Fibroids and Reproductive Outcomes: A Systemic Literature Review from Contraception to Delivery
Fibroids and Reproductive Outcomes: A Systemic Literature Review from Contraception to Delivery
Abstract & Commentary
By John C. Hobbins, MD, Professor and Chief of Obstetrics, University of Colorado Health Sciences Center, Denver, is Associate Editor for OB/GYN Clinical Alert
Dr. Hobbins reports no financial relationship to this field of study.
Synopsis: This meta-analysis shows a modest increase in some pregnancy complications when patients are diagnosed to have fibroids.
Source: Klatsky PC, et al. Fibroids and reproductive outcomes: a systematic literature review from conception to delivery. Am J Ob Gyn. 2008;198:357-366.
Fibroids seem to strike fear in the hearts of both pregnant patients and their providers when they are found—often for the first time during an ultrasound examination in early pregnancy. In a newly published comprehensive review, Klatsky et al1 scanned the recent literature to find articles that dealt with the relationship between the presence of fibroids and infertility, miscarriages, and pregnancy complications. The authors tried to choose studies with control data, some of which represented case controls. However, as we will describe later, confounding variables were rarely addressed in the individual studies included in the review. For each outcome variable the data were pooled. For brevity, I will only deal with pregnancy complications.
The authors found the strongest association with fibroids to be lower abdominal pain, although no data were presented. The size of the myoma did not seem to correlate with the degree of pain, and the most effective agents to relieve pain were non-steroidal anti-inflammatory drugs (NSAIDs), suggesting the role of prostaglandins in the etiology of the pain.
The strongest association involved the need for Cesarean section (48.8% vs 13.3%, with an odds ratio of 3.7). Next came the risk of abruption (3.0% vs 0.9%, OR=3.2), followed by malpresentation (13% vs 4.5%, OR=2.9) and retained placenta (1.4% vs .6%, OR=2.3). All had acceptable confidence intervals. Interestingly, the one I expected to have the highest differential, postpartum hemorrhage, only had an OR of 1.8 (2.5% vs 1.4%). Weak associations or no differences were found with premature rupture of the membranes, IUGR, and neonatal morbidity (despite a slightly higher rate of preterm birth, OR=1.5).
Commentary
Pooling data through meta-analysis enables investigators to show a statistical relationship between variables when individual studies do not have the power to show a significant difference. A typical example of this was in a cumulative meta-analysis which demonstrated that Doppler ultrasound diminished perinatal mortality, but only after a seventh study was added to the pooled data. However, including studies which are completely out of sync with the other studies in the analysis can have a misleading effect on the final results. For example, with regard to fibroids and IUGR, the OR was 1.4. Yet, 6 studies did not show an association, while only one did. Also, with abruption, not all the study results were in accord. Three studies showed no association with fibroids, but 4 studies demonstrated a positive relationship.
Perhaps the greatest problem with this type of study, which the authors have pointed out, is that there is no way to rule out confounding variables with this approach, since it simply was not addressed in the individual studies. Fibroids are often identified in patients who are examined with ultrasound because of another problem, having its own inherent complications. Most importantly, fibroids most often emerge in patients who are of advanced maternal age or who have infertility problems—both patient categories having higher rates of most of the outcomes studied in the above meta-analysis, and, as the authors state, this could not be taken into consideration in their analysis.
I started a subsection in a recent book with the statement "Fibroids are overrated." Interestingly, I thought those words would have to be eaten when I first skimmed the above article. However, after dissecting it further, it was clear that, although rates of a few problems were higher in patients with documented fibroids, the absolute rates were still modest and should not cause the patient or provider to obsess over the negative aspects of having them. Also, as an aside, contrary to some current thinking, fibroid growth is greatest during the first trimester, and falls off or stops after the thirteenth week. It is extremely rare for any fibroid to increase in size after the 20th week of gestation and, certainly, when the fibroid gets into a competition with the fetus for the blood supply, the fibroid always loses. One can monitor the growth and tissue characteristics of fibroids with ultrasound (but rarely needs to). A mottled tissue texture is indicative of a myoma outstripping its blood supply, and is often initially accompanied by pain which can be localized on touch to the area identified with ultrasound. However, once these ultrasound characteristics have been attained, the pain usually diminishes in intensity.
So, while having fibroids may increase the chances of various adverse outcomes, the actual incidence of these complications is only modestly raised, and their effect, directly or indirectly, on the fetus/infant is negligible.
References
- Klatsky PC, et al. Fibroids and reproductive outcomes: a systematic literature review from conception to delivery. Am J Obstet Gyn. 2008; 198: 357-366.
- Divon MY. Umbilical artery Doppler velocimetry: clinical utility in high risk pregnancies. Am J Obstet Gyn. 1996;174:10-14.
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