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Maggard M, Li Z, Yermilov I, et al. Bariatric Surgery in Women of Reproductive Age: Special Concerns for Pregnancy. Rockville (MD): Agency for Healthcare Research and Quality (US); 2008 Nov. (Evidence Reports/Technology Assessments, No. 169.)

4Discussion

Limitations

Publication Bias

Our literature search procedures were extensive and included canvassing experts regarding studies we may have missed. However, it is possible that we may have missed studies, and even more possible that some data relevant to these questions exist but have not been published.

Study Quality

The most important limitation to this review is the quality of the original studies. The clinical questions of interest are best answered by studies using a prospective cohort design (for studies of risk and prognosis, such as key questions 2 and 4) or randomized clinical trials (for questions of management, such as key questions 3 and 5). We found no such study, and therefore were compelled to use data from study designs of lesser theoretical strength—even case series and case reports. Most studies were not designed to address issues of fertility and pregnancy outcomes following bariatric surgery. Many publications reporting the results of cohort studies and case series for bariatric surgery fail to clearly report the method of assembly, fail to report the dropout rates clearly, or report high dropout rates. The inherent limitations in these study designs preclude us from drawing strong conclusions to most questions.

Conclusions

Overall, relevant evidence is scant. Only one case control study and 12 cohort studies were found. All of the other data were from case series or case reports. Given this major limitation in data, these are the preliminary findings:

1)

What is the incidence of bariatric surgery in women of reproductive age? What are the trends in incidence of bariatric surgery in women of reproductive age?

  • More than 50,000 women between the ages of 18 and 45 undergo bariatric procedures each year in an inpatient setting. The rate of use is increasingly rapidly—more than six-fold in the past 7 years. It is possible that even more women in the 18–45 age group are undergoing outpatient bariatric surgery procedures, like laparoscopic adjustable gastric band, that were not reported in our dataset.

2)

What is the evidence that bariatric surgery affects (directly or indirectly) future fertility?

  • It is likely that fertility in the context of the polycystic ovarian syndrome improves following bariatric surgery. This finding is consistent with improvements in fertility seen when obese women lose weight with nonsurgical methods.84, 85 Data are too sparse to reach definitive conclusions about other effects of bariatric surgery on fertility.

3)

What is the evidence that bariatric surgery affects (directly/indirectly) choice of contraception?

  • There is almost no evidence on this topic. A small case series of 40 patients who had undergone BPD and who were advised to avoid pregnancy for at least 2 years reported 2 failures for oral birth control, one at 9 months postoperatively and the other at 24 months. However, the reported failure rate of OCPs in typical use is 3 percent, so this result may not be atypical.

4)

In patients who have had bariatric surgery, what is the evidence for prenatal risk factors (e.g., reduced nutrient absorption, unusual weight gain) that may result in poor pregnancy outcomes?

5)

What is the evidence that certain management strategies for addressing nutrient absorption and weight gain reduce the risks of poor pregnancy outcomes?

  • Some case reports/case series stated that the patients who had nutritional deficiencies did not take the recommended multivitamin and iron.
  • In some reports, the gastric band needed adjustment to allow sufficient oral nutrition intake.

6)

For women who have had bariatric surgery, what is the evidence for morbidity and mortality risks for a) mother and b) neonate?

  • Obese women who had bariatric surgery may have a lesser risk than obese women for certain pregnancy complications, such as gestational diabetes, preeclampsia, and pregnancy-induced hypertension.
  • Reports of mean birth weight, rates of low birth weight, and rates of premature delivery are no different in babies born to women following bariatric surgery than babies in the general population, although firm conclusions cannot be drawn due to small sample sizes.
  • There are case reports of surgical adverse events following bariatric surgery in women who then became pregnant, including maternal deaths and fetal death—but there are similar reports in nonpregnant patients who had bariatric surgery. These events are uncommon and the majority appeared to be due to internal hernias. Delays in diagnosis were a common factor in many case reports, and use of the CT scan, even though the patients were pregnant, was helpful in reaching a diagnosis. Therefore, women who elect to have bariatric surgery will have an increased risk of certain complications that would not have occurred had they not had bariatric surgery, but it is unknown if pregnancy affects the risk. Although the net benefit-to-risk for pregnancy following bariatric surgery is still likely to be favorable, these additional risks must be acknowledged.

7)

What is the evidence that cesarean section for women who have had bariatric surgery affects the risks of morbidity and mortality for a) mother and b) neonate?

  • One case-control study attempted to answer this specific question, and found no significant difference in rates of cesarean section postsurgery The rates of cesarean section vary greatly from among the observational studies. The case-control study found no difference in delivery complications such as transfusions, need for antibiotics, or thromboembolic events. No study specifically assessed possible operative injury following cesarean section.

Future Research

Much more research is needed to answer almost every key question in this report.

Regarding rates of use, methods are needed to capture the rise in outpatient delivery of bariatric procedures, mainly the laparoscopic adjustable gastric band. Without this data, estimates of use based on the Nationwide Inpatient Sample will underestimate the total number of cases.

For all issues related to risk and prognosis, such as the effects on fertility, timing of pregnancy, development of complications of pregnancy, outcomes of pregnancy, and cesarean section rates, prospective cohorts are required to provide better estimates. For example, to address the issue of impact of surgery on fertility a large, prospective cohort study comparing a consecutive group of women who underwent bariatric surgery and desire pregnancy, for ability to get pregnant compared to a matched obese group who is also attempting pregnancy. Groups will need to be matched on presurgery parity, age, and type of procedure.

For the issues related to management, such as choice of contraceptive and nutritional management, randomized controlled trials are needed. With regards to understanding the effectiveness of contraception methods following surgery, we will first need clinical studies assessing changes in absorption of oral contraceptive pill (OCP). Then RCTs or matched cohort study comparing barrier methods, OCP, and other methods for contraception in women not desiring pregnancy and follow them for one year looking at pregnancy as an outcome. Because pregnancy rates will be low, a large sample size will be required in each arm to adequately power the study [n=750 in each arm to detect 50 percent absolute difference (3 percent to 6 percent)].

Cover of Bariatric Surgery in Women of Reproductive Age
Bariatric Surgery in Women of Reproductive Age: Special Concerns for Pregnancy.
Evidence Reports/Technology Assessments, No. 169.
Maggard M, Li Z, Yermilov I, et al.

AHRQ (US Agency for Healthcare Research and Quality)

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