Preeclampsia and the risk of chronic kidney disease: a national registry-based cohort study

Background

Preeclampsia is associated with increased risk of future cardiovascular disease, but evidence for associations with chronic kidney disease (CKD) has been inconsistent to date. We aimed to measure associations between preeclampsia and long-term CKD in a population-based sample of parous women, and to identify whether the risk differs by CKD subtype.

Methods

Using data from the Swedish Medical Birth Register, singleton live births from 1973-2012 were identified and linked to data from the Swedish Renal Register and National Patient Register (up to 2013). Preeclampsia was the main exposure of interest and was treated as a time-dependent variable. The primary outcome was maternal CKD, and this was classified into 5 subtypes: hypertensive, diabetic, glomerular/proteinuric, tubulo-interstitial, other/non-specific CKD. Cox proportional hazard regression models were used for analysis. Women with pre-pregnancy comorbidities were excluded.

Results

The dataset included 1,924,591 unique women who had 3,726,819 singleton pregnancies. The median follow-up was 20.7 (interquartile range 9.9-30.0) years. Overall, 90,964 women (4.7%) experienced preeclampsia and 18,146 (0.9%) developed CKD. Women who had preeclampsia had higher risk of developing any CKD during follow-up (aHR 1.88, 95% CI 1.79-1.98). The risk differed by CKD subtype, and was higher for hypertensive CKD (aHR 3.76, aHR 3.09-4.57), diabetic CKD (aHR 3.45, 95% CI 2.83-4.21) and glomerular/proteinuric CKD (aHR 2.08, 95% CI 1.90-2.29). Women who had preterm preeclampsia, recurrent preeclampsia, or preeclampsia complicated by pre-pregnancy obesity were also at greater risk of any CKD.

Conclusions

Women with a history of preeclampsia are at increased risk of long-term CKD. The risk is most marked for hypertensive CKD, diabetic CKD, and glomerular/proteinuric CKD. The absolute risk of CKD related to preeclampsia is substantial, and these women may warrant systematic renal monitoring in the years following delivery.

Key messages

Preeclampsia is an independent predictor of long-term risk of chronic kidney disease in otherwise healthy parous women. Women with a history of preeclampsia may warrant systematic renal monitoring through additional blood pressure, blood glucose, and proteinuria checks.

Adverse pregnancy outcomes and long-term risk of maternal renal disease: a systematic review

Background

Little is known about the long-term risk of renal disease following adverse pregnancy outcomes, such as hypertensive disorders of pregnancy (HDP), gestational diabetes (GDM) or preterm delivery. We aimed to investigate associations between adverse pregnancy outcomes and maternal chronic kidney disease (CKD) and end-stage kidney disease (ESKD), by synthesising results of relevant studies.

Methods

A systematic search of PubMed, EMBASE and Web of Science was done up to July 2018. Case-control and cohort studies were eligible for inclusion if they provided original effect estimates for associations between adverse pregnancy outcomes (HDP, GDM, preterm) and maternal renal disease (primary outcomes: CKD, ESKD; secondary outcomes: renal hospitalisation, renal mortality). Two independent reviewers extracted data and assessed risk of bias. Random effects meta-analyses were conducted to determine pooled adjusted odds ratio (AOR) and 95% confidence interval (95%CI) for each association.

Results

Of 5,120 studies retrieved, 21 studies met inclusion criteria (4,483,847 participants). HDP was associated with increased odds of ESKD (AOR 6.58, 95%CI 4.06-10.65), CKD (AOR 2.08, 95%CI 1.06-4.10), renal hospitalisation (AOR 2.29, 95%CI 1.42-3.71). The magnitude of association was dependent on HDP subtype: AOR for preeclampsia and ESKD was 4.87 (95%CI 3.01-7.87); gestational hypertension and ESKD was 3.65 (95%CI 2.34-5.67); other HDP (including chronic hypertension) and ESKD was 14.67 (95%CI 3.21-66.97). Preterm delivery was associated with increased odds of ESKD (AOR 2.16, 95%CI 1.64-2.85). GDM was associated with increased odds of CKD among black women (AOR 1.78, 95%CI 1.18-2.70), but not Caucasian women (AOR 0.81, 95%CI 0.58-1.13)

Conclusions

Women who experience adverse pregnancy outcomes have increased odds of renal disease, especially after HDP. Risk stratification and preventive interventions may be needed to reduce the risk of clinically significant renal disease in mothers.

Key messages

This is the first study to summarise the long-term risk of renal disease among women who experience a range of adverse pregnancy outcomes. Women who experience hypertensive disorders in pregnancy, preterm delivery, or gestational diabetes are at increased odds of renal disease.

Preterm delivery is associated with long-term risk of maternal renal disease

Background

Preterm delivery is an independent risk factor for maternal cardiovascular disease. Little is known about the association between preterm delivery and maternal renal function, and whether any association is independent of preeclampsia or intra-uterine growth restriction. This study aimed to examine the association between gestational age and long-term maternal chronic kidney disease (CKD) and end-stage kidney disease (ESKD).

Methods

Using data from the Swedish Medical Birth Register, singleton live births from 1973-2012 were identified and linked to data from the Swedish Renal Register and National Patient Register (up to 2013). Women with pre-pregnancy CKD/ESKD, cardiovascular disease, diabetes, hypertension, systemic lupus erythematosus were excluded. Gestational age at delivery was the main exposure, treated as a time-dependent variable. Primary outcomes were maternal CKD or ESKD. Cox regression was used, adjusting for maternal age, year of delivery, country of origin, education, parity, interpregnancy interval, smoking, BMI, gestational diabetes. Models were stratified by exposure to preeclampsia or small for gestational age (SGA).

Results

There were 3,847,694 pregnancies among 1,990,273 unique women. Nine percent of women (n = 172,915) had at least one preterm delivery (<37 weeks). Exposure to preterm delivery was associated with higher risk of CKD (aHR 1.48, 95%CI 1.41-1.54) and ESKD (aHR 2.52, 95%CI 2.17-2.92). Earlier gestational age at delivery was associated with increasing risk of CKD and ESKD. Women with spontaneous preterm delivery were at higher risk of CKD (vs. normal term, aHR 1.33, 95% CI 1.26-1.40) and ESKD (aHR 2.02, 95%CI 1.69-2.40) independently of preeclampsia/SGA. Associations persisted after excluding women who developed postpartum cardiovascular disease, hypertension or diabetes.

Conclusions

Women who gave birth at earlier gestation were at higher risk of later CKD and ESKD. This association persisted independently of preeclampsia and SGA.

Key messages

Preterm delivery is an independent predictor of long-term maternal renal disease. Obstetric history should be considered as part of overall risk stratification for chronic kidney disease in women.

Simulator training in fetoscopic laser surgery for twin-twin transfusion syndrome: a pilot randomized controlled trial

OBJECTIVE

To evaluate the effect of a newly developed training curriculum on the performance of fetoscopic laser surgery for twin-twin transfusion syndrome (TTTS) using an advanced high-fidelity simulator model.

METHODS

Ten novices were randomized to receive verbal instructions and either skills training using the simulator (study group; n = 5) or no training (control group; n = 5). Both groups were evaluated with a pre-training and post-training test on the simulator. Performance was assessed by two independent observers and comprised a 52-item checklist for surgical performance (SP) score, measurement of procedure time and number of anastomoses missed. Eleven experts set the benchmark level of performance. Face validity and educational value of the simulator were assessed using a questionnaire.

RESULTS

Both groups showed an improvement in SP score at the post-training test compared with the pre-training test. The simulator-trained group significantly outperformed the control group, with a median SP score of 28 (54%) in the pre-test and 46 (88%) in the post-test vs 25 (48%) and 36 (69%), respectively (P = 0.008). Procedure time decreased by 11 min (from 44 to 33 min) in the study group vs 1 min (from 39 to 38 min) in the control group (P = 0.69). There was no significant difference in the number of missed anastomoses at the post-training test between the two groups (1 vs 0). Subsequent feedback provided by the participants indicated that training on the simulator was perceived as a useful educational activity.

CONCLUSIONS

Proficiency-based simulator training improves performance, indicated by SP score, for fetoscopic laser therapy. Despite the small sample size of this study, practice on a simulator is recommended before trainees carry out laser therapy for TTTS in pregnant women.

Routine ultrasound examination at 12 or 18 gestational weeks for prenatal detection of major congenital heart malformations? A randomised controlled trial comprising 36,299 fetuses

OBJECTIVE

To compare the rate of prenatal diagnosis of heart malformations between two policies of screening for heart malformations.

DESIGN

Randomised controlled trial.

SETTING

Six university hospitals, two district general hospitals.

SAMPLE

A total of 39 572 unselected pregnancies randomised to either policy.

METHODS

The 12-week policy implied one routine scan at 12 weeks including measurement of nuchal translucency (NT), and the 18-week policy implied one routine scan at 18 weeks. Fetal anatomy was scrutinised using the same check-list in both groups, and in both groups, indications for fetal echocardiography were ultrasound findings of any fetal anomaly, including abnormal four-chamber view, or other risk factors for heart malformation. In the 12-week scan group, NT >or=3.5 mm was also an indication for fetal echocardiography.

MAIN OUTCOME MEASURE

Prenatal diagnosis of major congenital heart malformation.

RESULTS

In the 12-week scan group, 7 (11%) of 61 major heart malformations were prenatally diagnosed versus 9 (15%) of 60 in the 18-week scan group (P= 0.60). In four (6.6%) women in the 12-week scan group, the routine scan was the starting point for investigations resulting in a prenatal diagnosis versus in 9 (15%) women in the 18-week scan group (P=0.15). The diagnosis was made <or=22 weeks in 5% (3/61) of the cases in the 12-week scan group versus in 15% (9/60) in the 18-week scan group (P=0.08).

CONCLUSIONS

The prenatal detection rate of major heart malformations was low with both policies. The 18-week scan policy seemed to be superior to the 12-week scan policy, although the differences in prenatal detection rates were not statistically significant.

Detection of malformations in chromosomally normal fetuses by routine ultrasound at 12 or 18 weeks of gestation-a randomised controlled trial in 39,572 pregnancies

OBJECTIVE

To compare the antenatal detection rate of malformations in chromosomally normal fetuses between a strategy of offering one routine ultrasound examination at 12 gestational weeks (gws) and a strategy of offering one routine examination at 18 gws.

DESIGN

Randomised controlled trial.

SETTING

Multicentre trial including eight hospitals.

POPULATION

A total of 39,572 unselected pregnant women.

METHODS

Women were randomised either to one routine ultrasound scan at 12 (12-14) gws including nuchal translucency (NT) measurement or to one routine scan at 18 (15-22) gws. Anomaly screening was performed in both groups following a check-list. A repeat scan was offered in the 12-week scan group if the fetal anatomy could not be adequately seen at 12-14 gws or if NT was >or=3.5 mm in a fetus with normal or unknown chromosomes.

MAIN OUTCOME MEASURES

Antenatal detection rate of malformed fetuses.

RESULTS

The antenatal detection rate of fetuses with a major malformation was 38% (66/176) in the 12-week scan group and 47% (72/152) in the 18-week scan group (P= 0.06). The corresponding figures for detection at <22 gws were 30% (53/176) and 40% (61/152) (P= 0.07). In the 12-week scan group, 69% of fetuses with a lethal anomaly were detected at a scan at 12-14 gws.

CONCLUSIONS

None of the two strategies for prenatal diagnosis is clearly superior to the other. The 12-week strategy has the advantage that most lethal malformations will be detected at <15 gws, enabling earlier pregnancy termination. The 18-week strategy seems to be associated with a slightly higher detection rate of major malformations, although the difference was not statistically significant.

Ultrasound dating at 12-14 weeks of gestation. A prospective cross-validation of established dating formulae in in-vitro fertilized pregnancies

OBJECTIVES

To determine the accuracy of established ultrasound dating formulae when used at 12-14 weeks of gestation.

METHODS

One-hundred and sixty-seven singleton pregnancies conceived after in-vitro fertilization (IVF) underwent a dating scan at 12-14 weeks of gestation. Gestational age at the dating scan was calculated by adding 14 days to the number of days between the date of oocyte retrieval and the date of the ultrasound scan. Gestational age according to oocyte retrieval was regarded as the true gestational age. True gestational age was compared to gestational age calculated on the basis of 21 dating formulae based on fetal crown-rump length (CRL) measurements and to three dating formulae based on fetal biparietal diameter (BPD) measurements. In a previous study the three BPD formulae tested here had been shown to be superior to four other BPD formulae when used at 12-14 weeks of gestation. The mean of the differences between estimated and true gestational age and their standard deviation (SD) were calculated for each formula. The SD of the differences was assumed to reflect random measurement error. Systematic measurement error was assumed to exist if zero lay outside the mean difference+/-2SE (SE: standard error of the mean).

RESULTS

The three best CRL formulae were associated with mean (non-systematic) measurement errors of -0.0, -0.1 and -0.3 days, and the SD of the measurement errors of these formulae varied from 2.37 to 2.45. All but two of the remaining CRL formulae were associated with systematic over- or under-estimation of gestational age, and the SDs of their measurement error varied between 2.25 and 4.86 days. Dating formulae using BPD systematically underestimated gestational age by -0.4 to -0.7 days, and the SDs of their measurement errors varied from 1.86 to 2.09.

CONCLUSIONS

We have identified three BPD formulae that are suitable for dating at 12-14 weeks of gestation. They are superior to all 21 CRL formulae tested here, because their random measurement errors were much smaller than those of the three best CRL formulae. The small systematic negative measurement errors associated with the BPD formulae are likely to be clinically unimportant.

Screening for Down syndrome based on maternal age or fetal nuchal translucency: a randomized controlled trial in 39,572 pregnancies

OBJECTIVES

Nuchal translucency (NT) screening increases antenatal detection of Down syndrome (DS) compared to maternal age-based screening. We wanted to determine if a change in policy for prenatal diagnosis would result in fewer babies born with DS.

METHODS

A total of 39,572 pregnant women were randomized to a scan at 12-14 gestational weeks including NT screening for DS (12-week group) or to a scan at 15-20 weeks with screening for DS based on maternal age (18-week group). Fetal karyotyping was offered if risk according to NT was > or = 1:250 in the 12-week group and if maternal age was > or = 35 years in the 18-week group. Both policies included the offer of karyotyping in cases of fetal anomaly detected at any scan during pregnancy or when there was a history of fetal chromosomal anomaly. The number of babies born with DS and the number of invasive tests for fetal karyotyping were compared.

RESULTS

Ten babies with DS were born alive with the 12-week policy vs. 16 with the 18-week policy (P = 0.25). More fetuses with DS were spontaneously lost or terminated in the 12-week group (45/19,796) than in the 18-week group (27/19 776; P = 0.04). All women except one with an antenatal diagnosis of DS at < 22 weeks terminated the pregnancy. For each case of DS detected at < 22 weeks in a living fetus there were 16 invasive tests in the 12-week group vs. 89 in the 18-week group. NT screening detected 71% of cases of DS for a 3.5% test-positive rate whereas maternal age had the potential of detecting 58% for a test-positive rate of 18%.

CONCLUSIONS

The number of newborns with DS differed less than expected between pregnancies that had been screened at 12-14 weeks' gestation by NT compared with those screened at 15-20 weeks by maternal age. One explanation could be that NT screening--because it is performed early in pregnancy--results in the detection and termination of many pregnancies with a fetus with DS that would have resulted in miscarriage without intervention, and also by many cases of DS being detected because of a fetal anomaly seen on an 18-week scan. The major advantage of the 12-week scan policy is that many fewer invasive tests for fetal karyotyping are needed per antenatally detected case of DS.

Ultrasound dating at 12-14 or 15-20 weeks of gestation? A prospective cross-validation of established dating formulae in a population of in-vitro fertilized pregnancies randomized to early or late dating scan

OBJECTIVES

To determine the accuracy of established ultrasound dating formulae when used at 12-14 and 15-20 gestational weeks.

METHODS

A total of 363 singleton pregnancies conceived after in-vitro fertilization (IVF) and randomized to a dating scan at 12-14 or 15-20 gestational weeks were studied. 'True' gestational age was calculated on the basis of the day of oocyte retrieval and was compared to gestational age calculated on the basis of seven dating formulae including the fetal biparietal diameter (BPD) and three dating formulae including BPD and fetal femur length (FL). The mean of the differences between estimated and true gestational age (systematic measurement error) and their SD (random measurement error) were calculated for each formula.

RESULTS

Three formulae showed systematic errors of less than -0.7 days at both early and late scanning. Two formulae overestimated gestational age at both early and late scanning by 5.7 and 3.1 vs. 2.3 and 2.8 days, respectively, while five formulae manifested very different systematic errors at early and late scanning. The formulae used for clinical management underestimated gestational age by a mean of 3 days when dating was performed at 12-14 weeks, and by a mean of 0.8 days when dating was done at 15-20 weeks. The random error was on average 1 day less when the scan was carried out early (2 vs. 3 days; P < 0.0005). Mean true gestational age at delivery in IVF pregnancies with spontaneous start of labor was 279 days (SD 12.9); excluding preterm deliveries it was 281 days (SD 8.1).

CONCLUSIONS

Ultrasound dating formulae originally intended for use in the middle of the second trimester do not necessarily perform well when used for dating earlier in gestation. The systematic and random error of any dating formula must be assessed for the gestational age interval in which the formula is intended to be used.

Predictive value of fetal scalp blood lactate concentration and pH as markers of neurologic disability

OBJECTIVES

We aimed to analyze the predictive value of the fetal scalp blood lactate concentration and pH, especially in regard to outcome variables that are strong predictors of impaired long-term outcome. An additional aim was to establish cutoff lactate levels in fetal scalp blood.

STUDY DESIGN

We conducted a retrospective study of all patients who had fetal scalp blood sampling performed because of an ominous fetal heart rate pattern at Huddinge University Hospital from October 1993 to October 1998. Fetal scalp blood sampling was performed in 1709 patients. The pH and the lactate concentration were determined in fetal scalp blood of 1221 and 814 of these patients, respectively. Outcome variables included pH <7.0 in umbilical artery blood; base deficit >16.0 mmol/L in umbilical artery blood; Apgar scores <7 at 1 minute, <7 at 5 minutes, and <4 at 5 minutes; and hypoxic-ischemic encephalopathy.

RESULTS

Sensitivity and specificity were generally higher in the lactate group than in the pH group, particularly in relation to an Apgar score <4 at 5 minutes and moderate to severe hypoxic-ischemic encephalopathy. In 326 patients the scalp blood lactate concentration and pH value had been obtained at the same time, thus allowing a comparison between these methods. The areas under the receiver operating characteristic curves were significantly higher for the lactate concentration than for the pH value with 2 outcome variables: Apgar score <4 at 5 minutes (P =.033) and moderate to severe hypoxic-ischemic encephalopathy (P =.015).

CONCLUSIONS

Our findings suggest that determination of the lactate concentration in fetal scalp blood is a more sensitive diagnostic tool than is determination of the pH value for predicting either an Apgar score <4 at 5 minutes or moderate to severe hypoxic-ischemic encephalopathy. In previous studies we also showed lactate measurements to be more often successful than pH analysis. Therefore we consider the measurement of lactate in fetal scalp blood to be an attractive alternative to pH analysis, and determination of the lactate concentration in fetal scalp blood seems to be a useful tool for monitoring the condition of the fetus. A suitable cutoff limit for fetal scalp blood lactate concentration as an indicator of fetal asphyxia could be 4.8 mmol/L.

Role of lactate measurements during labor

Lactate can safely and easily be determined in fetal scalp and umbilical artery blood with a new microvolume (5 microliters) lactate meter. Comparison between lactate and pH in scalp blood revealed a significant correlation (r = -0.43; P < .001). In a management trial where scalp lactate was compared to scalp pH, the lactate group underwent significantly more successful blood sampling procedures and fewer number of scalp incisions per blood sampling attempt. The mode of delivery and neonatal outcome were similar in patients managed with lactate and those using pH. Lactate concentration in umbilical artery blood had the same predictive properties as pH or base deficit in relation to poor neonatal outcome. Our data suggest that this method for lactate determination is robust and feasible and is suitable as a tool for fetal monitoring. Additional clinical management trials will be required to define the clinical usefulness of this method and how it should be combined with other modalities for fetal monitoring.

Lactate in scalp and cord blood from fetuses with ominous fetal heart rate patterns

OBJECTIVE

We investigated lactate concentrations in fetal scalp and cord blood to determine the sources of fetal lactacidosis in fetuses with ominous heart rate patterns.

METHODS

Cord blood was collected from newly delivered infants who had been monitored by fetal scalp blood sampling during labor. In 250 cases umbilical arterial and venous cord blood lactate levels were measured. We assessed the umbilical arterial lactate concentrations in relation to the venous lactate levels, the arterial pH level, base excess, and arteriovenous lactate differences in cord blood. In 103 cases the levels of lactate in fetal scalp blood, sampled within 60 minutes of delivery, were compared with those in the umbilical artery and vein and the pH level and base excess immediately after birth.

RESULTS

Lactate level in the umbilical artery showed a significant correlation to that in umbilical venous blood (r = .84, P < .001), to arteriovenous lactate differences (r = .52, P < .001), as well as to pH (r = -.55, P < .001) and base excess (r = -.63, P < .001) in arterial cord blood. Lactate concentrations in fetal scalp blood shortly before delivery showed a significant correlation to lactate levels in the umbilical arterial (r = .65, P < .001) and venous blood (r = .62, P < .001).

CONCLUSION

The study indicates a close correlation between lactate levels in arterial and venous cord blood, as well as between the lactate levels and pH and base excess in cord arterial blood in patients with ominous fetal heart rate patterns. We also found an increased fetal contribution with increasing lactacidemia. Lactate concentrations in fetal scalp blood correlated well with those in cord arterial and venous blood.

[Successively improved prognosis in erythrocyte immunization]

Prognosis in cases of erythrocyte immunisation has improved continuously over the past decades. Morbidity and mortality have been reduced by improvements in management, including screening programmes, non-invasive ultrasound evaluation and invasive procedures. The article provides an outline of the latest developments in the management of erythrocyte immunisation, and several controversial issues are discussed, such as antibody screening, strategies for the reduction of antibody titres, and the organisation of care.

Lactate compared with pH analysis at fetal scalp blood sampling: a prospective randomised study

OBJECTIVE

Fetal scalp blood sampling is a widely used method for assessing fetal condition in the event of ominous fetal heart rate patterns. The purpose of this randomised trial was to compare the value of fetal scalp blood lactate and pH management in cases of abnormal intrapartum fetal heart rate tracings.

METHODS

Of 341 cases of ominous fetal heart rate patterns, 169 were randomly assigned to pH analysis, and 172 to lactate measurements. Lactate was measured using a lactate card requiring 5 microL of blood and yielding the result within 60 seconds. pH analysis was performed with an ABL 510 acid-base analyser requiring 35 microL of blood and yielding the results within 47 seconds.

RESULTS

Unsuccessful fetal blood sampling procedures (no result or an unreliable result) occurred significantly more often in the pH subgroup than in the lactate subgroup (OR 16.1 with 95% CI 5.8-44.7). In the pH subgroup the failure rate was inversely related to the degree of cervical dilatation. Compared with the pH subgroup, the lactate subgroup was characterised by fewer fetal scalp incisions per blood sampling attempt (median 1.0 [interquartile range (IQR) 1-1] vs 2.0 [IQR 1-2]), and significantly less time required for the sampling procedure (median 120 s [IQR 90-147] vs 230 s [IQR 180-300]). The groups did not differ in mode of delivery, neonatal outcome and umbilical artery acid-base balance and lactate levels.

CONCLUSION

This trial showed the levels of lactate and pH in fetal scalp blood to be comparable in predicting perinatal outcome, but the procedure to measuring lactate was more successful than that for pH. Owing to its simplicity of performance, lactate analysis is an attractive alternative for intrapartum fetal monitoring.

A comparison of myogenic and endothelial properties of myometrial and omental resistance vessels in late pregnancy

OBJECTIVE

Our purpose was to compare myometrial and omental resistance arteries from term pregnant women with respect to myogenic behavior in the presence or absence of a nitric oxide synthase inhibitor and to compare distensibility and acetylcholine-mediated dilatation in these vessels.

STUDY DESIGN

Intramyometrial (n = 17) and omental (n = 14) resistance arteries from term normal pregnant women were studied in a pressurized arteriograph system. Myogenic tone was evaluated during increments in intraluminal pressure from 20 to 120 mm Hg with and without inhibition of nitric oxide synthase. Endothelium-dependent relaxation was assessed by evaluating the response to acetylcholine (10(-6) mol/L) in arteries pressurized at 70 mm Hg.

RESULTS

Myogenic tone was greater at all pressure steps in the myometrial than in the omental arteries (p < 0.05). Inhibition of nitric oxide synthase with N(omega)-nitro-L-arginine had no influence on myogenic tone in either group. Relaxation to acetylcholine was greater in myometrial (18% +/- 4%) compared with omental vessels (7% +/- 2%, p < 0.05). The passive distensibility (Ca++-free solution and in the presence of papaverine) of arteries from the myometrium and the omentum was similar.

CONCLUSION

Normal pregnancy is associated with different mechanical properties of resistance vessels from the two vascular beds studied. Basal nitric oxide release does not modify myogenic tone, at least under no-flow conditions. Acetylcholine-induced relaxation is greater in myometrial than in omental arteries.

Maternal renal artery blood flow velocimetry in normal and hypertensive pregnancies

OBJECTIVE

To investigate the effect of normal pregnancy and hypertensive disorders of pregnancy on the maternal renal artery Doppler blood flow velocity indices.

METHODS

The patient material consisted of 30 normal pregnant women, 29 women with pregnancy induced hypertension, 43 women with preeclampsia and 22 pregnant women with chronic hypertension. Blood flow velocities in the segmental renal arteries from the right kidney were analysed by pulsed and color Doppler. The systolic/diastolic (s.d.) ratio, resistance index (RI) and pulsatility index (PI) were used for Doppler waveform analysis.

RESULTS

In all of the groups of hypertensive pregnant women renal artery Doppler indices were significantly lower compared to the normal pregnant women group. There was a significant negative relationship between renal artery PI and mean arterial pressure in the preeclampsia group and in the chronic hypertension group.

CONCLUSION

The present results demonstrate that the mechanism of renal autoregulation in preeclampsia might be altered, leaving glomerulus unprotected from increased blood pressure. It seems that the concept of renal vasoconstriction in preeclampsia might be disputed and needs further investigation.

Effects of endothelin-1 and the ETA receptor antagonist BQ-123 on resistance arteries from normal pregnant and preeclamptic women

OBJECTIVE

To compare the effect of endothelin on isolated resistance arteries from different vascular beds in normal and preeclamptic women before and after pretreatment with the ETA receptor antagonist BQ-123.

MATERIALS AND METHODS

Resistance arteries from myometrial and omental biopsies obtained at cesarean section of normal pregnant and preeclamptic women were dissected and mounted in organ baths for recording of isometric tension. The contractile response to endothelin-1 in presence and absence of BQ-123 was recorded.

RESULTS

Endothelin-1 induced similar concentration-dependent contractions in all arteries investigated. In women with preeclampsia the contractile response induced by endothelin-1 was significantly higher in omental as compared to myometrial vessels. Pretreatment with BQ-123 significantly shifted the concentration-response curve to the right but only reduced the maximum contractile response in omental vessels.

CONCLUSION

Endothelin-1 is a potent constrictor of resistance arteries from different vascular beds in normal pregnancy and preeclampsia. The contractile effect is at least in part mediated by ETA receptors, since it was significantly reduced after pretreatment with BQ-123. In preeclamptic but not in normal pregnant women the response to endothelin-1 was reduced in myometrial as compared to omental arteries, possibly secondary to receptor down regulation.

Scalp blood lactate: a new test strip method for monitoring fetal wellbeing in labour

OBJECTIVE

To determine fetal scalp blood lactate with a new test strip method in parturients with normal and abnormal cardiotocograms during labour and to describe the relation to maternal lactate, fetal scalp blood pH, cord artery lactate and acid-base balance.

SETTING

Labour wards at the University Hospitals of Huddinge and Lund and at the County Hospital of Ostersund, Sweden.

MATERIALS AND METHOD

Fetal scalp blood was sampled for lactate (n = 269) and pH (n = 285) determination in 177 parturients with abnormal intrapartum CTG. Lactate and pH were also analysed in a group of 64 women with normal pregnancies and with a reactive fetal heart rate tracing prior to sampling of fetal scalp blood. At fetal blood sampling lactate was also determined in maternal capillary blood, while at birth lactate and acid-base balance in cord artery blood was performed in almost all cases.

MAIN OUTCOME MEASUREMENTS

Medians and percentiles (lactate and acid-base balance). Correlation between fetal scalp blood lactate (dependent) and scalp blood pH, cord artery blood lactate and acid-base parameters and labour time prior to fetal blood sampling.

RESULTS

In the group with abnormal cardiotocograms, fetal scalp and umbilical artery blood lactate and acid-base parameters differed significantly from the same parameters in the normal group. The fetal-maternal lactate gradient changed from negative in the normal group to positive in the fetal distress group. Multiple regression analysis, with scalp lactate as the dependent parameter, revealed a significant correlation with fetal scalp blood pH (P < 0.001) and umbilical artery lactate (P < 0.01).

CONCLUSIONS

Intrapartum scalp blood lactate was significantly correlated with pH and cord artery lactate. The results indicate that increased lactate levels in fetal blood sampling describes fetal lactacidosis. The new disposable test strip requiring only 5 microliters of blood for lactate determination may be better than traditional methods for monitoring fetal wellbeing in labour.

Routine measurements of umbilical artery lactate levels in the prediction of perinatal outcome

OBJECTIVE

Our purpose was to compare lactate levels with acid-base balance in the umbilical artery with respect to the prediction of pregnancy outcome.

STUDY DESIGN

A prospective study of 4045 cord samples was performed. Lactate was measured with a new method that requires 5 microliters of blood and provides the result within 1 minute.

RESULTS

The umbilical artery lactate concentrations were significantly elevated in instrumental deliveries (2.65 +/- 1.2 mmol/L) and in emergency cesarean sections (2.44 +/- 1.7 mmol/L) compared with spontaneous vaginal delivery (1.87 +/- 0.94 mmol/L) (p < 0.001, p < 0.001). Lactate correlated significantly to fetal pH, hemoglobin, base deficit, PCO2, and HCO3-. Lactate was comparable to pH and base deficit in sensitivity, specificity, and positive and negative predictive values in relation to morbidity and mortality.

CONCLUSION

Umbilical artery lactate concentration and acid-base balance predicted perinatal outcomes with similar efficacies; however, its simplicity makes lactate analysis an interesting alternative in obstetric care.

Effects of nitroglycerin on the uterine and umbilical circulation in severe preeclampsia

OBJECTIVE

To determine the effects of nitroglycerin on placental circulation in severe preeclampsia.

METHODS

Twelve women with severe preeclampsia were examined. Uterine and umbilical artery pulsatility indices (PI) were assessed by pulsed Doppler ultrasound before and after infusion of nitroglycerin, starting at 0.25 micrograms/kg per minute with stepwise dosage increases until a diastolic blood pressure (BP) of 100 mmHg was achieved. Blood pressure and heart rate were recorded every 5 minutes. Blood was sampled for analysis of the second messenger of nitric oxide, cyclic guanosine monophosphate (cGMP), before and at the end of the infusion.

RESULTS

During the infusion, the mean systolic BP decreased from 161 (95% confidence interval [CI] 154-169) to 138 mmHg (95% CI 131-146), and the diastolic pressure decreased from 116 (95% CI 111-122) to 103 (95% CI 96-110) mmHg (P < .01). The PI of the uterine artery did not change significantly (1.23 [95% CI 1.01-1.61]) versus 1.30 [95% CI 1.01-1.88]), whereas umbilical artery PI decreased significantly (P < .01), from 1.35 (95% CI 1.09-1.73) to 1.20 (95% CI 1.05-1.40), with a more pronounced decrease in patients with high basal values. Cyclic GMP remained essentially unchanged (6.4 [95% CI 5.4-7.7] versus 5.5 [4.7-6.6] nmol/L).

CONCLUSION

The reduction in the PI of the umbilical artery during nitroglycerin-induced BP reduction implies vasodilation in the umbilical circulation. The absence of an increase in cGMP does not support the view that the nitroglycerin effect is reflected by the plasma concentration of cGMP.

Continuous maternal glucose infusion during labor: effects on maternal and fetal glucose and lactate levels

Fetal and neonatal glucose and lactate levels and acid-base balance after continuous maternal infusion of 5% dextrose at 180 mL/h (9 g/h) was compared with 0.9% saline solution in a prospective, randomized study from selected monitored labors. An infusion of 5% dextrose produced significantly increased glucose levels in maternal (p < 0.01), cord artery (p < 0.01), and cord vein (p < 0.001) blood. An increased maternal insulin level was also present (p < 0.05), but no differences in cord insulin levels were observed. beta-Hydroxybutyrate was lower in maternal (p < 0.05) and cord vein (p < 0.01), but not in cord artery blood, after maternal dextrose infusion. No significant changes occurred in blood lactate levels between the two groups in either mother, fetus, cord, or neonate. Acid-base balance in cord blood did not differ between the two groups. Maternal infusion of 5% dextrose at 180 mL/h (9 g/h), compared with saline solution, produces higher glucose levels in both mother and fetus, but increased insulin concentrations only in the mother. Dextrose infusion also lowers beta-hydroxybutyrate in maternal and cord vein blood. No differences were seen in lactate levels or cord acid-base balance. Both regimens seem safe according to risks for lactacidosis and neonatal hypoglycemia in the normoxemic, normal size fetus.

Effects of atrial natriuretic peptide and cyclic guanosine monophosphate on isolated human myometrial arteries preconstricted by endothelin-1

In the present in vitro study we investigated the possible vasorelaxing effect of atrial natriuretic peptide (ANP) and cyclic guanosine monophosphate (cGMP) on small intramyometrial arteries precontracted by endothelin-1 (ET-1). Myometrial biopsies from normotensive pregnant women were obtained during cesarean section and arteries of resistance vessel size were dissected and mounted in a tissue chamber for isometric registration of contractile tone. In arteries preconstricted with ET-1 (10(-8)M), ANP produced a concentration-dependent relaxation of 19 +/- 5% (mean +/- SEM) and 27 +/- 7% at concentrations of 10(-7) and 3 x 10(-7) M, respectively. cGMP induced a relaxation of 13 +/- 2, 18 +/- 3, 25 +/- 4 and 30 +/- 7% at concentrations of 10(-5), 10(-4), 3 x 10(-4) and 10(-3) M, respectively. Pretreatment with ANP did not attenuate the contraction produced by ET-1. We suggest that ANP may have a vasodilating effect on preconstricted human uteroplacental vessels. It also provides evidence for the role of other endogenous or exogenous vasodilators acting via cGMP-dependent mechanisms in the counteraction of ET-1-induced contraction of the myometrial resistance vessels during pregnancy.

The interpretation of uterine artery pulsatility index in normal and hypertensive pregnancy

The Doppler flow velocity pulsatility index (PI) of the uteroplacental vascular bed is of debatable value for the interpretation of hemodynamic changes, when these are due both to pathological alterations in the vasculature, as in mild pre-eclampsia, and to physiological adjustments to vasoactive substances. The aim of this study was to apply a mathematical model, which includes maternal pulse pressure and mean arterial pressure, to the PI and to investigate whether this formula would add information with respect to discrimination between normal women and those with mild or severe pre-eclampsia. The subjects were patients with mild (n = 41) and severe (n = 34) pre-eclampsia and, as a control group, healthy pregnant women (n = 46). The uterine artery PI was studied by spectral Doppler analyses and compared to a P(z) value, theoretically representing a 'back pressure' in the uteroplacental circulation. Additionally, P(z) values were computed from earlier data concerning the dynamic circulatory effects of dihydralazine and acute volume expansion. The basal PI was significantly higher in the severely pre-eclamptic patients but not in the mildly pre-eclamptic patients compared to the controls. However, the P(z) was significantly higher in patients with both mild (p < 0.001) and severe pre-eclampsia (p < 0.0001) compared to the normal group. In the severely pre-eclamptic patients receiving dihydralazine, the P(z) tended to decrease (p = 0.07), in contrast to the volume-expansion group where P(z) was unaffected by the procedure. In conclusion, it seems that including measurement of the mean arterial pressure and pulse pressure with the PI adds valuable information about the circulatory status in this particular vasculature, regarding both 'basal' values and hemodynamic changes.

Possible improvement in uteroplacental blood flow during atrial natriuretic peptide infusion in preeclampsia

OBJECTIVE

To study the effects of low doses of the hormone atrial natriuretic peptide (ANP) on uteroplacental blood flow in patients with preeclampsia.

METHODS

Eleven women with preeclampsia were infused intravenously with ANP (10 ng/kg/minute). Uteroplacental blood flow index was measured using dynamic placental scintigraphy with indium-113m. Regional blood flows were assessed by pulsed Doppler ultrasound and expressed as pulsatility index (PI). Hemodynamic measurements and blood sampling for peripheral venous plasma analysis of cyclic guanosine monophosphate (cGMP), an ANP second messenger, were performed before and after 30 minutes of infusion. Nonparametric statistics were used.

RESULTS

The uteroplacental blood flow index increased by 28% (-2 to 58%; mean and 95% confidence interval). The Doppler findings were unaffected. Mean arterial blood pressure decreased from 112 (108-117) to 108 (103-114) mmHg (P < .01). Cyclic GMP increased significantly from 9.2 (6.2-12.3) to 17.4 (12.3-22.6) nmol/L (P < .01). Subjects exhibiting a substantial increase in uteroplacental blood flow index (25% or more) demonstrated a significantly greater cGMP response (P < .01) than those who did not (6% or less increase).

CONCLUSION

A tendency to an increased uteroplacental blood flow index combined with minor blood pressure reduction after ANP infusion suggest the possibility of uteroplacental vasodilatation.

Effects of isradipine on endothelin-induced constriction of myometrial arteries in normotensive pregnant women

The results of our previous studies suggested that endothelin-1 (ET-1) might be contributory to the impaired uteroplacental blood flow seen in preeclampsia. The aim of this study was to investigate the in vitro influence of isradipine on ET-1-induced contraction of myometrial resistance arteries from pregnant women, as these vessels are partly responsible for the regulation of uteroplacental blood flow in preeclampsia. Small myometrial arteries were dissected from myometrium obtained from 20 normotensive term pregnant women undergoing elective cesarean section and mounted in a tissue chamber. Tension was recorded isometrically. When ET-1 (10(-8) mol/L)-contracted vessels were exposed to increasing concentrations (10(-6), 10(-5), and 10(-4) mol/L) of isradipine, the myometrial arteries demonstrated essentially no relaxation. A significant mean relaxation of 31% was seen only with the highest isradipine concentration of 10(-3) mol/L. Pretreatment with isradipine attenuated ET-1-induced contraction by 26% at 3 x 10(-4) mol/L and by up to 80% at 10(-3) mol/L. Preincubation with lower concentrations of isradipine did not significantly reduce subsequent ET-1 contraction. The present study has thus shown that isradipine at high concentrations counteracts ET-1-induced constriction of myometrial arteries in term pregnant women. Pretreatment with isradipine at high concentrations attenuates the ET-1 contraction.

Acute volume expansion in normal pregnancy and preeclampsia. Effects on plasma atrial natriuretic peptide (ANP) and cyclic guanosine monophosphate (cGMP) concentrations and feto-maternal circulation

OBJECTIVE

To compare normal pregnancy with pregnancy-induced hypertension (PIH)/preeclampsia with respect to the effects of acute volume expansion on plasma atrial natriuretic peptide (ANP), cyclic guanosine monophosphate (cGMP) and fetal-maternal circulation.

DESIGN

Observational study.

SETTING

University hospital.

SUBJECTS

Fifteen women with PIH/preeclampsia and 15 healthy pregnant controls.

INTERVENTIONS

Before and after 30 minutes' infusion of a crystalloid solution (15 ml/kg), maternal venous blood was sampled for ANP and cGMP analysis and echocardiographic and Doppler investigations were performed.

RESULTS

Basal median (range) ANP and cGMP levels were significantly higher in the PIH/preeclampsia group compared to the controls: 6.5 (3.8-30.4) compared to 3.9 (2.0-6.7) pmol/l, p < 0.01 and 5.8 (2.4-11.6) compared to 4.0 (2.3-10.8) nmol/l, p < 0.05. The response to volume load was enhanced: 4.6 (-4.5-21.8) compared to 0.7 (-4.1-8.8), p < 0.05 and 2.9 (0.1-10.9) compared to 1.2 (-5.0-6.0), p < 0.05, respectively. Systemic vascular resistance was initially higher in the patient group, 22.3 (14.1-36.7) compared to 15.6 (10.0-25.5) peripheral resistance units, p < 0.01 but the response to volume load was similar in both groups (12-13% decrease). The pulsatility index of the uterine artery, 0.85 (0.46-1.38) compared to 0.72 (0.49-1.26) and umbilical artery 0.89 (0.66-1.57) compared to 0.97 (0.74-1.31) did not differ between the groups. Volume expansion did not affect any of these variables.

CONCLUSIONS

The pulsatility index of the uterine artery remained unaffected in both preeclamptic patients and healthy controls despite an increase of ANP and cGMP concentration and a systemic vasodilatation during acute volume expansion. This finding may indicate the absence of a vasodilation of the uteroplacental vascular bed.

Effect of variations of heart rate within the normal range on renal artery Doppler indices in nonpregnant and pregnant women

The effect of heart rate on Doppler indices in the renal artery was studied in 21 nonpregnant, 17 normal and 27 preeclamptic pregnant patients. The central hemodynamics was evaluated by Doppler ultrasound in all pregnant women. The study demonstrated no influence of heart rate on renal artery Doppler indices. Central hemodynamic parameters, such as cardiac output, stroke volume, mean arterial pressure and total systemic resistance did not change with increasing heart rate. We do not recommend any correction of the renal artery Doppler indices for heart rate in the range considered clinically normal (60 to 95 beats/min). Above or below this range further investigations are required to determine if corrections would be necessary.

The minimum number of cardiac cycles necessary for calculation of renal blood flow velocity indices in pregnant and non-pregnant women

In this study Doppler ultrasound was used to measure the blood flow velocity in the main and segmental renal arteries in 16 healthy non-pregnant women. There were no differences in blood flow indices between the right and left kidneys as well as between the main and segmental arteries. The variability of the indices in the main and segmental renal arteries in healthy non-pregnant and in the segmental renal artery in normal pregnant women (32-37 weeks of gestation) was investigated. The within-patient error standard deviations of ten cycles and two, and three to nine averaged cycles were compared. In non-pregnant women, values for the error standard deviation comparable with those obtained from ten cycles for the systolic/diastolic ratio and pulsatility index from both main and segmental arteries were obtained by averaging from five to six consecutive cycles, while the error standard deviation for the resistance index stabilized when averaging only two to four cycles. In pregnant women, the error standard deviations for both the systolic/diastolic ratio and pulsatility index reached quite stable values after three cycle had been averaged as did the error standard deviation for the resistance index. We speculate that this difference between non-pregnant and pregnant women is due to more favorable conditions for renal visualization and consequently higher quality Doppler signals during pregnancy. A knowledge about the number of cardiac cycles required for an accurate calculation of renal blood flow velocity indices may prevent time-consuming calculations and inaccurate conclusions.