Having weight loss surgery before having a child may be good for the mother but not necessarily the baby, hints research published this month in Obstetrics and Gynaecology.
"Our findings would suggest that bariatric surgery confers an improvement in maternal outcomes, but possibly at the expense of an increase in SGA (small for gestational age) neonates, preterm delivery and perinatal mortality," the two authors of the paper wrote.
Dr Jennifer Lesko and Dr Alan Peaceman from North-western University in Chicago note that an increasing number of reproductive age women are obese when they become pregnant. Others are turning to bariatric surgery before becoming pregnant, when they fail to shed weight with diet and exercise.
"Other studies have demonstrated improved pregnancy outcomes for obese women who have undergone bariatric surgery, but those studies have generally been small," Dr Lesko said.
Improvements in maternal outcome
She and Dr Peaceman reviewed data on 70 women who had a singleton pregnancy after bariatric surgery. Nine of the women had laparoscopic gastric banding, 60 had either open or laparoscopic Roux-en-Y gastric bypass, and one procedure was not specified.
The authors compared these women with two other sets of pregnant women: 140 who were obese, and another 140 who were morbidly obese. Women in the control groups had pre-pregnancy BMIs similar to what the bariatric surgery patients had before their operations.
"Overall there is an improvement in maternal outcomes in obese women who have undergone bariatric surgery - in particular, a large reduction in the risk of acquiring gestational diabetes," Dr Lesko said.
None of the women in the bariatric surgery group developed gestational diabetes, whereas 21 (16.4%) morbidly obese and 13 (9.3%) obese women did. "Our study supports the findings of other studies in the literature that have documented reductions in rates of gestational diabetes after bariatric surgery," the investigators say.
Preterm birth frequent in bariatric surgery
Bariatric surgery did not affect women's risk of pregnancy-related hypertensive disorders.
Preterm birth, however, was more frequent in the bariatric surgery group (14 cases; 20.0%) than in the obese group (9 cases; 6.4%).
In terms of neonatal outcomes, bariatric surgery patients had fewer larger infants (macrosomia) but more SGA babies.
"We believe that may have had to do with the fact that most of our study patients had undergone gastric bypass instead of lap-banding, the latter being a more common procedure in young women now. There is physiologic evidence that the lap-band has less effect on malnutrition," Dr Lesko said.
Mean birth weights were 2,951 g in the bariatric surgery group, 3,463 g in the morbid obesity group, and 3,351 g in babies born to obese women.
Prenatal deaths in bariatric surgery
When birth weight was stratified by gestational age to evaluate foetal growth, 12 babies in the bariatric surgery group (17.4%) were SGA compared with seven (5.0%) in the morbidly obese group and 12 in the obese group (8.6%).
Odds ratios for SGA in the bariatric surgery group were 3.94 compared to the morbid obesity group (p<0.01) and 2.25 compared to the obese group (p=0.06).
There were also a "surprisingly high" number of prenatal deaths in the bariatric surgery group (four vs one in the morbidly obese group and none in the obese group). All deaths involved "normally grown foetuses" between 22 and 40 weeks gestation. Their mothers had no evidence of hypertensive disorders of pregnancy or diabetes, and no significant pre-existing medical comorbidities.
Three were preterm deliveries, one with cervical insufficiency at 22.5 weeks; this patient was the only patient who conceived within one year of her surgery. The fourth was a term intrauterine foetal demise without a laboratory or pathologic diagnosis, the clinicians report.
Bariatric surgery recommended for obese women
Commenting on the prenatal mortality data, Dr Lesko said: "It hasn't been described in other similar studies so it may be a random finding. Additionally, it did not remain significant when we controlled for other maternal characteristics, except in the comparison of bariatric surgery patients with obese controls, but it was barely so, with wide confidence intervals, making it statistically less powerful."
"Furthermore," she continued, "our study population was mostly gastric bypass, and these findings may not bear out in a population of reproductive-age women who are currently more likely to receive lap-bands, since they are purely restrictive and not malabsorptive in their mechanism, thus making their nutrition status more optimal. We believe that more studies would have to be done to determine if it is a true risk."
Dr Lesko and Dr Peaceman conclude in their paper, "In general, patients may be reassured that there are significant health benefits of bariatric surgery before pregnancy, but they also should be cautioned that there may be consequences for the pregnancy and the foetus."
They added, "With the numbers of women of reproductive age seeking weight loss surgery increasing, it is important to consider the physiologic consequences of both restrictive and malabsorptive procedures and to work closely with patients and their surgeons to optimise both pre-pregnancy and gestational nutritional status."
"We would recommend bariatric surgery for young obese and morbidly obese women who are interested in becoming pregnant, because we found that it lowers their risks of gestational diabetes in pregnancy. We would also recommend waiting at least a year after surgery before conceiving," Dr Lesko said.
(Megan Brooks, Reuters Health, March 2012)
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