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Nomogram of fetal penile length during pregnancy: A systematic review
Lomani A O'Hagan1, Aniruddh Deshpande2, Yoon Hi Cho3
1Department of Pediatric Surgery, Wellington Children's Hospital, Wellington, New Zealand; Department of Anatomy and Medical Imaging, University of Auckland, Auckland, New Zealand.
Insights
This study provides the first comprehensive reference values for fetal penile length (OPL) across gestation. A new growth formula, y = 0.9x - 9, aids in prenatal assessments for DSD and genetic conditions.
Area of Science:
- Prenatal Medicine
- Fetal Development
- Medical Imaging
Background:
- Fetal penile length (OPL) is crucial for prenatal assessments, including detecting differences in sex development (DSD), genetic syndromes, and endocrinopathies.
- Standardized normative data for OPL across gestation are currently lacking, hindering accurate clinical evaluation.
- Establishing reliable reference values is essential for improving diagnostic capabilities in fetal medicine.
Purpose of the Study:
- To conduct a systematic review and meta-analysis to establish reference values for fetal penile length (OPL).
- To develop a clinically applicable growth formula for OPL based on gestational age.
- To provide standardized data for improved prenatal assessments and early detection of fetal abnormalities.
Main Methods:
- A systematic literature search was conducted following PRISMA guidelines across MEDLINE and EMBASE databases.
- Studies reporting outer penile length (OPL) in fetuses without genitourinary abnormalities, measured via ultrasonography, MRI, or cadaveric methods, were included.
- Data extraction focused on sample size, gestational age, measurement techniques, and penile length metrics, followed by meta-analysis of nine studies (n=2264).
Main Results:
- Eighteen studies (n=3369) met the inclusion criteria for the systematic review.
- A meta-analysis of nine studies (n=2264) generated a weighted mean growth curve for OPL from 14 to 40 weeks of gestation.
- Fetal penile length demonstrated a predominantly linear growth trajectory, accurately modeled by the equation y = 0.9x - 9 (x=gestational age in weeks, y=OPL in mm).
Conclusions:
- This systematic review and meta-analysis provides the first comprehensive normative data and a practical growth formula for fetal penile length (OPL).
- The findings offer a valuable tool for clinical application in prenatal assessments, aiding in the early identification of potential developmental abnormalities.
- Future research should focus on standardizing measurement methods and including diverse populations to enhance the generalizability and clinical utility of these findings.
Introduction:
Fetal penile length is an important parameter in prenatal assessments, aiding in the early detection of differences in sex development (DSD), genetic syndromes, and endocrinopathies. However, standardized normative data across gestation are lacking.
Objective:
This systematic review aimed to establish reference values for fetal penile length and provide a clinically useful growth formula.
Methods:
Following PRISMA guidelines, MEDLINE and EMBASE were searched through March 2025 for studies reporting outer penile length (OPL) in fetuses without genitourinary abnormalities, using ultrasonography, MRI, or cadaveric measurements. Data extracted included sample size, gestational age, measurement methods, and penile length metrics.
Results:
Eighteen studies (n = 3369) met inclusion criteria. A meta-analysis of nine studies (n = 2264) was performed to generate a weighted mean growth curve for OPL from 14 to 40 weeks of gestation. The results revealed a predominantly linear growth trajectory of penile length, best approximated by the equation y = 0.9x - 9, where x is gestational age (weeks) and y is OPL (mm).
Conclusions:
This study presents the first comprehensive systematic review and meta-analysis of fetal penile length, providing normative data and a practical formula for clinical application. Future research should aim to standardize measurement methods and include diverse populations to enhance the generalizability of these findings.
