Neonatal lupus (NL) occurs in a baby when autoantibodies are passively transferred from mother to fetus during pregnancy. NL is associated with the presence of Ro or SSA antibodies in the mother, and can cause transient rashes, low blood counts, elevated liver tests, or permanent Congenital Heart Block (CHB). A baby with neonatal lupus does NOT have systemic lupus and is not at an elevated risk for developing lupus or other rheumatic disease.
Maternal Testing for Antibodies
Women with rheumatic disease, especially those positive for ANA antibodies associated with lupus, should be tested for Ro/SSA and La/SSB antibodies prior to or early in pregnancy. If these are negative, they do not need to be re-checked frequently as it is rare that they appear mid-pregnancy. The risks of neonatal lupus are NOT related to the mother’s rheumatic disease, they are only related to her antibody status.
The risk of neonatal lupus increases if the mother has:
- High Ro/SSA titers
- La/SSB in addition to Ro/SSA antibodies
- Anti-thyroid antibodies in addition to Ro/SSA antibodies
There is no data about the risks for a woman with a prior positive Ro/SSA antibody that has disappeared during pregnancy, but her offspring is likely at lower risk for neonatal lupus.
Rarely, a woman will have a positive La/SSB antibody without a positive Ro/SSA antibody. These La/SSB antibodies typically disappear on re-check and are likely falsely elevated. This woman’s risk for neonatal lupus is unknown but is likely lower than for a woman with Ro/SSA antibodies.
Congenital Heart Block
Congenital heart block (CHB) results in a permanently slow heartbeat in the baby. It occurs when maternal Ro/SSA antibodies target the fetal heart atrial-ventral node (AV node), which conducts the heartbeat from the atrium to the ventricle. The resulting inflammation leads to permanent scarring of the AV node. The window of risk for CHB is highest between 16 and 26 weeks of gestation.
Some babies with CHB do very well and can live full and normal lives with a slow heartbeat. Unfortunately, up to 10% with CHB will not survive, often with a loss prior to delivery. The rest, around 60% of children with CHB, will require a pacemaker either soon after delivery or in subsequent years.
The risk of CHB depends on whether the mother has previously given birth to babies with neonatal lupus. When there has been no prior pregnancy OR a mother has given birth to infants without NL, there is only about a 2% likelihood her infant will have CHB. However, if the mother has had a prior infant with neonatal lupus (CHB or the rash), then there is an approximately 18% chance that her current pregnancy will result in the birth of an infant with CHB.
A study has demonstrated that taking Hydroxychloroquine 400mg/day reduces the risk of CHB by half for women with a prior infant with neonatal lupus.
ACR Reproductive Health Guidelines recommend treating all women with Ro/SSA antibodies, especially those with a prior infant with neonatal lupus, with 400mg of Hydroxychloroquine (HCQ) every day during pregnancy. HCQ levels can fall during pregnancy as a woman’s weight increases. It is therefore recommended that women take 400mg of HCQ every day regardless of maternal weight. Because HCQ takes multiple weeks to be effective, HCQ should be started prior to pregnancy or as early in pregnancy as possible. It is unlikely that starting HCQ at the time of CHB risk (~17-24 weeks) will be helpful. ACR Guidelines, Sammaritano 2020
Identifying early changes can be challenging as a fetal heart can go from normal to complete heart block within a single day. Some centers assess the fetal heart frequently with a fetal echocardiogram between weeks 17 and 26. ACR guidelines suggest testing every other week for women without a prior baby with NL, and weekly for women that have had a prior baby with NL.
Some centers are testing whether home monitoring of the fetal heartbeat twice a day using a home doppler can be helpful. The mother uses a home doppler to monitor the fetal heartbeat pattern twice a day and calls her provider if abnormalities are detected. The provider than performs an emergent fetal echocardiogram. There will likely be more information about the usefulness and practicality of this procedure in the coming years.
If 1st or 2nd degree heart block are found with fetal echocardiogram, ACR Guidelines recommend treatment with oral dexamethasone 4mg a day. Dexamethasone crosses the placenta better than prednisone and may decreased inflammation in the fetal AV node. The benefits of this treatment are currently anecdotal. Once complete (3rd degree) heart block has occurred, dexamethasone will not reverse the scarring process in the AV node.
The Pediatric Cardiologist is typically in charge of management beyond dexamethasone. They may prescribe medications that can help support the fetal heart rate, if needed. They will also work closely with the Maternal Fetal Medicine Team to carefully schedule delivery and post-delivery care.