Postcoital contraception

DES used as an emergency contraception, The Netherlands, 1981

Abstract

Some form of postcoital contraception for protection against unwanted pregnancy is indispensable today especially in cases of rape, failed mechanical contraception, or 1st sexual contact without contraception.

A tablet form of postcoital contraceptive would be acceptable if 100% certainty is assured and it doesn’t involve adverse effects.

Postcoitally administered high-dose estrogens proved effective in Macaca mulatta.

Diethylstilbestrol in variable dosages with or without ethinylestradiol was used in various studies and with variable results.

Pregnancy rates depended on time of coitus in cycle, contraceptive dosage, and time of administration after coitus (within 72 hours).

Conjugated estrogens and various progestagens or combinations of both have been tried with variable success.

Another form of postcoital contraception is IUD insertion within 7 days following unprotected coitus. Advantages of this method are the time factors and absence of adverse effects of hormonal contraceptives.

Postcoital hormonal contraceptives cause changes in the endometrium which prevent blastocyst implantation. They alter tubal function affecting zygote movement towards the uterus. They have an antiovulatory effect and may be luteolytic. Estrogens have more severe side effects than progestagens.

Nausea, vomiting, mastodynia, fluid retention, and vaginal bleeding can result from estrogens. Progestagens can cause irregular bleeding. Combination of both can cause menstrual irregularity.

Postcoital hormonal contraceptives are contraindicated in heart and liver diseases, thrombosis, and pregnancy (teratogenic and carcinogenic effects on offspring).

Pregnancy despite postcoital contraception results in extrauterine pregnancy in 10% of patients. The most important reservations in evaluating publications on this subject are:

  1. lack of control group;
  2. estimation of pregnancy probability is not reliable because of study population used;
  3. patient fertility cannot be ascertained;
  4. and reliability of information provided by patient.

Conclusion from literature studies is that postcoital hormonal contraception is of value but effectiveness is not proven. More research is needed and indications are that other less radical drugs may be found in near future.

Sources

  • Postcoital contraception, Nederlands tijdschrift voor geneeskunde, NCBI PubMed, PMID: 7254397, 1981 Jul 11.
  • Image credit Helen Keen.
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