Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114, USA.
Malar J. 2013 Jun 4;12:183. doi: 10.1186/1475-2875-12-183.
Malaria during pregnancy is associated with an increased risk for low birth weight (<2500 grams). Distinguishing infants that are born premature (< 37 weeks) from those that are growth-restricted (less than the 10th percentile at birth) requires accurate assessment of gestational age. Where ultrasound is accessible, sonographic confirmation of gestational age is more accurate than menstrual dating. The goal was to pilot the feasibility and utility of adding ultrasound to an observational pregnancy malaria cohort.
In July 2009, research staff (three mid-level clinical providers, one nurse) from The Blantyre Malaria Project underwent an intensive one-week ultrasound training to perform foetal biometry. Following an additional four months of practice and remote image review, subjects from an ongoing cohort were recruited for ultrasound to determine gestational age. Gestational age at delivery established by ultrasound was compared with postnatal gestational age assessment (Ballard examination).
One hundred and seventy-eight women were enrolled. The majority of images were of good quality (94.3%, 509/540) although a learning curve was apparent with 17.5% (24/135) images of unacceptable quality in the first 25% of scans. Ultrasound was used to date 13% of the pregnancies when menstrual dates were unknown and changed the estimated gestational age for an additional 25%. There was poor agreement between the gestational age at delivery as established by the ultrasound protocol compared to that determined by the Ballard examination (bias 0.8 weeks, limits of agreement -3.5 weeks to 5.1 weeks). The distribution of gestational ages by Ballard suggested a clustering of gestational age around the mean with 87% of the values falling between 39 and 41 weeks. The distribution of gestational age by ultrasound confirmed menstrual dates was more typical. Using ultrasound confirmed dates as the gold standard, 78.5% of preterm infants were misclassified as term and 26.8% of small-for gestational age infants misclassified as appropriately grown by Ballard.
Ultrasound should be strongly considered in prospective malaria studies with obstetric endpoints to confirm gestational age and avoid misclassification of infants as premature or growth-restricted. The use of ultrasound does require a significant investment of time to maintain quality image acquisition.
孕妇疟疾会增加低出生体重（<2500 克）的风险。区分早产儿（<37 周）和生长受限儿（出生时体重低于第 10 百分位）需要准确评估胎龄。在有超声的情况下，超声确认胎龄比月经日期更准确。本研究旨在探索在观察性妊娠疟疾队列中添加超声检查的可行性和实用性。
2009 年 7 月，来自布莱顿疟疾项目的 3 名中级临床医生和 1 名护士接受了为期一周的高强度超声培训，以进行胎儿生物测量。在额外的四个月实践和远程图像审查后，从正在进行的队列中招募了一些孕妇进行超声检查以确定胎龄。将超声确定的分娩胎龄与产后胎龄评估（ Ballard 检查）进行比较。
共纳入 178 名孕妇。尽管在扫描的前 25%中，有 17.5%（24/135）的图像质量不可接受，但大多数图像质量良好（94.3%，509/540），且存在学习曲线。当月经日期未知时，超声用于确定 13%的妊娠日期，并额外改变了 25%的估计胎龄。超声协议确定的分娩胎龄与 Ballard 检查确定的胎龄之间存在较差的一致性（偏差 0.8 周，一致性界限为-3.5 周至 5.1 周）。根据 Ballard 检查确定的胎龄分布表明胎龄围绕平均值聚集，87%的数值落在 39 至 41 周之间。超声确认的月经日期的胎龄分布更为典型。使用超声确认的日期作为金标准，78.5%的早产儿被错误地归类为足月产，26.8%的小于胎龄儿被错误地归类为 Ballard 检查的正常生长儿。
在具有产科终点的前瞻性疟疾研究中，应强烈考虑使用超声来确认胎龄，以避免将婴儿错误地归类为早产或生长受限儿。使用超声确实需要大量时间投入来保持高质量的图像获取。
