Fetal weight prediction by ultrasound measurements. A prospective study

Fetal weight prediction with ultrasonic measurements of biparietal diameter (BPD) and abdominal circumference (AC) using the equation by Shepard et al. [1982] was tested prospectively in 310 fetuses. Fetuses of all weight categories were included. The error of weight prediction was in the range of +684 to -880 g. One SD of prediction error was 242 g or 8.5% of birth weight. An overestimation was seen in a fetus with a birth weight of less than 2,500 g (1 SD = 183 g or 10% of birth weight). An underestimation could be observed in a fetus with a birth weight of more than 4,000 g (1 SD = 259 g or 5.7% of birth weight). The use of a combination of BPD and AC is more accurate than the use of each of these parameters. In a fetus with a birth weight of less than 2,500 g, the equations by Thurnau et al. [1983] and Weinberger et al. [1984] are of equal clinical value. The method of Shepard et al. should be complemented with measurements of the 'cephalic index' to exclude fetuses with brachycephaly or dolichocephaly, but one should be aware that the variability of weight prediction is high (2 SD = 11.4-19.8% of birth weight).     

Fetal middle cerebral artery Doppler waveforms in twin-twin transfusion syndrome

The aim of this study was to compare the fetal middle cerebral artery (MCA) Doppler waveforms in growth-retarded twin fetuses with (n = 11) and without (n = 24) twin-twin transfusion syndrome (TTTS). Umbilical artery (UA) and fetal MCA Doppler velocity waveforms were recorded on admission. The mean values of the UA pulsatility index (PI) of smaller twin fetuses with and without TTTS were significantly higher than those of normal singleton pregnancies. The mean values of the MCA PI of smaller twin fetuses in the TTTS group (+0.7 +/- 1 SD) were significantly higher than those of normal singleton pregnancies on admission, and these levels did not markedly change following amniocentesis. On the other hand, the values of the MCA of the growth-retarded fetuses without TTTS (-0.9 +/- 1 SD) were significantly lower than those of normal singleton pregnancies. Our findings suggest that measurement of fetal MCA PI is a useful method to assess growth-retarded fetuses in monochorionic twin pregnancies. Copyright Copyright 1999 S. Karger AG, Basel     

Estimation of birth weight by two-dimensional ultrasonography: a critical appraisal of its accuracy

OBJECTIVE: To assess the accuracy and characterize two-dimensional ultrasonographic formulas for the estimation of birth weight according to the type of fetal biometric parameters these formulas rely on to make fetal weight predictions. METHODS: A prospective recruitment of 589 pregnant women was carried out for this cross-sectional study. Different biometric parameters were taken ultrasonographically to estimate birth weight using 35 different formulas. Only those patients who delivered within 48 hours were considered for the analysis (n=441). Differences between the estimated and actual birth weight were assessed by percentage error, accuracy in predictions within +/-10% and +/-15% of error, and use of the Bland-Altman method. All formulas were assessed individually and clustered on the basis of the type of fetal biometric information that they incorporate. RESULTS: Twenty-nine formulas provided an overall mean absolute percentage error less than or equal to 10%, with overall predictions within +/-10% and +/-15% of the actual birth weight (69.2% and 86.5%, respectively). Twenty formulas showed a good accuracy (bias 0.50 or less) and low variability (mean standard deviation 1.2). Among the categorized algorithms, formulas based on head-abdomen-femur measurements showed the lowest mean absolute percentage error. Upon stratification for birth weight, the group of formulas that rely on abdomen and femur measurements performed best for fetuses weighing more than 3,500 g (P<.01). CONCLUSION: Our findings show that most formulas are relatively accurate at predicting birth weight up to 3,500 g, and all algorithms tend to underestimate large fetuses. LEVEL OF EVIDENCE: III.     

Validity of sonographic formulas for estimating fetal weight below 1,250 g: a series of 119 cases.

OBJECTIVE: The aim of this study was to determine the accuracy of sonographic methods for estimating fetal weight < 1,250 g on the basis of ten published formulas falling into two principal categories: general formulas applied to all fetuses, and formulas specifically developed for very-low-weight fetuses. METHODS: Recent biometric data (obtained less than 7 days before birth) on 119 fetuses weighing < 1,250 g were used retrospectively. Estimated fetal weights derived from ten published formulas were compared to actual weights. For each equation, the errors in predicting fetal weight were used to calculate mean percentage error and standard deviation of the mean error. The t test was used to determine whether the mean errors were significatively different from zero. The F test was used to determine if there were significant differences in the standard deviation of the mean errors. RESULTS: The mean birth weight of infants was 956 +/- (SD) 183 g at a gestational age of 29 +/- (SD) 2.3 weeks. The best three formulas were the Hadlock, Sabbagha and Mielke which generated a mean error of -0.25, 2.81 and 0.29 not statistically different from zero with standard deviations of 13.02, 9.14 and 11.96, which were not statistically different. CONCLUSION: In our population of very-low-birth-weight infants, the use of specific formulas targeted to those fetuses does not provide a more accurate estimation of fetal weight.     

Good accuracy of ultrasound estimations of fetal weight performed by midwives

BACKGROUND: This study was undertaken to evaluate the quality of ultrasound estimation of fetal weight when performed by midwives experienced in ultrasound examinations. We also examined whether the accuracy was affected by fetal presentation, twin pregnancy or birth weight category. The results of 5 different formulas were compared to determine which was most accurate in our study population. METHODS: The study population consisted of 620 fetuses in 607 pregnancies, on whom fetal weight estimations had been performed within 3 days prior to delivery. The group of twins (n=27) was analysed separately. Results achieved by Hadlock 2 formula used in our unit were compared with 4 other widely used formulas for estimation of fetal weight. RESULTS: With Hadlock 2 formula, mean absolute percent error was 6.2% and SD of error was 7.6% of mean birth weight. A total of 81% of estimates were within 10% of the actual birth weight. All the formulas tended to overestimate the weight of twins and fetuses weighing <2,500 g, and underestimate the weight of fetuses >4,000 g. Presentation of the fetus did not significantly influence the accuracy. The formula Hadlock 2, using 3 parameters (biparietal diameter, abdominal circumference and femur length) gave the highest ICC of 0.910. CONCLUSIONS: Ultrasound estimation of fetal weight performed by midwives is feasible and of similar accuracy as in the original studies. Major errors may occur both in small and large birth weight groups.     

Reference curves of symphysis-fundus height in twin pregnancies

OBJECTIVE: To generate reliable new reference ranges for symphysis-fundus height (SFH) in twin pregnancies using modern statistical methods and to evaluate whether small-for-gestational age (SGA) babies of women who had a SFH measurement after the 25th gestational week could be predicted by the SFH measurement in the reference curves and other maternal data. STUDY DESIGN: In a retrospective cross-sectional study at the obstetric outpatient clinic, Zurich University Hospital, SFH was determined in 257 twin-pregnant women with accurately dateable twin pregnancies (Caucasians: N=217, Asians: N=15, Blacks: N=10, and 15 others). Exclusion criteria were intrauterine fetal death, and known fetal and maternal diseases, which influence SFH. Pregnant women with twins were divided in three groups according to the birth weight of the babies. Group I: both babies were appropriate for gestational age (AGA), group II: one baby was AGA and one SGA, and group III: both babies were SGA. RESULTS: SFH measurements increased linearly with gestational age (GA). The following rule of thumb is suggested for the 50th centile of SFH (cm)=gestational week+10% of gestational week. Age, height, weight and body mass index (BMI) before pregnancy, parity and ethnic group were insignificant determinants in SFH measurement. A prognostic score for identification of group III was created for a GA> or =25 weeks and BMI<30 kg/m2. CONCLUSIONS: Measuring SFH is simple, inexpensive and non-invasive and may be of some use for identifying twin mothers with SGA twin pairs.     

Usefulness of symphysis-fundal height in predicting fetal weight in healthy term pregnant women

BACKGROUND: There are some works reporting that the measurement of the symphysis-fundal height (SFH) of a full-term uterus is a simple method for estimating the fetal weight. AIM: Evaluating the goodness of distance between the symphysis and uterine fundus in predicting both low-weight fetuses and high-weight fetuses, comparing it with the third quarter ultrasound estimation of fetal weight and then assessing the clinical effectivity of symphysis-fundal measurement associated with third quarter echography in predicting birth weight. METHODS: A prospective study was carried out on 96 single physiologically full-term pregnancies. The diagnostic accuracy of the SFH, echographic fetal growth estimated between the 32nd and the 35th week (expressed in percentiles), and of both was expressed as sensitivity, specificity, predictive positive and negative value, likelihood ratios and compared. RESULTS: There was a correlation between the SFH and fetal birth weight. A SFH below 33 cm is predictive of a fetus whose weight is less than 3,100 g whereas a SFH above 34 cm is predictive of a fetus whose weight is more than or equal to 4,000 g. The diagnostic effectiveness of the SFH was not significantly higher than the ultrasound scanning evaluation of fetal weight in the third quarter and could be slightly improved if it is taken into account along with the ultrasound scanning data. CONCLUSIONS: The measurement of the SFH at term may be helpful in foretelling the fetal birth weight and may improve the diagnostic accuracy of the third quarter echographic estimation of birth weight.     

Accuracy and modifying factors of the sonographic estimation of fetal weight in a high-risk population

There have been a number of reviews assessing the accuracy of different methods of sonographic estimation of fetal weight, without identifying any clearly superior equation. In order to optimise accuracy in a high-risk population, we decided to compare some of the most popular early equations with the newer volume-based equations, and to try and identify factors that affect the ability of these equations to estimate fetal weight accurately We collected the scan and delivery details of 192 fetuses born within one week of a sonographic estimation of fetal weight. We then applied three of the most popular equations and two newer volume-based equations to the recorded fetal biometric parameters to assess the performance of each equation overall, and under varying maternal, fetal, and scan conditions. The equations of Shepard, Hadlock A, Hadlock B and Combs produced similar results with systematic (mean) errors in the range 1.2-1.9% and random error characterised by one standard deviation in the range of 8.6-9.5%. Dudley's volume-based equation produced a significant systematic error in the form of a mean error of 7.4%, which corresponds to a mean birthweight (BW) which is 7.4% above the mean estimated fetal weight (EFW). When we stratified the study group by birthweight, Combs' equation produced significant differences in the mean error, (p < 0.00001), that ranged from a mean overestimation in fetal weight of 8.5% for babies with BW < 1000 g to a mean underestimation in fetal weight of 6.2% for babies with BW > 3000 g. Oligohydramnios resulted in a trend towards an increased mean error for all equations which was only statistically significant for Hadlock B. The equations Shepard and Hadlock A performed best in our high-risk population. They produced the smallest systematic errors across the entire study group and were not adversely affected by variations in birthweight, liquor volume, or fetal presentation. The newer, volume-based equations were disappointing, producing large systematic errors. Large random errors in all equations continue to be the Achilles' heel that limit the value of sonographic EFW.     

Symphysis-fundal height measurement--a reliable parameter for assessment of fetal growth

Intrauterine growth retardation (IUGR) is one of the major causes of perinatal mortality in countries like India. Fundal height traditionally measured in relation to umbilicus and xiphisternum is of little value in predicting the fetal growth. Some workers have found that symphysis fundal height (SFH) measurements could be useful in screening pregnancies for growth retardation. A prospective study was taken up in 109 pregnant women attending the antenatal clinic of our Institution. Serial measurements of SFH, abdominal girth, double abdominal wall thickness (DAWT) and maternal weight gain were recorded. SFH measurements obtained were arranged on the basis of 10th, 50th and 90th percentile and represented graphically. Statistical analysis showed that the coefficient of variation was smallest for SFH as compared to abdominal girth and maternal weight gain. The babies (single born) delivered were between 2600 g and 3700 g irrespective of whether the maternal weight gain was 143 g/week or 424 g/week. The abdominal wall thickness had no influence on the measurement of SFH. An attempt was made to develop a nomogram of SFH for our population. This is a simple, reliable and inexpensive method in the screening of pregnancies for IUGR.     

Blood coagulation and fibrinolysis activities during normal pregnancy and fetal growth--study based on estimated fetal body weight

There are many factors influencing the growth of the fetus. Since these factors have complex interrelations, they are difficult to clarify. The authors studied the effects of blood coagulation and fibrinolysis on the growth of the fetus during pregnancy, especially from the 2nd trimester into the 3rd trimester. The subjects were 86 normal pregnant women, and the subjects of study were blood coagulation, fibrinolysis activity of the mother, and estimated fetal birth weight after the 28th (2nd trimester) and 36th weeks of gestation (3rd trimester) in each case. 1. Changes in blood coagulation activity and fibrinolysis varied from the 2nd trimester into the 3rd trimester. The percentage of cases showing lowered platelets was 68.6% of the total, and the percentages of cases with reduced platelet ADP, epinephrine, and collagen aggregation were 60.5%, 55.8%, and 51.2%, respectively. The percentages of cases showing shortened prothrombin time and activated partial thromboplastin time were 58.1% and 51.2% of the total, respectively. The percentage of cases with reduced fibrinogen was 24.4% of the total. The percentages of cases with reduced antithrombin III, plasminogen, and alpha 2-plasmin inhibitor activity were 66.3%, 55.8%, and 75.6% of the total, respectively. 2. The birth weight of babies in a group with shortened prothrombin time was 2,935.1 +/- 395.2g(n = 50, mean +/- SD), while that in a group with prolonged prothrombin time was 3,106.2 +/- 357.9g(n = 36). The estimated fetal birth weight gain from the 2nd trimester to the 3rd trimester was 1,431.6 +/- 296.5g in the former group and 1,644.5 +/- 390.5g in the latter group. The differences were significant (p less than 0.05, p less than 0.01). The birth weight of babies in a group with lowered antithrombin III activity was 2,960.1 +/- 341.3g(n = 57), and that in an acceleration group was 3,157.8 +/- 370.0g(n = 29). The estimated fetal weight gain from the 2nd trimester to the 3rd trimester was 1,477.7 +/- 281.9g in the former group and 1,637.1 +/- 390.6g in the latter group. The differences were significant (p less than 0.02, p less than 0.05). 3. The estimated fetal weight gain from the 2nd trimester to the 3rd trimester in the group showing prolongated prothrombin time and activated partial thromboplastin time in this period was significantly larger than in the group showing shortened prothrombin time and activated partial thromboplastin time (p less than 0.001). These results suggested that the changes in blood coagulation and fibrinolysis activity of mothers from the 2nd trimester to the 3rd trimester affected the growth of the fetus.     

Ultrasonic prediction of term birth weight in Hispanic women. Accuracy in an outpatient clinic

OBJECTIVE: To investigate the accuracy of ultrasonic fetal biometric algorithms for estimating term fetal weight. STUDY DESIGN: Ultrasonographic fetal biometric assessments were made in 74 Hispanic women who delivered at 37-42 weeks of gestation. Measurements were taken of the fetal biparietal diameter, head circumference, abdominal circumference and femur length. Twenty-seven standard fetal biometric algorithms were assessed for their accuracy in predicting fetal weight. Results were compared to those obtained by merely guessing the mean term birth weight in each case. RESULTS: The correlation between ultrasonically predicted and actual birth weights ranged from 0.52 to 0.79. The different ultrasonic algorithms estimated fetal weight to within +/- 8.6-15.0% (+/- 295-520 g) of actual birth weight as compared with +/- 13.6% (+/- 449 g) for guessing the mean birth weight in each case (mean +/- SD). The mean absolute prediction errors for 17 of the ultrasonic equations (63%) were superior to those obtained by guessing the mean birth weight by 3.2-5.0% (96-154 g) (P < .05). Fourteen algorithms (52%) were more accurate for predicting fetal weight to within +/- 15%, and 20 algorithms (74%) were more accurate for predicting fetal weight to within +/- 10% of actual birth weight than simply guessing the mean birth weight (P < .05). Ten ultrasonic equations (37%) showed significant utility for predicting fetal weight > 4,000 g (likelihood ratio > 5.0). CONCLUSION: Term fetal weight predictions using the majority of sonographic fetal biometric equations are more accurate, by up to 154 g and 5%, than simply guessing the population-specific mean birth weight.     

Doppler assessment of the renal blood flow velocity waveform during indomethacin therapy for preterm labor and polyhydramnios

To investigate the effects of indomethacin on the human fetal renal blood flow velocity waveform, 17 fetuses whose mothers were treated for preterm labor (N = 8) or polyhydramnios (N = 9) were studied. There were five growth-retarded fetuses (all in the group with polyhydramnios), 11 normal fetuses, and one fetus with red-cell alloimmunization. The indomethacin dose in all patients was 25 mg orally every 6 hours. The gestational age of the fetuses studied varied between 24-35 weeks (mean +/- SD 29.6 +/- 2.8). The fetal renal artery was studied at its origin from the aorta before and during the first 24 hours of indomethacin therapy. Seven fetuses manifested ductal constriction. Three fetuses also manifested tricuspid regurgitation. All ductal constrictions and the tricuspid regurgitations resolved in utero after discontinuation of indomethacin. There were no significant differences in the pulsatility index values of the renal artery before and during indomethacin therapy. These results suggest that there is no change in fetal renovascular parameters detectable with pulsatility index measurements during the first 24 hours of maternal indomethacin therapy.     

Influence of gestational age and fetal heart rate on the fetal mechanical PR interval.

OBJECTIVE: The fetal mechanical PR interval obtained via pulsed Doppler has previously been demonstrated to correlate with electrocardiographic PR interval measured in the neonate. We sought to further analyze the influence of fetal heart rate and gestational age upon the fetal mechanical PR interval. METHODS: We searched our database for mechanical PR intervals, which were obtained during fetal echocardiography performed in our antenatal diagnostic unit. We included fetuses with a normal cardiac structural survey. The mechanical PR interval is measured from the A wave of the mitral valve to the beginning of ventricular systole corresponding to the opening of the aortic valve. Linear regression curves were generated to examine the correlation of mechanical PR interval with gestational age and fetal heart rate. Analysis of variance was used to compare the mean variation across three gestational age groups: 17-21.9 weeks (n = 24), 22-25.9 weeks (n = 52) and 26-38 weeks (n = 20). RESULTS: Mechanical PR intervals were measured in 96 fetuses with normal fetal echocardiography. The mechanical PR interval was 123.9 +/- 10.3 ms (mean +/- SD), with a range of 90-150 ms. Linear regression curves correlating mechanical PR interval with fetal heart rate and gestational age demonstrated a flat slope with R2 = 0.016, p = 0.22 and R2 = 0.0004, p = 0.85, respectively. The mechanical PR interval measured over the three gestational ages was as follows (mean +/- SD): 122.3 +/- 10.5 ms for 17-21.9 weeks; 125.0 +/- 9.6 ms for 22-25.9 weeks; and 123.1 +/- 11.9 ms for 26-38 weeks. Analysis of variance revealed no difference among the mechanical PR interval means measured over the three gestational age groups (p = 0.53). CONCLUSIONS: Fetal mechanical PR interval ranges from 90 to 150 ms in fetuses with sonographically normal fetal cardiac structure and rate. The mechanical PR interval appears to be independent of gestational age and fetal heart rate.     

Obstetric problems of newborn infants with a birth weight over 4,500 g

Analysis of birth records of neonates a birth weight of 4,500 g or more (n = 83) has been made in order to compare the course of pregnancy and delivery to a normal birth weight of 3,000-3,500 (n = 100) among 14,193 newborns observed from 1983 to 1987 in Obstetric department of district hospital Berlin-Friedrichshain. On both groups mortality rate amounted to nil. Maternal morbidity is mainly caused by delivery injuries and postpartal atony. The perinatal morbidity which accounts for 7.2% is caused to increased acidosis rate (9.6%), complications of birth traumas such as shoulder dystocia (4.8%), fractures (2.4%) and paresis of nerve plexes (2.4%). The antenatal ultrasound assessment of fetal weight has been emphasized. Caesarean section is advised in cases of a fetal weight of 5,000 g, or more malpresentation and in a primipara with a history of previous caesarean section and with fetal weight more than 3,500-4,000 g. The problems of shoulder dystocia are being discussed.     

Birth-weight-specific perinatal mortality in Japan, 1989-1993: singleton versus multifetal pregnancies.

OBJECTIVE: To investigate the relation between birth weight and perinatal mortality in multifetal pregnancies, which is more than 5 times higher than for singleton infants. METHODS: We assessed the incidence of perinatal deaths based on birth weight in 89,566 infants of multifetal pregnancies and 6,025,199 infants of singleton pregnancies in Japan. Perinatal death was defined as stillbirth and early neonatal death (death <1 week of age). RESULTS: The incidence of perinatal death was consistently lower for infants of multifetal pregnancies than for infants of singleton pregnancies at birth weights of 500-2,499 g. However, the incidence of infants of multifetal pregnancies with birth weights >/=2,500 g consistently exceeded that in singleton infants weighing >/=2,500 g. The relative risk (95% CI) of perinatal death among infants of multifetal pregnancies compared with singleton infants in the same category of birth weight was 0.88 (0.84-0.93) at 500 g. The relative risk decreased to 0.31 (0.25-0.39) at 1,900 g, increased to >1.0 at 2,500 g, to 3.7 (2.2-6.1) at 3,000 g, and to 14.9 (7.8-28.4) at >/=3,500 g. CONCLUSIONS: Japanese infants of multifetal pregnancies reaching >/=2,500 g in body weight have a significantly higher risk of perinatal death than singleton infants in the same category of body weight. Increased monitoring of fetuses of multifetal pregnancies who weigh >/=2,500 g may be helpful in reducing the incidence of perinatal mortality.     

Correlation between intrapartum fundal height and birth weight

In a prospective cross-sectional study, the correlation between symphysiofundal height (SFH) and birth weight was evaluated in 2646 consecutive parturients at the University of Nigeria Teaching Hospital, Enugu, over a 19-month period. The standard deviations of the observed birth weight were least when the SFH measured 33-39 cm, which corresponded to the birth weight range 2500-3999 g. The overall standard deviation was 275 g. A second order polynomial fitted the data best, giving the equation y +/- 258.1-62.9x -3.8x2, where y represents the observed birth weight in grams and x the SFH in centimetres. The R2 statistic for the model was 0.82. This and other assessment showed a good model fit. The birth weight centiles for the various SFH measurements were derived and their usefulness discussed. It was concluded that the SFH-derived birth weight centiles are useful alternatives to ultrasonography especially in the birth weight range 2500-3999 g.     

Clinical and ultrasonographic weight estimation in large for gestational age fetus

OBJECTIVE: To examine prospectively the effect on pregnancy outcome of a management protocol, that adds ultrasonographic weight estimation in fetuses suspected clinically as large. STUDY DESIGN: Prospective follow up study of all singleton deliveries during a 1 year period. All patients underwent routine clinical estimation of fetal weight. When clinical estimation of fetal weight was > or = 3700 g, patients were referred for ultrasonographic estimation of fetal weight. When the latter was > or = 4000 g the patient was informed about the risks of birth trauma. Cesarean section was recommended only when > or = 4500 g. Ultrasonography was repeated every 4 days when possible. Predictive values of clinical and ultrasonographic estimations of fetal weight for diagnosing macrosomia, defined for the purpose of this study as 4000 g or more, and their effect on the rate of cesarean sections. RESULTS: Five hundred fifty-five (14.4%) out of 3844 singletons were estimated as 3700 g or more. Only 315 fetuses had ultrasonographic estimation of weight within 3 days of delivery. The sensitivity of clinical and ultrasonographic prediction of macrosomia was 68 and 58%, respectively. Cesarean section rate in newborns weighing 4000 g or more was 22% when macrosomia was clinically suspected compared to 11% when it was not (P<0.05). In fetuses estimated ultrasonographically as 4000 g or larger the cesarean section rate was doubled (50.7% versus 24.9%, P<0.05) compared to those estimated as smaller than 4000 g, although actual weight of 4500 g or more was recorded in 10.6 and 8.5% of these groups, respectively. There were no cases of shoulder dystocia in macrosomic babies when macrosomia was not detected by ultrasound compared to two cases of shoulder dystocia (2.7%) when macrosomia was detected by ultrasound. CONCLUSION: Antenatal suspicion of macrosomia increased the cesarean section rate while the associated improvement in pregnancy outcome remains questionable. The contribution of ultrasound, added to routine clinical estimation of fetal weight, was clinically insignificant apart from a further increase in cesarean section rate.     

Weight estimation for low birth weight fetuses and macrosomic fetuses in Chinese population

Objective  

Compared with normal birth weight fetuses (2,500–4,000 g), accurate fetal weight estimation for fetuses with low or excessive weight is considered more important for fetal compromise prediction and labor management. New formulas were developed to estimate weight for low birth weight (LBW) fetuses and macrosomic fetuses, respectively.     

Concentrations of growth hormone, prolactin and thyroid-stimulating hormone in the maternal, fetal and amniotic compartments

GH, PRL and TSH in the maternal, fetal and amniotic compartments were measured by radioimmunoassay in normal pregnant women (group I, n = 16) and patients with anencephalic fetuses (group II, n = 10). The concentrations of GH (20.6 +/- 8.5 ng/ml, mean +/- SD) in cord blood of normal fetuses were significantly higher (p less than 0.001) than those (5.1 +/- 3.5 ng/ml) in anencephalic fetuses. Both maternal PRL levels in group I and group II were lower than their respective cord bloods. The concentrations of PRL (283.1 +/- 127.5 ng/ml) in normal fetuses were higher, but not significantly, than those (199.4 +/- 111.8 ng/ml) in anencephalic fetuses. Also, compared with PRL levels in the maternal and cord blood, those in amniotic fluid were significantly higher (p less than 0.001) in both groups. On the contrary, GH and TSH levels in amniotic fluid were much lower than those in the maternal and fetal blood. The concentration of TSH (10.2 +/- 4.6 microU/ml) in normal fetuses was significantly higher (p less than 0.05) than those (7.1 +/- 3.1 microU/ml) in maternal blood, but not significantly different from those (11.3 +/- 3.6 microU/ml) in anencephalic fetuses. These results suggest that GH, PRL and TSH do not cross human placenta and biosyntheses of these hormones in the maternal and fetal pituitaries are independent.