Past kidney injury may raise risk of poor pregnancy outcomes

The risk of preeclampsia and other pregnancy complications may be greater for expectant mothers who have a history of acute kidney injury, a new study finds, even when kidney function is normal prior to pregnancy.

Study leader Dr. Jessica Sheehan Tangren, of the Division of Nephrology at Massachusetts General Hospital (MGH) in Boston, and colleagues believe that their results indicate it is important for obstetricians to get a clear picture of past kidney health for pregnant women.

The researchers recently published their findings in the Journal of the American Society of Nephrology.

Acute kidney injury (AKI) is the sudden onset of kidney damage or failure. The condition can lead to an accumulation of waste products in the blood, an imbalance of body fluids, and it may also affect the function of other organs, including the brain, heart, and lungs.

According to the National Kidney Foundation, AKI is most common among older adults, but it can also affect children and young adults.

Causes of AKI include severe infections (such as sepsis), vasculitis (inflammation and scarring of the blood vessels), allergic reactions, low blood pressure, and major surgery.

Dr. Tangren and colleagues note that existing kidney disease is known to increase the risk of pregnancy complications for expectant mothers, but previous studies have not investigated how a history of AKI might impact pregnancy outcomes.

Preeclampsia risk 5.9 times greater with history of AKI

With the aim of finding out, the team analyzed the medical records of 24,745 women who gave birth at MGH between 1998-2007. Of these women, 24,640 had no history of kidney disease (the controls), while 105 had a history of AKI, from which they had fully recovered prior to pregnancy.

Compared with women who had no history of kidney disease, those with a history of recovered AKI (r-AKI) were found to be at much greater risk of pregnancy complications.

The rate of preeclampsia – a condition characterized by high blood pressure, swelling, and protein in the urine – was 4 percent for the controls, compared with 23 percent for women with a history of r-AKI.

Babies of women with a history of r-AKI were also more likely to be born earlier than those of the controls, at 37.6 weeks versus 39.2 weeks, respectively, and they were more likely to be born small for their gestational age, at 15 percent versus 8 percent, respectively.

Additionally, the team found that women with previous r-AKI were more likely to have a cesarean delivery than controls, at 40 percent versus 27 percent, respectively.

After adjusting for a number of possible confounding factors, the researchers found that women with a history of r-AKI were at 2.4 times greater risk of any adverse fetal outcome and 5.9 times increased risk of preeclampsia.

The researchers are unable to explain the mechanisms underlying the link between a history of r-AKI and greater risk of poor pregnancy outcomes. However, they say that it is possible for changes in small blood vessels that occur during kidney injury recovery to affect the kidney’s ability to function effectively during pregnancy.

“We know that kidneys undergo major changes during pregnancy, and that sort of ‘renal stress test’ may reveal previously undetected kidney disease in women with a history of acute kidney injury,” notes Dr. Tangren.

Findings highlight importance of past kidney health for pregnant women
While further studies are needed to confirm their findings, the researchers believe the current results indicate that expectant mothers with a history of AKI should be closely monitored throughout their pregnancy.

“Information like this helps obstetric providers know what to be vigilant for in pregnant women with a history of acute kidney injury and indicates that asking about such history is important,” notes study co-author Dr. Jeffrey Ecker, chief of obstetrics and gynecology at MGH.

“Being especially watchful for signs and symptoms of preeclampsia in such patients is one immediate application of this work,” he adds.

“In a longer view, work like this offers important hypotheses for future study. Can interventions in patients with a history of acute kidney injury prevent complications like preeclampsia?

Taking a baby aspirin each day during pregnancy is recommended for some women at high risk for preeclampsia. Should such preventive treatment be used in women with a history of acute kidney injury? Questions like this deserve further thought and study.”

Dr. Jeffrey Ecker

Leave a comment