically dilates the cervical opening by absorbing water and swelling to several times its original diameter. Laminaria is a marine algae which provides a good source of protein, vitamins, minerals, and carbohydrates. It only contains small amounts of fat.

Botany: The marine kelps derived from Laminaria species are found primarily in the cold waters of the North Atlantic and North Pacific oceans.

History: Laminaria for cervical dilation is used in the form of "tents." A tent is any material, usually hygroscopic (readily absorbs water), which is placed in a canal or chamber to maintain the opening or cause dilation. Laminaria tents are made from the dried stems of Laminaria seaweeds. When dried and rounded into a stick-like shape, the tent is approximately 6 cm (2 1/2 inches) long with a diameter of 0.3 to 0.5 cm. A strong thread is attached to one end and a collar prevents its migration into the uterus. The stem is hygroscopic and can swell to 3 to 5 times its original diameter within 12 to 24 hours. Other natural products have been used in the past as tents, including sponges, dried corn stalks, slippery elm bark and tupelo wood. The use of laminaria became popular in the 1800s; hollow laminaria tents were developed to improve uterine drainage and laminaria coated with wax was designed to release antiseptics as it melted.

Tents fell into disuse because of complications due to infections. This was especially evident in tents derived from land plants because of the inability to sterilize Clostridium spores (the causative agents of tetanus, botulism and gas gangrene). Although laminaria from the ocean contain relatively nonpathogenic bacterial contaminants, polluted waters and poor packaging extended the problems of infection to its use. However, with the advent of ethylene oxide and gamma irradiation sterilization techniques, interest in laminaria tents returned.

Uses of Laminaria

Laminaria has been used as a hygroscopic cervical dilator and inducer of labor.

Side Effects of Laminaria

Laminaria may cause or contribute to maternal and neonatal infection.

Dosage: Talk with your caregiver about how much Laminaria you should take. The amount depends on the strength of the medicine and the reason you are taking Laminaria. If you are using this medicine without instructions from your caregiver, follow the directions on the medicine bottle. Do not take more medicine or take it more often than the directions tell you to.

Toxicology: A review of the findings from the early studies with laminaria suggests that it may be associated with a risk of neonatal and maternal infection. One manufacturer recommends swabbing the cervical canal with a suitable lubricant and antibacterial agent prior to inserting the tent, then packing the canal with antibacterial gel. The followup of 17 women who had laminaria tents inserted for the induction of abortion and then decided to continue the pregnancy found no evidence of infection at term.

The spontaneous uterine contractions that may accompany the use of laminaria have been implicated in the induction of fetal hypoxia and subsequent intrauterine death. Fetal activity should be monitored closely. Other potential problems with the use of laminaria include difficulty removing the tent, breaking the tent during removal or rupturing the cervical wall and subsequent infection. Blood loss does not appear to increase following the use of laminaria tents in first-trimester abortions.

Although laminaria tents possess many qualities of an ideal cervical dilator (easy to insert/remove, slow expansion, painless dilation), persistent problems of infection and cervical injury have spurred the search for alternate types of dilators. Synthetic laminaria tents prepared from hydrophilic polymers provide increased levels of structure stability. Synthetic tents have efficacy similar to that of prostaglandin E2 tablets.

Summary: Laminaria tents are effective in stimulating the dilation of the cervical canal and in ripening the cervix at term. Their effectiveness in facilitating labor is variable. Clinical studies suggest that laminaria tents may increase the incidence of maternal and neonatal infections. Other pharmacologic properties of laminaria derivatives include the ability to limit the absorption of radioactive strontium and to impart anticoagulant properties.