Bariatric surgery affects risk of pregnancy complications

Bariatric surgery has both a positive and negative influence on the risk of complications during subsequent pregnancy and delivery, concludes a new study from Karolinska Institutet. The results, which are published in the New England Journal of Medicine, indicate that maternal health services should regard such cases as risk pregnancies.

Pregnant women with obesity run a higher risk of developing complications during pregnancy and risks of fetal/infant complications are also higher. There has been a sharp rise in the number of women becoming pregnant after bariatric surgery; in 2013 almost 8,000 such operations were performed in Sweden, 80 per cent of which were on women.

“The effects of bariatric surgery on health outcomes such as diabetes and cardiovascular disease have been studied, but less is known about the effects on pregnancy and perinatal outcomes,” says the study’s lead author, Kari Johansson, PhD, from the Department of Medicine in Solna. “Therefore we wanted to investigate if the surgery influenced in any way the risk of gestational diabetes, preterm birth, stillbirth, if the baby was small or large for its gestational age, congenital malformations and neonatal death.”

Using data from nationwide Swedish health registries, the researchers identified 596 pregnancies to women who had given birth after bariatric surgery between 2006 and 2011. These pregnancies were then compared with 2,356 pregnancies to women who had not been operated upon but who had the same body mass index (BMI, weight divided by height squared) as the first group prior to surgery.

What researchers found was that the women who had undergone surgery were much less likely to develop gestational diabetes – 2% compared to 7% – and give birth to large babies. Just over 22% of women in the comparison group had babies that were large for gestational age, and barely 9% of the operated women. On the other hand, the operated women were twice as likely to give birth to babies who were small for gestational age, and the pregnancies were also of shorter duration.

“Since bariatric surgery followed by pregnancy has both positive and negative effects, these women, when expecting, should be regarded as risk pregnancies,” says Dr Johansson. “They ought to be given special care from the maternal health services, such as extra ultrasound scans to monitor fetal growth, detailed dietary advice that includes checking the intake of the necessary post-surgery supplements.”

The study was financed by the Swedish Research Council, The Obesity Society, Karolinska Institutet and the Stockholm County Council.    

Publication: Outcomes of Pregnancy in Women with Prior Bariatric Surgery”, Kari Johansson, Sven Cnattingius, Ingmar Näslund, Nathalie Roos, Ylva Trolle-Lagerros, Fredrik Granath, Olof Stephansson, & Martin Neovius, New England Journal of Medicine online 26th February 2015.

For further information, please contact:

Kari Johansson, PhD, Postdoc
Clinical Epidemiology Unit, Department of Medicine (Solna), Karolinska Insititutet
Tel: +46 (0)70-695 49 26
Email: kari.johansson@ki.se

Olof Stephansson, PhD, Docent, Senior Physician in gynaecology and obstetrics, Karolinska University Hospital
Tel: +46 (0)70 00 11639
Email: olof.stephansson@ki.se       

Martin Neovius,  PhD, Docent, Senior Scientist
Clinical Epidemiology Unit, Department of Medicine (Solna), Karolinska Insititutet
Tel: +46 (0)73-903 37 74
Email: martin.neovius@ki.se

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Karolinska Institutet is one of the world's leading medical universities. Its vision is to significantly contribute to the improvement of human health. Karolinska Institutet accounts for over 40 per cent of the medical academic research conducted in Sweden and offers the country´s broadest range of education in medicine and health sciences. The Nobel Assembly at Karolinska Institutet selects the Nobel laureates in Physiology or Medicine.

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Since bariatric surgery followed by pregnancy has both positive and negative effects, these women, when expecting, should be regarded as risk pregnancies.
Dr. Kari Johansson, Karolinska Institutet