Is Previous Bariatric Surgery Linked to Smaller Fetal Size and Birthweight?

BACKGROUND AND PURPOSE:

• While bariatric surgery has benefits, including an association with improved pregnancy outcomes, there have also been reports of greater prevalence of small babies
• Maric et al. (BJOG, 2020) investigated the intrauterine fetal growth pattern and fetoplacental circulation in pregnancies following bariatric surgery

METHODS:

• Prospective study
• Participants
  • Pregnant women
  • Similar BMIs, with and without history of bariatric surgery
• Study design
  • An oral glucose tolerance test (OGTT) was performed at 27 to 30 weeks
  • At three time-points (20 to 24w; 30 to 33w; 35 to 37w) in pregnancy, the following fetal biometric measurements were measured
    • AC
    • FL
    • EFW
    • Fetoplacental Dopplers
  • Birthweight (BW) was recorded
  • Variables were modelled after adjustment for maternal/pregnancy characteristics
    • Model estimates are reported as posterior means and quantile-based 90% credible intervals (CrI)
• Primary outcome measurements
  • Fetal biometry
  • Fetoplacental Doppler
  • BW

RESULTS:

• 162 women included | No difference in mode of delivery
  • Bariatric surgery: 54
  • Control: 108
• Compared with the no surgery control group, the bariatric surgery group had lower EFW, smaller AC and FL with differences increasing from earlier to later gestational time points
  • EFW at 35 to 37 weeks: Difference −120 g (90% Crl, −189 g to −51 g) lighter
  • AC at 35 to 37 weeks: Difference -6.1 mm (90% Crl, -10.0 to -2.1)
  • FL at 35 to 37 weeks: Difference -0.9 mm (90% Crl, -1.6 to -0.3)
  • No difference in HC
• Infants born to mothers in the bariatric surgery group were lighter
  • −202 g (90% Crl, −330 g to −72 g)
  • Adjusted for maternal age, parity, smoking status, first trimester BMI, GDM status and and gestational age at delivery
• There was no difference in the fetoplacental Doppler indices between groups
• Maternal glucose levels
  • Were positively correlated with third-trimester EFW and BW
  • Fasting and 2 hour glucose levels were lower in the post‐bariatric vs no surgery group

CONCLUSION:

• Offspring of women who had previous bariatric surgery were smaller both during pregnancy and after birth vs women with comparable BMI who had no surgery
• The authors suggest that the size difference may be related to lower maternal glucose levels in the bariatric surgery group
• Fetoplacental circulation does not appear to be altered by maternal bariatric surgery

Learn More – Primary Sources:

Fetal growth and fetoplacental circulation in pregnancies following bariatric surgery: a prospective study