Pregnancy outcomes are improving for women on dialysis and kidney transplant recipients, new research suggests. Investigators continue to discover both protective factors and risk factors affecting outcomes. In addition, a new guide can help nephrologists answer important pregnancy questions posed by their patients from “Can I have a baby? to “What care do I need?”
Women on Dialysis
During 2010-2020, the frequency of pregnancy among women on dialysis has increased, Hayet Baouche, MPH, of APHP-Necker-Enfants Malades Hospital, REIN Registry in Paris, France and colleagues reported in Clinical Kidney Journal. The team found a decrease in hypertensive disorders of pregnancy and polyhydramnios and lower rates of neonatal and perinatal deaths compared with previous decades. Progress in dialysis treatment, fetal monitoring, and advances in obstetric and neonatal care likely played major roles.
The investigators performed a systematic review of 14 retrospective and prospective studies, representing 2364 women on dialysis (92.6% hemodialysis; 7.4% peritoneal dialysis) and 2754 pregnancies. Among 402 pregnancies, the investigators found 71.4% live births, 16.9% spontaneous miscarriages, and 5.2% therapeutic abortions. They also noted 8.3% stillbirths, 7.6% neonatal deaths, and 15.3% perinatal deaths.
The premature birth rate was high, ranging from 50%-100% across studies. Gestational age at delivery was 25.2 to 36 weeks. Birth weight ranged from 590 to 3500 g. Previous research linked longer dialysis duration with better fetal outcomes. In this review, dialysis duration was 14 to 43 hours per week, with a maximum of 3 to 6 sessions. According to the investigators, increasing the dialysis dosage also may reduce pre-dialysis blood urea nitrogen (BUN) levels, which may improve size for gestational age, live birth rates, birth weight, and rates of maternal hypertension and hydramnios. “A pre-dialysis mid-week serum BUN level <35 mg/dL could be used as a threshold for dialysis dose adjustment as it seems to be a reliable criterion for dialysis performance,” Baouche’s team wrote.
The most common maternal complications were preeclampsia in 11.9%, hypertension in 7.7%, and anemia in 3.9%. In addition to dialysis, older patient age, obesity, and pre-existing hypertension and diabetes played a role in maternal and fetal outcomes.
Considering the risk of pregnancy complications in dialysis, women of childbearing age should wait for a kidney transplant because it is associated with better outcomes, according to Baouche’s team.
Kidney Transplant Recipients
Among 5,408, 215 hospital deliveries from 2009 to 2014 in the United States, 405 women had stage 3-5 chronic kidney disease (CKD) and 295 women had functioning kidney transplants.
Pregnant kidney transplant recipients had 3.1-, 3.4-, 2.5-, 1.7-, and 10.5-fold increased odds of hypertensive disorders of pregnancy, preeclampsia/eclampsia/HELLP (hemolysis, elevated liver enzymes, low platelet count) syndrome, preterm delivery, fetal growth restriction, and acute kidney injury (AKI), respectively, compared with pregnant women without kidney disease, Vesna D. Garovic, MD, PhD, of Mayo Clinic in Rochester, Minnesota, and colleagues reported in Nephrology.
Compared with pregnant kidney transplant recipients, those with stage 3-5 CKD had 5.3-, 1.7-, and 3.2-fold increased odds of AKI, preeclampsia/eclampsia/HELLP syndrome, and fetal deaths, respectively.
Investigators of a nationwide Dutch cohort study also found relatively good pregnancy outcomes after kidney transplantation.
During 1971-2017, 192 kidney transplant recipients had 288 pregnancies. The live birth rate was 93%, mean gestational age was 35.6 weeks, and mean birthweight was 2383 grams. Hypertensive disorders of pregnancy occurred in 26% of pregnancies.
Lower prepregnancy graft function and poor hemodynamic adaptation to pregnancy were the most important risk factors for adverse outcomes, Margriet E. Gosselink, MD, of the University Medical Centre Utrecht in the Netherlands, and colleagues reported in Kidney International. The combined adverse pregnancy (cAPO) outcome including severe hypertension in the third trimester, more than 15% increase in serum creatinine in the third trimester as compared with prepregnancy values, birth weight less than 2500 g, or preterm birth occurred in 78% of pregnancies. Prepregnancy estimated glomerular filtration rate (eGFR) was significantly associated with 2% reduced odds of cAPO for each 1 mL/min/1.73 m2 increase in eGFR. Midterm percentage serum creatinine dip and midterm dip in mean arterial pressure were significantly associated with 5% and 6% decreased odds of cAPO for each percentage drop in creatinine and each 1 mm Hg decline, respectively.
Graft loss occurred in 23% pregnancies within a median 6.44 years, but was not affected by pregnancy. A nationwide Netherlands study published in Transplantation also found no worse graft function after pregnancy.
In an editorial published in Kidney International, Shilpanjali Jesudason, MD, of Central Northern Adelaide Renal and Transplantation Service, Royal Adelaide Hospital in South Australia and Giorgina Barbara Piccoli, MD, of Centre Hospitalier du Mans in Le Mans, France, highlighted the challenges of success in kidney transplant recipients achieving pregnancy: “Current international guidelines suggest waiting at least 1 year after transplantation, proceeding with pregnancy when there is stable graft function and favorable immunological activity after cessation of teratogenic drugs. The best approach for patients who do not fall into this ‘ideal’ remains less certain and requires individualized consideration.”
Answering Patient Questions
Despite the increase in pregnancies among patients on dialysis and with functioning grafts, pregnancy still carries risks in these populations. In Kidney International Reports, Dr Jesudason and colleagues provided a helpful traffic light system for explaining risks to patients. Stable kidney transplant recipients with good graft function are considered at lower risk (green light) for adverse pregnancy outcomes. Those with unstable graft function, past rejection, immune concerns, high blood pressure, anemia, proteinuria, or previous injection are considered at moderate risk (yellow light). Recipients with worse graft function, recent rejection or infection and uncontrolled blood pressure are considered at high risk (red light).
Women on dialysis with good residual kidney function, hemoglobin levels, blood pressure, and nutrition who can receive extended dialysis sessions are at moderate risk (yellow light). Dialysis recipients with minimal residual kidney function, poor blood pressure control, anemia, malnutrition, or poorly functioning dialysis access are at high risk (red light).
“The ideal scenario is a planned pregnancy at the safest time, with a well-counseled patient, specialized multidisciplinary team, proximity to high-risk antenatal care, and contraception in place until ready for pregnancy. Referral to maternal-fetal medicine specialists ahead of pregnancy is ideal. Patients may also benefit from genetics, fertility, dietitian, and psychology input.”
Baouche H, Jais JP, Meriem S, et al. Pregnancy in women on chronic dialysis in the last decade (2010–2020): a systematic review. Kidney Int Rep. 2022 Jul; 7(7):1477–1492.
Chewcharat A, Kattah AG, Thongprayoon C, et al. Comparison of hospitalization outcomes for delivery and resource utilization between pregnant women with kidney transplants and chronic kidney disease in the United States. Nephrology. 2021 Nov;26(11):879-889. doi:10.1111/nep.13938
Gosselink ME, van Buren MC, Kooiman J, et al. A nationwide Dutch cohort study shows relatively good pregnancy outcomes after kidney transplantation and finds risk factors for adverse outcomes. Kidney Int. 2022 Oct;102(4):866-875. doi:10.1016/j.kint.2022.06.006
van Buren MC, Gosselink M, Groen H, et al. Effect of pregnancy on eGFR after kidney transplantation: A national cohort study. Transplantation. 2022 Jun; 106(6):1262-1270. Published online August 27, 2022. doi:10.1097/TP.0000000000003932
Jesudason S and Piccoli GB. Pregnancy outcomes after kidney transplantation: the challenges of success. Kidney Int. 102(4):697-699. doi:10.1016/j.kint.2022.08.007
Meinderts JR, Schreuder MF, de Jong MFC. Pregnancy after kidney transplantation: more attention is needed for long-term follow-up of the offspring. Kidney Int. 2022 Nov;102(5):1190-1191. doi:10.1016/j.kint.2022.08.015
Jesudason S, Williamson A, Huuskes B, Hewawasam E. Parenthood with kidney failure: Answering questions patients ask about pregnancy. Kidney Int Rep. Published online April 29, 2022. doi:10.1016/j.ekir.2022.04.081