Maternal smoking in the first trimester has not been proven to directly cause cerebral palsy, but it may contribute to some of the conditions that increase the risk of cerebral palsy, and most experts advise avoiding all tobacco throughout pregnancy because of its effects on the developing brain and placenta.
Cerebral palsy, or CP, is a lifelong disorder that affects movement, posture, and sometimes thinking and behavior. It usually results from damage to the developing brain during pregnancy, birth, or early infancy. Well known risk factors include extreme prematurity, very low birth weight, infections during pregnancy, lack of oxygen to the baby, certain genetic problems, and bleeding in the brain around the time of birth. Smoking is not at the top of the traditional risk factor list in the same way as early birth or severe birth complications, but research shows that it can harm the placenta and the fetal brain in ways that could indirectly raise the chance of CP.
When a pregnant woman smokes, nicotine, carbon monoxide, and many other toxic chemicals quickly cross the placenta and reach the baby’s circulation and brain. A 2025 review on prenatal exposure to tobacco smoke and vaping aerosols explains that nicotine crosses both the placenta and the fetal blood brain barrier and is broken down more slowly in the fetus than in the mother, so the baby can be exposed for longer periods after every cigarettehttps://pmc.ncbi.nlm.nih.gov/articles/PMC12737246/[2][3]. Even brief exposure, such as a single cigarette, can increase resistance in placental blood vessels and reduce gas exchange, which promotes fetal hypoxia, meaning the baby receives less oxygen than normal[2]. Reduced oxygen delivery is important, because lack of oxygen is one of the major pathways that can injure the developing brain and is also a recognized pathway toward cerebral palsy in more severe cases.
The same review describes how toxic substances in tobacco smoke can interfere with white matter development in the fetal brain[2][3]. White matter consists of the nerve fibers and their myelin covering that help different parts of the brain communicate efficiently. During pregnancy, especially the second and third trimesters, the brain is building these connections very rapidly. Researchers report that prenatal exposure to cigarette smoke and related products may disrupt oligodendrocytes, the cells that form myelin, through mechanisms that involve oxidative stress, inflammation, endocrine disruption, and altered glial metabolism[2][3]. These disruptions can lead to long lasting changes in white matter microstructure and have been associated in some studies with cognitive and sensorimotor problems later in life[2][3]. Motor and sensorimotor problems overlap with some of the difficulties seen in cerebral palsy, although not every child with such changes has CP.
Other studies focus on learning and behavior outcomes and show that maternal smoking during pregnancy affects the child’s brain and development in broader ways. A large US cohort study found that maternal smoking during pregnancy roughly tripled the risk of learning disabilities in offspring, even after carefully adjusting for many confounding factorshttps://www.tobaccoinduceddiseases.org/Association-between-maternal-smoking-during-pregnancy-nand-learning-disabilities,214128,0,2.html[1]. That study and related work describe several mechanisms that are also relevant to cerebral palsy: nicotine disrupts neurotransmitter systems in the fetal brain and interferes with early processes such as neurite outgrowth, cell survival, cell proliferation, and neurogenesis[1]. Carbon monoxide binds to hemoglobin and forms carboxyhemoglobin, decreasing oxygen delivery and causing chronic fetal hypoxia, while smoking also reduces placental blood flow[1]. All of these changes can negatively affect fetal brain development and increase the risk of multiple neurodevelopmental problems.
These findings support the broader idea that prenatal smoking harms brain development, but they do not show a simple one to one link between smoking in the first trimester and a diagnosis of cerebral palsy. Most epidemiologic studies on smoking in pregnancy focus on outcomes such as miscarriage, stillbirth, low birth weight, preterm birth, sudden infant death syndrome, learning problems, or ADHD, rather than CP specifically. Where cerebral palsy is studied, smoking usually appears as one factor among many that influence risk, often mediated through preterm birth, poor fetal growth, or placental problems. For example, prenatal and childhood tobacco exposure has been linked to higher risk of some autoimmune disorders, which illustrates that tobacco exposure can have complex effects on the immune and vascular systems as well as on the brainhttps://www.endocrinologyadvisor.com/news/prenatal-and-childhood-tobacco-exposure-linked-to-higher-autoimmune-risk/[5]. Disturbed immune or inflammatory responses are also thought to play a role in some cases of CP, though the exact connections remain under active study.
The timing of exposure is another important point. The first trimester is when the basic structures of the brain are laid down, including the earliest neuronal populations and initial wiring. Nicotine and other tobacco toxicants can interfere with cell proliferation and differentiation during this stage[1][2][3]. As pregnancy progresses into the second and third trimesters, the brain enters phases of rapid growth, white matter formation, and myelination, which also appear highly vulnerable to tobacco related toxins[2][3]. Some neuroimaging studies report that children exposed to tobacco in utero, especially in mid pregnancy, show altered white matter microstructure on MRI, with changes in measures such as fractional anisotropy and radial diffusivity in major brain tracts[2]. These kinds of structural alterations are biologically plausible contributors to motor and coordination difficulties, but again, they do not equate directly to a specific diagnosis like cerebral palsy in every case.
Researchers also point out that the effects of maternal smoking are shaped by genetics and epigenetics. Certain genetic variants involved in metabolizing tobacco smoke or in neurotransmitter systems may make some fetuses more vulnerable than others to the same level of exposure[1]. Epigenetic studies show that prenatal smoking can alter DNA methylation patterns in the fetus, which may have lasting effects on brain function and behavior[1]. In the context of CP, which itself is thought to arise from a mix of environmental and genetic influences, this interaction suggests that smoking could be one more environmental hit in a susceptible baby, especially if combined with other risks such as infection, growth restriction, or birth complications.
From a practical perspective, clinicians and public health agencies uniformly recommend that pregnant women avoid smoking altogether before conception and throughout pregnancy. This advice is not only because of possible links to cerebral palsy, but because smoking is clearly associated with miscarriage, placental abruption, placenta previa
