Fetal and maternal contributions to risk of pre-eclampsia: population based study

Pre-eclampsia, the placenta and the maternal systemic inflammatory response--a review

The central role of the placenta in the pathogenesis of pre-eclampsia is undisputed. The evidence that maternal syndrome of pre-eclampsia is caused by a maternal systemic inflammatory response (MSIR) is reviewed. The polymorphic nature of the inflammatory network explains the diversity of the varied signs of this condition. A key observation is that an MSIR is also a feature of normal third trimester pregnancy, but less severe than in pre-eclampsia. Hence pre-eclampsia is simply the extreme end of a continuum common to all pregnancies, with multiple contributing factors. Evidence is presented that apoptotic or necrotic debris shed from the syncytial surface of the placenta constitutes the inflammatory stimulus in all pregnancies. This model explains many features of pre-eclampsia including its occurrence with either larger placentae or small oxidatively stressed placentae. The clinical implications are that in terms of diagnosis or prediction there can never be a clear distinction between normal and abnormal. No test, predictive or diagnostic, can be expected to distinguish absolutely between different degrees of a problem that is common to all pregnancies. The possibility that the MSIR associated with third trimester pregnancy is nothing more than the maternal price for sustaining gestation is considered. Insulin resistance is a feature of normal pregnancy and also of systemic inflammatory states in non-pregnant individuals. It has been previously proposed that the insulin resistance of pregnancy is an important adaptation to divert maternal glucose to meet the needs of the foetus. Hence the MSIR, by causing maternal insulin resistance, may have substantial foetal advantages so long as it is not too severe.

Obstetric and prenatal outcome in menopausal women: a 12-year clinical study

The obstetric and prenatal outcome in post-menopausal women of advanced age in an oocyte donation programme is described in this paper, the oldest being aged 63 years. A total of 2729 candidates were visited up to November 2000. Only 1150 (42%) were accepted, with 1579 being rejected during a rigorous selection procedure. Several excluding clinical conditions were noted, including hypertension of varying severity, cardiovascular disease, smoking, dysfunctions of the hepatic, thyroid and renal systems and diabetes. Overall, 489 (38%) clinical pregnancies were established in 1288 recipient cycles, with 390 healthy babies delivered out of 363 pregnancies (28%), while 126 (25.7%) were lost. In all, 327 (90%) of the pregnancies reached full term, with 36 involving premature deliveries, 24 involving multiple gestation, 21 sets of twins, three sets of triplets (0.9%) and no quadruplets. Antenatal complications arising in 86 patients (23.6% of deliveries) included 33 preterm deliveries, 43 cases of gestational hypertension, four cases of pre-eclampsia, three cases of gestational diabetes and three of abruptio placentae. A total of 272 (75%) of all deliveries were by Caesarean section. Neonatal complications included two cases of growth retardation. There were no neonatal or maternal deaths. The 63-year-old woman reached full term pregnancy in July 1994, with delivery by Caesarean section of a boy in good health. Proper screening for risks has enabled this treatment to be given to a preselected group of patients.

Obstetric prognosis in sisters of preeclamptic women - implications for genetic linkage studies

BACKGROUND: To investigate obstetric prognosis in sisters of preeclamptic women. METHODS: We identified consecutive 635 sib pairs from the Birth Registry data of Kuopio University Hospital who had their first delivery between January 1989 and December 1999 in our institution. Of these, in 530 pairs both sisters had non-preeclamptic pregnancies (the reference group), in 63 pairs one of the sisters had preeclampsia and the unaffected sisters were studied (study group I). In 42 pairs both sister's first delivery was affected (study group II). Pregnancy outcome measures in these groups were compared. RESULTS: Unaffected sisters of the index patients had uncompromised fetal growth in their pregnancies, and overall, as good obstetric outcomes as in the reference group. The data on affected sisters of the index patients showed an increased prematurity rate, and increased incidences of low birth weight and small-for-gestational age infants, as expected. CONCLUSION: Unaffected sisters of the index patients had no signs of utero-placental insufficiency and they were at low risk with regard to adverse obstetric outcome, whereas affected sisters were high-risk. Clinically, affected versus unaffected status appears to be clear-cut in first-degree relatives regardless of their genetic susceptibility and unaffected sisters do not need special antepartum surveillance.

Molecular epidemiology of preeclampsia

Numerous articles have been published that address the possible genetic influences on the development of preeclampsia (PE). However, to our knowledge, a complete review of the results has not yet been completed. We undertook a MEDLINE search to identify English-language articles published after January 1, 1990 that examined the possible role of specific genes in the etiology of PE. After a brief introduction and a concise review of the prevailing etiologic hypotheses, we have categorized the candidate genes into six categories, based on their hypothesized role in PE etiology. The purpose of this paper is to review the literature, comment on its quality, and provide a reference for researchers interested in the molecular epidemiology of preeclampsia.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians.

LEARNING OBJECTIVES

After completion of this article, the reader will be able to list the prevailing etiologic hypotheses of preeclampsia, to outline the published data on possible genetic influence on the development of preeclampsia, and to clearly state the definition of preeclampsia.

Susceptibility loci for preeclampsia on chromosomes 2p25 and 9p13 in Finnish families

Preeclampsia is a common, pregnancy-specific disorder characterized by reduced placental perfusion, endothelial dysfunction, elevated blood pressure, and proteinuria. The pathogenesis of this heterogeneous disorder is incompletely understood, but it has a familial component, which suggests that one or more common alleles may act as susceptibility genes. We hypothesized that, in a founder population, the genetic background of preeclampsia might also show reduced heterogeneity, and we have performed a genomewide scan in 15 multiplex families recruited predominantly in the Kainuu province in central eastern Finland. We found two loci that exceeded the threshold for significant linkage: chromosome 2p25, near marker D2S168 (nonparametric linkage [NPL] score 3.77; P=.000761) at 21.70 cM, and 9p13, near marker D9S169 (NPL score 3.74; P=.000821) at 38.90 cM. In addition, there was a locus showing suggestive linkage at chromosome 4q32 between D4S413 and D4S3046 (NPL score 3.13; P=.003238) at 163.00 cM. In the present study the susceptibility locus on chromosome 2p25 is clearly different (21.70 cM) from the locus at 2p12 found in an Icelandic study (94.05 cM) and the locus at 2q23 (144.7 cM) found in an Australian/New Zealand study. The locus at 9p13 has been shown to be a candidate region for type 2 diabetes in two recently published genomewide scans from Finland and China. The regions on chromosomes 2p25 and 9p13 may harbor susceptibility genes for preeclampsia.

Searching for preeclampsia genes: the current position

Although there is substantial evidence that preeclampsia has a genetic background, the complexity of the processes involved and the fact that preeclampsia is a maternal-fetal phenomenon does not make the search for the molecular basis of preeclampsia genes easy. It is possible that the single phenotype 'preeclampsia' in fact should be divided into different sub-groups on genetic or biochemical level. In the present review, the preeclampsia phenotype and its pathophysiologic features are discussed. Family studies and postulated inheritance models are summarized. A systematic overview is given on the numerous candidate gene studies and gene-expression studies performed so far and on the currently available genome-wide scan data. Despite extensive research the molecular genetic basis of preeclampsia remains unclear. Future studies will hopefully enhance our insights in the molecular pathogenesis of preeclampsia.

Paternal age and preeclampsia

BACKGROUND

Paternal aging is associated with premeiotic damage to spermatogonia, a mechanism by which new point mutations are introduced into the gene pool. We hypothesized that paternal age might contribute to preeclampsia.

METHODS

We studied the incidence of preeclampsia in 81,213 deliveries surveyed in 1964-1976 in the Jerusalem Perinatal Study. We controlled for maternal age, parity and other risk factors using logistic regression.

RESULTS

Preeclampsia was reported in 1303 deliveries (1.6%). Compared with fathers age 25-34 years, the odds ratios (ORs) for preeclampsia were 1.24 (95% confidence interval = 1.05-1.46) for age 35-44 and 1.80 (1.40-2.31) for age 45+. For fathers age <25, the OR was 1.25 (1.04-1.51). Although weaker than maternal age effects, paternal effects were consistent within subgroups of other variables.

CONCLUSIONS

These findings support the hypothesis that a modest proportion of preeclampsia might be explained by new mutations acquired from fathers and add to a growing body of evidence for paternal age effects in birth defects, neuropsychiatric disease and neoplasia.

[Pregnancy-related hypertension]

PURPOSE

Hypertension occurs in 10 to 15 p cent of pregnancies. Among them, 10 to 20% also have proteinuria. This situation defines preeclampsia, and involves a serious threat on fetal and even maternal prognosis. Presence of the hepatic (HELLP) syndrome still severely worsens the prognosis.

CURRENT KNOWLEDGE AND KEY POINTS

Pathophysiology of preeclampsia is based on a very early abnormality of placentation, leading to insufficient blood supply to the feto-placental unit. At the maternal level, the main consequence of placental ischemia is generalized endothelial dysfunction, responsible for systemic vasoconstriction and clotting abnormalities. In such a context, lowering blood pressure with drugs is quite inefficient, or even harmful. The prognosis of this disease is mainly related to the pertinence of obstetrical management.

FUTURE PROSPECTS AND PROJECTS

An early preventive strategy is the most logical approach of preeclampsia, its modalities remain under discussion.

Pre-eclampsia in pregnancy and subsequent risk for breast cancer

Women who experience pre-eclampsia or hypertension during pregnancy may have a reduced risk for breast cancer later in life. The evidence is based on case-control studies, and here we report the results of a cohort study exploring the link between pre-eclampsia and gestational hypertension diagnosed in the first pregnancy and subsequent risk for breast cancer. We combined information from the Medical Birth Registry and the Cancer Registry in Norway, which are both nation-wide. Between 1967, when the birth registry was established, and 1998, 694 657 women were recorded with a first birth, and classified according to whether pre-eclampsia and/or hypertension was diagnosed in the first pregnancy. Linkage to the Norwegian Cancer Registry identified 5474 new cases of breast cancer diagnosed subsequently to their first delivery. Compared to other parous women, women with pre-eclampsia and/or hypertension diagnosed in their first pregnancy had 19% lower risk (95% confidence interval, 9 to 29%) for breast cancer, after adjustment for attained age, calendar period of diagnosis, age at first birth, and parity. This result was similar for term and preterm deliveries, across the range of offspring birth weight, and for pre- and postmenopausal women. These results suggest that the pathophysiology surrounding pre-eclampsia and gestational hypertension plays an important role in breast cancer etiology. A better understanding of the underlying processes could provide an insight into the pathogenesis of breast cancer.

The partner's role in the etiology of preeclampsia

The etiology of preeclampsia is often considered to be purely maternal, i.e. maternal constitutional factors that impair maternal cardiovascular/endothelial mechanisms normally required to cope with the specific pregnancy demands, being primarily a generalised inflammatory response and a hyperdynamic circulation. Recent data strongly indicate an important role for the male partner in the causation of this common pregnancy disorder. The aim of this review is to discuss the relevant literature and to explain how paternal, relational and sexual factors play an important role in the etiology of preeclampsia.

Preeclampsia: a multifactorial disease resulting from the interaction of the feto-maternal HLA genotype and HCMV infection

PROBLEM

To clarify the possible influence of human leukocyte antigen (HLA) mother-child genotypes and human cytomegalo virus (HCMV) presence on the development of preeclampsia.

METHODS OF STUDY

One hundred and four DNA samples from mothers with preeclampsia, mothers with a normal history of pregnancies and their neonates were tested by polymerase chain reaction-sequence specific oligonucleotide probes (PCR-SSOP) for HLA-A, -G, -DRB1, -DQA1, -DQB1 alleles. The HCMV sequences were analyzed using a PCR-SSOP method and the four primers described by Chou (Chou S: J Clin Microb 1992; 30:2307-2310).

RESULTS

Compared with their respective controls, a significant increase of DRB1*07 among neonates (P(c) = 0.05) and of DRB1*07 and/or DRB1*06 among pre-eclamptic mothers (P(c) = 0.003, RR = 8,5) was found. When HCMV sequences were detected in pre-eclamptic mothers carrying those phenotypes the RR increased up to 40. Furthermore, the fetal inheritance of a maternal HLA-G*0104 increased the risk for the appearance of the disease (RR = 30; P = 0.025).

CONCLUSION

The results suggest that the presence of alleles HLA-G*0104, DRB1*07/06, HCMV sequences and the fetal inheritance of maternal G*0104, should be considered as conditioning factors for the development of preeclampsia.

Preeclampsia in the parous woman: who is at risk?

OBJECTIVE

The purpose of this study was to identify risk factors for preeclampsia in second pregnancies and to determine whether gestational age at delivery in the first pregnancy increases the risk of recurrent preeclampsia.

STUDY DESIGN

We conducted a population-based, case-control study using birth certificate data from the Missouri maternally linked cohort. Data from women delivered of their first 2 singleton pregnancies between 1989 and 1997 (2332 cases with preeclampsia in the second pregnancy and 2370 control cases) were analyzed with logistic regression.

RESULTS

Significant risk factors for preeclampsia in a second pregnancy include longer birth interval, previous preterm delivery, previous small-for-gestational-age newborn, renal disease, chronic hypertension, diabetes mellitus, obesity, black race, and inadequate prenatal care. Smoking and same paternity are protective. A history of preeclampsia confers the highest risk for preeclampsia in the second pregnancy; the risk is inversely proportional to gestational age at delivery of the first pregnancy: adjusted odds ratio, 15.0; 95% CI, 6.3-35.4 for 20 to 33 weeks; adjusted odds ratio, 10.2; 95% CI, 6.2-17.0 for 33 to 36 weeks; and adjusted odds ratio, 7.9; 95% CI, 6.3-10.0 for 37 to 45 weeks.

CONCLUSION

The relative risk of recurrent preeclampsia increases with earlier gestational age at delivery of the first pregnancy that was complicated by preeclampsia.

Familial risk of preeclampsia in Newfoundland: a population-based study

This study sought to quantify the familial risk of preeclampsia (proteinuric hypertension) in Newfoundland and to identify characteristics in probands that predict increased familial risk. Reviewed were 5173 obstetric charts from 10 hospitals, representing 99% of deliveries on the island of Newfoundland for a 1-yr period from April 1996 to March 1997; pregnancy-induced hypertension was diagnosed according to strict criteria. Family obstetric histories were obtained from identified probands with preeclampsia, and sisters and mothers of probands were interviewed. In addition, the obstetric charts from sisters and mothers were reviewed to identify preeclampsia. The incidence of preeclampsia in the population was 5.6% (n = 292), and in primiparous women it was 7.9%. Factors independently associated with increased risk of preeclampsia included primiparous delivery, multiple gestation, pregestational and gestational diabetes, maternal age of more than 35 yr, and region of the province. Of 330 sisters identified, 217 had 445 pregnancies, with 331 charts located for review. The incidence of preeclampsia (based on chart review) in 163 primiparous sisters was 20.2%. The relative risk of preeclampsia in primiparous sisters of probands with preeclampsia compared with primiparous women in the population was 2.6 (95% confidence interval, 1.8 to 3.6). Factors in probands independently associated with a higher risk of preeclampsia in sisters included at least 2+ proteinuria and region of the province. This population-based study, which used unbiased ascertainment and strict diagnostic criteria, demonstrated a significantly higher risk of preeclampsia in sisters of probands with preeclampsia, particularly when probands were defined by severity of preeclampsia and by geographic region.

Linkage and association studies of IL1B and IL1RN gene polymorphisms in preeclampsia

OBJECTIVE

To determine whether preeclampsia is either associated with or linked to two polymorphisms in the IL1B gene (IL1B-TaqI and IL1B-511) and one polymorphism in the IL1RN gene (IL1RN-IVS2).

METHODS

Genotyping was performed in 150 affected sib-pair families and 104 healthy Dutch blood donors. Genotype and allele frequencies as well as allelic associations were assessed in three groups of unrelated women from these 150 families; 133 with either eclampsia, preeclampsia or the haemolysis, elevated liver enzymes, low platelets (HELLP) syndrome, 101 with preeclampsia only, and 63 with HELLP syndrome only. These frequencies were compared to those in controls. Frequencies of transmitted and nontransmitted haplotypes, inferred from the three polymorphisms, were compared. Allele sharing between affected siblings from all 150 families was assessed by means of multipoint nonparametric affected sib-pair analyses.

RESULTS

No significant differences in genotype and allele frequencies were found between the unrelated study groups and controls. No allelic associations were apparent, nor were there differences in frequencies of transmitted and nontransmitted haplotypes within affected families. Excess allele sharing for any of the three polymorphic markers was absent in affected sib-pairs.

CONCLUSIONS

None of the IL1B and IL1RN polymorphisms provided evidence for either association or linkage with the risk for (pre)eclampsia/HELLP syndrome, preeclampsia only or HELLP syndrome only.

Alpha-foetoprotein in umbilical cord in relation to severe pre-eclampsia, birth weight and future breast cancer risk

Women born after pre-eclamptic pregnancies have been reported to be at reduced risk of breast cancer as adults, because of reduced intrauterine oestrogen influence on breast tissue; high levels of alpha-foetoprotein (a glycoprotein with anti-oestrogenic properties), however, could also be important. In severe pre-eclampsia, placental function and foetal growth are reduced, and umbilical cord plasma levels of alpha-foetoprotein could reflect the underlying processes. Umbilical cord blood was collected in 12804 consecutive deliveries. Among 307 pregnancies with clinical pre-eclampsia, 66 singleton pregnancies were identified as clinically severe, and 610 singleton pregnancies were selected as controls. Oestradiol and alpha-foetoprotein were measured from umbilical plasma, and birth weight was standardized as the ratio between the observed and expected birth weight, adjusted for differences in gestation length and offspring sex. Cord plasma levels of alpha-foetoprotein were significantly higher in severe pre-eclampsia than controls (P<0.01) after adjustment for gestational age and birth weight. For oestradiol, there was no difference in cord plasma levels between the severe pre-eclampsia group and controls, after adjustment for length of gestation and birth weight. These results suggest that an anti-oestrogenic effect associated with pre-eclampsia may be mediated through high levels of alpha-foetoprotein rather than low levels of oestradiol.

Is there an increased maternal-infant prevalence of Factor V Leiden in association with severe pre-eclampsia?

OBJECTIVE

To compare the prevalence of the Factor V Leiden mutation in children and maternal-infant pairs in pregnancies affected by severe pre-eclampsia with unmatched normal controls.

DESIGN

Prospective cohort study.

SETTING

Department of Women's and Children's Health, The Canberra Hospital, Garran, ACT, Australia.

SAMPLE

Forty-eight maternal-infant pairs where the index pregnancy was affected by severe pre-eclampsia; 46 unmatched maternal-infant pairs where the index pregnancy was defined as normal.

METHODS

DNA analysis of cheek swab samples obtained from maternal-infant pairs for the Factor V Leiden mutation.

MAIN OUTCOME MEASURE

The prevalence of the Factor V Leiden mutation in mothers, infants and maternal-infant pairs in association with severe pre-eclampsia compared with unmatched controls.

RESULTS

No difference was detected in the prevalence of Factor V Leiden mutation between the women and children of both groups, nor the maternal-infant pairs from each group.

CONCLUSIONS

No evidence was found of an increased prevalence of the Factor V Leiden mutation in either the mothers or children in association with severe pre-eclampsia. This result argues against a Factor V Leiden fetal or maternal contribution to the development of severe pre-eclampsia.

The interval between pregnancies and the risk of preeclampsia

BACKGROUND

The risk of preeclampsia is generally lower in second pregnancies than in first pregnancies, but not if the mother has a new partner for the second pregnancy. One explanation is that the risk is reduced with repeated maternal exposure and adaptation to specific antigens from the same partner. However, the difference in risk might instead be explained by the interval between births. A longer interbirth interval may be associated with both a change of partner and a higher risk of preeclampsia.

METHODS

We used data from the Medical Birth Registry of Norway, a population-based registry that includes births that occurred between 1967 and 1998. We studied 551,478 women who had two or more singleton deliveries and 209,423 women who had three or more singleton deliveries.

RESULTS

Preeclampsia occurred during 3.9 percent of first pregnancies, 1.7 percent of second pregnancies, and 1.8 percent of third pregnancies when the woman had the same partner. The risk in a second or third pregnancy was directly related to the time that had elapsed since the preceding delivery, and when the interbirth interval was 10 years or more, the risk approximated that among nulliparous women. After adjustment for the presence or absence of a change of partner, maternal age, and year of delivery, the odds ratio for preeclampsia for each one-year increase in the interbirth interval was 1.12 (95 percent confidence interval, 1.11 to 1.13). In unadjusted analyses, a pregnancy involving a new partner was associated with higher risk of preeclampsia, but after adjustment for the interbirth interval, the risk of preeclampsia was reduced (odds ratio for preeclampsia with a change of partner, 0.73; 95 percent confidence interval, 0.66 to 0.81).

CONCLUSIONS

The protective effect of previous pregnancy against preeclampsia is transient. After adjustment for the interval between births, a change of partner is not associated with an increased risk of preeclampsia.

Interest in preeclampsia for researchers in reproduction

Gestational hypertension/preeclampsia, is a major disease of human reproduction, with 10% of human births being affected. It is due to the failure of extravillous cytotrophoblast to invade the maternal uterine spiral arteries to a sufficient depth at the second physiological invasion around the 14-16th week of gestation, inducing poor vascular exchanges between the mother and the placenta. The rise of blood pressure in the human mother is then a compensatory mechanism to increase the exchanges and try to save the fetus from poor supplies. Indeed, it is only in the late 1970s that a puzzling phenomenon has been described: in human pregnancy, in contrast with other mammals, implantation of the embryo occurs by two physiological invasions of the cytotrophoblast inside the uterine wall: (a) at the beginning of pregnancy after fecundation (like all mammals); (b) then follows an apparent long pause (6-8 weeks) and (c) late at the end of first trimester (14-16th week) of gestation, a second very deep (1/3 of the uterine wall) invasion. This two-wave physiological endovascular trophoblast invasion represents a remarkable immunological placental-maternal interaction. Moreover, preeclampsia which has been considered as 'the disease of primigravidae' during all the XXth century may be in fact associated with new paternity especially in couples conceiving very shortly after the beginning of their sexual relationship. 'Primipaternity', rather than primigravidity, is probably the leading cause of preeclampsia. Comprehension in the near future of the physiological immunological tolerance in normal pregnancies and immunological rejection (preeclampsia) of the second trophoblastic invasion will give the biological clue of this puzzling disease, real plague of human reproduction.

Changing paternity and time since last pregnancy; the impact on pre-eclampsia risk. A study of 547 238 women with and without previous pre-eclampsia

BACKGROUND

Long time interval between pregnancies has been found to increase the risk of pre-eclampsia in second pregnancy. Our aim was to investigate whether this effect is influenced by a history of pre-eclampsia or a change in paternity.

METHODS

We studied 547 238 women with a first and second pregnancy registered in the Medical Birth Registry of Norway, 1967-1998. The relative risk of pre-eclampsia in the second delivery according to time interval between deliveries was estimated as odds ratios (OR) in logistic regression models, controlling for changing paternity, maternal age and calendar time period in women with and without previous pre-eclampsia.

RESULTS

A change of paternity for the second pregnancy was associated with a reduced risk of pre-eclampsia after controlling for the time since first delivery (adjusted OR = 0.80, 95% CI : 0.72-0.90), but the interaction between change in paternity and time between deliveries was significant only for women with no previous pre-eclampsia. The interaction between history of pre-eclampsia and time interval between the two deliveries was highly significant, and for women with no previous pre-eclampsia the risk of pre-eclampsia in second pregnancy increased with increasing time interval (for intervals longer than 15 years the adjusted OR was 2.11, 95% CI : 1.75-2.53). For women with previous pre-eclampsia the risk tended to decrease with increasing time interval between deliveries.

CONCLUSIONS

The protective impact of a new father for the second pregnancy challenges the hypothesis of primipaternity, and implies that the increase in pre-eclampsia risk ascribed to new father by others is due to insufficient control for interpregnancy interval.

Long term mortality of mothers and fathers after pre-eclampsia: population based cohort study

OBJECTIVE

To assess whether mothers and fathers have a higher long term risk of death, particularly from cardiovascular disease and cancer, after the mother has had pre-eclampsia.

DESIGN

Population based cohort study of registry data.

SUBJECTS

Mothers and fathers of all 626 272 births that were the mothers' first deliveries, recorded in the Norwegian medical birth registry from 1967 to 1992. Parents were divided into two cohorts based on whether the mother had pre-eclampsia during the pregnancy. Subjects were also stratified by whether the birth was term or preterm, given that pre-eclampsia might be more severe in preterm pregnancies.

MAIN OUTCOME MEASURES

Total mortality and mortality from cardiovascular causes, cancer, and stroke from 1967 to 1992, from data from the Norwegian registry of causes of death.

RESULTS

Women who had pre-eclampsia had a 1.2-fold higher long term risk of death (95% confidence interval 1.02 to 1.37) than women who did not have pre-eclampsia. The risk in women with pre-eclampsia and a preterm delivery was 2.71-fold higher (1.99 to 3.68) than in women who did not have pre-eclampsia and whose pregnancies went to term. In particular, the risk of death from cardiovascular causes among women with pre-eclampsia and a preterm delivery was 8.12-fold higher (4.31 to 15.33). However, these women had a 0.36-fold (not significant) decreased risk of cancer. The long term risk of death was no higher among the fathers of the pre-eclamptic pregnancies than the fathers of pregnancies in which pre-eclampsia did not occur.

CONCLUSIONS

Genetic factors that increase the risk of cardiovascular disease may also be linked to pre-eclampsia. A possible genetic contribution from fathers to the risk of pre-eclampsia was not reflected in increased risks of death from cardiovascular causes or cancer among fathers.

Higher risk of pre-eclampsia after change of partner. An effect of longer interpregnancy intervals?

Epidemiologic studies have shown that pre-eclampsia is mainly a disease of first pregnancy, possibly associated with primipaternity. The interpregnancy interval, which is strongly associated with change of partner, has received little attention. In this study, based on Danish hospital records, we evaluated whether the interpregnancy interval may confound or modify the paternal effect on pre-eclampsia. We studied the outcome of the second birth in a cohort of Danish women with pre-eclampsia in the previous birth (8,401 women) and in all women with pre-eclampsia in second (but not first) birth together with a sample of women with two births (26,596 women). A long interpregnancy interval was associated with a higher risk of pre-eclampsia in women with no previous pre-eclampsia when the father was the same. We estimated the risk of pre-eclampsia in second birth according to paternal change in different models. Although partner change was associated with an increased risk of pre-eclampsia in women with no history of pre-eclampsia, this effect disappeared after adjustment for the interpregnancy interval. We saw, however, different results when we stratified on the length of the interval. Our results indicate that the interval between births should be taken into consideration when studying the effect of changing partner on pre-eclampsia.

Is preeclampsia an infectious disease?

BACKGROUND

Studies have suggested a strong paternal factor in the etiology of preeclampsia. If preeclampsia is caused by an infectious agent transmitted by the woman's partner, seronegative women who may experience primary infection in pregnancy should be at increased risk of preeclampsia as compared to previously infected women. The aim of this study was to assess the impact of being seronegative for some viruses transmitted by close contact on the risk of developing preeclampsia.

METHODS

Nine hundred and seventy-eight women were randomly drawn from a basic study population of 35,940 pregnant women in Norway. A serum sample drawn at the first antenatal visit was analyzed for specific IgG antibodies against herpes simplex virus type-2, cytomegalovirus and Epstein-Barr virus. For comparison, antibody status against Toxoplasma gondii was also assessed. Information on preeclampsia in pregnancy was obtained through linkage to the Medical Birth Registry of Norway.

RESULTS

Thirty-three (3%) women developed preeclampsia. The risk of developing preeclampsia seemed to be increased for women who were seronegative for the viruses studied. Seronegativity for Toxoplasma gondii did not show such a pattern.

INTERPRETATION

Women who are seronegative for antibodies against viral agents transmitted through close contact seem more likely to develop preeclampsia. This finding indicates that women who are seronegative to such agents may acquire primary infection in pregnancy, and subsequently be at increased risk of preeclampsia. This hypothesis could represent a new approach to the causes of preeclampsia, and encourage search for yet unidentified microbes as a possible causal factor.

A genome-wide scan for preeclampsia in the Netherlands

Preeclampsia, hallmarked by de novo hypertension and proteinuria in pregnancy, has a familial tendency. Recently, a large Icelandic genome-wide scan provided evidence for a maternal susceptibility locus for preeclampsia on chromosome 2p13 which was confirmed by a genome scan from Australia and New Zealand (NZ). The current study reports on a genome-wide scan of Dutch affected sib-pair families. In total 67 Dutch affected sib-pair families, comprising at least two siblings with proteinuric preeclampsia, eclampsia or HELLP-syndrome, were typed for 293 polymorphic markers throughout the genome and linkage analysis was performed. The highest allele sharing lod score of 1.99 was seen on chromosome 12q at 109.5 cM. Two peaks overlapped in the same regions between the Dutch and Icelandic genome-wide scan at chromosome 3p and chromosome 15q. No overlap was seen on 2p. Re-analysis in 38 families without HELLP-syndrome (preeclampsia families) and 34 families with at least one sibling with HELLP syndrome (HELLP families), revealed two peaks with suggestive evidence for linkage in the non-HELLP families on chromosome 10q (lod score 2.38, D10S1432, 93.9 cM) and 22q (lod score 2.41, D22S685, 32.4 cM). The peak on 12q appeared to be associated with HELLP syndrome; it increased to a lod score of 2.1 in the HELLP families and almost disappeared in the preeclampsia families. A nominal peak on chromosome 11 in the preeclampsia families showed overlap with the second highest peak in the Australian/NZ study. Results from our Dutch genome-wide scan indicate that HELLP syndrome might have a different genetic background than preeclampsia.

Risks of hypertensive disorders in the second pregnancy

This study examined the incidence of and risk factors for recurrent and newly developed hypertensive disorders in the second pregnancy. We analysed data on 1641 women who had both the first and second pregnancies in the Collaborative Perinatal Project, a large prospective cohort study at 12 hospitals in the US. Nineteen per cent [95% CI 14%, 24%] of women who had gestational hypertension in the first pregnancy, 32% [95% CI 17%, 48%] of those with pre-eclampsia and 46% [95% CI 32%, 60%] of patients with gestational hypertension or pre-eclampsia superimposed on chronic hypertension, had recurrent hypertensive disorders in the second pregnancy. Risk factors for recurrence included history of chronic hypertension and thromboembolism, early onset of hypertension in the first pregnancy or persistent hypertension after 5 weeks postpartum and high baseline blood pressure in the second pregnancy. Women with a normotensive first pregnancy but a severe small-for-gestational-age birth had twice the risk of developing hypertension in the second pregnancy (RR = 2.1, 95% CI, 1.1, 4.0). In summary, hypertensive disorders have a 20--50% recurrence rate in the second pregnancy. The earlier the onset of hypertension in the first pregnancy, the higher the overall recurrence rate. Intrauterine growth restriction of the first birth is an independent risk factor for hypertension in the second pregnancy.

New insights in hypertensive disorders of pregnancy

Research reported during the past year has enhanced our understanding of conditions that lead to the complex changes that are observed in hypertensive disorders of pregnancy. An association between placental pathology and a multisystem disorder that is characterized by endothelial dysfunction which involves genetic and immunological investigations has been identified. On the basis of these findings, promising screening tools for early detection of pre-eclampsia were identified. No marked changes in anaesthetic approach to hypertensive disorders of pregnancy occurred during the period of review, apart from a reappraisal of spinal anaesthesia as a safe technique in caesarean section, even in patients with severe pre-eclampsia. A multidisciplinary approach to management and therapy is needed and the right balance must be sought between the needs of the mother and baby, both of which are jeopardized by the hypertensive disorders of pregnancy.

Paternal and maternal components of the predisposition to preeclampsia

BACKGROUND

There is an inherited maternal predisposition to preeclampsia. Whether there is a paternal component, however, is not known.

METHODS

We used records of the Utah Population Database to identify 298 men and 237 women born in Utah between 1947 and 1957 whose mothers had had preeclampsia during their pregnancy. For each man and woman in the study group, we identified two matched, unrelated control subjects who were not the products of pregnancies complicated by preeclampsia. We then identified 947 children of the 298 male study subjects and 830 children of the 237 female study subjects who had been born between 1970 and 1992. These children were matched to offspring of the control subjects (1950 offspring of the male control group and 1658 offspring of the female control group). Factors associated with preeclampsia were identified, and odds ratios were calculated with the use of stepwise logistic-regression analysis.

RESULTS

In the group whose mothers had had preeclampsia (the male study group), 2.7 percent of the offspring (26 of 947) were born of pregnancies complicated by preeclampsia, as compared with 1.3 percent of the offspring (26 of 1973) in the male control group. In the female study group, 4.7 percent of the pregnancies (39 of 830) were complicated by preeclampsia, as compared with 1.9 percent (32 of 1658) in the female control group. After adjustment for the offspring's year of birth, maternal parity, and the offspring's gestational age at delivery, the odds ratio for an adult whose mother had had preeclampsia having a child who was the product of a pregnancy complicated by preeclampsia was 2.1 (95 percent confidence interval, 1.0 to 4.3; P=0.04) in the male study group and 3.3 (95 percent confidence interval, 1.5 to 7.5; P=0.004) in the female study group.

CONCLUSIONS

Both men and women who were the product of a pregnancy complicated by preeclampsia were significantly more likely than control men and women to have a child who was the product of a pregnancy complicated by preeclampsia.

Is oxidative stress involved in the aetiology of pre-eclampsia?

Pre-eclampsia is one of the major indications for elective premature delivery. Several lines of evidence suggest that pre-eclampsia is associated with a state of oxidative stress, offering hope of prevention by antioxidant supplementation. It was recently shown by the present authors that supplementation with vitamin C and E from early in pregnancy leads to a reduction in the incidence of the disease in "high-risk" women.

Primary, secondary, and tertiary prevention of pre-eclampsia

Pre-eclampsia remains one of the major obstetrical problems in less-developed countries. The causes of this condition are still unknown, thus effective primary prevention is not possible at this stage. Research in the past decade has identified some major risk factors for pre-eclampsia, and manipulation of these factors might result in a decrease in its frequency. In the early 1990s aspirin was thought to be the wonder drug in secondary prevention of pre-eclampsia. Results of large trials have shown that this is not the case: if there is an indication for using aspirin it is in the patient at a very high risk of developing severe early-onset disease. The calcium story followed a more or less similar pattern, with the difference that existing evidence shows that women with a low dietary calcium intake are likely to benefit from calcium supplementation. Proper antenatal care and timed delivery are of utmost importance in tertiary prevention of pre-eclampsia. There is evidence to suggest that the intrinsic direct effect of moderate degrees of maternal hypertension is beneficial to the fetus. Severe hypertension needs treatment. If antihypertensive is indicated, there is no clear choice of a drug. Hydralazine should no longer be thought of as the primary drug, most studies show a preference for calcium channel blockers.

Pathogenesis and genetics of pre-eclampsia

After more than a century of intensive research, pre-eclampsia and eclampsia remain an enigmatic set of conditions. Aberration of the interaction between placental and maternal tissue is probably the primary cause, but the exact nature of the differences from normal pregnancy remain elusive. In this review attempts to understand the sequence of physiological changes have concentrated on vascular endothelium and oxidative stress issues. There are genetic components to susceptibility, but the relative contributions of maternal and fetal genotypes are still unclear. Whole-genome mapping could ultimately define the causative genes.

A genome scan in families from Australia and New Zealand confirms the presence of a maternal susceptibility locus for pre-eclampsia, on chromosome 2

Epidemiological studies have shown that genetic factors contribute to the etiology of the common and serious pregnancy-specific disorder pre-eclampsia (PE)/eclampsia (E). Candidate-gene studies have provided evidence (albeit controversial) of linkage to several genes, including angiotensinogen on 1q42-43 and eNOS on 7q36. A recent medium-density genome scan in Icelandic families identified significant linkage to D2S286 (at 94.05 cM) on chromosome 2p12 and suggestive linkage to D2S321 (at 157.5 cM) on chromosome 2q23. In the present article, the authors report the results of a medium-density genome scan in 34 families, representing 121 affected women, from Australia and New Zealand. Multipoint nonparametric linkage analysis, using the GENEHUNTER-PLUS program, showed suggestive evidence of linkage to chromosome 2 (LOD=2.58), at 144.7 cM, between D2S112 and D2S151, and to chromosome 11q23-24, between D11S925 and D11S4151 (LOD=2.02 at 121.3 cM). Given the limited precision of estimates of the map location of disease-predisposing loci for complex traits, the present finding on chromosome 2 is consistent with the finding from the Icelandic study, and it may represent evidence of the same locus segregating in the population from Australia and New Zealand. The authors propose that the PE/E-linked locus on chromosome 2p should be designated the "PREG1" (pre-eclampsia, eclampsia gene 1) locus.

Analysis of the role of HLA-G in preeclampsia

Preeclampsia (PE) is a multisystem disorder of human pregnancy, occurring in 5%-10% of all population births and represents the leading cause of both fetal and maternal morbidity and mortality in pregnancy. Although the disorder only becomes clinically apparent late in pregnancy, the underlying pathology indicates that invasion of fetal trophoblasts into maternal spiral arteries during early pregnancy is shallow or absent in PE. A large number of epidemiologic studies have been carried out and they demonstrate that the disorder is highly heritable and occurs with a high incidence in all populations. Studies have shown that PE is largely under genetic control, but the mode of its inheritance remains unclear. Genetic studies have been carried out using both large scale linkage analysis and candidate gene approaches; however, the genetic mechanisms underlying the disorder have yet to be determined. We focus on the potential role of HLA-G, a nonclassical class I HLA located on chromosome 6, which appears to be a key component in trophoblast invasion. We examine the hypothesis that HLA-G may have a key role in both genetic susceptibility to, and pathogenesis of, PE.

Risk factors and clinical manifestations of pre-eclampsia

OBJECTIVE

To study associations between established risk factors for pre-eclampsia and different clinical manifestations of the disease.

DESIGN

A population-based, nested case-control study.

SETTING

Information from 12,804 consecutive deliveries that took place over three years at a birth clinic, which alone serves a population of nearly 240,000 in Rogaland county, Norway.

SUBJECTS

Cases of pre-eclampsia (n = 323) and healthy controls (n = 650) were selected. Pre-eclampsia was defined as increase in diastolic blood pressure (> or = 25 mmHg to > or = 90 mmHg) and proteinuria (> or = 1+ by dipstick testing) after 20 weeks of pregnancy.

MAIN STUDY MEASURES

Parity, previous pre-eclampsia, blood pressure, maternal weight, and maternal smoking were included as study variables. Women with pre-eclampsia were grouped according to clinical manifestations of the disease (i.e. severity [mild, moderate or severe]) and time of onset (early or late gestation). Associations with the study factors were estimated as relative risks (odds ratio, OR).

RESULTS

Both nulliparity and hypertension increased pre-eclampsia risk, with no clear preference for any clinical subtype. High maternal weight was related to a higher risk of mild and moderate, but not severe, pre-eclampsia. Previous pre-eclampsia strongly increased the risk for pre-eclampsia in the current pregnancy, and the risk of early onset disease was especially high (OR 42.4; 95% CI 11.9-151.6). Overall, smoking was associated with a reduced risk for pre-eclampsia (OR 0.6; 95% CI 0.4-0.9). However, no effect of smoking was observed in the early onset disease group and among women with repeated pre-eclampsia.

CONCLUSION

Nulliparity and hypertension increased the risk for each subgroup of pre-eclampsia, but high maternal weight, previous pre-eclampsia and smoking were not consistently associated with each clinical subtype. This observation may suggest that heterogeneous clinical manifestations of pre-eclampsia may be preceded by different pathological mechanisms.

Pre-eclampsia

Pre-eclampsia is associated with significant morbidity and mortality for mother and baby, but it resolves completely post partum. Despite a steady reduction in maternal mortality from the disorder in more developed countries, it remains one of the most common reasons for a woman to die during pregnancy. The disorder starts with a placental trigger followed by a maternal systemic response. Because both this systemic response and the woman's reaction to it are inconsistent, the clinical presentation varies in time and substance, with many different organ systems affected. With the increasing understanding of the disease process, there have been advances in management, such as antihypertensive therapy, magnesium sulphate, and fluid restriction.

Immunology of implantation

During implantation, the uterine decidua is invaded by extravillous trophoblast (EVT) cells whose function is to destroy the walls of the uterine spiral arteries in order to provide an adequate blood flow to the fetus. These EVT cells express an unusual combination of HLA class I molecules-HLA-C, HLA-E and HLA-G. The decidua is infiltrated by a population of natural killer (NK) cells with a distinctive phenotype of CD56(bright)CD16(-)CD3(-). These cells are particularly numerous in the decidua basalis at the implantation site where they come into close contact with invading EVT cells. These NK cells express a variety of receptors (CD94/NKG2, KIR and ILT) which are known to recognize HLA class I molecules. We believe that interaction between these NK cells and EVT cells provides the controlling influence for implantation.

Origins of fetal growth restriction

Regulation of growth of the fetus and its placenta begins before pregnancy. Early in pregnancy the mother sets the rate of growth of the fetus on a trajectory, which may be modified by events later in pregnancy. Low maternal weight for height, history of previous small babies, maternal undernutrition, pregnancy disorders, e.g. pre-eclampsia, are associated with low birthweight. Maternal smoking is a major factor in developed countries; infections and undernutrition in developing countries.Recently, there has been emphasis on adverse long-term outcomes including ischaemic heart disease, hypertension and diabetes associated with poor fetal growth. Experimental studies in animals show that some of these outcomes can readily be induced by restriction of fetal growth. Progress in determining successful treatments to improve the growth of the fetus has lagged behind these epidemiological and experimental findings. However, nutrient supplements improve growth in undernourished women and smoking cessation also improves fetal size and outcome.

The L10F mutation of angiotensinogen is rare in pre-eclampsia

BACKGROUND

A mutation in the gene for angiotensinogen, changing the leucine residue at position 10 to a phenylalanine (L10F), has been reported in a patient with proteinuric pre-eclampsia. In vitro enzymatic studies suggest this mutation would increase production of the vasoactive peptide, angiotensin II in vivo, and therefore explain the etiology of the maternal hypertension.

OBJECTIVE

To determine whether mutation of codon 10 of angiotensinogen is common in pre-eclampsia, and therefore likely to be involved in disease susceptibility.

DESIGN

We collected a cohort of 32 women with 'true' pre-eclampsia. All were normotensive prior to the 20th week of pregnancy, developed blood pressures consistently above 140/90 mmHg and had proteinuria of greater than 300 mg/day during the third trimester. All had blood pressures that returned to normal within 1 month of delivery; 31 women were primigravida. Genomic DNA was isolated from their peripheral blood lymphocytes for genetic analyses.

METHODS

A polymerase chain reaction-restriction enzyme-based assay was devised to screen for mutation of codon 10 of the angiotensinogen gene. In addition, we determined the frequency of a threonine residue at position 235 in the angiotensinogen gene, given previous controversial findings of association of this polymorphism with disease.

CONCLUSIONS

We detected no mutation of codon 10 in angiotensinogen in any of the 32 women studied, indicating that this mutation is not commonly associated with proteinuric pre-eclampsia. Furthermore, there was no increased frequency of threonine 235 in the affected individuals studied compared with respective normotensive Caucasian-American and African-American populations.

Risk factors for pre-eclampsia in a large cohort of Latin American and Caribbean women

OBJECTIVE

To study risk factors for pre-eclampsia in a large cohort of Latin American and Caribbean women.

DESIGN

Retrospective cross-sectional study from the Perinatal Information System, the database of the Latin American Center for Perinatology and Human Development, Montevideo, Uruguay.

SETTING

Latin America and the Caribbean, 1985-1997. Population 878,680 pregnancies at 700 hospitals; of these 42,530 were complicated by pre-eclampsia and 1,872 by eclampsia.

MAIN OUTCOME MEASURES

Crude and adjusted relative risks (RR) of risk factors for pre-eclampsia. Adjusted relative risks were obtained after adjustment for potential confounding factors through multiple logistic regression models based on the method of generalised estimating equations.

RESULTS

The following risk factors were significantly associated with increased risk of pre-eclampsia: nulliparity (RR 2 x 38; 95% CI 2 x 28-2 x 49); multiple pregnancy (RR 2 x 10; 95% CI 1 x 90-2 x 32); history of chronic hypertension (RR 1 x 99; 95% CI 1 x 78-2 x 22); gestational diabetes mellitus (RR 1 x 93; 95% CI 1 x 66-2 x 25); maternal age > or = 35 years (RR 1 x 67; 95% CI 1 x 58-1 x 77); fetal malformation (RR 1 x 26; 95% CI 1 x 16-1 x 37); and mother not living with infant's father (RR 1 x 21; 95% CI 1 x 15-1 x 26). Pre-eclampsia risk increased according to pre-pregnancy body mass index (BMI). In comparison with women with a normal pre-pregnancy BMI (19 x 8 to 26 x 0), the RR estimates were 1 x 57 (95% CI 1 x 49-1 x 64) and 2 x 81 95% CI 2 x 69-2 x 94), respectively, for overweight women (pre-pregnancy BMI = 26 x 1 to 29 x 0) and obese women (pre-pregnancy BMI > 29 x 0). Cigarette smoking during pregnancy and a pre-pregnancy BMI < 19 x 8 were significant protective factors against the development of pre-eclampsia. The pattern of risk factors among nulliparous and multiparous women was quite similar.

CONCLUSIONS

Risk factors for pre-eclampsia observed among Latin American and Caribbean women are similar to those found among North American and European women.