Weight-loss surgery ups risk of preterm delivery

Pregnant patients who have undergone some form of bariatric surgery are at greater risk of preterm birth than women who haven’t had the procedure, according to a study published in the British Medical Journal. The risk of small for gestational age (SGA) was also increased in women with previous bariatric surgery.

Investigators at the Karolinska Institute in Sweden looked at more than 1.7 million  singleton births that occurred between 1992 and 2009 and found 2562 deliveries to former bariatric patients. Up to five control births were matched with each post-surgery birth, using maternal age, parity, early pregnancy body mass index (BMI), early pregnancy smoking status, educational level, and year of delivery.

Preterm births were found to occur more in post-surgery patients than in the matched controls, (9.7% [243/2511] vs. 6.1% [750/12,379]; odds ratio [OR] 1.7, 95% confidence interval [CI] 1.4 to 2.0; P<0.001). However, BMI appeared to be an effect modifier (P=0.01) and the increased risk of preterm birth was only seen in women with BMI <35. Preterm births in post-surgery women were both spontaneous (5.2% [130/2511] vs. 3.6% [441/12,379]; OR 1.5, 1.2 to 1.9; P<0.001) and medically indicated (4.5% [113/2511] vs. 2.5% [309/12,379]; OR 1.8, 1.4 to 2.3; P<0.001).

Bariatric surgery was also associated with an increased risk of SGA birth: 5.2% (131/2507) vs. 3.0% (369/12,338); OR 2.0, 1.5 to 2.5; P<0.001. The risk of large for gestational age, however, was lower in post-surgery women, 4.2% (105/2507) vs. 7.3% (895/12,338); OR 0.6, 0.4 to 0.7; P<0.001). No differences were found in the incidences of stillbirth or neonatal death.

The researchers concluded that women with a history of bariatric surgery should be considered a risk group for preterm delivery and SGA infants. They recommended that women in this group receive an extra ultrasound to check fetal growth and recommendations on dietary supplementation as needed. The study authors underscored the numerous health benefits of the surgery and the pregnancy complications of untreated obesity.

To get weekly advice for today's Ob/Gyn, subscribe to the Contemporary Ob/Gyn Special Delivery.