Reproductive Outcomes in Women With Uterine Anomalies

Paul C. Lin, M.D.

Disclosures
In This Article

Abstract and Introduction

Purpose: Because of diagnostic improvements in the evaluation of uterine anomalies, more patients desirous of pregnancy come to clinicians with identified uterine anomalies. It is desirable for the family physician, internist, and obstetrician/gynecologist to provide accurate information during preconceptional counseling of these patients. This review attempts to provide a concise summary of the current English-speaking literature concerning the reproductive outcome in women with uterine anomalies following both natural conceptions and those pregnancies occurring with assisted reproductive techniques (ART).
Methods: A literature review of reproductive anomalies and pregnancy outcomes was performed using PubMed databases. Obstetrical outcomes were compiled from the medical literature and compared with the known rates of pregnancy outcomes in subjects presumed to have normal uterine anatomy.
Results: In general, obstetrical complications, such as preterm delivery and first trimester miscarriage, are higher in women with abnormal uteri. Women with an arcuate uterus have a similar reproductive outcome to women with a normal uterus. The unicornuate uterus has the poorest overall reproductive outcome, and the septate uterus has an increased miscarriage rate. The didelphic uterus, historically thought to have no adverse reproductive outcomes, also has poor obstetrical outcomes. Didelphic, bicornuate, unicornuate, and septate uteri have lower pregnancy rates in ART.
Conclusions: Women with uterine anomalies have poorer reproductive outcomes and lower pregnancy rates with all conceptions whether spontaneous or induced with ART compared with women with normal uteri.

More couples in which the female partner has a uterine anomaly are seeking care in the current clinical practice of reproductive medicine. This apparent increase is not due to a change in the prevalence of uterine anomalies in the population but to availability of better imaging techniques of the uterus itself and the practice of assisted reproductive technology (ART). In this era of ART, there has been more attention paid to the impact of müllerian anomalies and their potential therapies on the outcomes of such assisted pregnancies.

The true prevalence of uterine anomalies in the population is unknown. It is insufficient to consult the older medical literature because of inconsistent diagnostic techniques used in the past and the heterogeneity of the subject populations that were studied. With the general widespread use of transvaginal ultrasound and hysterosalpingogram (HSG) in reproductive age women, increased detection of uterine anomalies in the general population can be expected, especially in the infertile and recurrent miscarriage subgroups. Following detection of uterine anomalies by ultrasound and HSG, the availability of magnetic resonance imaging (MRI) and three-dimensional ultrasound (3D US) should increase the accurate diagnosis of these anomalies as diagnostic criteria are applied more consistently.

A recent major study indicated the prevalence of uterine anomalies (including minor anomalies, such as hypoplastic or arcuate uteri) is 7%–8% in the normal fertile population and >25% in women with recurrent spontaneous abortions.[1] The prevalence of major uterine anomalies is estimated to be 5% in the general population, 2%–3% in fertile women, 3% in infertile women, and 5%–10% in the recurrent miscarriage population. Historically, the most common uterine malformation has been the bicornuate uterus. However, in a study of 127 uterine anomalies that were examined by a combination of HSG and laparoscopy, the prevalences of arcuate uteri and partial uterine septum were more frequent (32.8% and 33.6%, respectively), and true bicornuate uteri were found in only 20.3% of subjects.[2] A similar distribution of uterine anomalies has been found by 3D US, which is a new technology found to be comparable with older studies that used HSG and laparoscopy as the gold standard.[3]

In 1998, the former American Fertility Society, now the American Society for Reproductive Medicine, classified müllerian anomalies in an attempt to provide clinicians with a tool to better document the actual anomaly and subsequently follow their patients in regard to both conception and pregnancy outcome.[4] I review the published medical literature since 1960 concerning the reproductive outcome of women with müllerian anomalies, especially those who have undergone ART procedures. This review is intended to assist healthcare providers in giving timely and accurate preconception counseling for women with uterine anomalies.

Table 1 is a compilation of data from selected studies that have examined pregnancy outcomes for each specific uterine anomaly. Studies included employed a compatible classification system for uterine anomalies for which the diagnostic studies used to make these determinations seemed reasonable. For reference, historical controls in regard to pregnancy outcomes are included for comparison purposes only. A general acceptable preterm delivery rate was determined from several sources.[5–7] For comparison purposes, the live birth rates were compiled from accumulated data from the National Vital Statistics database, 1976–1996.[8] Based on these historical controls, preterm delivery rate and live birth rates are estimated to be 9%–12% and 82%, respectively. Likewise, for comparison purposes, the ectopic pregnancy rate in the general population was estimated to be 2%, and first trimester spontaneous abortion rates were estimated to be 10%–15% in women without uterine anomalies.[9,10] In general, this literature is too heterogeneous to make valid statistical comparisons.

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