Go Big: Why the Forefinger Beats the Pinky for Finger Feeding
Marie-Celine Farver RN BSN IBCLC
Lactation Lead, Sutter Davis Hospital Birthing Center
10.24.2026
When finger feeding is used in place of breastfeeding, the goal is to come as close as possible to what breastfeeding is like for the baby. A forefinger does that better than a pinky, for five reasons:
Size: it is much closer to the size of a nipple.
Texture: it is softer and more nipple-like.
Suction: it lets the baby create suction with less effort.
Suck reflex: it stimulates more of the area that triggers the suck.
Tongue and jaw position: it encourages a wider gape, more similar to the white gape a baby should have to properly breastfeed.
1. Size: A Forefinger Is Closer to Nipple-Sized
A forefinger is 55% or more larger than a pinky. A pinky is smaller and more narrow. A forefinger has more volume. This is the case with the mother, father, or staff.
This does not need to be an exact science. There is no need to measure the millimeters of a nipple against the millimeters of a finger. This is general sizing: when you are finger feeding in place of breastfeeding, you want to accommodate, as closely as you can, what the nipple does in breastfeeding. A forefinger accomplishes that better than a pinky. (See "Putting Numbers on It" below for estimated measurements.)
2. Texture: More Soft Tissue
A forefinger has more soft tissue around it. A pinky is bonier, because the ratio of flesh to bone is smaller in a pinky than in a forefinger. In texture and softness, a forefinger more closely approximates a nipple.
3. Filling the Intra-Oral Space (The Vacuum Physics)
To draw milk effectively, a baby must create negative intra-oral pressure (a vacuum).
• The Pinky Problem: Because a pinky finger has roughly 55% less total volume (~7.2 mL vs. ~11.3 mL), it leaves significant empty space on the sides of the mouth. The infant has to work drastically harder, collapsing their cheeks and exhausting their masseter and buccinator muscles just to seal those lateral gaps and achieve a vacuum.
• The Forefinger Advantage: The index finger's larger mass and 1.5 cm average diameter fill the oral cavity far more efficiently. This structural bulk minimizes the dead air space the infant needs to evacuate, allowing them to create a functional vacuum with significantly less structural effort.
Using an index finger rather than a pinky provides a vastly superior physiological match for a newborn's oral mechanics. A forefinger has more mass, and that helps the baby create intraoral suction than a pinky does. The larger finger takes up more of the volume of the baby's mouth, so the baby doesn't have to create as much negative pressure to make enough suction to draw out milk.
With a smaller object in the mouth, the baby has to work harder:
The baby must pucker the lips to make a seal around a smaller object, since it doesn't fill the oral opening.
The baby typically puckers the cheeks as well, to reduce the volume inside the mouth.
That is a lot of adaptation just to accommodate a pinky. With a forefinger, the baby can focus on the suction needed to withdraw milk, rather than on adjusting to the small volume and circumference of a pinky. The mechanics are simply more favorable and more like proper breastfeeding technique.
4. Stimulating the Suck Reflex
The larger surface area of a forefinger can stimulate more of the soft tissue that triggers the suck reflex.
The suck reflex center is the soft tissue at the end of the baby hard palate, where the hard palate meets the soft palate. You can feel it with your own finger: the hard palate feels like bone, and as you slide your finger back you reach a ridge, and then the soft palate begins. That area is the suck reflex center. A larger-diameter finger, like a forefinger, is able to stimulate more of that area, which means a larger surface area to stimulate the suck reflex mechanism.
The forefinger is also somewhat longer than the pinky, which adds to the surface volume that reaches the palate.
5. Tongue and Jaw Position
For a good latch, the baby needs to extend the tongue forward over the lower gum line and keep it cupped. Newman (2011) describes finger feeding the same way: the baby keeps the tongue down and forward over the gums, the mouth wide open, and the jaw forward. He adds that “the larger the finger used, the better.” The width of a finger influences how the mouth is held while feeding:
A narrow pinky lets the mouth close down more narrowly, which can encourage a biting or pinching motion rather than a wide gape.
A forefinger is broader, so the jaw drops wider, closer to the wide gape needed for the breast. Its width also provides a stable platform that tends to press the tongue down and forward.
Newman’s (2011) guidance supports the general principle that a larger finger is better. The specific comparison of a forefinger with a pinky is clinical reasoning based on how the mouth and finger interact.
Putting Numbers on It: Estimated Finger Size
To put numbers on the size difference, each finger can be modeled as a simple cylinder using average adult hand measurements. Finger lengths come from published measurements of young adults (Chatzıoglou et al., 2024). The diameters are assumed average values, not figures taken from a cited study.
Mass is approximated by assuming tissue has roughly the density of water, about 1 g per mL.
Because the forefinger is both longer and thicker, the difference compounds when you look at three-dimensional volume instead of flat length. Dividing 11.3 by 7.2 gives about 1.57, so the forefinger has more than 50% more volume than the pinky. That matches the general sizing point made at the start of this piece.
These figures are estimates from a simplified model, not measurements of any one person's fingers or of a baby's mouth. Only the tip of the finger goes into the baby's mouth, so total finger volume illustrates the general size difference rather than exact intraoral fit.
What Published Finger-Feeding Guidance Says
Published patient handouts and clinical articles on finger feeding describe placing the feeding tube along the soft pad of the index finger (Breastfeeding Answers, 2020; Malta Midwives Association, 2019; Newman, 2011). Newman (2011) allows for the index or another finger, and notes that a larger finger is better for keeping the mouth wide open. Malta Midwives Association (2019) directs that the soft side of the finger face the roof of the mouth, keeping the tongue flat and forward, and that the finger can go in as far as about the first knuckle line.
A retrospective study from a breastfeeding counseling clinic concluded that finger feeding is an effective alternative feeding method that can support successful breastfeeding, and called for larger studies (Karabayır et al., 2022). Finger feeding is also described as similar to breastfeeding in the motion of the baby’s tongue and jaw (Newman, 2011).
A Note on the Evidence
The points in this article are not based on randomized controlled trials. They come from examining and comparing the anatomy and physiology involved in fingerfeeding. We are talking in generalities, and the reasoning rests on the mechanics of sucking and how the mouth, finger, and nipple relate.
References
Breastfeeding answers: Finger feeding. (2020, November). myhealthunit.ca. https://www.myhealthunit.ca/en/health-professionals-and-partners/resources/Health-Care-Professionals/Finger-Feeding.pdf
Chatzıoglou, G. N., Pınar, Y., & Govsa, F. (2024). Biometric analysis hand parameters in young adults for prosthetic hand and ergonomic product applications. Anatomy & Cell Biology, 57(2), 172–182. https://doi.org/10.5115/acb.23.310
Karabayır, N., Merttürk Potak, E., Karaman, S., Sebirli, M. F., İstanbullu, M. B., Potak, M., & Teber, B. G. (2022). The finger feeding method and relactation. Cureus, 14(4), Article e24044. https://doi.org/10.7759/cureus.24044
Malta Midwives Association. (2019, January 13). Finger feeding. https://maltamidwivesassociation.com/mma-blog/f/finger-feeding
Newman, J. (2011, November 2). Finger feeding. Contemporary OB/GYN. https://www.contemporaryobgyn.net/view/finger-feeding
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