Johannes Keunen

Johannes Keunen
Mount Sinai Hospital, Toronto · OB/Gyn

MD PhD

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54
Publications
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Introduction
Skills and Expertise

Publications

Publications (54)
Article
Background: Doppler ultrasound measurements of the peak systolic velocity of the middle cerebral artery can be used to noninvasively diagnose fetal anemia but are less precise following fetal blood transfusion and in late gestation. We have previously demonstrated the feasibility of estimating fetal hematocrit in vitro using magnetic resonance ima...
Article
Microcystic congenital cystic adenomatoid malformations (CCAM), when associated with hydrops, carry a dismal prognosis. Options for treatment are limited and experimental, including antenatal corticosteroids, open fetal surgery, laser ablation and, more recently, sclerotherapy. We describe a case of a large, predominantly microcystic CCAM in a hydr...
Article
Objectives To evaluate the impact of introduction of non-invasive prenatal testing (NIPT) on the uptake of invasive testing in pregnancies complicated by fetal central nervous system (CNS) anomalies. Methods Retrospective review of all singleton pregnancies complicated by fetal CNS anomalies seen at a single tertiary center between 2010 and 2017....
Article
Objective: To evaluate the impact of introduction of noninvasive prenatal testing (NIPT) on the uptake of invasive testing in pregnancies complicated by fetal central nervous system (CNS) anomalies. Methods: Retrospective review of all singleton pregnancies complicated by fetal CNS anomalies seen at a single tertiary center between 2010 and 2017...
Article
Objectives: To delineate the etiology and outcome of prenatally diagnosed isolated bilateral hyperechogenic kidneys (IBHK). Study design: Pregnancies with IBHK on prenatal ultrasound identified and followed by us between January 1, 2000 and January 1, 2015 were evaluated regarding the etiology and outcome by evaluation of family history, targete...
Article
The introduction of chromosomal microarray (CMA) into the prenatal setting has involved considerable deliberation due to the wide range of possible outcomes (e.g., copy number variants of uncertain clinical significance). Such issues are typically discussed in pre-test counseling for pregnant women to support informed decision-making regarding pren...
Article
Objectives The detection of fetal anemia by middle cerebral artery peak systolic velocity is less reliable with advancing gestational age (GA) and prior transfusion. We sought to investigate the feasibility and accuracy of a new MRI method for measuring fetal hematocrit (Hct) in vivo in anemic fetuses. Methods We recruited 4 pregnant women suspec...
Article
Congenital limb deficiency defects (LDDs) are etiologically heterogeneous. Acquired causes include amniotic bands, teratogens exposure, and chorionic villus sampling before 10 weeks' gestation and intrinsic causes include single-gene disorders and chromosome abnormalities. However, a substantial number of cases, especially terminal transverse defic...
Article
Background: Late-onset intrauterine growth restriction (IUGR) results from failure of the placenta to supply adequate nutrients and oxygen to the rapidly growing late gestation fetus. Limitations in current monitoring methods present the need for additional techniques for more accurate diagnosis of IUGR in utero. New magnetic resonance imaging (MR...
Article
Full-text available
Fetal infection with human parvovirus B19 (hParvo-B19) has been mainly associated with fetal anemia, while data regarding other fetal hematological effects are limited. Our aim was to assess the rate and consequences of severe fetal thrombocytopenia following fetal hParvo-B19 infection. We conducted a retrospective study of pregnancies complicated...
Conference Paper
Congenital limb reduction defects (LRDs) comprise an etiologically hetero- geneous group of conditions caused by amniotic bands, early chorionic villus sampling, single-gene disorders, chromosome abnormalities, and teratogen exposure. However, a substantial number of cases occur without an obvious cause. Vascular disruption events may be responsibl...
Article
To evaluate the incidence and consequences of "misdiagnosed" cases of twin-twin transfusion syndrome (TTTS). Chorionicity and referral diagnoses were reviewed in pregnant women with monochorionic twin pregnancies complicated by TTTS treated by fetoscopic laser ablation. "Misdiagnosed" cases, defined as failure to correctly identify chorionicity and...
Article
Both "early" (< 16 weeks' gestation) and "late" (> 26 weeks' gestation) presentations of twin-twin transfusion syndrome (TTTS) are rare and challenging complications of monochorionic/diamniotic twin pregnancies. Growing evidence suggests that fetoscopic laser therapy for both "early" and "late" TTTS is feasible, safe, and yields similar outcomes to...
Article
What's already known about this topic? Monochorionic pregnancies are 1/200 pregnancies, one in seven of whom will develop twin-twin transfusion syndrome (TTTS)TTTS is usually lethal to both twins if untreated. Timely fetoscopic laser ablation of the 'culprit' placental anastomoses is curative What does this study add?Surveillance is the chorionicit...
Article
Full-text available
Pregnancy is rare in women with ESRD and when it occurs, it is often accompanied by significant maternal and fetal morbidity and even mortality. Preliminary data from the Toronto Nocturnal Hemodialysis Program suggested that increased clearance of uremic toxins by intensified hemodialysis improves pregnancy outcomes, but small numbers and the absen...
Article
To review fetal and maternal outcomes after management of the compromised perinatal airway via operation on placental support (OOPS) or ex utero intrapartum treatment (EXIT). To discuss implications for future management of these complex and rare cases. Retrospective case series of 12 fetuses requiring airway management on placental support at a si...
Article
Background: Pregnancy in a rudimentary uterine horn is a rare form of ectopic pregnancy with a high risk of rupture. Management usually involves excision of the rudimentary horn. If diagnosed after the first trimester, it has been managed in the past by laparotomy. Case: A primigravid woman was found on routine ultrasound to have a rudimentary h...
Article
Pregnancy in patients with ESRD is rare and remains especially challenging. Because endocrine abnormalities and sexual dysfunction decrease fertility, conception rates have been remarkably low in this patient population. Moreover, when pregnancy does occur, hypertension, preeclampsia, anemia, intrauterine growth restriction, preterm delivery, still...
Article
Objective: Women with spinal cord lesions present special challenges during pregnancy. We studied their pregnancy outcomes with regard to medical, obstetrical, and social concerns. Methods: We reviewed the records of pregnant women with spinal cord injury who attended our institution between 1999 and 2009. Results: Thirty-two women with a tota...
Article
Objective: The purpose of this study was to compare perinatal outcomes of pregnancies that undergo "early" (<17 weeks' gestation) or "late" (>26 weeks' gestation) fetoscopic laser ablation of placental vascular anastomoses for twin-twin transfusion syndrome (TTTS) with "conventional" cases that were treated at 17-26 weeks' gestation. Study design...
Article
The ovulatory menstrual cycle is known to be affected on multiple levels in women with advanced renal disease. Menstrual irregularities, sexual dysfunction, and infertility worsen in parallel with the renal disease. Pregnancy in women with ESRD on dialysis is therefore uncommon. Furthermore, when pregnancy does occur, it can prove hazardous to both...
Article
To conduct a pilot randomized controlled trial of unfractionated heparin (UFH) in women considered at high risk of placental insufficiency in the second trimester. Women with either false-positive first trimester (pregnancy-associated placental protein-A [PAPP-A] < 0.35 MoM) or second trimester (alpha-fetoprotein [AFP] > 2.0 MoM, inhibin > 3.0 MoM,...
Article
Congenital megalourethra is a rare urogenital malformation characterized by dilation and elongation of the penile urethra associated with absence or hypoplasia of the corpora spongiosa and cavernosa. Postnatal complications include voiding and erectile dysfunction as well as renal insufficiency and pulmonary hypoplasia. To date, only a few prenatal...
Article
Complicating up to 8% of pregnancies, preeclampsia is, in fact, the most common glomerular disease worldwide. In this article, we review the effect of normal pregnancy on the kidney as well as the role of the kidney in preeclampsia. We discuss blood pressure in pregnancy and preeclampsia, followed by the physiology of hyperfiltration in normal preg...
Article
To review the performance of a variety of biometry formulae for estimated fetal weight (EFW) in the management of severely growth restricted fetuses with abnormal umbilical artery Doppler at a single perinatal institution. Forty-three pregnancies were retrospectively reviewed. Inclusion criteria were: chromosomally/ structurally normal fetus; compl...
Article
An otherwise healthy 31-year-old gravida 2 para 1 woman with a spontaneous dichorionic, diamniotic twin pregnancy presented with hypertension, nephrotic syndrome and renal insufficiency at 19 weeks' gestation. Fetal ultrasound revealed severe intrauterine growth restriction of one fetus and measurement of serum anti-angiogenic and angiogenic factor...
Article
The congenital myasthenia syndromes form a heterogeneous group of genetic diseases characterized by defective neuromuscular transmission. Although they have muscle fatigability in common with the acquired immune myasthenia syndrome, there are important pathophysiological, diagnostic, management and progression pattern differences between them. We r...
Article
Women of childbearing age on conventional hemodialysis (CHD) have decreased fertility when compared with the general population. Even in women who conceived, maternal morbidity and fetal mortality remained elevated. We hypothesized that nocturnal hemodialysis (NHD) (3 to 6 sessions per week, 6 to 8 h per treatment), by augmenting uremic clearance,...

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