High Pregnancy Heme Precursor Levels Not Tied to Worse Symptoms

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by Vanda Pinto, PhD |

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In women with acute hepatic porphyria (AHP), increased levels of heme precursors during pregnancy were not accompanied by symptom worsening, and most patients had no AHP-related complications, a Swedish study reports.

Nonetheless, given that “it can be challenging to differentiate between manifestations of an acute attack and obstetrical, neurological and psychological complications,” the researchers urged “the involvement of porphyria specialists in … patients’ maternal care.”

Care from physicians who specialize in the heme production cycle-related disorder “is recommended for reducing risk and improving the probability of good pregnancy outcomes,” the researchers wrote.

The study, “Acute hepatic porphyria and maternal health: Clinical and biochemical follow-up of 44 pregnancies,” was published in the Journal of Internal Medicine.

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Porphyria comprises a group of disorders caused by the accumulation of porphyrins and other heme precursors. Porphyrins are molecules that go through several chemical changes to produce heme, a component of hemoglobin that is required for blood oxygen transport in the body.

There are several types of AHP, each resulting from the lack of a specific enzyme in the heme production pathway. These include acute intermittent porphyria (AIP), hereditary coproporphyria (HCP), variegate porphyria (VP), and ALAD porphyria.

In AHP, there may be a buildup of heme precursors, mainly porphobilinogen (PBG) and delta-aminolevulinic acid (ALA). Increased levels of heme precursors may, in turn, lead to an acute porphyria attack, which is characterized by abdominal pain, fast heart rate, and gastrointestinal symptoms, as well as mental health problems.

Female reproductive hormones play an important role in AHP symptoms, and women with acute porphyria appear to be most vulnerable to an acute attack during early pregnancy and about six weeks after childbirth. However, few studies have examined heme production during pregnancy.

Now, researchers at the Karolinska University Hospital, in Sweden, sought to find out how hormonal changes affect the heme production pathway in pregnant women with AHP.

The team monitored 33 women with AHP — with a total of 44 pregnancies among them — between 2001 and 2020. Of these expectant mothers, 26 had AIP, six had VP, and one had HCP. Their age at the time of delivery ranged from 24 to 40, with a median age of 31. Eight women had previous fertility treatment and 10 were monitored for more than one pregnancy.

Four women had acute porphyria attacks during pregnancy, and one during the postpartum period after developing a urinary tract infection. No triggers besides pregnancy were found, except for a woman who had undergone fertility treatment eight weeks before having an attack.

Although these patients were hospitalized, they recovered following treatment, the researchers said.

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Hypertension, or high blood pressure, can be a problem for women with AHP. Five of the expectant mothers developed this complication during seven of the monitored pregnancies, and three women with AIP had preeclampsia during four of the monitored pregnancies. Preeclampsia is a pregnancy complication characterized by high blood pressure, liver and kidney damage.

“Due to the potential risk of preeclampsia, in combination with the known risk of [kidney damage] in AHP we recommend that kidney function be closely monitored in pregnancies with acute hepatic porphyria and gestational hypertension,” the researchers wrote.

No babies died during the study; one infant was diagnosed with a heart problem that was not related to AHP.

In 32 of 38 pregnancies, patients had excessive urinary levels of PBG and/or ALA on at least one occasion during pregnancy, the data showed. An upward trend in the levels of heme precursors also was observed during pregnancy, reaching a peak in the third trimester. However, this increase was not linked to clinical signs and symptoms of acute porphyria.

“Our observations align with contemporary reports that pregnancy in patients with AHP is frequently uncomplicated,” the researchers wrote.

“We believe that the critical factors in ensuring a safe pregnancy for a woman with AHP are a well-informed individual and access to clinical and biochemical monitoring by a porphyria specialist, throughout the pregnancy and the postpartum period,” they concluded.

The team also suggested that it is “advantageous to continue observation postpartum and to avoid early discharge from the hospital.”