Fetal development of the hand, digits and digit ratio (2D:4D)

OBJECTIVE: The purpose of this study was to investigate growth patterns in human hands, digits and digit ratio (2D:4D) during the fetal period. METHODS: The study is carried out on 161 human fetuses (83 males, 78 females) free from external pathology or malformation with ages ranging between 9 and 40 weeks of gestation. Following general external measurements, length and width of the hand, digit lengths separate for each hand was measured, hand index and the ratio of the lengths of the 2nd finger to the 4th finger (2D:4D index) was computed. RESULTS: Means and standard deviations of the parameters with respect to gestational weeks, months and trimesters were calculated. There was a significant correlation between all parameters and gestational age (p<0.001). No significant differences were observed between sexes or sides for any of the parameters (p>0.05). 2D:4D ratio was significantly higher in females compared to males (p<0.05) and mean 2D:4D did not change with gestational age. CONCLUSION: Detailed information of hand and digit parameters related to the fetal period will reveal the extent of biological variations of hand and digit parameters to be used in future studies. We hope that data acquired in this study will facilitate other studies on hand and digit anomalies, pathologies and variations as well as diagnoses and treatments of such conditions conducted in obstetrics, perinatology, forensic medicine and fetal pathology departments.     

Prediction of chronic neonatal lung disease in very low birthweight neonates using clinical and radiological variables.

In a prospective observational study, the fatty acid content of human umbilical artery and vein wall phospholipids was determined in fetuses classified according to their change in abdominal circumference during the third trimester. Three groups were identified: appropriate for gestational age (AGA; 24 infants) and small for gestational age (SGA; 38 infants) with normal antenatal growth rate, and SGA with fetal growth retardation (22 infants). The venous linoleic acid (18:2 omega 6) content (expressed as a percentage of the total fatty acids identified) was greater in growth retarded SGA fetuses (3.5 (0.6)%) than in SGA fetuses with a normal growth rate (3.1 (0.5)%) and AGA fetuses (3.0 (0.5)%), whereas the venous contents of eicosatrienoic (20:3 omega 6) and docosahexaenoic acid (22:6 omega 3) were lower. In growth retarded SGA fetuses, the venous and arterial 20:3 omega 6 content correlated with the change in abdominal circumference. In SGA fetuses with a normal growth rate, lower contents of arterial 18:2 omega 6 and 22:6 omega 3 were associated with a smaller change in abdominal circumference and birth weight. Different metabolic derangements appear to underly normal and subnormal growth rate in SGA fetuses, suggesting that different strategies of dietary intervention may be required to aid fetal growth and reduce the sequelae of fetal growth retardation.     

Urogenital anomalies in human male fetuses

BACKGROUND: There are few studies in the literature performed in human fetuses evaluating the incidence of genitourinary anomalies. AIMS: Analyze the incidence of congenital urogenital malformations in human male fetuses. STUDY DESIGNS AND SUBJECTS: We analyzed 166 human male fetuses well preserved. The gestational age was determined in weeks post conception (WPC) according to the foot length criterion and ranged from 10 to 35 WPC. The fetuses were dissected with the aid of a stereoscopic lens with 2.5x magnification. We performed abdominal and pelvic incisions to expose the urogenital organs. We studied the incidence of renal, ureteral, vesicle, urethral, testicular, epididymal, vas deferens, prostate and penile anomalies. RESULTS: Of the 166 fetuses, 7 (4.2%) presented some kind of anomaly of the urogenital system. Renal anomalies were found in two fetuses (1.2%). Unilateral renal agenesis was found in a 25 WPC fetus. Horseshoe kidney was found in a 20 WPC fetus. In a 23 WPC fetus (0.6%) the two testes were absent. Epididymal disjunction anomalies were found in four fetuses (2.4%). CONCLUSIONS: The urogenital anomalies in human male fetuses are rare and have an incidence around 4%.     

The development of large intestine during the fetal period

OBJECTIVE: The aim of this study is to determine the colon types, developmental change of the colon morphology during the fetal period. METHODS: The study was realised on 131 human fetuses (male 69, female 62) ages between 10 and 40 weeks, which have no external pathology and anomalies. The colon types were evaluated in two parts. As the first part, the colon part between the ileal orifice and sigmoid colon was typed. The sigmoid colon was typed as the second part. The macroscopic diameters of parts of the colon and the thicknesses of wall layers of ascending and descending colons were measured under the light microscope. RESULTS: For the proximal part of the colon, there were seven types of colon, and there were five types for the sigmoid colon. For the first part, transverse type colon was a rare type during the fetal period (3%). The oblique type colon was observed mostly in the first and second trimester during the fetal period. Adult type colon was the most common type in the third trimester and full-term groups. The pendulous type colon was observed mostly in the third trimester. The development of the haustra and tenia coli in the first trimester was quite slow, but later the development increased more and more, and during the full-term period, the haustra and tenia coli could be seen clearly. CONCLUSION: The percentage distribution of the colon types between the trimesters was significant. It was observed that the maturation of haustra and tenia coli started from the ascending colon and progressed towards the sigmoid colon. The thickness of the tunica mucosa layer both in the ascending and in descending colon part increased considerably in the middle of the second trimester.     

Fetal plasma leptin concentrations: relationship with different intrauterine growth patterns from 19 weeks to term

The relationship between in utero fetal growth and fetal leptin concentrations was investigated between 19 and 41 wk in 40 normal (appropriate for gestational age, AGA) fetuses, in 25 intrauterine growth-restricted (IUGR) fetuses, and in 18 fetuses from gestational diabetic mothers (GDM), representing different intrauterine growth patterns. Umbilical venous plasma leptin concentrations were determined at the time of either in utero fetal blood sampling or delivery. Plasma leptin was measurable as early as 19 wk of gestation. A significant difference was observed between umbilical venous and arterial plasma leptin concentrations (0.6+/-0.6 ng/mL; p<0.01). In AGA and in IUGR fetuses, significant positive relationships were found between fetal leptin concentrations and both gestational age (p<0.001) and fetal weight (p<0.001). Leptin concentrations were significantly higher in AGA than IUGR only after 34 wk (p<0.05), but leptin per kilogram fetal weight (leptin/kg) was not significantly different. In IUGR with abnormal umbilical arterial Doppler velocimetry and fetal heart rate, leptin/kg significantly higher than in IUGR with normal biophysical and biochemical parameters was found (p<0.05). Both circulating plasma leptin and leptin/kg were significantly higher in GDM than in normal fetuses (p<0.001) and correlated with abdominal fat mass measured by ultrasound. No gender differences were observed in any group of fetuses. These findings indicate a clear relationship between fetal leptin concentrations and fetal fat mass. Data in severe IUGR suggest the presence of increased leptin concentrations associated with in utero signs of fetal distress.     

Ultrasound evaluation of the normal fetal pharynx

OBJECTIVE: To obtain normative data for fetal pharyngeal diameter and to investigate the ability to visualize pharynx at different gestational ages during routine prenatal sonography. METHODS: Sonographic studies were performed in 292 consecutive pregnant women. The diameters of the pharynx were measured and our ability to visualize pharynx was evaluated at different gestational ages. RESULTS: Sonographic measurements of the pharyngeal diameter were obtained in 153 of the 292 fetuses. The diameter of the pharynx increased from a mean of 4.5+/-0.53 mm at 16 weeks to 9.1+/-1.72 mm at 36 weeks. Pharyngeal diameters showed a significant positive relationship with advancing gestational age (p<0.0001, R2=0.571). The differences in visualization among different gestational age groups were found to be significant (p<0.05 by Chi-Square). CONCLUSION: This study reports normative data for fetal pharyngeal diameter. Pharyngeal measurements were similar to previous reports in the literature. Our success in visualizing the pharynx was best between 21 and 30 weeks of gestation. This period might be the optimum time for evaluating fetal pharynx.     

Fetal plasma testosterone correlates positively with cortisol

BACKGROUND: Fetal exposure to testosterone has been implicated in programming childhood behaviour, but little is known about the determinants of fetal testosterone concentrations. AIMS: To investigate the relation between fetal testosterone and maternal and fetal cortisol. METHODS: Clinically indicated blood samples taken from 44 human fetuses (mean gestational age 27 weeks, range 15-38), together with paired maternal samples, were analysed for testosterone and cortisol concentrations. RESULTS: Male fetuses had significantly higher concentrations of testosterone than females. Female but not male fetal concentrations rose significantly with gestational age. Fetal testosterone correlated positively with both fetal cortisol and maternal testosterone concentrations. Multiple regression showed that maternal testosterone and fetal cortisol were independently correlated with fetal plasma testosterone in both sexes. CONCLUSION: Unlike the norm in the adult, where testosterone production is often inhibited by cortisol, in the fetus there is a positive link between the two.     

Anatomical development of the fetal uterus

OBJECTIVE: The objective of this study was to gather data on the morphology of the uterus during its development, to provide detailed information regarding the neighboring structures and its variations using anatomical dissections. STUDY DESIGN: Eighty uteri acquired from female fetuses aged 10-40 weeks of gestation were used in this study. Firstly, the relationship between the fetal uterus and the linea terminalis and the position of the uterus within the pelvic cavity was noted. Then the distance between the fundus of the uterus to the promontory and pubic symphysis were measured. Fetal uteri were classified according to their physical appearances. Finally the lengths of the corpus and cervix in three planes and the anteflexion angle were measured. RESULTS: During the fetal period, the fundus of the uterus was above the linea terminalis in 94% and below it in 6% of the cases. The distance between the fundus of the uterus and the promontory significantly correlated with the distance between the fundus of the uterus and the pubic symphysis (p<0.001). This was true for the correlation between the gestational age and the orthogonal lengths of the uterine corpus and cervix (p<0.001). As the gestational age advanced, the anteflexion angle was noted to reduce from 177 degrees to 120 degrees . The shape of the uterus was either cylindrical, pear-shaped, heart-shaped or hourglass-shaped during the fetal period. CONDENSATION: We believe that the data obtained through dissections of the human fetuses in this study will help identifying uterine developmental variations, anomalies and pathologies and will contribute to the studies carried out in obstetrics, perinatology, forensic medicine and fetal pathology departments.     

Congenital fibrosarcoma of the jejunum in a premature infant with meconium peritonitis.

We report an unusual case of perforation of a congenital fibrosarcoma of the jejunum in utero and secondary meconium peritonitis. Prenatal ultrasound showed polyhydramnios and fetal ascites from 25 gestational weeks in the absence of other fetal congenital anomalies. A 2200 g baby girl was born at 34 weeks gestation, presenting with severe generalized edema and respiratory distress immediately after birth. Plain radiography revealed progressive abdominal distension and pneumoperitoneum. The baby subsequently underwent surgery at the age of one day. A perforation of the upper jejunum, which had resulted in meconium peritonitis, was discovered intraoperatively and the perforated section of the intestine was resected and anastomosed successfully. The postoperative course was uneventful. Pathological examination confirmed that the perforation was caused by rupture of a congenital fibrosarcoma originating from the jejunum. Rupture of a malignant tumor is an extremely rare cause of peritonitis in the fetus and neonate.     

Behavioural states in growth-retarded human fetuses

Behavioural state observations were carried out on 12 fetuses which subsequently had birthweights below the 10th percentile. Their gestational ages at the time of study ranged from 32 to 40 weeks. Real-time ultrasound scanning was used to detect fetal body and eye movements, and the fetal heart rate was continuously recorded using a clinical fetal monitor. None of these fetuses was severely acidemic or depressed at birth. Findings in the growth-retarded fetuses were compared with those obtained in the fetuses of 14 low risk nulliparae and 14 low risk multiparae by means of the same techniques (van Vliet et al. (1985) Early Hum. Dev., 12, 121-135.; Nijhuis et al. (1982) Early Hum. Dev., 6, 177-195). The appearance of states seemed to be delayed in the growth-retarded fetuses. States were present in only three of eight growth-retarded fetuses studied at 40 weeks, whereas only one of 16 low risk fetuses did not show states at this age. Also at 40 weeks, the proportion of discordant association of the state variables was increased in the growth-retarded fetuses in comparison to the low risk group. There were no consistent differences between the two groups in the occurrence of defined combinations of parameters of the state variables at earlier ages. The growth-retarded fetuses showed differences in the quality and quantity of somatic motility in comparison to low risk fetuses of equivalent gestational age. These observations suggest that some aspects of central nervous system function are disturbed in growth-retarded fetuses, even in the absence of fetal distress.     

兔胎仔腹裂模型实验研究

目的制作兔胎仔腹裂模型，探讨肠管病理损害机制和有关胎仔实验外科的技术。方法40只孕兔随机分成三组，分别于妊娠21d、23d、25d行宫内手术，每只孕兔制作胎仔模型1～3只，包括假手术、腹腔内注射羊水和腹裂三组，至孕30d时自然产仔或行剖宫产同收胎仔模型，分别测量出生体重、小肠重量、长度、密度、厚度，并观察肠壁的组织学和细胞超微结构变化。结果孕21d组腹裂模型存活率(37．04％)显著低于孕23d组(70．59％)和25d组(70．83％)；与对照组相比，腹裂模型组胎仔体重低，小肠重量轻、长度短、密度低、厚度增加，病理组织学和超微结构也发生改变。结论胎仔外科的成功受实验对象、胎龄、麻醉、宫内操作技术等诸多因素影响；腹裂胎仔肠管大体形态和组织结构的改变是受羊水浸泡和腹壁裂口缩窄共同作用的结果。     

人胎脑海马部位神经干细胞形态学观察

目的 探讨人胎脑海马部位神经干细胞的形态学发育特点。方法 收集胎龄20～36周的自愿水囊引产胎儿75例，采用免疫组织化学和光镜观察技术对胎脑海马部位神经干细胞的分布、形态、存在方式进行检测。结果 神经干细胞主要分布于海马多形细胞层、锥体细胞层及颗粒细胞层，分子层也可见，细胞呈圆形、椭圆形、三角形及星形，以圆形细胞多见，0～2个突起不等，以1个突起多见。细胞胞浆丰富；核呈圆形及椭圆形，染色质疏松，2～5个核仁不等。多数单个散在分布，可见对称分裂现象，有的干细胞呈簇状分布，有的干细胞突起与别的细胞保持联系。结论 人胎脑海马部位各层均存在神经干细胞，海马可能存在齿状回之外的神经干细胞生发中心。     

Carbonic anhydrase in the human fetal gastrointestinal tract

Tissues from human fetuses with a gestational age of 19-26 weeks were studied by histochemical and biochemical methods. In gastric homogenates both the catalytic activity and the immunoassayable amount of carbonic anhydrase increased with gestational age. The enzyme activity and isoenzyme pattern in a fetus of 26 weeks were similar to those found in adult gastric mucosa. High enzyme activity was demonstrated histochemically in the gastric surface epithelium at a gestational age of 19 weeks. At this age, the number of stained parietal cells was low, but it increased considerably with gestational age. In all fetal gastrointestinal tissues tested there was a total lack of capillary staining for carbonic anhydrase activity, which contrasts to the clear staining found in adult tissues. The amounts of carbonic anhydrase in the small intestine were lower in the isoenzyme HCA-B than for HCA-C. Histochemically, the staining of jejunal epithelial cells in the fetuses was clearly reduced, both on the villi and in the crypts. In the ileum, single epithelial cells on the villi were distinctly stained, a finding similar to that in adult ileal epithelial cells in the fetuses was clearly reduced, both on the villi and in the crypts. In the ileum, single epithelial cells on the villi were distinctly stained, a finding similar to that in adult ileal epithelium. The colon showed the most striking differences between fetal and adult tissues, with much lower levels of both isoenzymes HCA-B and HCA-C and less staining of the epithelium in the fetal colon. Thus, the developmental pattern of carbonic anhydrase varied considerably among the intestinal tissues. The functional significance of the differences between fetal and adult tissues is only partly understood at present.     

Estimating the testis volume during the fetal period using the stereological method

The purpose of the present study is to assess the development of seminiferous tubule volume, stromal volume and total testis volume in the human fetal testis during the fetal period using the stereological method.In this study, we examined 90 testes of 45 human fetuses with no congenital anomalies and pathologies. They were aged between 12 and 40 weeks and localized between the scrotum and the abdomen. Total testis volume, seminiferous tubule volume, and stromal volume were estimated using Cavalier Principles. The weight and density of the testes were calculated as well.During the fetal period, the testes were firstly found on the right in the 27th week and on the left in the 32nd week in the scrotum. At the end of the third trimester and full term, the migration of the testes into scrotum was completed (98%). When the second trimester, third trimester and full term fetuses were compared, the differences between testis volumes were significant (p<0.001). The density of the testes between the groups was not significant (p>0.05). Testis parameters during the fetal period were not significantly (p>0.05) different between the right and left testes localization. The correlation between the fetal testis parameters was significant (p<0.001).Towards the end of the fetal period, the rate of seminiferous tubule volume to stromal volume changed in the favor of seminiferous tubule volume. It was observed that interstitial tissue became more regular and had a good organized structure with the progress of gestational age. In the third trimester, the lumen in the seminiferous tubules became more regular and clear and the interstitial tissue had a clear appearance.     

Third trimester fetal growth and umbilical venous blood concentrations of IGF-1, IGFBP-1, and growth hormone at term.

Insulin-like growth factor-1 (IGF-1), insulin-like growth factor binding protein-1 (IGFBP-1) and growth hormone (GH) concentrations were measured in umbilical venous blood after delivery of 78 term newborn infants. Three groups of pregnancies were prospectively identified during the third trimester, according to fetal size and subsequent fetal growth, assessed by repeated ultrasound scans. Fetal size was considered either appropriate for gestational age (AGA) or small for gestational age (SGA), according to whether the first ultrasound measurement of abdominal circumference was equal to or above, or below the tenth centile for gestational age, respectively. Subsequent fetal growth was quantified by the change in the standard deviation score of abdominal circumference measurements between the first and last scans before delivery. Fetal growth retardation (FGR) was defined as a (negative) change in SD score of greater than -1.5. Eighteen SGA fetuses with evidence of FGR had significantly lower IGF-1 (median 0.05 (range 0.0-0.24) U/ml) at delivery than 35 SGA fetuses with normal growth (median 0.13 (range 0.0-0.94) U/ml; P < 0.05) and 25 AGA fetuses with normal growth (median 0.31 (range 0.0-0.84) U/ml; P < 0.05). The median concentration in the SGA group with normal growth was also significantly lower than that of the AGA group with normal growth. There were no significant differences in IGFBP-1 or GH concentrations between the three groups. These observations indicate that umbilical blood concentrations at birth of IGF-1, but not IGFBP-1 or GH, relate to both fetal size and fetal growth during the third trimester of pregnancies reaching term.     

产前诊断胎儿心脏病孕妇及家庭对妊娠态度影响因素的分析

目的 探讨产前诊断心脏病的胎儿,孕妇及其家庭选择终止妊娠的影响因素。方法 2011年1月至2014年12月在上海第一妇婴保健院胎儿医学部经超声心动图确诊的心脏病胎儿。每个胎儿家庭接受了多学科咨询会诊,被详细告知疾病的诊断、严重程度、治疗策略和远期预后。回顾性收集孕妇及胎儿的详细临床资料和家庭最终的妊娠选择,行多因素Logistics回归分析,探讨孕妇及家庭选择终止妊娠的主要影响因素。结果 162例胎儿进入分析,平均孕周26.5（17.4~39.5）周,24例（14.8%）胎儿合并有显著心脏外畸形。67例（41.4%）孕妇及家庭选择终止妊娠,其中罹患轻度、中度及重度心脏病胎儿中,孕妇及家庭选择终止妊娠的比例分别为16.0%、51.1%和76.2%;合并有显著心脏外畸形的胎儿中,终止妊娠率高达79.2%。多因素Logistic回归分析显示,胎儿心脏病的严重程度（OR=9.001,95％CI: 4.143~19.557,P<0.001）,是否合并有显著心脏外畸形（OR=3.801,95%CI: 1.814~7.962,P<0.001）及诊断孕周（OR=0.750, 95%CI: 0.653~0.861,P<0.001）是影响孕妇及其家庭选择终止妊娠的3个主要因素。结论 对于合并有重度心脏病或显著心脏外畸形胎儿,孕妇及其家庭更倾向于选择终止妊娠。     

Linear and complex heart rate dynamics vary with sex in relation to fetal behavioural states

BACKGROUND: A better understanding of gender influences on fetal heart rate can help to improve analysis of the latter and perhaps elucidate the increased risk of perinatal death that occurs in males. AIM: To assess differences in linear and complex heart rate dynamics according to fetal sex, in the antepartum period of normal term pregnancies, for patterns associated with fetal behavioural states. STUDY DESIGN AND SUBJECTS: One hundred and eighty seven fetal heart rate segments of 10-minute duration, acquired with a system for computerized analysis of cardiotocograms and classified into fetal behavioural patterns A, B, C or D were analysed. They had been acquired from 24 female and 23 male term fetuses, with uneventful perinatal outcomes. Four different comparative studies between female and male fetuses were conducted, considering different adjustments for gestational age, weight and FHR pattern. OUTCOME MEASURES: Indices of linear and nonlinear fetal heart rate variability, namely, long-term irregularity index, very low, low and high frequency spectral indices, approximate entropy and sample entropy. RESULTS: Pattern B was the most frequent, both in female and male fetuses. Pattern A was more likely to be associated to female than male fetuses, whereas the opposite occurred with patterns C and D. Linear indices were significantly higher in male than in female fetuses, whereas the opposite occurred with nonlinear indices. CONCLUSIONS: Male fetuses exhibited significantly more linear and significantly less complex fetal heart rate activity than female fetuses, expressing signs of a more active autonomous nervous system and of less active complexity control systems. These aspects may need to be considered when interpreting FHR tracings.     

Two-dimensional and M-mode assessment of aortic growth in the normal and growth-retarded (IUGR) human fetuses

Summary This study compares human fetal aortic dimensions in 128 normal and 30 intrauterine growth-retarded (IUGR) fetuses using two-dimensional (2D) and M-mode echocardiography. We found that the fetal aortic root in the normally grown fetuses is significantly larger than the descending aorta at all gestational ages. Furthermore, IUGR fetuses had smaller descending aortic dimensions then did normally grown fetuses. When the descending aortic dimension in the IUGR fetuses was corrected for estimated fetal weight, it was found to be of comparable size to those of the normal fetuses. The difference in aortic size of growth-retarded fetuses is proportional to growth and therefore probably a secondary phenomenon.     

Influence of breech presentation on the development of fetal arm posture

BACKGROUND: In previous research, an age-related developmental trend towards increasing arm flexion has been found for cephalic fetuses. AIM: To determine if the development of arm posture in breech fetuses is comparable to that of cephalic ones. SUBJECTS AND METHODS: Fetal arm posture was studied longitudinally by means of real-time ultrasound in 13 healthy breech and 10 healthy cephalic fetuses. Observations started from 33 weeks gestational age until birth and were performed weekly in the breech group and every 2 weeks in the cephalic group. RESULTS: No difference could be found in arm posture between the left and the right arm in either group. Both breech and cephalic fetuses showed a clear preference for flexion in elbow and finger joints at all studied ages. After 36 weeks gestational age, the breech group showed significantly less wrist flexion when compared to the cephalic group (p = 0.037). A clear preference for location of the fetal hands near the fetal head could be observed for both groups. CONCLUSIONS: As there is no evidence for an abnormal neuromotor development in healthy breech fetuses, the observed difference in wrist flexion is probably due to differences in intrauterine environment. Because of the preference for location of the hands in the vicinity of the fetal head, breech fetuses probably experience a less restricted environment (in the upper part of the uterus) than cephalic fetuses (in the lower part of the uterus).     

Fetal habituation to vibroacoustic stimulation in relation to fetal states and fetal heart rate parameters

OBJECTIVES: Fetal habituation to repeated stimulation has the potential to become a tool in the assessment of fetal condition and of the function of the fetal central nervous system (CNS). However, the influence of fetal quiescence and activity on habituation remains to be clarified. We studied habituation and the influence of fetal state and fetal heart rate (FHR) parameters on habituation in healthy term fetuses. SUBJECTS AND METHOD: We studied habituation in 37 healthy fetuses in two tests with an interval of 10 min. The vibroacoustic stimuli were applied to the maternal abdomen above the fetal legs for a period of 1 s every 30 s. A fetal trunk movement within 1 s after stimulation was defined as a positive response. Habituation rate is defined as the number of stimuli applied before an observed non-response to four consecutive stimuli. The FHR patterns (FHRP) of the 10 min observation period before and after the tests were visually classified. Fetal states were defined according to the FHRP. Baseline FHR, FHR variability and the number of accelerations were calculated in a subgroup of 25 fetuses. RESULTS: Of the 32 fetuses that responded normally during the first test, 26 habituated and six had persistent responses. The median habituation rate decreased significantly in the second test (P=0.001). There was no difference in habituation rate between fetuses that where initially in a quiet state and those in an active state. The FHR parameters before the first test and the difference between these FHR parameters before and after the test did not correlate with the habituation rate. CONCLUSIONS: Although the majority of healthy fetuses was able to habituate, the interfetal variability in habituation performance is such that testing of habituation seems not to be a sensitive tool for the assessment of the fetal CNS. This variability is neither the result of differences in fetal state nor of the various FHR parameters before testing, nor of the difference in change of FHR parameters arising from stimulation.