Pregnancy and HHT

Pregnant HHT patients should consult an HHT expert to make the best decisions for their specific pregnancy. With the right screening, most women with HHT can have a normal pregnancy and delivery with no more risk than someone without HHT.

Pregnant women with HHT should be managed at a tertiary care center by a multi-disciplinary team if they have untreated pulmonary AVMs and/or brain VMs OR have not been recently screened for pulmonary AVMs (Lausman et al., 2021).The multidisciplinary team should include:

Obstetricians
Maternal-fetal medicine specialists
Pulmonologists
Anesthetists
Interventional radiologists
Pediatricians
Thoracic/neurosurgeons

Most HHT pregnancies proceed without any higher risk than the average pregnancy:

People who have been diagnosed with HHT and screen negative for AVMs are just as likely to have a “typical” pregnancy as their non-HHT counterparts.
Pregnant people with HHT are not at higher risk of miscarriage than the general population.
People with HHT are no more likely to bleed excessively during or after delivery than the average person because HHT is not a clotting disorder.

Some pregnant women with HHT are labeled as “high-risk”, as there is a 1% overall risk of complication in an HHT pregnancy in patients with HHT.

There can be risks to both the mother and the fetus in a high-risk pregnancy.

High-risk pregnancies have additional monitoring to ensure complications are caught early.

Screenings

Brain VM

Asymptomatic patients do not require routine screening during pregnancy. There is very limited data and lack of evidence about specific risk of BAVM bleeding in pregnant women with HHT. There is no conclusive evidence of an increased risk of first bleed from a brain VM during pregnancy (Davidoff 2019).
Pregnant people with HHT who have symptoms suggestive of brain VMs, including those with previous brain bleed, should be screened using unenhanced MRI.

Pulmonary (Lung)

PAVMs can occur at any time during pregnancy.

85-90% of PAVM complications occur in the second or third trimesters.

Screening and treatment of PAVMs should occur as early as possible at ~12-20 weeks.

For patients who have had prior negative PAVM screening, additional screening during pregnancy is not needed, in the absence of symptoms.
Pregnant people with HHT who have not been recently screened and/or treated for pulmonary AVM should be screened and treated in pregnancy.
For previously treated PAVMs, the risk of complications during pregnancy is not precisely known, but may be about ~5%.
During pregnancy there is an increase in cardiac output, an increase in blood volume, and high progesterone levels. This combination can result in enlargement and/or rupture of PAVMs during pregnancy.

Asymptomatic patients should receive initial pulmonary AVM screening.

Labor and Delivery Considerations

Spinal VM

Pregnant people with HHT should not withhold an epidural because of a diagnosis of HHT, and screening for spinal vascular malformations is not required.
Incidence of spinal vascular malformations (SVM) in people with HHT is not known, but is rare.
The incidence of symptomatic SVMs is 0.5% (4/800)

- Mainly pediatric (82%)
- Predominantly male (69%)

Epidural/Spinal Anesthesia

On a case by case basis, an effective epidural can be used to allow the fetus to come down the birth canal and an assisted delivery (e.g. forceps) may be recommended if higher risk circumstances are identified.

There are two large studies of pregnant people with HHT and neither reported complications from epidural/spinal anesthesia; no spinal hemorrhage reported in either study.

- de Gussem 2014 : 92 spinal/epidurals in 185 deliveries

- Shovlin 2008: 484 pregnancies

There are no case reports of pregnant people with HHT developing complications of spinal VMs from epidural/spinal anesthesia during pregnancy/delivery

Although screening the general HHT population for SVMs is not recommended, it is prudent to have an epidural/spinal anesthetic performed by an experienced anesthetist.

Pregnancy may exacerbate the symptoms of SVM

In case of a known SVM, an anesthetist should be consulted to address anesthetic options on a case by case basis.

Brain VM

Women with known, non-high risk brain VMs can labor and proceed with vaginal delivery. Patients may require an assisted second stage (i.e. non-surgical assistance such as forceps or vacuum) on a case by case basis.

There are no reports of pregnant people with HHT having a brain VM bleed during labor.
In symptomatic patients (and even in asymptomatic patients who have a known diagnosis of brain VM) it is prudent to review with a multidisciplinary neurovascular team.
There may be cases in which the multidisciplinary team’s opinion, including that of a neurosurgeon, may be to deliver the baby by Caesarean section.

Preconception and Prenatal Genetic Diagnostic Options

Pre-Implantation Genetic Diagnosis

A procedure performed prior to implantation to help identify embryos with and without the HHT gene. This means the affected HHT parent would need to undergo genetic testing prior to IVF in order to identify the family HHT gene mutation. There is the option to transfer non-affected embryos.

Post-Conception Options

Include Chorionic Villus Sampling (CVS) and Amniocentesis which are tests that can determine if the HHT gene is present. These invasive diagnostic options carry a small risk of miscarriage (1% and <0.5% respectively). Given the risks, a discussion about what path the pregnant person would take once results are available is important. If there is no scenario where the pregnancy would be terminated, these tests may not be worth the risk.

Post-Delivery

Parents can be offered genetic testing on cord blood of the infant at time of delivery to determine if their infant has HHT. Childhood AVM screening is recommended for HHT so testing cord blood to diagnose an infant is appropriate. If genetic testing is declined, then children should be considered affected until proven otherwise.

COVID-19

The COVID-19 vaccine is safe in pregnancy.
Pregnant people who get COVID-19 in pregnancy have an increased risk of hospitalization and ICU admission.
After you get the vaccine, antibodies that your body makes will protect you and your baby - in utero and after birth.
After you baby is born, your antibodies will be transmitted to your baby through your breast milk.

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