NCT07525726

The Relationship Between Finger Ratio and Development in Infants

The Relationship Between Digit Ratio and Motor Development and Sensory Processing in Infants

• Status: Enrolling By Invitation
• Phase: —
• Study type: Observational
• Enrollment: 80 (estimated)
• Sponsor: Nigde Omer Halisdemir University · Academic / Other
• Sex: All
• Age: 12 Months – 18 Months
• Healthy volunteers: Accepted

Summary

One of the most prominent indicators of prenatal androgen exposure is considered to be the ratio of second and fourth finger lengths (2D:4D). The 2D:4D finger ratio refers to the ratio of the length of the second finger (2D; index finger) and the fourth finger (4D; ring finger). Evidence suggests that 2D:4D is developmentally stable and stabilizes from the second trimester of pregnancy. It has been reported that the 2D:4D ratio correlates positively with estrogen and negatively with testosterone. In both sexes, prenatal testosterone levels are inversely related by a 2D:4D ratio, which does not change with age. Androgens can have direct trophic effects on target cells or indirectly affect neuronal growth through neurotrophic mediators released locally by steroid-sensitive neuronal or glial cells. Prenatal testosterone can have long-term organizational effects on the structure and function of various body systems (e.g., cardiovascular and musculoskeletal systems) that are important for physical activity and exercise.

Detailed description

One of the most prominent indicators of prenatal androgen exposure is considered to be the ratio of second and fourth finger lengths (2D:4D). The 2D:4D finger ratio refers to the ratio of the length of the second finger (2D; index finger) and the fourth finger (4D; ring finger). Evidence suggests that 2D:4D is developmentally stable and stabilizes from the second trimester of pregnancy. It has been reported that the 2D:4D ratio correlates positively with estrogen and negatively with testosterone. In both sexes, prenatal testosterone levels are inversely related by a 2D:4D ratio, which does not change with age. From a gender perspective, differences have been found in the basic motor skills of boys and girls. Boys have greater object control skills than girls. Gender is one of the most studied variables in motor development. Many longitudinal studies show that boys perform better in gross motor skills such as running and jumping, while girls are more successful in fine motor tasks such as drawing or manipulating small objects. Sensory processing involves the capacity to receive, interpret, organize, and respond to sensory input from both one's own body and the external environment. Sensory processing disorders can be observed in infants due to the immaturity of their systems. There are very few studies on measuring finger length in the early stages of newborns. To our knowledge, the relationship between intrauterine androgen exposure (2D:4D) and motor development and sensory processing has not yet been investigated. Therefore, the planned study aims to evaluate the 2D:4D finger ratio in 12-18-month-old infants and to examine the relationship between this ratio and motor development and sensory processing.

Conditions

• Infant Developmental Assessment

Interventions

Type	Name	Description
BEHAVIORAL	Digit Ratio	The lengths of the second (2D) and fourth (4D) fingers will be measured separately on each hand. Measurements will be taken with the baby's hands placed flat on a surface with palms facing upwards. Finger length will be defined as the distance from the midpoint of the proximal crease at the base of the finger to the distal end of the finger. A digital caliper with a precision of 0.01 mm will be used, and two separate measurements will be taken for each finger, with the average value recorded. Based on these measurements, the 2D:4D finger ratio for each hand will be calculated by dividing the length of the second finger by the length of the fourth finger.
BEHAVIORAL	Motor development	The Peabody Developmental Motor Scale-2 (PDMS-2) is planned to be used to assess motor development. The PDMS-2 test is designed to identify developmental delays in children aged 0-72 months. It is used to evaluate children's motor development with separate tests and rating scales for both gross and fine motor skills.
BEHAVIORAL	Sensory processing functions	The Test of Sensory Functions in Infants was planned for use to assess babies' sensory development. The TSFI is frequently used to evaluate the sensory processing functions of infants aged 4-18 months. It is used to determine whether and to what extent a baby has a sensory processing problem. It consists of 24 items. The TSFI requires the baby to be stimulated and interact with various materials. The total score ranges from 0-49, and the test has normative values for different age groups. Although it can be used from the fourth month onwards, the most reliable and valid results are obtained between 7-18 months.

Timeline

• Start date: 2026-04-06
• Primary completion: 2027-04-01
• Completion: 2027-04-01
• First posted: 2026-04-13
• Last updated: 2026-04-15

Locations

1 site across 1 country: Turkey (Türkiye)