The outcome of pregnancies after bariatric surgery: an observational study of pregnancies during 2004–2016 in Finland

{"Background": "Overweight and obesity are major risk factors for perinatal morbidity and mortality, and the prevalence of obesity among fertile-aged women is rising. In 2019, 42% of parturients in Finland were overweight (BMI \u226525 kg/m\u00b2) and 17% were obese (BMI \u226530 kg/m\u00b2). Bariatric surgery (BS) is the most effective treatment for severe obesity, and around 1,000 patients undergo BS annually in Finland. Since many women of reproductive age undergo BS, understanding the risks and benefits for future pregnancies is critical. Previous studies have reported overall improved pregnancy outcomes after BS but also increased risks for preterm delivery and SGA neonates. This study aimed to evaluate the overall effect of BS on pregnancy, delivery, and neonatal outcomes using national register-based data.", "Methods": "All pregnancies and deliveries in Finland between 2004 and 2016 were included. Women with previous BS were identified from the hospital discharge register, and the medical birth register provided data on pregnancies, deliveries, and perinatal outcomes. Data were matched using personal identification codes. The bariatric group (n=314) was compared to the non-bariatric group (n=750,019). To isolate the effect of BS from residual obesity, outcomes were also compared across four BMI-specific categories: \u226424.9, 25.0\u201329.9, 30.0\u201334.9, and \u226535.0 kg/m\u00b2. Statistical analyses used SAS version 9.4; continuous variables were compared with Mann\u2013Whitney U test, categorical with \u03c7\u00b2 or Fisher's exact test; p<0.05 was considered significant.", "Key Results": "Women in the bariatric group were older (33.9 vs 30.2 years; p<0.001), had higher BMI (33.6 vs 24.4 kg/m\u00b2; p<0.001), and smoked more (25.8% vs 15.0%; p<0.001). Only 7.0% of bariatric women were normal weight vs 62.8% in the non-bariatric group. Overall, the bariatric group had significantly higher incidences of pregnancy-induced hypertension (5.7% vs 2.9%; p=0.002), GDM (16.2% vs 11.9%; p=0.018), preterm contractions (7.0% vs 4.4%; p=0.023), preterm delivery <37 weeks (8.9% vs 5.1%; p=0.003), labour induction (33.9% vs 19.5%; p<0.001), planned CS (12.4% vs 6.6%; p<0.001), unplanned CS (13.4% vs 9.9%; p=0.036), SGA (7.6% vs 3.3%; p<0.001), and 5-minute Apgar <7 (5.87% vs 2.40%; p<0.001). LGA was decreased (1.9% vs 2.7%; p<0.001). No significant differences were found for pre-eclampsia, insulin treatment for GDM, post-term delivery, or stillbirth. In BMI-specific analysis, GDM was significantly higher in bariatric women across all BMI groups <35 kg/m\u00b2 (all p<0.001), but not in the \u226535 kg/m\u00b2 group (50.9% vs 43.5%; p=0.113). SGA was significantly higher in bariatric women with BMI 25.0\u201329.9 (7.1% vs 2.8%; p=0.028), 30.0\u201334.9 (9.3% vs 2.8%; p<0.001), and \u226535.0 kg/m\u00b2 (7.8% vs 2.9%; p=0.002). No difference in hypertensive disorders was seen in BMI-matched comparisons.", "Clinical Implications": "Bariatric surgery is a safe and advisable treatment for obesity among fertile-aged women, and pregnancy prognosis is highly associated with achieved weight loss. However, even after BS, women have significantly higher risks of GDM and SGA compared to BMI-matched non-bariatric controls. The risk for hypertensive disorders is comparable to BMI-matched controls. The increased SGA risk is likely explained by nutritional deficiencies following malabsorptive procedures. The study highlights that post-BS pregnancies require specialist obstetric surveillance. Limitations include lack of data on BS technique type, timing of surgery relative to pregnancy, and potential diagnostic differences for GDM in post-BS women (home glucose monitoring instead of oral glucose tolerance test to avoid dumping syndrome). Despite these limitations, the findings support BS as a treatment for obesity while emphasizing the need for careful monitoring of post-BS pregnancies."}