SMA treatment pause during pregnancy tied to mild motor decline
Walking endurance partly recovered after Spinraza was restarted postpartum
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- A Spinraza treatment pause during pregnancy was followed by mild motor decline and partial recovery postpartum.
- SMA treatment decisions during pregnancy require individualized assessment based on disease severity, functional dependence, and patient preference.
- Spinraza is expected to have minimal placental transfer; prior reports found no consistent adverse fetal outcomes.
A woman with spinal muscular atrophy (SMA) type 3 experienced a mild decline in motor function after pausing Spinraza (nusinersen) during her pregnancy.
After she restarted treatment following delivery, however, her motor function stabilized and her walking endurance partially recovered.
Overall, the case suggests that women with milder SMA and better-preserved function may be better able to tolerate a temporary treatment pause during pregnancy. “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 report, “Managing nusinersen therapy during pregnancy in spinal muscular atrophy type 3,” was published in BMJ Case Reports.
How Spinraza works in SMA
SMA is chiefly caused by mutations in the SMN1 gene. These mutations lead to the gradual loss of motor neurons, the nerve cells that control movement. Disease-modifying therapies such as Spinraza have greatly improved survival and motor function, enabling more people with SMA to reach adulthood and consider having children. However, doctors have little evidence to guide the use of these treatments during pregnancy.
Biogen’s Spinraza works by increasing production of the survival motor neuron (SMN) protein from a backup gene called SMN2. The treatment is delivered directly into the spinal canal and is expected to show little, if any, transfer across the placenta to the fetus. The placenta is a temporary organ that develops in the uterus during pregnancy and supplies the fetus with oxygen and nutrients through the umbilical cord.
The researchers described the case of a woman in her mid-20s with SMA type 3. She was diagnosed at age 5 and began taking Spinraza in her early teens. With treatment, her condition remained stable. She had only mild leg weakness and could perform daily activities independently.
About two weeks after conceiving during a planned pregnancy, she received her final maintenance dose of Spinraza before pausing treatment. After discussing the decision with her neurologist and a maternal-fetal medicine specialist, she chose not to receive Spinraza for the remainder of her pregnancy because little was known about its safety for the fetus. Her doctors explained that the treatment was expected to show minimal, if any, transfer across the placenta because of its large molecular size and chemical properties.
Her pregnancy was uncomplicated aside from greater-than-recommended weight gain. She delivered a healthy baby by planned C-section, with no complications for her or the baby. She breastfed for eight weeks before switching to formula. At 9 months old, the child was healthy and developing normally.
She restarted Spinraza about eight weeks after giving birth, 11 months after her last dose, and received two loading doses to resume treatment.
Motor function stabilizes after treatment restart
Physical therapy assessments one and five months after she restarted treatment showed slight declines in general motor function and walking endurance. However, her Revised Upper Limb Module (RULM) score, which measures arm and hand function, remained stable. Since giving birth, her walking distance had decreased, and she used a walker or wheelchair when traveling in the community. At another assessment about 11 months after she restarted Spinraza, her walking endurance had improved, while her RULM score and general motor function, measured with the Hammersmith Functional Motor Scale-Expanded, remained stable.
Previous reports involving women with SMA who paused Spinraza during pregnancy — all from outside the U.S. — have generally described declines in motor function during pregnancy, “with stabilisation or partial improvement observed after postpartum resumption of treatment.”
No adverse fetal outcomes have been reported consistently, and most deliveries have been uncomplicated.
A previous report described a woman with SMA type 3 who stopped Spinraza early in pregnancy and experienced an irreversible decline in motor function despite restarting treatment after giving birth. “In contrast, our patient who remained ambulatory and had milder baseline weakness demonstrated a smaller and partially reversible decline following therapy interruption,” the investigators wrote. “Differences in baseline function, timing of discontinuation and duration off treatment may explain the variability in recovery between the two cases.”
Overall, “these findings highlight the importance of individualised, multidisciplinary care and underscore the need for prospective studies to guide reproductive counselling and therapy management in SMA,” the team concluded.
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