INTRODUCTION: These Guidelines aim to describe appropriate assessment of fetal biometry and diagnosis of fetal growth disorders. These disorders consist mainly of fetal growth restriction (FGR), also referred to as intrauterine growth restriction (IUGR) and often associated with small‐for‐gestational age (SGA), and large‐for‐gestational age (LGA), which may lead to fetal macrosomia; both have been associated with a variety of adverse maternal and perinatal outcomes. Screening for, and adequate management of, fetal growth abnormalities are essential components of antenatal care, and fetal ultrasound plays a key role in assessment of these conditions.The fetal biometric parameters measured most commonly are biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC) and femur diaphysis length (FL). These biometric measurements can be used to estimate fetal weight (EFW) using various different formulae¹. It is important to differentiate between the concept of fetal size at a given timepoint and fetal growth, the latter being a dynamic process, the assessment of which requires at least two ultrasound scans separated in time. Maternal history and symptoms, amniotic fluid assessment and Doppler velocimetry can provide additional information that may be used to identify fetuses at risk of adverse pregnancy outcome.Accurate estimation of gestational age is a prerequisite for determining whether fetal size is appropriate‐for‐gestational age (AGA). Except for pregnancies arising from assisted reproductive technology, the date of conception cannot be determined precisely. Clinically, most pregnancies are dated by the last menstrual period, though this may sometimes be uncertain or unreliable. Therefore, dating pregnancies by early ultrasound examination at 8–14 weeks, based on measurement of the fetal crown–rump length (CRL), appears to be the most reliable method to establish gestational age. Once the CRL exceeds 84 mm, HC should be used for pregnancy dating^2–4. HC, with or without FL, can be used for estimation of gestational age from the mid‐trimester if a first‐trimester scan is not available and the menstrual history is unreliable. When the expected delivery date has been established by an accurate early scan, subsequent scans should not be used to recalculate the gestational age¹. Serial scans can be used to determine if interval growth has been normal.In these Guidelines, we assume that the gestational age is known and has been determined as described above, the pregnancy is singleton and the fetal anatomy is normal. Details of the grades of recommendation used in these Guidelines are given in Appendix 1. Reporting of levels of evidence is not applicable to these Guidelines.

PURPOSE AND SCOPE: The purpose of these Guidelines is to review the published techniques of ultrasound in labor and their practical applications, to summarize the level of evidence regarding the use of ultrasound in labor and to provide guidance to practitioners on when ultrasound in labor is clinically indicated and how the sonographic findings may affect labor management. We do not imply or suggest that ultrasound in labor is a necessary standard of care.

Objective: To investigate the ability of intrapartum translabial sonography to diagnose fetal station in the second stage of labor.Methods: Patients with uncomplicated pregnancies at term gestation with fetuses in vertex presentation in the second stage of labor underwent serial translabial sonography and digital examinations. In a sagittal section of the maternal pelvis, the direction of the head was noted and categorized as downward, horizontal or upward. By rotating the transducer in the transverse plane the cerebral midline echo was also visualized and the rotation of the head was noted. Clinical and ultrasound data were compared using Somer's d‐test.Results: Sixty patients underwent a total of 168 clinical and sonographic examinations. When on the sonogram the fetal head was directed downward, the station assessed clinically was most frequently ≤ + 1 cm from the ischial spines (44/57 (77.2%) cases); when the direction was horizontal, the station was most frequently ≤ + 2 cm (53/59 (89.8%) cases); when the fetal head was directed upward, the station was usually ≥ + 3 cm (46/52 (88.5%) cases). Failure to visualize the cerebral midline or a rotation ≥ 45° were associated with a station of + 2 cm or less in 98/103 (95.1%) examinations. Conversely, a rotation of < 45° was associated with a station of + 3 cm or more in 45/65 (69.2%) examinations. All comparisons between clinical and sonographic findings demonstrated a statistically significant relationship (P < 0.0001). The probability of a station + 3 cm or more was particularly high when an upward direction of the head was seen in combination with a rotation of < 45° (40/42 (95.2%) examinations). The interobserver variability (Cohen's kappa 0.795 and 0.727 for station and rotation, respectively; P < 0.001) and intraobserver variability (0.845 for both station and rotation, P < 0.001) suggested good reproducibility of the method.Conclusions: Translabial sonography allows a diagnosis of fetal station with an accuracy comparable to that of digital examination and may provide useful information for diagnosing obstructed labor in the second stage as well as assisting in the choice of instrumental delivery. Copyright © 2009 ISUOG. Published by John Wiley & Sons, Ltd.