Tropical Diseases Can Harm Pregnancy

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Tropical Diseases Can Harm Pregnancy

Contraceptive concerns are few, but anemia from tropical diseases merits careful attention.

By Boaz Otieno-Nyunya, MD
Moi University, Eldoret, Kenya
FHI Fellow in Contraceptive Technology Research

Network: Winter 1999, Vol. 19, No. 2

Copyright Family Health International, 1999.
Network is reprinted with permission from Family Health International.

Many common tropical diseases -- such as malaria, schistosomiasis, intestinal helminths or filariasis -- affect reproductive health dramatically. These diseases can harm a pregnant woman or her fetus. For couples, they may complicate contraceptive use or reduce fertility, usually either by physically blocking parts of the reproductive tract in men or women or by affecting reproductive hormonal function in women.

Malaria's effects on pregnancy can be so severe that preventive treatment with antimalarial drugs during pregnancy is recommended in areas where the disease is endemic. Such treatment should focus primarily on women experiencing their first pregnancy because they are most vulnerable.

Chloroquine and proguanil, two drugs widely used to prevent or treat malaria, are safe to use during pregnancy. Preferably, sulfadoxine-pyrimethamine should not be given in late pregnancy due to the risk of provoking jaundice in the newborn. Mefloquine has been considered safe to use only during the third trimester of pregnancy. However, the World Health Organization's (WHO) malaria unit recently reported that the risk to the fetus from taking mefloquine in the first trimester of pregnancy is no greater than that associated with any other antimalarial, and is considerably lower than the risk associated with Plasmodium falciparum malaria, the most severe form of malaria in humans.¹ Quinine, in recommended doses, is safe for use in life-threatening infections in pregnancy. The newer antimalarials -- artemether and artesunate -- do not cross the placenta as easily as the quinoline antimalarials and thus have less potential to harm the fetus.²

Prophylactic treatment of malaria in pregnant women is important because pregnancy decreases a woman's immunity and makes her more susceptible to numerous complications from malaria, which include cerebral malaria, renal failure, hypoglycemia, pulmonary edema, and circulatory collapse. Pregnant women are particularly susceptible to severe forms of malaria infrequently seen in other adults living in malaria-endemic areas.

The mechanism of immunity against malaria is still unclear, but epidemiological evidence, primarily from Africa, suggests that in malaria-endemic areas, prevalence of malaria infection increases gradually from early weeks of pregnancy to a peak during the second trimester before falling. At delivery, the prevalence is similar to that before pregnancy.³ On the other hand, levels of the malarial antibody, IgG, were observed to drop progressively in pregnant women in Gambia, reaching their lowest levels in the last 10 weeks of pregnancy.⁴

Women with lower parity (fewer previous births) tend to have lower immunity and can suffer more severely from malaria than women with higher parity.⁵ Pregnancy reduces previously acquired antimalarial immunity, while infections in previous pregnancies confer some protection in the current pregnancy.

Placental malaria, in which malarial parasites replicate in the placenta and block the exchange of oxygen and nutrients to the fetus, is particularly frequent and severe during first pregnancies. Placental malaria can result in low birth-weight, mainly by retarding intrauterine growth, which increases the risk of infant death and disease during the first year of life.⁶

Malaria and other tropical diseases also are important causes of spontaneous abortion, and many cases of unexplained pregnancy loss may, in fact, be due to undiagnosed tropical diseases.

The harmful consequences of other tropical diseases to a pregnant woman or her fetus largely depend on the severity of the infection, as well as the stage of pregnancy. For example, drugs used to treat schistosomiasis -- such as prazi-quantel, oxamniquine or metrifonate -- may be toxic to the fetus. Unless the disease is severe, it may be advisable to withhold treatment until the end of pregnancy.

Malnutrition or anemia caused by intestinal worms can make pregnancy difficult and, simultaneously, be worsened by pregnancy. Not uncommonly, the diagnosis of nutritional anemia in a woman with intestinal worms is first made during pregnancy. Lack of folic acid and other micronutrients, which may result from intestinal worms or chronic malaria, has also been associated with premature placental separation.⁷

Major Tropical Diseases Affecting Reproductive Health

Tropical diseases of significant prevalence¹ that affect reproductive health include the following:

Malaria -- Caused by a protozoan parasite transmitted by mosquito bite, malaria is a major global health problem, with 300 million to 500 million new cases and more than 2 million deaths each year. In much of Africa, more than 25 percent of all hospital visits are due to malaria.

Schistosomiasis -- An infection caused by parasitic worms transmitted by exposure to infested water, schistosomiasis creates significant health problems in many parts of the world, including the Near and Far East, Africa, South America and the Caribbean region. It is endemic in 74 developing countries and approximately 200 million people are infected. Some 20,000 people die from it each year.

Intestinal helminths -- Intestinal helminths, which are parasitic worms transmitted primarily through food, do not cause the degree of disease and death associated with malaria. But they are found nearly everywhere in the tropics and significantly harm health. Three prevalent parasitic worms are Ascariasis lumbricoides, Trichuris trichura and hookworm species. Some 250 million people have Ascariasis and 60,000 die annually as a result.

Filariasis -- Yet another disease found in most warm, humid regions of the world, filariasis is caused by long, thread-like worms transmitted by mosquitoes, mites or flies. Worm larvae invade lymphoid tissues; later, mature adult worms can block lymphatic circulation, causing swelling, inflammation and pain. Endemic in 73 countries, lymphatic filariasis afflicts about 120 million people worldwide. Affected parts of the body may also become enlarged. When extreme enlargement (elephantiasis) occurs, the affected part may grow to many times its normal size. Chronic and repeated filarial infections in regions where the disease is endemic tend to result in elephantiasis.

-- Boaz Otieno-Nyunya, MD

Reference

World Health Organization. The World Health Report 1998. Life in the 21st Century. A Vision for All. (Geneva: World Health Organization, 1998)48.

Contraception

While tropical diseases seldom affect the use of contraceptive methods, a few concerns merit careful attention, especially those involving anemia. Anemia resulting from chronic infestation with intestinal worms or from malaria may require greater care during the use of general anesthesia. This problem should always be considered in clients with tropical diseases who undergo voluntary tubal ligation.

Irregular or prolonged bleeding due to progestin-only contraceptives may worsen preexisting anemia caused by tropical diseases. However, the levonogestrel-releasing intrauterine device (IUD) or long-term use of progestin-only injectables (such as depot-medroxyprogesterone or DMPA) tend to decrease menstrual flow, and thus would be good contraceptive choices for anemic women.

Studies of the effects of OCs on the metabolism of mefloquine and chloroquine suggest that OCs do not significantly change the metabolism of these drugs.⁸ Similarly, use of chloroquine to prevent malaria does not have a clinically significant effect on OC efficacy.

Current evidence suggests that OCs are safe and effective in women with early active schistosomiasis, even when women are being treated with praziquantel or metrifonate.⁹ In two studies of women with schistosomiasis, OCs -- one containing 0.05 mg mestranol and 1 mg norethisterone, and the other containing 0.05 mg ethinyl estradiol and 0.5 mg levonorgestrel -- did not adversely affect liver function after six months of OC use.¹⁰

In men with scrotal swelling due to filariasis, vasectomy may be impossible. Elephantiasis of the vulva can interfere with speculum examination, making IUD insertion difficult. Either scrotal or vulvar swelling also may make use of barrier methods, such as condoms and diaphragms, difficult.

Fertility

The degree to which tropical diseases can affect fertility is suggested by the fact that the Base-Uele district of the Democratic Republic of Congo (formerly Zaire) had the world's lowest recorded fertility rate during the 1960s, with 50 percent of women ages 30 to 34 years being childless.¹¹ Among conditions thought to have contributed to the low fertility rate in the Congo and surrounding central African countries -- called the "infertility belt" -- are filariasis, malaria, schistosomiasis, sexually transmitted diseases, genital tuberculosis, and nutritional deficiencies.

Tropical diseases can potentially reduce fertility in a variety of ways. Tropical parasitic diseases such as filariasis and schistosomiasis have been associated with infection of the upper genital tract and chronic pelvic inflammatory disease.¹² A case of infertility due to bilateral tubal blockage from pelvic schistosomiasis -- clearly identified because it responded to drug therapy -- has been reported,¹³ and similar damage of the vas in men can also occur. Partial fallopian tubal blockage that allows sperm to reach and fertilize an egg but does not allow the egg to move to the uterus can result in life-threatening ectopic pregnancy.¹⁴ Swelling of the genitalia caused by filariasis may impede sexual intercourse, effectively causing infertility.

In addition, animal studies have shown that schistosomiasis inhibits reproductive hormonal function as a result of an immune response to schistosomal eggs.¹⁵

Finally, all parasitic infections have the potential to reduce fertility by causing anemia or malnutrition, or generally damaging overall health.

References

Phillips-Howard PA, Steffen R, Kerr L, et al. Safety of mefloquine and other antimalarial agents in the first trimester of pregnancy. J Travel Med 1998;5(3):121-26.

Gilles HM. Management of Severe and Complicated Malaria. A Practical Handbook. Geneva: World Health Organization, 1991.

Brabin BJ. An analysis of malaria in pregnancy in Africa. Bull WHO 1983;61(6):1005-16.

McGregor IA, Rowe DS, Wilson ME, et al. Plasma immunoglobulin concentrations in an African Gambian community in relation to season, malaria and other infections and pregnancy. Clin Exp Immunol 1970;7:51.

Brabin; Miller LH, Smith JD. Motherhood and malaria. Nature Medicine 1998;4(11):1244-45.

Matteelli A, Caligaris S, Castelli F, et al. The placenta and malaria. Ann Trop Med Parasitol 1997;91(7):803-10.

Nesbitt REL Jr. Coincidental medical disorders complicating pregnancy. In Danforth DN, ed. Obstetrics and Gynecology, Third Edition. New York: Harper & Row, 1997.

Karbwang J, Looareesuwan S, Back DJ, et al. Effect of oral contraceptive steroids on the clinical course of malaria infection and on the pharmacokinetics of mefloquine in Thai women. Bull WHO 1988; 66(6):763-67; Gupta KC, Joshi JV, Desai NK, et al. Kinetics of chloroquine contraceptive steroids in oral contraceptive users during concurrent chloroquine prophylaxis. Indian J Med Research 1984;80:658-62.

El-Raghy I, Back DJ, Osman F, et al. Contraceptive steroid concentrations in women with early active schistosomiasis: lack of effect of antischistosomal drugs. Contraception 1986;33(4):373-77.

Sy FS, Osteria TS, Opiniano V, et al. Effect of oral contraceptives on liver function tests on women with schistosomiasis in the Philippines. Contraception 1986;34(3):283-94; Shaaban NM, Hammad WA, Fathalla MF, et al. Effects of oral contraception on liver function tests and serum proteins in women with active schistosomiasis. Contraception 1982;26(1):75-82.

McFalls JA Jr. Population subfecundity. Intercom 1978;6(4):7-9.

Lawson JB, Stewart DB. Obstetrics and Gynecology in the Tropics and Developing Countries. London: Edward Arnold Publishers, 1988; Stewart GK. Impaired fertility. In Hatcher RA, Trussell J, Stewart F, et al., eds. Contraceptive Technology, Seventeenth Revised Edition. (New York: Ardent Media, Inc., 1998)657-60.

Oguuniyi SO, Nganwuchu AM, Adenle MA, et al. Pregnancy following infertility due to pelvic schistosomiasis: a case report. West Afr J Med 1994;13(2):132-33.

Bugalho A, Strolego F, Pregazzi R, et al. Extrauterine pregnancy in Mozambique. Int J Gynaecol Obst 1991;34(3):239-42.

Amano T, Freeman GL Jr, Colley DG. Reduced reproductive efficiency in mice with Schistosomiasis mansoni and in uninfected pregnant mice injected with antibodies against Schistosoma mansoni soluble egg antigens. Am J Trop Med Hyg 1990;43(2):180-85.

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