Avoiding pregnancy for 12 months after bariatric surgery


New findings support current guidelines to avoid pregnancy for 12 to 24 months after bariatric surgery, adding emphasis on achieving gestational weight gain.

They also found that inadequate weight gain during pregnancy was associated with lower gestational age at delivery and lower neonatal birth weight in comparison with adequate gestational weight gain. In addition, (very) preterm births were more frequently observed in pregnancies of the inadequate weight gain group.

It is known that weight loss after bariatric surgery improves fertility and even reduces the risk of gestational diabetes (GDM), hypertensive disorders, and large-for-gestational-age (LGA) infants.1 However, new research in Obesity Surgery found that pregnancies within the first 12 months or less after surgery faced increased risk for lower gestational age at delivery, lower gestational weight gain, and lower neonatal birth weight.2

Researchers conducted a multicenter retrospective analysis of 196 singleton pregnancies of women who previously underwent bariatric surgery (Roux-en-Y gastric bypass, sleeve gastrectomy, and anastomosis gastric bypass) between 2005 and 2018. All deliveries occurred between October 2007 and August 2019. Pregnancies were divided into 3 groups of surgery-to-conception interval: the early group (≤ 12 months), the middle group (12-24 months), and the late group (>24 months). According to the National Academy of Medicine (NAM) recommendations, to evaluate pregnancy outcomes, they were also divided by gestational weight gain as inadequate, adequate, or excessive.

Pregnancies in the early group (23.5%) were associated with lower gestational age at delivery (267.1± 19.9 days vs 272.7 ± 9.2 and 273.1 ± 13.5 days, P = .029), lower gestational weight gain (− 0.9 ± 11.0 kg vs + 10.2 ± 5.6 and + 10.0 ± 6.4 kg, P < .001), and lower neonatal birth weight (2979 ± 470 g vs 3161 ± 481 and 3211 ± 465 g, P = .008) than pregnancy in the middle (21.9%) and late group (54.6%).

Gestational weight gain was calculated as the difference between late pregnancy weight and pre-pregnancy weight (kg). Pre-pregnancy weight was reported at the first antenatal visit or self-reported before pregnancy, and late pregnancy weight was extracted from medical records 4 weeks before delivery. Weight gain was classified as inadequate, adequate, or excessive, according to the NAM recommendations. Preterm birth was defined as <37 weeks of gestation, and very preterm birth as <32 weeks of gestation.

Late pregnancy weight data was available for 170 pregnancies. Gestational weight gain was adequate in only 29.4%, inadequate in 40.6%, and excessive in 30% of pregnancies. For the inadequate weight gain group, the mean gestational age was significantly lower than the adequate weight gain group 266.5 ± 20.2 days vs 273.8 ± 8.4 days, P = .002). Researchers observed 3 times as many preterm births in the inadequate weight gain group (15.9% vs 6.0%, P = .037), which included the study’s three very preterm births (>32 weeks).

Women in the early group had a higher risk of inadequate gestational weight gain compared to women in the middle and late group (75.0% vs 24.4%, and 32.6%, P < .001), whereas the risk of excessive weight gain was lower (5.0% vs 34.1%, and 39.3%, P = .007). The mean neonatal birth weight was significantly lower in the early group when compared to the late group (2979 ± 470 g vs 3211 ± 465 g, P = .008).

According to the authors, gestational weight gain was below the NAM recommendations in 75% of the women who conceived within 12 months, and in 30% of the women who conceived after 12 months. The authors recommend encouraging women who wish to conceive after bariatric surgery to avoid pregnancy until their weight has stabilized to minimize the risk of inadequate gestational weight gain. “In daily practice, we encounter many women who are afraid to gain weight during pregnancy. Healthcare professionals should be aware of the underlying factors and encourage these women to have adequate weight gain during pregnancy,” they wrote.

Future research, wrote the authors, “should focus on the effect of inadequate gestational weight gain and maternal undernutrition on the duration of pregnancy and fetal growth.”


  1. Edison E, Whyte M, van Vlymen J, et al. Bariatric surgery in obese women of reproductive age improves conditions that underlie fertility and pregnancy outcomes: retrospective cohort study of UK National Bariatric Surgery Registry (NBSR). Obes Surg. 2016;26(12):2837-2842. doi:10.1007/s11695-016-2202-4
  2. Heusschen L, Krabbendam I, van der Velde JM, et al. A matter of timing-pregnancy after bariatric surgery. Obes Surg. 2021;31(5):2072-2079. doi:10.1007/s11695-020-05219-3
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