A woman with spinal muscular atrophy (SMA) type 3 experienced a mild decline in motor function after pausing Spinraza (nusinersen) during pregnancy, but partially recovered her walking endurance after restarting the disease-modifying therapy post-delivery, according to a case report published in BMJ Case Reports. The findings suggest that patients with milder disease forms may tolerate temporary treatment pauses, though researchers emphasize that clinical decisions must remain individualized.
Managing Spinraza During Pregnancy in Spinal Muscular Atrophy Type 3
Spinal muscular atrophy is primarily caused by mutations in the SMN1 gene, leading to the gradual loss of motor neurons that control movement, according to background data in the report. Disease-modifying treatments like Biogen’s Spinraza have significantly improved survival rates and motor function, allowing more individuals with SMA to reach adulthood and plan families. However, clinical evidence guiding the use of these therapies during pregnancy remains scarce.
Spinraza works by increasing the production of survival motor neuron (SMN) protein from a backup gene named SMN2. Administered directly into the spinal canal, the therapy is expected to show little to no transfer across the placenta to the fetus due to its large molecular size and specific chemical properties, according to the patient’s medical team.
Patient Case Details and Treatment Pause
The published case details a woman in her mid-20s diagnosed with SMA type 3 at age five who began receiving Spinraza in her early teens. With consistent treatment, her condition remained stable, characterized only by mild leg weakness and independence in daily activities. Approximately two weeks after conceiving during a planned pregnancy, she received her final maintenance dose.
Following discussions with her neurologist and a maternal-fetal medicine specialist, she opted to pause Spinraza for the duration of her pregnancy because safety data regarding fetal exposure were limited. Her pregnancy proceeded without complications aside from greater-than-recommended weight gain. She delivered a healthy baby via a planned C-section without complications for herself or the child. She breastfed for eight weeks before switching to formula, and at nine months old, the child was developing normally.
Did you know? Spinraza is delivered intrathecally—meaning it is injected directly into the fluid-filled space surrounding the spinal cord—which limits its systemic distribution and placental transfer during pregnancy, according to clinical reports.
Motor Function Stabilization After Postpartum Restart
The patient restarted Spinraza about eight weeks after giving birth, which was 11 months after her last dose, receiving two loading doses to resume the regimen. Physical therapy assessments conducted one and five months post-restart revealed slight declines in general motor function and walking endurance. However, her Revised Upper Limb Module (RULM) score—which measures hand and arm function—remained stable.
Because her walking distance decreased following childbirth, she utilized a walker or wheelchair for community travel. By an 11-month assessment following her treatment restart, her walking endurance improved, while her RULM score and general motor function, measured via the Hammersmith Functional Motor Scale-Expanded, held steady.
Comparing Recovery Outcomes in SMA Cases
Previous international reports involving women with SMA who paused Spinraza during pregnancy generally describe motor function declines during gestation, followed by stabilization or partial improvement after resuming treatment post-delivery. No consistent adverse fetal outcomes have been reported, and most deliveries remain uncomplicated.
By contrast, an earlier published report detailed a woman with SMA type 3 who stopped Spinraza early in pregnancy and suffered an irreversible decline in motor function despite resuming therapy after birth. Investigators noted that differences in baseline function, discontinuation timing, and total time off treatment likely account for the differing recovery trajectories between the two cases.
“From a clinical perspective, current evidence does not support a uniform recommendation to continue or discontinue nusinersen [Spinraza] during pregnancy,” the researchers wrote. “Instead, therapy decisions should be individualised based on disease severity, functional dependence and patient preference.” The team concluded that these findings emphasize the need for individualized, multidisciplinary care and prospective studies to guide reproductive counseling.
Frequently Asked Questions
Does Spinraza cross the placenta during pregnancy?
According to the case report, Spinraza is expected to show minimal to no transfer across the placenta to the fetus because of its large molecular size and chemical properties.
What happened when the patient restarted Spinraza after delivery?
After receiving two loading doses about eight weeks postpartum, the patient experienced initial slight declines in walking endurance, but her arm function remained stable. Her walking endurance partially recovered by an 11-month follow-up assessment.
What do current guidelines recommend for Spinraza use during pregnancy?
Researchers state that current evidence does not support a uniform recommendation to continue or stop the medication, meaning therapy choices must be individualized based on disease severity, functional dependence, and patient preference.
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