Anatomy & Physiology
Occupational & Environmental Medicine
Methods of detecting SGA fetuses include antenatal clinical examination, measurement of symphysis-fundal height (SFH), fetal anthropometry and ultrasound estimated fetal weight (EFW). All measurements require an accurate estimation of gestational age based on fetal crownrump length prior to 13 weeks’ gestation or fetal head circumference between 16 and 24 weeks’ gestation (95% prediction interval ± 5d). Abdominal palpation remains a routine part of obstetric examination, despite the fact that the sensitivity for detection of a SGA infant is only 20–30% and the positive predictive value (PPV) no greater than 40%. Measurement of SFH is an alternative but a systematic review, which identified only one controlled trial which showed that SFH measurement did not improve perinatal outcome. Serial SFH measurements may improve sensitivity and specificity as may the use of customized SFH charts. The customized antenatal growth chart displays computer generated curves for fetal weight and SFH, adjusted for physiological variables (maternal height, weight at booking, parity and ethnic group). One controlled trial has shown that use of customized charts improved detection rate of SGA infants (48% versus 29%, OR 2.2 [95% CI 1.1–4.5]) and reduced the number of women admitted (OR 0.6, 95% CI 0.4–0.7). SFH should be measured at each antenatal assessment after 24 weeks of pregnancy. Ultrasound assessment is indicated if the SFH falls below the 10th centile.
Source: Forfar and Arneil's Textbook of Pediatrics, 7E
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