Every neonate requires a detailed examination of the external genitalia for sex assignment. Conventional approaches for the examination in female extremely low birthweight (ELBW) neonates in the closed incubator are challenging. Under direct visual inspection from outside the closed incubator, evaluation may be insufficient, owing to the small body size. It is necessary to lift the lower limbs and buttocks to enable physicians to examine the perineum thoroughly. However, this practice is potentially against the minimal handling protocol for ELBW neonates. In a previous study, an endoscope-assisted technique helped physicians to identify the urethral meatus in a male ELBW neonate with hypospadias.¹ It remains unknown whether this endoscope-assisted technique can be applied to examinations of perineum of female ELBW neonates. Here, using a mobile airwayscope with a monitor, we examined the external genitalia in a 483 g female neonate.

The patient was born via vaginal delivery to a healthy mother at 22 weeks and 3 days of gestation due to impending preterm labor caused by cervical incompetence. The birthweight was 483 g (−0.78 SD). The patient was intubated and on mechanical ventilation in a closed incubator. The external genitalia of the patient were too small for adequate examination from outside the incubator (Figure 1a). On postnatal day 5, using a flexible mobile airwayscope, we examined the external genitalia of the patient remaining in the incubator for 7 min (Figure 1b). The mobile airwayscope (Olympus MAF-DM2, Olympus Corporation, Tokyo, Japan) had the following specifications: (i) a monitor allowing the inspector to manipulate the scope safely and effectively; (ii) a picture or video recording function; (iii) light emitting diode at the tip to illuminate objects; (iv) a 3.1 mm tip diameter, and (v) a length of 600 mm. During the mobile airwayscope-assisted examination, we identified a vaginal vestibule-like structure with no swelling of the labioscrotal folds; however, we could not identify the urethral meatus (Figure 1c). By retrospectively evaluating still images, the anogenital ratio and clitoral width were estimated to be 0.45, and 5.8 mm, respectively (Figure 1c,d). After the examination, the patient did not develop any fluctuations in vital signs or infectious diseases. Since the patient was not in good condition, abdominal ultrasonography for internal genitalia was not performed. We extracted DNA from the umbilical cords. A polymerase chain reaction revealed the absence of SRY (data not shown). Our medical differences of sex development team discussed the clinical information and results of the examinations, including images of the external genitalia. We shared the discussion and limitations with the parents, namely no reference ranges or normal findings in ELBW neonates' external genitalia. On postnatal day 11, the parents assigned and registered their baby's sex as female.

We comprehensively examined the external genitalia in the 483 g female neonate using a mobile airwayscope with no adverse events. Using a mobile airwayscope, we overcame the two limitations of the conventional approach in our patient. Inspection of the external genitalia in female ELBW neonates may be insufficient, owing to the small size of neonates. Identification of the urethral meatus and vaginal vestibule is difficult. The mobile airwayscope enables us to obtain magnified image of the external genitalia at arbitrary angles. This allowed detailed observation of the perineum in a normal posture. Furthermore, by retrospectively evaluating still images, we estimated the anogenital ratio and clitoral size accurately. Accurate measurement with a 1 mm scale ruler is impossible because each part of the external genitalia in female ELBW neonates is small.

Using the mobile airwayscope-assisted examination of the patient, the anogenital ratio and clitoral width were estimated to be 0.45, and 5.8 mm, respectively. However, external genitalia findings obtained by our method alone may not be sufficient for sex assignment in ELBW neonates. This is due to the lack of reference data for the structures of the external genitalia of ELBW neonates. The appearance of external genitalia in female ELBW neonates varies widely between individuals, particularly the size of the clitoris.^{2, 3} To evaluate the external genitalia of neonates with such wide variations precisely, we must establish the references that adjust for factors such as sex, weight, and gestational age. When we evaluate the external genitalia of term neonates using our method, we cannot apply the reference data of neonates obtained by conventional measuring methods. Using the conventional measuring method, the penis length is measured in a manually stretched position,⁴ whereas using our method, the penis length is measured on the image in a flaccid position.

In our patient, the identification of a vaginal vestibule-like structure and the absence of SRY assisted physicians and parents in assigning the baby's sex as female. We suppose that non-invasive genetic testing using umbilical cord samples provides valuable supplementary information for sex assignment.^{1, 5}

In summary, we reported a female ELBW infant whose external genitalia were safely and effectively examined using a mobile airwayscope with a monitor.

每个新生儿都需要对外生殖器进行详细检查以确定性别。在封闭式培养箱中对女性极低出生体重 (ELBW) 新生儿进行常规检查具有挑战性。由于体型较小，在封闭培养箱外部直接目视检查时，评估可能不充分。需要抬起下肢和臀部，以便医生能够彻底检查会阴。然而，这种做法可能违反了 ELBW 新生儿的最低限度处理方案。在之前的一项研究中，内窥镜辅助技术帮助医生识别患有尿道下裂的男性 ELBW 新生儿的尿道口。¹目前尚不清楚这种内窥镜辅助技术是否可以应用于女性 ELBW 新生儿的会阴检查。在这里，我们使用带有监视器的移动气道镜检查了 483 克女性新生儿的外生殖器。

该患者因宫颈机能不全导致即将早产，在妊娠 22 周零 3 天时由健康母亲经阴道分娩出生。出生体重为 483 克（−0.78 SD）。患者在密闭培养箱中接受插管和机械通气。患者的外生殖器太小，无法在培养箱外进行充分检查（图 1a）。出生后第 5 天，我们使用灵活的移动气道镜检查了留在培养箱中的患者的外生殖器 7 分钟（图 1b）。移动气道镜（奥林巴斯 MAF-DM2，奥林巴斯公司，日本东京）具有以下规格：（i） 监视器，允许检查员安全有效地操作气道镜； (ii) 图片或视频录制功能； (iii) 尖端的发光二极管用于照亮物体； (iv) 尖端直径为 3.1 毫米，(v) 长度为 600 毫米。在移动气道镜辅助检查过程中，我们发现了阴道前庭样结构，阴唇皱襞没有肿胀；然而，我们无法识别尿道口（图1c）。通过回顾性评估静态图像，肛门生殖器比例和阴蒂宽度估计分别为 0.45 和 5.8 毫米（图 1c，d）。检查后，患者未出现任何生命体征波动或感染性疾病。由于患者情况不佳，未进行内生殖器腹部超声检查。我们从脐带中提取了 DNA。聚合酶链式反应显示不存在SRY（数据未显示）。我们的性别发育医学差异团队讨论了临床信息和检查结果，包括外生殖器的图像。我们与家长分享了讨论和局限性，即 ELBW 新生儿外生殖器没有参考范围或正常结果。出生后第11天，父母将婴儿的性别指定并登记为女性。

我们使用移动气道镜全面检查了 483 克女性新生儿的外生殖器，没有出现不良事件。使用移动气道镜，我们克服了患者传统方法的两个局限性。由于新生儿体型较小，对女性 ELBW 新生儿的外生殖器检查可能不够充分。尿道口和阴道前庭的识别很困难。移动气道镜使我们能够以任意角度获得外生殖器的放大图像。这样可以在正常姿势下详细观察会阴。此外，通过回顾性评估静态图像，我们准确地估计了肛门生殖器比例和阴蒂尺寸。由于女性 ELBW 新生儿的外生殖器各部分都很小，因此用 1 毫米刻度尺进行精确测量是不可能的。

使用移动气道镜辅助检查患者，肛门生殖器比例和阴蒂宽度估计分别为 0.45 和 5.8 毫米。然而，仅通过我们的方法获得的外生殖器结果可能不足以用于 ELBW 新生儿的性别分配。这是由于缺乏ELBW新生儿外生殖器结构的参考数据。女性 ELBW 新生儿的外生殖器外观因人而异，尤其是阴蒂的大小。^{2, 3}为了准确评估差异如此之大的新生儿的外生殖器，我们必须建立根据性别、体重和胎龄等因素进行调整的参考值。当我们使用我们的方法评估足月新生儿的外生殖器时，我们不能应用通过常规测量方法获得的新生儿的参考数据。使用传统的测量方法时，阴茎长度是在手动拉伸位置测量的，⁴而使用我们的方法时，阴茎长度是在图像上处于松弛位置时测量的。

在我们的患者中，阴道前庭样结构的识别和SRY的缺乏帮助医生和父母将婴儿的性别指定为女性。我们认为使用脐带样本的非侵入性基因检测可以为性别分配提供有价值的补充信息。^{1, 5}

总之，我们报告了一名 ELBW 女性婴儿，使用带有监视器的移动气道镜安全有效地检查了其外生殖器。