Induced termination of pregnancy and future reproductive outcomes – current evidence

The effect of induced termination of pregnancy on future reproductive outcomes remains a controversial area. Current evidence is limited, and further research is needed to assess reproductive outcomes following the use of more recent techniques. The following briefing document provides a summary of current evidence on this topic.

Spontaneous abortion v. induced termination of pregnancy

An important distinction must be made between spontaneous abortion (miscarriage) and induced abortion (induced termination of pregnancy).  Spontaneous abortion refers to the loss of an embryo or fetus due to accidental trauma or natural causes. Induced abortion refers to the intentional termination of pregnancy for therapeutic or elective reasons. Evidence has suggested that spontaneous and induced termination of pregnancy may affect future reproductive outcomes differently. For example, a study by El-Bastawissi et al found that a history of spontaneous abortion (miscarriage) was a risk factor for preterm birth, while a history of induced abortion was not1.  For this reason, the following briefing document deals specifically with evidence relating to induced termination of pregnancy.

Current evidence - limitations

Much of the research on reproductive outcomes following termination of pregnancy involves older data. Over the last several decades, there have been significant changes to medical practice in this area. Currently, most terminations of pregnancy are done early, and more terminations are performed medically, eliminating the risk of surgically induced uterine cavity and cervical trauma.  If a termination is performed surgically, protocols include medication for cervical softening to minimise cervical trauma. Current surgical techniques are significantly less traumatic than those used in the past due to aspiration in place of curettage and the use of cervical priming agents2.  The widespread screening for infection and antibiotic prophylaxis has also reduced the risk of infective complications. Thus, subsequent pregnancy outcomes may differ from those observed in older studies.

As well, a number of biomedical, social, environmental, lifestyle-related, genetic and other factors contribute to reproductive outcomes. The confounding effects of socioeconomic factors, which are important, are considered in very few studies examining the effects of induced abortion.

A summary of current evidence is below:

Future reproductive outcomes

There are no proven associations between induced abortion and subsequent ectopic pregnancy, placenta praevia or infertility3.  Women with a previous induced abortion appear to be at an increased risk of infertility in countries where abortion is illegal but not in those where abortion is legal. Published studies strongly suggest that infertility is not a consequence of uncomplicated induced abortion4,5,6,7. There are small discrepancies among studies8,  but none of these studies was of sufficient power to detect a small association.

Preterm birth

Induced abortion may be associated with a small increase in the risk of subsequent miscarriage and preterm delivery9,  but further research is needed, particularly in relation to current techniques10.  A recent systematic review published in BJOG by Shah and Zao has suggested that previous termination of pregnancy is associated with an increased risk of preterm birth in subsequent pregnancies11.  However, a lack of consensus exists in this area. Some studies have found an association12,13,14,15,16,17,18,19, while others have not20,21,22,23. From the recent studies reviewed, no clear relationship between previous induced abortion and preterm birth was demonstrable.

Low birth weight

Some studies have similarly found previous abortion to be a risk factor for low birth weight24,25,    while others have concluded that induced abortion is not an independent risk factor26,27.

Small-for-gestational-age (SGA)

In general, studies have found no link between the rate of small-for-gestational-age newborns and previous induced termination of pregnancy28,29,30,31.

Cervical trauma

Studies have shown that the risk of damage to the cervix at the time of surgical abortion is moderate32.  Newer techniques, such as medical abortion and medication for cervical softening, may minimise cervical trauma. For example, a study reflecting practice in large hospitals in the US in the mid-1970s, where most operators were trainees, found a cervical injury rate of 10.3 in 1000. In comparison, a 2002 Danish cohort study33 found a rate of 0.89 in 1000. Evidence suggests that the risk is lower when abortion is performed early in pregnancy and when it is performed by an experienced clinician34.

Summary

Abortion remains an essential part of women’s health care services. Further research is needed to better understand the effects of induced termination of pregnancy on future reproductive outcomes. In particular, research is needed to evaluate outcomes following the use of current techniques, in order to ensure the safest possible procedures for women.

16 September 2009

References

1. El-Bastawissi AY, Sorenson TK, Akafomo CK, FrederickIO, Xiao R, Williams MA. History of fetal loss and other adverse pregnancy outcomes in relation to subsequent risk of preterm delivery. Maternal & Child Health Journal 2003; 7(1):53-8.
2. Kalish RB, Chasen ST, Rosenzweig LB, Rashbaum WK, Chervenak FA. Impact of midtrimester dilation and evacuation on subsequent pregnancy outcome.  A J Obstet Gynecol 2003;189(2):613-4.
3. RCOG. The Care of Women Requesting Induced Abortion: Evidence-based Clinical Guideline Number 7. September 2004, p.33.
4. RCOG. The Care of Women Requesting Induced Abortion: Evidence-based Clinical Guideline Number 7. September 2004, p.33.
5. Daling JR, Spadoni LR, Emanuel I. Role of induced abortion in secondary infertility. Obstet Gynecol 1981; 57:59-61.
6. Daling JR, Weiss NS, Voigt L, Sadoni LR, Soderstorm R, Moore DE, et al. Tubal infection in relation to prior induced abortion. Fertil Steril 1985; 43:389-94.
7. Hernadi Z, Smid I, Lampe L. Impact of patient termination on subsequent fertility. Acta Med Hung 1986; 43:155-60.
8. Tzonou A, Hsieh CC, Trichopoulos D, Aravandinos D. Induced abortions, miscarriages, and tobacco smoking as risk factors for secondary infertility. J Epidemiol Community Health 1993; 47:36-9.
9. RCOG. The Care of Women Requesting Induced Abortion: Evidence-based Clinical Guideline Number 7. September 2004, p.33.
10. A recent study of women who had had an induced abortion between 1999 and 2004 showed no increased risk of subsequent risk of ectopic pregnancy, miscarriage, premature delivery or low birth weight with medical termination of pregnancy compared to surgical termination of pregnancy. Virk J et al. Medical abortion and the risk of subsequent adverse pregnancy outcomes. JEJM 2007;357:648-653.
11. Shah P, Zao J on behalf of Knowledge Synthesis Group of Determinants of Preterm/LBW Births. Induced termination of pregnancy and low birthweight and preterm birth: a systematic review and meta-analyses. BJOG 2009; 116:1425–1442.
12. Berkowitz GS. An epidemiologic study of preterm delivery. Am J Epidemiol 1981; 113:81-92.
13. Martius JA, Steck T, Oehler MK, Wulf KH. Risk factors associated with preterm (<37+0 weeks) and early preterm birth (<32+) weeks) univariate and multivariate analysis of 106,345 singleton births from 1994 statewide perinatal survey of Bavaria. Eur J Obstet Gynecol Reprod Biol 1998;80:183-9.
14. Swingle HM, Colaizy TT, Zimmerman MB, Morriss FH Jr. Abortion and the risk of subsequent preterm birth: a systematic review with meta-analyses. Journal of Reproductive Medicine 2009; 54(2):95-108.
15. Voigt M, Henrich W, Zygmunt M, Friese K, Straube S, Briese V. Is induced abortion a risk factor in subsequent pregnancy? Journal of Perinatal Medicine 2009; 37(2):144-9.
16. Brown JS Jr, Adera T, Masho SW. Previous abortion and the risk of low birth weight and preterm births. Journal of Community Health 2008; 62(1):16-22.
17. MoreauC, Kaminski M, Ancel PY, Bouyer J, Escande B, Thiriez G, Boulot P, Fresson J, Arnaud C, Subtil D, Marpeau L, Roze JC, Maillard F, Larroque B.Previous induced abortions and the risk of very preterm delivery: results of the EPIPAGE study. BJOG 2005;112(4):430-7.
18. Henriet L, Kaminski M. Impact of induced abortions on subsequent pregnancy outcome: the 1995 French national perinatal survey. BJOG 2001;108(1):1036-42.
19. Ancel PY, Lelong N, papiernik E, Saurel-Cubizolles MJ, Kaminski M. History of induced abortion as a risk factor for preterm birth in European countries: results of the EUROPOP survey. Human Reproduction 2004;19(3):734-40.
20. Dalaker K, Lichtenberg SM, Okland G. Delayed reproductive complications after induced abortion. Acta Obstet Gynecol Scand 1979;58:491-4.
21. Meirik O, Nygren KG, Bergstrom R, Gunsjo A. Outcome of delivery subsequent to induced vacuum aspiration abortion in parous women. Am J Epidemiol 1982;116:415-29.
22. Raatikainen K, Heiskanen N, Heinonen S. Induced abortion: not an independent risk factor for pregnancy outcome, but a challenge for health counselling. Annals of Epidemiology 2006;16(8):587-92.
23. Jackson JE, Grobman WA, Haney E, Casele H. Mid-trimester dilation and evacuation with laminaria does not increase the risk for severe subsequent pregnancy complications. International Journal of Gynaecology & Obstetrics 2007;96(1):12-5.
24. Brown JS Jr, Adera T, Masho SW. Previous abortion and the risk of low birth weight and preterm births. Journal of Community Health 2008; 62(1):16-22.
25. Shah P, Zao J on behalf of Knowledge Synthesis Group of Determinants of Preterm/LBW Births. Induced termination of pregnancy and low birthweight and preterm birth: a systematic review and meta-analyses. BJOG 2009; 116:1425–1442.
26. Raatikainen K, Heiskanen N, Heinonen S. Induced abortion: not an independent risk factor for pregnancy outcome, but a challenge for health counselling. Annals of Epidemiology 2006;16(8):587-92.
27. Henriet L, Kaminski M. Impact of induced abortions on subsequent pregnancy outcome: the 1995 French national perinatal survey. BJOG 2001;108(1):1036-42.
28. Shah P, Zao J on behalf of Knowledge Synthesis Group of Determinants of Preterm/LBW Births. Induced termination of pregnancy and low birthweight and preterm birth: a systematic review and meta-analyses. BJOG 2009; 116:1425–1442.
29. Voigt M, Henrich W, Zygmunt M, Friese K, Straube S, Briese V. Is induced abortion a risk factor in subsequent pregnancy? Journal of Perinatal Medicine 2009; 37(2):144-9.
30. Parazzini F, Cipriani S, Chiaffarino F, Sandretti F, Bortolus R, Chiantera V. Induced abortion and risk of small-for-gestational-age birth. BJOG 2007; 114(11):1414-8.
31. Henriet L, Kaminski M. Impact of induced abortions on subsequent pregnancy outcome: the 1995 French national perinatal survey. BJOG 2001;108(1):1036-42.
32. RCOG. The Care of Women Requesting Induced Abortion: Evidence-based Clinical Guideline Number 7. September 2004, p.31.
33. Zhou W, Nielsen GL, Moller M, Olsen J. Short-term complications after surgically induced abortions: a register-based study of 56 117 abortions. Acta Obstet Gynecol Scand 2002;81:331-6.
34. RCOG. The Care of Women Requesting Induced Abortion: Evidence-based Clinical Guideline Number 7. September 2004, p.31.

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