Seizures during pregnancy may become harder to control if lamotrigine levels fall, while levels can rise quickly after birth and increase the risk of side effects if the dose was raised during pregnancy. These changes vary from person to person. Clinicians use your seizure history and symptoms, and when available a pre-pregnancy blood level, to guide monitoring and individual dose changes. Don’t adjust or stop treatment on your own; discuss changes with your clinician.
How Seizures During Pregnancy Can Relate to Falling Levels
Pregnancy changes how the body handles lamotrigine. In many people, the medicine is cleared from the body faster, so its concentration in the blood drops—even when the prescribed dose stays the same. The change can begin early and grow during pregnancy, but it is not the same for everyone.
A U.S. analysis of the MONEAD study, led by Ashwin Karanam and colleagues, followed 170 pregnant women with epilepsy taking lamotrigine and compared them with 51 nonpregnant women with epilepsy. The 20-site observational study recruited participants from December 2012 to February 2016 and measured plasma drug concentrations at scheduled visits. About 91% of the pregnant participants had a substantial increase in clearance; for this group, clearance rose to about 2.75 times the nonpregnant baseline at its maximum. About 9% had little or no significant change. This difference helps explain why a standard dose increase may not suit everyone.
In an earlier prospective study, Page Pennell and colleagues analyzed 305 blood samples from 53 pregnancies. Lamotrigine clearance peaked in the third trimester, rising by 94% for total drug and 89% for free drug compared with nonpregnant baseline. In that study, a blood level below 65% of an individual’s target level was associated with increased seizure frequency. That finding can help clinicians interpret a trend, but it is not a universal cutoff or a stand-alone dosing rule.
How Clinicians Use Symptoms and Baseline Levels
If you are planning a pregnancy, ask your epilepsy clinician whether a lamotrigine blood level should be measured while your seizures are well controlled. That result can serve as a personal reference point. A population “normal range” may be less useful than the concentration that has worked for you, because people can have different levels while maintaining seizure control.
During pregnancy, your clinician may consider blood tests alongside changes in seizure frequency, side effects, dose and other medicines. If no pre-pregnancy level is available, the care team can still follow your symptoms and use blood levels to help assess changes. Monitoring schedules and dose decisions need to be individualized; the studies do not establish one schedule or target that fits everyone. Keep track of seizures and new or worsening side effects, and share those changes promptly with your care team.
Why the Plan Needs to Change Again After Birth
After delivery, pregnancy-related changes in drug clearance reverse, and lamotrigine levels can climb as clearance returns toward its pre-pregnancy rate. If your dose was raised during pregnancy, continuing it unchanged may increase the chance of side effects. The postpartum shift can happen quickly, so a plan for reviewing your dose and symptoms after birth matters as much as monitoring during pregnancy.
A retrospective study at Tel Aviv Sourasky Medical Center examined 81 pregnancies in 75 women with epilepsy from 2018 to 2023. It compared continued postpartum blood-level monitoring with an empiric taper plan that scheduled dose checks and adjustments on days 1, 7 and 21 after birth. The taper approach was reported as well tolerated and was not linked to increased seizure risk. The study was small, included both lamotrigine and levetiracetam, and cannot establish the best taper schedule for every patient.
There is no single postpartum dose reduction that can be safely applied to everyone. Your clinician can make a plan based on the dose you needed during pregnancy, your usual dose, seizure control, side effects and any blood-level results. Arrange this plan before delivery if possible, so you know whom to contact and when follow-up is due.
Do Not Change or Stop Lamotrigine on Your Own
Low levels may raise concern about seizure control, and rising levels may raise concern about side effects—but changing the dose without guidance can create new risks. Do not reduce, increase or stop lamotrigine yourself, including if you become pregnant unexpectedly. Contact your epilepsy clinician and pregnancy care team to discuss monitoring and a coordinated plan. If you have a seizure or concerning new symptoms, seek prompt medical advice.