First-trimester maternal serum levels of placenta growth factor as predictor of preeclampsia and fetal growth restriction

OBJECTIVE

To determine whether the reported decrease in maternal serum placenta growth factor concentration in preeclampsia is evident from the first trimester and before clinical onset of the disease. We also examined levels in pregnancies that subsequently resulted in fetal growth restriction (FGR).

METHODS

Placenta growth factor concentration was measured in stored maternal serum samples obtained at 11-14 weeks of gestation from 131 women who subsequently developed preeclampsia, 137 women who subsequently developed FGR, and 400 randomly selected controls who did not develop preeclampsia or FGR. Preeclampsia was defined as diastolic blood pressure of 90 mmHg or more on two occasions 4 hours apart, accompanied by proteinuria (more than 300 mg of total protein in a 24-hour urine collection or a positive test for albumin on reagent strip) in women with no pre-existing hypertensive or renal disease. Fetal growth restriction was considered present if a woman subsequently delivered a live infant with a birth weight below the fifth centile for gestation.

RESULTS

In the control group, maternal serum placenta growth factor concentration increased with gestation. Compared with the controls (median multiple of the median 0.98, standard deviation [SD] 0.51), levels in the preeclampsia group (median multiple of the median 1.09, SD 0.52) were not significantly different (t = 1.83, P = .07), but in the FGR group (median multiple of the median 1.57, SD 0.74), levels were significantly increased (t = 10.85, P < .001).

CONCLUSION

The previously reported decrease in serum placenta growth factor levels in women with preeclampsia might not precede clinical onset of the disease and is not apparent in the first trimester of pregnancy. Levels are significantly increased in pregnancies resulting in FGR.

Cervical length and funneling at 23 weeks of gestation in the prediction of spontaneous early preterm delivery

OBJECTIVES

To establish the relationship of cervical length at 23 weeks of gestation to the risk of spontaneous delivery before 33 weeks and to determine the possible additional risk if funneling is present.

METHODS

During a 36-month period, 6819 women with singleton pregnancies underwent transvaginal sonographic cervical assessment at 22-24 weeks as a screening test for preterm delivery. The distribution of cervical length and the prevalence of funneling, defined as dilatation of the internal os of > or = 5 mm in width, were established. Women who underwent cervical cerclage, iatrogenic preterm delivery or were lost to follow-up were excluded from further analysis. In the remaining 6334 pregnancies, logistic regression was used to examine the contribution of cervical length and funneling to the risk of spontaneous preterm delivery before 33 weeks.

RESULTS

The median cervical length was 36 mm and in 1.6% of cases the length was < or = 15 mm. There was a significant inverse association between cervical length and percentage rate of spontaneous delivery before 33 weeks. Funneling of the internal os was present in about 4% of pregnancies and the prevalence decreased with increasing cervical length from 98% when the length was < or = 15 mm to about 25% for lengths of 16-30 mm and less than 1% at lengths of > 30 mm. The rate of preterm delivery was 6.9% in those with funneling compared to 0.7% in those without funneling (chi2 = 86.7; P < 0.0001). However, logistic regression analysis demonstrated that funneling did not provide a significant additional contribution to cervical length in the prediction of spontaneous delivery before 33 weeks (odds ratio for short cervix = 24.9, Z = 4.43, P < 0.0001; odds ratio for funneling = 1.8, Z = 0.84, P = 0.40).

CONCLUSION

In the prediction of preterm delivery, funneling does not provide any significant contribution in addition to cervical length.

Fetal bone metabolism in normal and rhesus isoimmunised pregnancies

OBJECTIVE

To construct gestation-specific reference intervals for fetal concentrations of biochemical markers of bone metabolism and assess the effect of rhesus isoimmunisation on these.

METHODS

Fetal blood samples were obtained by cordocentesis from 175 pregnancies (43 complicated by rhesus isoimmunisation) and assayed for carboxy terminal pro-peptide of type I pro-collagen (PICP) and cross-linked carboxyterminal telopeptide of type I collagen (ICTP) which directly monitor the rate of bone formation and resorption respectively.

RESULTS

Both plasma PICP and ICTP were negatively correlated with gestational age (r = -0.351 and -0.472 for PICP and ICTP, respectively, and P < 0.001 for both). In fetuses affected by rhesus isoimmunisation PICP levels were lower (P=0.030) and more variable (P <0.001) than expected, compared with normal unaffected fetuses. However, no such differences were found in the ICTP levels. In the fetuses affected by rhesus isoimmunisation there was a significant correlation between haemoglobin concentration and both PICP (r = 0.504, P = 0.001) and ICTP (r = 0.343, P = 0.030).

CONCLUSIONS

Fetal bone turnover declines from early second trimester to term, and may be deranged in fetuses affected by rhesus isoimmunisation.

Individualized risk assessment for adverse pregnancy outcome by uterine artery Doppler at 23 weeks

OBJECTIVE

To provide individualized risk prediction of severe adverse pregnancy outcome based on uterine artery Doppler screening at 23 weeks.

METHODS

Color Doppler assessment of the uterine arteries was carried out in 5121 women attending for routine care at 23 weeks in two inner-city obstetric units. The mean uterine artery pulsatility index (PI) was calculated, and the likelihood ratios in relation to PI were generated for severe adverse outcome. This was defined as fetal death, placental abruption, and delivery before 34 weeks associated with preeclampsia and birth weight less than the 10th centile.

RESULTS

The likelihood of severe adverse pregnancy outcome increased quadratically with mean uterine artery PI. This relationship was not affected by maternal age, ethnicity, or parity. At a mean PI of 1.45, the 95th centile for our population, the likelihood ratio for severe adverse pregnancy outcome was 5. Cigarette smoking had an additional contribution to PI in predicting severe adverse outcome, roughly doubling the risk for a given PI.

CONCLUSION

The individualized risk of severe adverse pregnancy outcome can be determined by uterine artery Doppler screening at 23 weeks and knowledge of cigarette smoking history. Such individualized risk would allow ultrasound resources and clinical follow-up to be tailored to the pregnant woman for the most appropriate use of antenatal care.

Twin chorionicity and pre-eclampsia

OBJECTIVE

To determine whether the incidence of pre-eclampsia is different in dichorionic compared to monochorionic twin pregnancies.

METHODS

The study involved 666 twin pregnancies resulting in two live births after 24 weeks of gestation. Ultrasound examination at 10-14 weeks of gestation demonstrated that 171 (25.7%) were monochorionic and 495 (74.3%) were dichorionic twins. Pregnancy outcome information regarding the development of pre-eclampsia was obtained from the maternity units. The incidence of pre-eclampsia in the dichorionic and monochorionic twin pregnancies was compared.

RESULTS

The incidence of pre-eclampsia in monochorionic twin pregnancies (9.4%) was not significantly different from that in dichorionic pregnancies (7.3%) ( P = 0.48). Multiple logistic regression revealed that chorionicity has no effect on the development of pre-eclampsia after adjusting for maternal age, ethnic group, maternal smoking, parity and gestational age at delivery ( P = 0.6; odds ratio for monochorionic compared with dichorionic twin pregnancies, 1.19; 95% confidence interval, 0.61-2.3).

CONCLUSION

In twin pregnancies chorionicity does not affect the incidence of pre-eclampsia.

First trimester maternal serum placenta growth factor (PIGF)concentrations in pregnancies with fetal trisomy 21 or trisomy 18

Placenta growth factor (PIGF), an angiogenic factor belonging to the vascular endothelial growth factor family, pregnancy-associated plasma protein A (PAPP-A) and free beta-human chorionic gonadotrophin (beta-hCG) were measured in maternal serum from 45 pregnancies with trisomy 21, 45 with trisomy 18 and 493 normal controls at 10-13 completed weeks of gestation. In the normal pregnancies maternal serum PIGF levels increased exponentially with gestation. The median multiple of the median (MoM) PIGF concentration in the trisomy 21 group (1.26 MoM) was significantly higher (p<0.0001) than in the control group (1.00 MoM). In the trisomy 18 group the median PIGF was lower (0.889 MoM) but this did not quite reach significance (p=0.064). The corresponding median MoM values for PAPP-A were 1.00 MoM for the controls, 0.49 MoM for trisomy 21 and 0.16 MoM for trisomy 18. The median MoM values for free beta-hCG were 1.00 MoM for the controls, 2.05 MoM for trisomy 21 and 0.38 MoM for trisomy 18. In the control group there was a small but significant correlation of PIGF with free beta-hCG (r=+0.1024) and PAPP-A (r=+0.2288). In the trisomy 18 group there was a significant association between PIGF and free beta-hCG (r=+0.2629) but not with PAPP-A (r=+0.0038). In the trisomy 21 group there was a small but significant association with PAPP-A (r=+0.1028) but not with free beta-hCG (r=+0.0339). The separation of affected and unaffected pregnancies in maternal serum PIGF is small, and therefore it is unlikely that measurement of PIGF would improve screening for these abnormalities provided by the combination of fetal nuchal translucency and maternal serum PAPP-A and free beta-hCG.

Prenatal ultrasound diagnosis of Leroy I cell disease

Leroy I cell disease is a rare autosomal recessive disorder which progressively leads to death within the first decade of life. Invasive prenatal diagnosis is possible but is only undertaken in families who have previously had an affected child. We describe the antenatal ultrasound diagnosis of the disease in a case referred at 30 weeks' gestation for suspected polyhydramnios.

Placental villus morphology in relation to maternal hypoxia at high altitude

Pregnancy at high altitude is associated with maternal hypoxaemic hypoxia with resultant intervillus blood hypoxia. Maternal haemoglobin concentration and blood gases were measured in pregnant women in two cities in Peru; Lima at sea level (n=18) and Cerro de Pasco at 4300 metres above sea level (n=12). Following delivery, placental sections from both groups were examined histomorphometrically using an image analysis system. Villus diameter, villus cross-sectional area, capillary diameter, capillary cross-sectional area and the percentage of villus cross-sectional area occupied by villus capillaries were calculated and parameters were compared between the two altitude groups. Maternal haemoglobin concentration and maternal blood pH were significantly higher, and maternal pO(2), pCO(2)and O(2)saturation were significantly lower in the high altitude group compared to those at sea level. The villus vessel area as a percentage of villus cross-sectional area and capillary diameter were significantly greater in the cases from the high altitude group and villus vessel area as a percentage of the villus cross-sectional area was significantly related to maternal pO(2)(r=-0.7, P=0.01), and maternal pCO(2)(r=0.7, P=0.02), but multiple regression analysis demonstrated that only pO(2)remained significantly independently associated with these villus histological findings (P=0.03). Placental terminal villi from term pregnancies at high altitude show different morphological features from pregnancies at sea level, and these changes are primarily related to maternal pO(2). The predominant morphological alteration is an increase in villus capillary diameter and therefore of the proportion of villus cross-sectional area occupied by capillary lumens.

First-trimester screening for trisomy 21 in singleton pregnancies achieved by assisted reproduction

BACKGROUND

The possible effect of assisted reproduction on first-trimester screening for trisomy 21 was examined by fetal nuchal translucency thickness (NT), maternal serum free beta-human chorionic gonadotrophin (HCG) and pregnancy-associated plasma protein-A (PAPP-A).

METHODS

Parameters were measured at 11-14 weeks in 411 singleton pregnancies achieved by controlled ovarian stimulation, including 220 that had undergone IVF. Results were compared with 1233 singleton pregnancies conceived spontaneously.

RESULTS

In the IVF pregnancies, the median fetal NT was not significantly different from that in controls, whilst the median free beta-HCG was significantly increased, and PAPP-A was significantly decreased. In the intracytoplasmic sperm injection group, fetal NT and free beta-HCG values were not significantly different from those in controls, but PAPP-A was significantly decreased. In those pregnancies achieved by ovarian stimulation, neither fetal NT, free beta-HCG nor PAPP-A were significantly different from the control group.

CONCLUSIONS

In IVF pregnancies, screening for trisomy 21 by fetal NT, maternal serum free beta-HCG and PAPP-A levels may be associated with a 1.2% higher false-positive rate than in natural conception.

Outcome of pregnancy in chromosomally normal fetuses with increased nuchal translucency in the first trimester

OBJECTIVES

To study the outcome of chromosomally normal pregnancies with increased nuchal translucency at the 10-14-week scan.

DESIGN

Retrospective study of 1320 chromosomally normal singleton pregnancies with nuchal translucency of > or = 3.5 mm. In addition to fetal karyotyping these patients were managed with follow-up scans at 14-16 and 20-22 weeks, specialist fetal echocardiography and in selected cases by infection screening and further genetic testing.

RESULTS

In the 1320 pregnancies there were 68 (5.15%) spontaneous abortions or intrauterine deaths, 18 (1.36%) neonatal and infant deaths and 154 (11.67%) terminations of pregnancy. In the 1080 (81.82%) survivors, 60 (5.56%) had abnormalities requiring medical or surgical treatment or leading to mental handicap. The chance of a livebirth with no defects in the group with nuchal translucency of 3.5-4.4 mm was 86%, for those with translucency of 4.5-5.4 mm it was 77%, for those with translucency of 5.5-6.4 mm it was 67%, and for those with translucency of > or = 6.5 mm it was 31%.

CONCLUSIONS

Increased fetal nuchal translucency is associated with chromosomal abnormalities, many fetal defects and genetic syndromes. In the majority of cases a series of antenatal investigations, including fetal karyotyping, detailed scans, fetal echocardiography, as well as genetic testing and infection screening, that can be completed by 20 weeks of gestation would distinguish between the pregnancies destined to result in adverse outcome and those leading to the delivery of infants without major defects.

Maternal serum activin A and inhibin A in trisomy 18 pregnancies at 10-14 weeks

In 45 cases of trisomy 18 and 493 control pregnancies at 10-14 weeks of gestation, maternal serum inhibin A, total activin A, free beta-hCG and PAPP-A were measured. In the trisomy 18 pregnancies the median values were 0.74 MoM for inhibin A, 1.23 MoM for activin A, 0.38 MoM for free beta-hCG and 0.16 MoM for PAPP-A. The degree of deviation from normal in the levels of inhibin and activin is small in comparison with free beta-hCG and PAPP-A and they are therefore unlikely to be of value in improving the sensitivity of 90% for a 1% false-positive rate achieved by screening with fetal nuchal translucency and maternal serum free beta-hCG and PAPP-A.

Maternal serum levels of dimeric inhibin A in pregnancies affected by trisomy 21 in the first trimester

Dimeric inhibin A was measured in maternal serum samples from 45 pregnancies affected by trisomy 21 and 493 samples from unaffected pregnancies at 10-14 weeks of gestation. Inhibin A levels in affected pregnancies were compared with levels of free beta-hCG and PAPP-A in the same series. In the trisomy 21 group, the median multiple of the median (MoM) inhibin A was not significantly elevated (1.28 vs 1.00) with only 15.5% being above the 95th centile. In contrast, the median MoM free beta-hCG was significantly increased (2.05 vs 1.00) with 36% above the 95th centile and PAPP-A was significantly reduced (0.49 vs 1.00) with 42% below the 5th centile. Inhibin A levels in the trisomy 21 group were significantly correlated with gestational age such that median levels rose from 1.04 at 11 weeks to 1.30 at 12 weeks and 1.67 at 13 weeks. These findings suggest that first trimester biochemical screening for trisomy 21, which is currently optimised using maternal serum free beta-hCG and PAPP-A and fetal nuchal translucency, will not benefit from the inclusion of inhibin A.

Glucose metabolism in pregnancy at high altitude

OBJECTIVE

To assess insulin sensitivity and beta-cell function associated with lower maternal fasting plasma glucose levels at high altitude compared with sea level.

RESEARCH DESIGN AND METHODS

We studied 215 pregnant women at 8-42 weeks of gestation in Peru. The women were recruited from Cerro de Pasco, which is situated 4,370 m (14,340 feet) above sea level, and Lima, which is at sea level. We also examined 53 nonpregnant control subjects (22 in Cerro de Pasco and 31 in Lima). Fasting plasma glucose, insulin, C-peptide, and proinsulin concentrations were measured in samples obtained from the antecubital vein between 8:00 a.m. and 10:00 a.m. after an overnight period of fasting for 10-14 h Insulin resistance and beta-cell function were calculated using homeostasis model assessment.

RESULTS

Fasting C-peptide levels and beta-cell function were similar, fasting concentrations of insulin and proinsulin were lower, and insulin sensitivity was higher at high altitude compared with sea level.

CONCLUSIONS

Maternal fasting plasma glucose that is lower at high altitude than at sea level in the presence of similar insulin secretion is associated with higher peripheral insulin sensitivity. This may partly explain the lower birth weights at high altitudes.

Haemorheological adaptation during pregnancy in a Latin American population

OBJECTIVE

To investigate haemorheological changes during pregnancy in a Latin American population and compare to previously published data from Caucasian populations.

DESIGN

Cross-sectional study.

POPULATION

75 pregnant women at 10-36 wk of gestation and 17 non-pregnant female controls in Lima, Peru. All the women and their ancestors for three generations were born and lived at sea level.

METHODS

Viscosity, haematocrit and plasma fibrinogen, albumin and total protein concentrations were determined in blood samples obtained after an overnight period of fasting.

RESULTS

At 10 wk of gestation, total protein concentration and plasma viscosity were above non-pregnant levels by about 15% and subsequently decreased linearly with gestation. Fibrinogen concentration was increased in the first trimester; it then decreased to a nadir at about 20 wk and subsequently increased. Albumin concentration decreased linearly with gestation. Haematocrit decreased from pre-pregnancy levels at 10 wk to a nadir at about 26 wk. Blood viscosity increased in the first trimester and then decreased with gestation to a nadir at about 26 wk.

CONCLUSION

In the first trimester of pregnancy blood and plasma viscosity are increased and they subsequently fall with advancing gestation. Plasma viscosity reflects the changes in total protein concentration, and blood viscosity is dependent on the interplay of changes in plasma viscosity and haematocrit.

Distribution of fetal and embryonic hemoglobins in fetal erythroblasts enriched from maternal blood

BACKGROUND AND OBJECTIVES

To determine the distribution of embryonic and fetal hemoglobin chains in fetal erythroblasts isolated from maternal blood in the first trimester of pregnancy and establish the feasibility of using these chains as markers for fetal cell identification.

DESIGN AND METHODS

Maternal blood was obtained from 187 singleton pregnancies at 11-14 weeks of gestation immediately before fetal karyotyping by chorionic villus sampling. In all cases included in this study the fetal karyotype was normal. Fetal erythroblasts were isolated using triple density gradient separation and anti-CD71 magnetic cell sorting techniques. The enriched erythroblasts were stained with Kleihauer-Giemsa and with fluorescent antibodies for the zeta (z), epsilon (e) and gamma (g) globin chains. The percentage of fetal cells positive for each stain was calculated. Fluorescent in situ hybridization (FISH) for X and Y chromosomes was also performed. Comparison was made with the percentage of cells with positive Y-signal FISH in pregnancies with male fetuses.

RESULTS

The percentage of fetal erythroblasts stained positive was 37% for the z and 95% for both e and g globin chains, as well as the Kleihauer-Giemsa staining. There was a significant association between the Kleihauer-Giemsa stained cells and those stained with e and g globin chains. There was also an association between cells with Y-signals and those stained with e and g globin chains.

INTERPRETATION AND CONCLUSIONS

Embryonic hemoglobin chains can be detected in the enriched fetal erythroblasts, with higher percentages of the e rather than the z globin chains. These chains are therefore potentially unique markers to be used in the identification of cells of fetal origin from maternal blood for prenatal diagnosis of genetic and chromosomal abnormalities.

Maternal serum levels of total activin-A in first-trimester trisomy 21 pregnancies

Maternal serum total activin-A concentration was measured in 45 pregnancies affected by trisomy 21 and 493 control unaffected pregnancies at 10-14 weeks of gestation. In the trisomy 21 pregnancies total activin-A concentration was significantly higher (1.36 MoM of the unaffected pregnancies) and in 16% of cases the level was above the 95th centile of normal. The log10 SD for the control group and the trisomy 21 group were 0.17 and 0.22, respectively. The median pregnancy associated plasma protein-A (PAPP-A) in this trisomy 21 series was 0.49 and for free beta-hCG was 2.05. In the trisomy group there were significant positive associations between total activin-A and PAPP-A (0.6071) and free beta-hCG (0.4255). The low median difference and the high overlap in values between trisomic and unaffected pregnancies make total activin-A of little practical use in first-trimester screening for trisomy 21.

Cervical length at 22-24 weeks of gestation: comparison of transvaginal and transperineal-translabial ultrasonography

OBJECTIVES

To investigate the feasibility of measuring cervical length by transperineal or translabial sonography and compare the measurements obtained by this approach with those obtained transvaginally.

METHODS

In 500 women measurement of cervical length by translabial-transperineal sonography was attempted immediately before transvaginal scanning at 22-24 (median 23) weeks of gestation. In the first phase of the study, considered to be the learning period, 200 patients were examined and their results reviewed, before carrying out the second phase in which 300 patients were examined. A comparison was made of the patient acceptability of both techniques.

RESULTS

Cervical length was successfully measured transvaginally in all cases. In the first phase of the study cervical length was measured by translabial-transperineal sonography in 84% of the 200 patients but there was poor agreement with measurements obtained transvaginally and the 95% tolerance interval for paired observations was -11.0 mm to 16.1 mm. After audit of results it became apparent that the translabially-transperineally derived images were inadequate in more than half of the cases but in those with adequate paired measurements there was a very good agreement between the two and the 95% tolerance interval for paired observations was -5.8 mm to 5.2 mm. In the second phase of the study special attention was paid towards recording measurements of cervical length only in cases where both the internal and external os were adequately visualized. Successful measurements by translabial-transperineal sonography were obtained in 78% of cases and the 95% tolerance interval for paired observations was -5.8 mm to 6.1 mm. The degree of patient acceptability of the two methods was similar.

CONCLUSIONS

The findings of this study suggest that at 22-24 weeks of gestation the cervix can be visualized adequately by translabial-transperineal sonography in about 80% of patients and the measurements of cervical length obtained by this approach are very similar to those obtained by transvaginal sonography.

Assessment of endothelial function in normal twin pregnancy

OBJECTIVE

To assess the maternal endothelial function in normal twin pregnancy.

DESIGN

Cross-sectional study.

SUBJECTS

Endothelial function was investigated in 74 women with normal twin pregnancy at 11-30 weeks of gestation and the results were compared to previous reported findings in 98 women with normal singleton pregnancy and 19 non-pregnant controls.

METHODS

Endothelial function was assessed by measuring the changes of the brachial artery diameter in response to reactive hyperemia (flow-mediated dilatation) using external high resolution ultrasound.

RESULTS

Flow-mediated dilatation of the brachial artery in both twin and singleton pregnancies was significantly higher than in non-pregnant women (P = 0.002 and P = 0.02, respectively). However, there was no significant difference in flow-mediated dilatation between women with twin and singleton pregnancy (9.61 +/- 4.36 vs. 8.84 +/- 3.18, P = 0.38). Resting vessel size, baseline flow and reactive hyperemia did not change significantly with gestation in twin pregnancy and were similar to values in singleton pregnancies and controls.

CONCLUSION

Our findings indicate that although in pregnancy endothelial function is enhanced, this change may not be affected by the number of fetoplacental units present.

Cervical assessment at the routine 23-week scan: standardizing techniques

OBJECTIVE

To examine the frequency of curvature of the cervix and to establish the degree of curvature with increasing cervical length. To assess the significance of this phenomenon in terms of the classification of patients as high risk for pre-term delivery.

METHOD

Cervical length was measured prospectively by transvaginal sonography in 301 women at 23 weeks of gestation. The distance between the internal and external os was measured both as a straight line and also as a curved line along the endocervical canal. In addition, a search of our database was made to identify all women who had undergone cervical assessment as part of a policy of routine screening. In those with cervical length of less than 26 mm the thermal images of the cervix were used to obtain straight and curved measurements. The frequency of curved cervix was calculated and the relationship between the ratio of straight to curved measurement to the curved one was determined.

RESULTS

In the prospective study curvature of the cervix was observed in 143 (48%) of the 301 women. Curvature was observed in 51% (135 of 267) with cervical length of 26-55 mm, 25% (8 of 32) with length of 16-25 mm, and none of the two with length of 1-15 mm. The ratio of the straight to the curved measurement decreased with increasing cervical length (r = -0.27, P = 0.001). In the retrospective study curvature of the cervix was found in 72 (15%) of 471 with length of 16-25 mm and in none of the 76 with length of 1-15 mm.

CONCLUSION

Cervical length is influenced by the degree of cervical curvature. The disparity of measurements between the internal and external os taken as a straight line or along the cervical canal increases with cervical length. However, this disparity may not have any clinical implications because at short cervical length (less than 16 mm) the cervix appears to be always straight.

Maternal plasma glucose at high altitude

OBJECTIVE

To compare plasma glucose in pregnant women living at very high altitude; pregnant women living at sea level; non-pregnant women living at very high altitude; and non-pregnant women living at sea level.

DESIGN

Cross-sectional study.

PARTICIPANTS

Ninety-four pregnant women attending for routine antenatal care at 8-42 weeks of gestation in Cerro de Pasco, Peru which is situated 4370 m above sea level; 122 pregnant women in Lima, which is at sea level; 22 non-pregnant women in Cerro de Pasco; and 31 non-pregnant women in Lima.

METHODS

Plasma glucose concentrations were measured in samples obtained from the antecubital vein between 8 am and 10 am after an overnight period of fasting for at least 10 hours.

RESULTS

Fasting plasma glucose was lower in women at high altitude than in those at sea level, and in both groups the level was lower in pregnant women than in non-pregnant controls. The body mass index was not significantly different between all four groups, and it did not have a significant independent contribution in explaining the variance in fasting plasma glucose.

CONCLUSION

Women native at high altitude have lower plasma glucose concentrations before and during pregnancy than those at sea level.

Vasoactive mediator release by fetal endothelial cells in intrauterine growth restriction and preeclampsia

OBJECTIVE

Preeclampsia and fetal growth restriction are associated with poor placental perfusion, which may be accompanied by a compensatory release of vasoactive substances in the fetoplacental circuit. This study examines the effects of preeclampsia and fetal growth restriction on nitric oxide and prostacyclin signaling pathways in fetal endothelial cells.

STUDY DESIGN

Human umbilical vein endothelial cells from 30 control pregnancies, 18 pregnancies with preeclampsia, and 9 pregnancies with intrauterine growth restriction were cultured. Intracellular cyclic guanosine monophosphate accumulation and 6-keto-prostaglandin F1alpha production were determined.

RESULTS

Intracellular accumulation of cyclic guanosine monophosphate was significantly higher in the preeclampsia group and lower in the growth restriction group than in the control group (9.8, 1.8, and 3.9 pmol/microg protein for 5 minutes, respectively), whereas 6-keto-prostaglandin F1alpha production was not significantly different in the 3 groups.

CONCLUSION

The data suggest that the fetoplacental vascular response to preeclampsia is to increase production of cyclic guanosine monophosphate, perhaps to maintain vessel dilatation and maximum flow through placental villi. In fetal growth restriction the umbilical vein endothelial cells do not or cannot respond to chronic hypoxia by increasing cyclic guanosine monophosphate, which may lead to fetoplacental vasoconstriction.

Improvement in outcomes of multifetal pregnancy reduction with increased experience

OBJECTIVE

This study was undertaken to evaluate a decade of data on multifetal pregnancy reductions at centers with extensive experiences.

STUDY DESIGN

A total of 3513 completed cases from 11 centers in 5 countries were analyzed according to year (before 1990, 1991-1994, and 1995-1998), starting and finishing numbers of embryos or fetuses, and outcomes.

RESULTS

With increasing experience there has been a considerable improvement in outcomes, with decreases in rates of both pregnancy loss and prematurity. Overall loss rates in the last few years were correlated strongly with starting and finishing numbers (starting number > or =6, 15.4%; starting number 5, 11.4%; starting number 4, 7.3%; starting number 3, 4.5%; starting number 2, 6.2%: finishing number 3, 18.4%; finishing number 2, 6.0%; finishing number 1, 6.7%). Birth weight discordance between surviving twins was increased with greater starting number. The proportion of cases with starting number > or =5 diminished from 23.4% to 15.9% to 12.2%. The proportion of patients >40 years old increased in the last 6 years to 9.3%. Gestational age at delivery did not vary with increasing maternal age but was inversely correlated with starting number.

CONCLUSION

Multifetal pregnancy reduction outcomes at our centers for both losses and early prematurity have improved considerably with experience. Reductions from triplets to twins and now from quadruplets to twins carry outcomes as good as those of unreduced twin gestations. Patient demographic characteristics continues to change as more older women use assisted reproductive technologies. In terms of losses, prematurity, and growth, higher starting numbers carry worse outcomes.

Prediction of preterm delivery in twins by cervical assessment at 23 weeks

OBJECTIVE

To establish the relation between cervical length at 23 weeks of gestation in twin pregnancies and risk of spontaneous delivery before 33 weeks.

METHODS

Cervical length was measured by transvaginal sonography at 23 (range 22-24) weeks of gestation in 464 twin pregnancies attending for routine antenatal care. In the patients who were managed expectantly the relation between cervical length and the rate of spontaneous delivery before 33 weeks was determined.

RESULTS

The cervical length distribution was skewed to the left and the median value was 36 mm. The rate of spontaneous delivery before 33 weeks was inversely related to cervical length at 23 weeks. It increased gradually from about 2.5% at 60 mm, to 5% at 40 mm and 12% at 25 mm, and exponentially below this length to 17% at 20 mm and 80% at 8 mm. Cervical length of 20 mm or less is found in about 8% of the population and this group contained about 40% of women delivering spontaneously before 33 weeks.

CONCLUSIONS

In twin pregnancies measurement of cervical length provides useful prediction of risk for spontaneous early preterm delivery.

Haematopoietic stem cell transplantation and gene therapy in the fetus: ready for clinical use?

Allogeneic haematopoietic stem cell transplantation in utero has been successfully used for the prenatal treatment of severe combined immunodefiency syndrome. However, this treatment has not been successful in the therapy of other conditions in which the fetus is immunologically competent. The main obstacles to success are lack of competitive advantage of donor versus host stem cells, preventing stable engraftment and graft rejection. Several strategies are being explored to overcome these problems, and some of them have been successful in animal studies. Prenatal gene therapy, using ex-vivo transduced autologous haematopoietic cells or direct gene targeting in utero, is another potential approach in the treatment of immunocompetent fetal recipients. Although this has been shown to be feasible in animal models, safety concerns regarding transduction of fetal germ cells or maternal cells should be addressed in preclinical experiments prior to initiation of clinical trials.

Fetal heart rate in chromosomally abnormal fetuses

OBJECTIVES

To determine the effects of chromosomal defects on fetal heart rate at 10-14 weeks of gestation.

METHODS

Fetal heart rate at 10-14 weeks of gestation in 1061 chromosomally abnormal fetuses was compared to that from 25,000 normal pregnancies. The chromosomally abnormal group included 554 cases of trisomy 21, 219 cases of trisomy 18, 95 of trisomy 13, 50 of triploidy, 115 of Turner syndrome and 28 of sex chromosome abnormalities other than Turner syndrome.

RESULTS

In the normal group, fetal heart rate decreased from a mean value of 170 beats per minute (bpm) at 35 mm of crown-rump length to 155 bpm at 84 mm crown-rump length. In trisomy 21, trisomy 13 and Turner syndrome fetal heart rate was significantly higher, in trisomy 18 and triploidy the heart rate was lower and in other sex chromosome defects it was not significantly different from normal. Fetal heart rate was above the 95th centile of the normal range in 10%, 67% and 52% of fetuses with trisomy 21, trisomy 13 and Turner syndrome, respectively. The fetal heart rate was below the 5th centile in 30% of fetuses with triploidy and 19% of those with trisomy 18.

CONCLUSIONS

Trisomy 21, trisomy 13 and Turner syndrome are associated with fetal tachycardia, whereas in trisomy 18 and triploidy there is fetal bradycardia. Inclusion of fetal heart rate in a first-trimester screening program for trisomy 21 by a combination of maternal age and fetal nuchal translucency thickness is unlikely to provide useful improvement in sensitivity.