First-trimester growth and the risk of low birth weight

BACKGROUND: Previous studies have demonstrated a correlation between first-trimester size and birth weight. It is not known, however, whether low birth weight is related to first-trimester growth. We sought to determine whether the risk of low birth weight and birth weight that was low for gestational age is related to the size of the embryo or the fetus in the first trimester. METHODS: From a data base of ultrasound records of more than 30,000 pregnancies, we identified women who had no important medical problems, a normal menstrual history, and a first-trimester ultrasound scan in which the crown-rump length of the embryo or fetus had been measured. We examined the relation between the outcome of 4229 pregnancies and the difference between the measured and the expected crown-rump length in the first trimester, expressed as equivalent days of growth. RESULTS: A first-trimester crown-rump length that was two to six days smaller than expected was associated with an increased risk (as compared with a normal or slightly larger than expected crown-rump length) of a birth weight below 2500 g (relative risk, 1.8; 95 percent confidence interval, 1.3 to 2.4), a birth weight below 2500 g at term (relative risk, 2.3; 95 percent confidence interval, 1.4 to 3.8), a birth weight below the fifth percentile for gestational age (relative risk, 3.0; 95 percent confidence interval, 2.0 to 4.4), and delivery between 24 and 32 weeks of gestation (relative risk, 2.1; 95 percent confidence interval, 1.1 to 4.0), but not with delivery between 33 and 36 weeks (relative risk, 1.0; 95 percent confidence interval, 0.7 to 1.5). CONCLUSIONS: Suboptimal first-trimester growth may be associated with low birth weight, low birth-weight percentile, and premature delivery.     

Impaired growth and risk of fetal death: is the tenth percentile the appropriate standard?

OBJECTIVE: Our purpose was to determine whether the 10th percentile of birth weight for gestational age is appropriate to identify fetuses at risk of death associated with impaired growth. STUDY DESIGN: All live births recorded in Virginia from Jan. 1, 1991, through Dec. 31, 1993, were examined. Percentile growth curves were constructed, and fetal, neonatal, and perinatal mortality rates were calculated for births within various percentile intervals. RESULTS: Significantly elevated fetal mortality was found for birth weights through the 15th percentile. The odds ratio for fetal mortality relative to the baseline for births < or = 5th percentile was 5.6, for the 5th through the 10th percentile 2.8, and for the 10th through the 15th percentile 1.9. These were all significant. CONCLUSION: Fetuses with birth weights between the 10th and 15th percentiles are at a significantly increased risk for fetal death. Therefore the use of the 15th percentile as a diagnostic threshold for the identification of the fetus at increased risk associated with impaired growth is recommended.     

Early intrauterine development: II. The rate of growth in Black and Central American populations between 10 and 20 weeks' gestation

The application of the growth-rate standards, extablished for Caucasian embryos and fetuses in a previous report, to Black and Central American racial groups has been investigated. Comparison between menstrual age and crown-to-rump length indicated differences in the 10 to 15 weeks' gestation range. However, growth rates for the same groups were practically identical between the 15th and 20th weeks of pregnancy. This finding suggests that the actual rate of growth is closely similar in the respective ethnic groups and that apparent discrepancies reflect erroneous, or purposefully false, menstrual histories rather than dissimilar growth patterns. Largely identical rates of development were suggested by the crown-rump length to foot length to body weight interrelations among the various racial groups. A moderate, but rather predictable, deviation from the earlier established standards was noted in the crown-rump length versus foot length ratios of Black American fetuses, providing the only exception to what appears to be a practically identical rate of growth for the investigated ethnic groups in the first half of gestation. The evaluation of the results was extended to involve the effect of educational and social factors on currently available data of embryonic and fetal growth. It is suggested that heretofore unconsidered factors may affect the validity of widely quoted standards of intrauterine growth.     

Study of intrauterine growth from birthweight at Maharaj Nakhon Chiang Mai Hospital

Intrauterine growth curve and normogram for newborns at Maharaj Nakhon Chiang Mai Hospital are constructed. Birthweight at various gestational weeks of deliveries were determined within 24 hrs after birth. All 1,311 Thai pregnant women selected, fitted the criteria of inclusion deliveries at Maharaj Nakhon Chiang Mai Hospital from May 1983 to April 1991 (8 yrs). Their gestational age distribution was between 28 wks to 42 wks. Clinical status at birth was satisfactory. There were no obstetric or medical complications during pregnancy. Mean birthweight and standard deviation of newborns for each gestational age at delivery were calculated and presented in tabular and graphic form. Mean birthweight for 40 wks of gestation was 3.144 +/- 382 g. In addition, normogram of 10th, 50th, 90th percentile ranks of birthweight for each gestational age was constructed. These values may be useful as baseline data of intrauterine growth curve to evaluate fetal growth in our population.     

Biparietal diameter: a useful measure for determining gestational age of human abortuses

BACKGROUND: The crown-rump length is conventionally used to determine the age of human abortuses. However, it is not reliable as it is dependent on the positioning of the conceptus. We compared this with the biparietal diameter and foot length for determining the gestational age. METHODS: Different measurements, commonly used to assess gestational age, were measured in 146 human abortuses for which an accurate obstetric history could not be elicited. Measurements taken were crown-rump length, biparietal diameter and foot length. These were correlated with the observations at antenatal examinations before finalizing the approximate age. RESULTS: Multiple regression analysis of the data indicated that of the three measurements, the biparietal diameter was the most reliable for determining foetal gestational age between 8 and 26 weeks. The age determined with the biparietal diameter correlated well with that of abortuses with an accurate obstetric history. CONCLUSION: The biparietal diameter of a human foetus may be used to determine its age if the obstetric history regarding the period of gestation is vague or not available.     

Ultrasonographic examination of intrauterine growth for multiple fetal dimensions in a Chinese population. Central-South China Fetal Growth Study Group

OBJECTIVE: We sought to construct an ultrasonography-based growth curve in a Chinese population. STUDY DESIGN: Routine ultrasonographic examination was performed in 5496 normal pregnancies (>95% first births) in five obstetric ultrasonography laboratories in Central-South China from January 1, 1992, to December 31, 1993. RESULTS: All the fetal growth measures increased with gestational age, whereas the ratios either decreased or remained constant across gestation. Biparietal diameter and cerebral hemispheric width were higher at early gestational ages, whereas femur length, thoracic circumference, and abdominal circumference were lower at later gestational ages in our study than in previous studies. The ratio of lateral ventricular width/cerebral hemispheric width was lower at an early gestational age but higher in later gestational ages in our study. CONCLUSIONS: A different standard of ultrasonography-based fetal growth is needed for different populations. The ultrasonography-based growth curve constructed in this large Chinese population provides an additional tool for the evaluation of fetal growth and development.     

Evaluation of the effect on heart rate variability of some agents acting at the beta-adrenoceptor using nonlinear scatterplot and sequence methods

There is evidence that the processes regulating heart rate variability (HRV) reflect nonlinear complexity and show "chaotic" determinism. Data analyses using nonlinear methods may therefore reveal patterns not apparent with the standard methods for HRV analysis. We have consequently used two nonlinear methods, the Poincaré plot (scatterplot) and cardiac sequence (quadrant) analysis, in addition to the standard time-domain summary statistics, during a normal volunteer investigation of the effects on HRV of some agents acting at the cardiac beta-adrenoceptor. Under double-blind and randomized conditions (Latin square design), 25 normal volunteers received placebo, salbutamol 8 mg (beta 2-adrenoceptor partial agonist), pindolol 10 mg (beta 2-adrenoceptor partial agonist), or atenolol 50 mg (beta 1-adrenoceptor antagonist). Single oral doses of medication (at weekly intervals) were administered at 22:30 hours, with sleeping heart rates recorded overnight. The long-term (SDNN, SDANN) and short-term (rMSSD) time-domain summary statistics were reduced by salbutamol 8 mg and increased by atenolol 50 mg compared with placebo. The reductions in both SDNN and SDANN were greater after salbutamol 8 mg compared with pindolol 10 mg. The reduced HRV after pindolol 10 mg differed from the increased HRV following atenolol 50 mg. The Poincaré plot, constructed by plotting each RR interval against the preceding RR interval, was measured using a reproducible computerized method. Scatterplot length and area were reduced by salbutamol 8 mg and increased by atenolol 50 mg compared with placebo; scatterplot length and area were lower after pindolol 10 mg compared with atenolol 50 mg. Geometric analysis of the scatterplots allowed width assessment (i.e., dispersion) at fixed RR intervals. At the higher percentiles (i.e., 90% of scatterplot length: low HR), salbutamol 8 mg reduced and atenolol 50 mg increased dispersion; at lower percentiles (i.e., 10%, 25%, and 50% length), atenolol 50 mg and pindolol 10 mg increased dispersion compared with placebo and salbutamol 8 mg. Cardiac sequence analysis (differences between three adjacent beats; delta RR vs. delta RRn + 1) was used to assess the short-term patterns of cardiac acceleration and deceleration. Four patterns were identified: +/+ (a lengthening sequencing), +/- or -/+ (balanced sequences), and finally -/- (a shortening sequence). Cardiac acceleration episodes (i.e., number of times delta RR and delta RRn + 1 were both changed) were increased in quadrants -/- and +/+ following pindolol 10 mg and salbutamol 8 mg; the beat-to-beat difference (delta RRn + 1) was reduced after salbutamol 8 mg compared with the three other groups. These results demonstrated a shift towards sympathetic dominance (beta-adrenoceptor partial agonist salbutamol 8 mg) or parasympathetic dominance (beta 1-adrenoceptor antagonist atenolol 50 mg); pindolol 10 mg exhibited HR-dependent effects, reducing HRV at low but increasing variability at high prevailing heart rates. These nonlinear methods appear to be valuable tools to investigate HRV in health and to study the implications of perturbation of HRV with drug therapy in disease states.     

Cervical ultrasonography compared with manual examination as a predictor of preterm delivery

OBJECTIVE: Our purpose was to compare the accuracy of ultrasonographic and manual cervical examinations for the prediction of preterm delivery. STUDY DESIGN: One hundred two singleton pregnancies at high risk for preterm delivery were followed up prospectively from 14 to 30 weeks with both serial cervical ultrasonography measurements and manual examinations of the length of the cervix. The primary outcome studied was preterm (< 35 weeks) delivery. RESULTS: Excluding six induced preterm deliveries, 96 pregnancies were analyzed. The mean cervical length measured by ultrasonography was 20.6 mm in pregnancies delivered preterm (n = 17) and 31.3 mm in pregnancies delivered at term (n = 79) (p = 0.003); the mean cervical lengths measured by manual examination were 16.1 mm and 18.6 mm in the same preterm and term pregnancies, respectively (not significant). The sixteenth- and twentieth-week ultrasonographic cervical lengths predicted preterm delivery most accurately (p < 0.0005). The 25th percentiles of ultrasonographic (25 mm) and manual (16 mm) cervical lengths showed relative risks for preterm delivery of 4.8 (95% confidence interval 2.1 to 11.1, p = 0.0004) and 2.0 (95% confidence interval 0.5 to 4.7, p = 0.1), respectively; sensitivity, specificity, and positive and negative predictive values were 59%, 85%, 45%, 91%, and 41%, 77%, 28%, and 86%, respectively. CONCLUSION: Cervical length measured by ultrasonography is a better predictor of preterm delivery than is cervical length measured by manual examination. Cervical ultrasonography in patients at high risk for preterm birth seems to be most predictive of preterm delivery when it is performed between 14 and 22 weeks' gestation.     

Estimation of the developmental age of the ovine fetus and lamb

Fifty-six fetuses and 33 lambs were obtained from a flock of ewes at set gestational intervals between 50 to 180 days after conception. The fetuses and lambs were killed, disected and the sizes and weights of a wide range of skeletal and soft tissues were measured. Five morphological parameters emerged as most suitable for the determination of normal foetal developmental age. By plotting the mean value and ninety-five per cent tolerance limits, the rates of growth and the variability of each parameter were studied. Crown-anus length is useful for determining fetal developmental age from 50 to 100 days gestation; brain weight, long bone length and the number of appendicular ossification centres can be used to determine fetal development age from 50 days gestation until term.     

Ubiquitin-immunohistochemical investigation of atypical Pick''s disease without Pick bodies

OBJECTIVE: To determine whether children between the ages of 8 and 12 years are able to reliably report internalizing symptoms over short to medium-length time intervals as measured by an objective self-report instrument of internalizing symptoms. METHOD: The Internalizing Symptoms Scale for Children (ISSC) was group-administered initially to 131 children and at subsequent intervals of 2 weeks, 4 weeks, and 12 weeks. RESULTS: Pearson product-moment correlations for the ISSC total scores of the participants were computed across the various retest intervals. At 2 weeks, the correlation was .84. At 4 weeks, the correlation was .76. After 12 weeks, the correlation was .74. CONCLUSIONS: These data indicate that children between 8 and 12 years old can reliably report their experience over short to medium-length intervals. These findings provide strong support for the ISSC as a research and clinical instrument for the assessment of internalizing symptoms in children between 8 and 12 years of age, which may ultimately prove beneficial in the identification and treatment of childhood internalizing disorders. Limitations and recommendations for future research are discussed.     

Relationship of initial chorionic sac diameter to abortion and abortus karyotype based on new growth curves for the 16th to 49th post-ovulation day

In order to determine whether initial chorionic sac diameter is related to subsequent abortion, abortus karyotype, or birth weight and length, chorionic sac diameter was prospectively measured by transvaginal ultrasound in 700 singleton pregnancies before post-ovulation day 31, the latest day cardiac activity becomes detectable in normal pregnancy. Results were compared to values for the 10th to the 90th centiles, determined from 227 measurements of in-vitro fertilization and gamete intra-Fallopian transfer pregnancies. The abortion rate was 23.9% [95% confidence interval (CI) 19.2%, 28.6%] when initial chorionic sac diameter was below the 50th centile, compared to 6.9% (95% CI 4.9%, 9.4%) when equal to or above the 50th centile. Chorionic sac diameter was below the 50th centile in all anembryonic abortions and in 62% of embryonic abortions. Triploidy, trisomy 47 + 16, or trisomy 16 and the presence of satellite bodies on chromosome 22 were the only abortus karyotypes significantly associated with small chorionic sac diameter. Initial chorionic sac diameter was not associated with birth weight or length. We conclude that chorionic sac diameter is decreased in anembryonic and embryonic abortion and that normal pregnancy outcome may be expected in 90-95% of pregnancies in which initial chorionic sac diameter is equal to or above average.     

Cerebellar growth in normal and growth-restricted fetuses of multiple gestations

OBJECTIVE: Our purpose was to evaluate growth of the cerebellum in growth-restricted fetuses of twin and triplet gestations versus growth in normal in utero sibling(s) and in singleton gestations. STUDY DESIGN: An ultrasonographic study was conducted in a population of pregnant women with twin and triplet gestations. The control group was either the normal in utero sibling(s) when one fetus was growth restricted or normal twin and singleton pregnancies. Standard biometric measurements were obtained on all fetuses throughout pregnancy, including the transverse cerebellar diameter. However, only the last measurement was used for the analysis. Statistical analyses were conducted comparing growth of the transverse cerebellar diameter among the growth-restricted fetuses versus growth in the normal in utero fetal sibling(s) or other normal twin and singleton gestations. RESULTS: Pregnancies were categorized on the basis of the growth status of women with twin and triplet gestations: Group 1 (151) contained women with two fetuses appropriately grown for gestational age; group 2 (52) had one appropriately grown fetus and one with intrauterine growth restriction; group 3 (19) had two fetuses with intrauterine growth restriction. In addition, there were 30 triplet gestations (group 4), five of which had growth-restricted fetuses, and group 5 contained 1405 singleton pregnancies. In all five groups there was a statistically significant relationship between transverse cerebellar diameter and gestational age (p < 0.0001). There was also no significant difference between growth of the transverse cerebellar diameter in the appropriately grown and growth-restricted siblings and among normal singleton and twin pregnancy groups. In most cases of growth-restricted fetuses, except for the transverse cerebellar diameter measurements, all other biometric parameters were < 10th percentile. CONCLUSION: These data confirm the relative preservation of normal cerebellar growth in growth-restricted fetuses and a similar rate of growth in singleton and multifetal gestations. The transverse cerebellar diameter therefore represents an independent biometric parameter that can be used in both singleton and multifetal pregnancies to assess normal and deviant fetal growth.     

Norethindrone acetate enhances the antiatherogenic effect of 17beta-estradiol: a secondary prevention study of aortic atherosclerosis in ovariectomized cholesterol-fed rabbits

OBJECTIVE: Premature delivery is difficult to predict and causes considerable neonatal morbidity and mortality. Despite much research, little progress has been made in timely identification of the mothers at risk. We examined the uterine cervix with ultrasonography to discover whether such a procedure would be helpful in determining which women will deliver prematurely. METHODS: We performed transvaginal ultrasound examinations in addition to routine transabdominal ultrasonography at 18 to 22 weeks' gestation in 3694 consecutive pregnant women with live singleton fetuses. We measured the length of the uterine cervix and evaluated the dilatation, if any, of the internal os. The results of cervical ultrasonography were not available to the clinicians. RESULTS: Spontaneous delivery occurred before 37 completed weeks in 88 women (2.4%) and before 35 weeks in 31 (0.8%). The relative risk of delivery before 35 weeks was 8 (95% confidence interval 3, 19) when the cervical length was 29 mm or shorter. When dilatation of the internal cervical os of 5 mm or greater was present, the relative risk of delivery before 35 weeks was 28 (95% confidence interval 12, 67). Either short cervix (29 mm or less) or dilatation of internal cervical os (5 mm or greater) was present in 3.6% of the population; this combination had a sensitivity of 29% in predicting delivery at earlier than 35 weeks. After adjusting for cervical dilatation and length by using multiple logistic regression, nulliparity also remained a risk factor for delivery before 35 weeks (odds ratio 3.6, 95% confidence interval 1.7, 7.5). CONCLUSION: Transvaginal ultrasonography performed as an addition to routine transabdominal ultrasonography at 18 to 22 weeks helps to identify many patients at significant risk for prematurity; however, low sensitivity and low positive predictive value limit its usefulness in screening low-risk obstetric populations.     

Depressive symptomatology during pregnancy: Evidence for an association with decreased fetal growth in pregnancies of lower social class women.

The relationship between depressive symptom scores on the Center for Epidemiological Studies Depression Scale (CES-D; L. S. Radloff, 1977) at each trimester of pregnancy and a decrement in either fetal growth or gestational duration was evaluated among 666 pregnant women. There was no association overall, but among 222 women from lower occupational status households, each unit increase on the CES-D at 28 weeks gestation was associated with a reduction of 9.1 g (95% confidence interval [CI]?=?–16.0, –2.3) in gestational-age-adjusted birth weight. When missing data were multiply imputed, the estimate was –4.6 g (95% CI?=?–10.7, 1.5). CES-D score was unrelated to fetal growth or gestational duration in analyses among other potentially high-risk subgroups: smokers, women with a history of adverse outcome, and women with social vulnerabilities. These results raise the possibility that among lower status women, depressive mood may be associated with restricted fetal growth. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Refractive and visual outcome of hyperopic cataract cases operated on before and after implementation of the Holladay II formula

OBJECTIVE: The primary objective was to evaluate the refractive and visual outcomes in a series of hyperopic cataract cases in which the Holladay II intraocular lens (IOL) power formula was used in conjunction with added eye measurements (measured anterior chamber depth [ACD], lens thickness, and corneal diameter) to improve predictability of refractive outcome. In addition, the impact of use of a double ("piggyback") IOL on refractive outcome was evaluated. DESIGN: Prospective, nonrandomized comparative clinical trial. PARTICIPANTS: A total of 136 consecutive hyperopic primary cataract-IOL cases operated on at in an outpatient eye surgery center were evaluated. The main inclusion criterion was the requirement of at least 30 D of emmetropia power. INTERVENTION: Implantation of a total implanted power calculated using a newly developed (Holladay II) formula, which uses additional eye measurements (measured ACD, lens thickness, corneal diameter) in addition to the axial length and keratometry normally used, was performed. In the first series, IOL powers were chosen using the Lloyd-Gills formula with modifiers; in the second series, powers were chosen using the Holladay II formula option in the Holladay IOL Consultant software. Selection criteria for both series were the same (requiring at least 30 diopters [D] of power for emmetropia). Keratometry and axial length measurements (by immersion) were taken using the same instrumentation and methodology in both series. Predicted postoperative refraction based on the IOL implanted and the method of power calculation used were computed for each case in both groups and compared to the actual achieved refraction. MAIN OUTCOMES MEASUREMENTS: Main clinical outcome parameters evaluated were the postoperative spherical equivalent (compared with the predicted spherical equivalent) and the best-corrected vision. These outcome parameters were evaluated within each surgical series, in the total group of cases (regardless of power calculation method). Further stratification according to the use of single or double implants also was done. RESULTS: In the group using an older formula system, mean preoperative spherical equivalent of 4.79 D was reduced to -0.67 D. Similarly, in the Holladay II group, the preoperative mean of 5.60 D was reduced to -0.58 D. However, there were fewer large deviations between predicted and achieved spherical equivalent in the Holladay II group as indicated by a smaller standard deviation of the absolute deviation (0.47 vs. 0.59), and the range of postoperative refractions was smaller with fewer large overcorrections or undercorrections. However, almost 90% of both groups were within a diopter of the predicted refraction. Visual results were comparable in the two groups. CONCLUSION: Both IOL calculation systems showed good predictability in these extremely short eyes. The Holladay II formula was simpler because it is incorporated into a user-friendly software package (Holladay IOL Consultant) and required only the input of IOL constants and preoperative measurements with no "fudge factor" modifiers. Results within the series using this formula had a tendency toward a smaller standard deviation with fewer outliers.     

Insulin-like growth factor I in fetal serum obtained by cordocentesis is correlated with intrauterine growth retardation

We examined whether insulin-like growth factor-I (IGF-I) and one of its binding proteins (IGFBP-1) in fetal serum obtained by cordocentesis is correlated with intrauterine growth retardation (IUGR) and weight estimation by ultrasound. Cordocentesis sera from 27 fetuses suspected of having IUGR were analysed for IGF-I and IGFBP-1 by radioimmunoassay. The results showed that IGF-I concentrations were correlated significantly with birth weight (P < 0.001) and placenta weight (P < 0.05). Mean fetal concentrations of IGF-I were 38 +/- 18 microg/l. In patients (n = 11) with a weight deviation at delivery <-33%, IGF-I concentrations were 24.1 +/- 13.2 microg/l. IGFBP-1 was inversely correlated with birth weight (P < 0.006) and concentrations of IGF-I. Mean plasma concentrations of IGFBP-1 were 234.2 +/- 161.4 microg/l. Furthermore, IGF-I concentrations were correlated with the weight deviation estimated by ultrasonography at the time of cordocentesis (P < 0.007), as well as with the weight deviation at delivery (P < 0.0001). The actual weight deviation at delivery was correlated more strongly with fetal IGF-I concentrations than with the estimated weight deviation at cordocentesis. The lowest concentrations of IGF-I were found in patients with a weight deviation <-33%. Very low concentrations of IGF-I are thus associated with IUGR, indicating that IGF-I measured in fetal serum may increase the predictive value of ultrasonographic weight estimation.     

Plasma cell and sclerosing osteomyelitis. A follow-up of 21 patients

Ten consecutive patients with incapacitating fecal incontinence were treated with 'anal dynamic graciloplasty' (transposition of the gracilis muscle around the anal canal and implantation of intramuscular electrodes connected with an implanted pulse generator, 6 weeks later) to achieve continence. We measured the gracilis muscle diameter immediately after transposition and before implantation of the stimulation device. It was found that gracilis diameter decreased from 12 (5 days after transposition) to 8 mm, 6 weeks later (mean decrease: 4 mm (95% confidence interval 3.6), n = 10, P < 0.05). In addition, morphology demonstrated a decrease of both Type I and Type II muscle fiber diameter and an increase in endomysial collagen. Despite this decrease in muscle (and muscle fiber) diameter, electrical stimulation of the transposed gracilis muscle increased the pressure into the anal canal from 37 to 55 mmHg (mean increase: 17 mmHg (95% confidence interval 6.29), P < 0.05). Fecal continence was achieved in seven (70%) of these patients. Further analysis revealed no correlations between reduction of the gracilis muscle diameter before implantation of the stimulation device and clinical outcome in terms of achieved continence and/or anal canal pressures. MRI is an excellent method to demonstrate the shape of gracilis muscle after transposition. However, the size of transposed gracilis muscle is not associated with the functional outcome.     

A standard of fetal growth for the United States of America

The appropriate interpretation of monitored fetal growth throughout pregnancy in individual patients and populations is dependent upon the availability of adequate standards. There is no adequate standard of fetal weight throughout pregnancy that is suitable for patients in the U.S.A. To determine such a standard for infants delivered at about sea level the 10th, 25th, 50th, 75th, and 90th percentiles of fetal weight for each menstrual week of gestation were calculated from 430 fetuses at 8 to 20 menstrual weeks' gestation aborted with prostaglandins and from 30,772 liveborn infants delivered of patients at 21 to 44 menstrual weeks' gestation. Median fetal crown-to-rump lengths and crown-to-heel lengths were derived from measurements of 496 aborted fetuses of 8 to 21 weeks' gestation. Fetal weight correction factors for parity, race (socioeconomic status), and fetal sex were calculated. The derived fetal growth curves are useful for clinical, public health, and investigational purposes.