<p>This paper examines how infant health complications at birth measured by low birth weight and prematurity affect maternal labor market outcomes over the first seven years of a child’s life. Using Canadian administrative data linking birth certificates to annual tax records for 640,500 first births between 2006 and 2015, I compare mothers of unhealthy infants-those born with low birth weight or preterm-to carefully matched mothers of healthy infants. I find that mothers of unhealthy infants experience a persistent 2.6% penalty in labor force income and an 8.7% increase in the probability of zero earnings, representing approximately 10% of the total motherhood penalty. The penalty is particularly pronounced among low-income mothers, who face earnings losses 3.5 times larger than high-income mothers, and among mothers with higher-parity births, who are twice as likely to exit the labor market entirely compared to first-time mothers. Evidence from disability benefit receipt, maternity leave exhaustion, and partnership stability argues against benefit-induced work reduction, fertility adjustments, and partnership dissolution as primary drivers, pointing instead to ongoing caregiving demands from persistent child health vulnerabilities.</p>