Incidence of lumbar discectomy during pregnancy and within 12 months post-partum in Finland between 1999 and 2017: a retrospective register-based cohort study.

Background Context: Both lumbar disc herniation in the general population and lower back pain in the pregnant population are known to be common conditions. The physiological and anatomical of the mother predispose to increased strain of the lumbar disc, whereas pregnancy may promote caution in physicians contemplating surgical care.

Purpose: We aimed to report the incidence of lumbar discectomy during pregnancy and 12 months postpartum in Finland between 1999 and 2017.

Study Design: Retrospective register-based cohort study.

Patient Sample: Using nationwide data from the Finnish Care Register for Health Care and the Finnish Medical Birth Register, all women aged 15 to 49 years with a lumbar discectomy or pregnancy ending in delivery from 1st January, 1999 to 31st December, 2017 were included.

Outcome Measures: Incidence rates and their 95% confidence intervals were calculated for lumbar discectomy. Incidence rate ratios (IRR) were calculated between the study population and the control population. The effect of smoking on surgery risk was reported using odds ratios.

Methods: A retrospective statistical analysis was performed to identify patients undergoing lumbar discectomy during pregnancy or the first 12 months after delivery. Incidence rates were compared with the age-adjusted values of the age-matched female general population. The effect of smoking on the risk of lumbar discectomy was analyzed using age-adjusted odds ratios.

Results: In total, 91 discectomies were performed during pregnancy and 508 within 12 months postpartum. The total incidence of lumbar discectomy during pregnancy was 11 operations per 100,000 person-years with an IRR of 0.2 (95% CI 0.1-0.2) when compared with the age-adjusted female general population. Women with active smoking before pregnancy were at a higher risk for lumbar discectomy during pregnancy (OR 2.0, 95% CI 1.2-3.2). Caesarean section was more common after lumbar discectomy (22%). No perinatal mortality was observed. During the first-year postpartum the rate of lumbar discectomy increased to 47 per 100 000 person-years with an IRR of 0.7 (95% CI 0.6-0.8). 90-day reoperation rates were higher than in the general population with an IRR of 1.7 (95% CI 1.1- 2.7).

Conclusions: Lumbar discectomy during pregnancy is rare, but smoking increases the risk. Lumbar discectomy during pregnancy seems to be safe for the neonate. Postpartum incidences increased towards the end of the first year, but remained below the rates in the general population with a higher risk for short-term reoperation.