Narrow hips: Can I deliver vaginally?
I am 31-weeks-pregnant and I am concerned about the size of my pelvic opening. I am only five feet tall and my hips measure 34 inches. My husband, and his entire family, are tall. Are there any tests that can tell me if the baby can make it through?
Question:Peg Plumbo CNM
Peg Plumbo has been a certified nurse-midwife (CNM) since 1976. She has assisted at over 1,000 births and currently teaches in the... Read more
While it is a woman's pelvic structure that determines the diameters that the baby must navigate, there is more to the pelvis than the apparent visual aspects of size and shape.
Although a woman may appear to have small hips, she may have more than adequate internal measurements. There are about 16 different aspects to the pelvis; however, a few of the most important are the internal diameters, the shape of the pelvis, the curve of the sacrum and the inclination of the pelvic bones.
Each of these aspects may be assessed at the initial prenatal visit, although some practitioners do not do this. Those who do not perform "pelvimetry" feel that this assessment is uncomfortable for the patient and would not change the course of the pregnancy or alter the initial stages of labor.
Other than the initial pelvimetry performed in the office, there are no specific tests that can be performed. MRI or Xray measurements of the pelvis would only assess one P, but the three others are just as important. Such tests are never requested during pregnancy as every mother deserves a trial of labor.
Genetics do play a small role in successful vaginal birth. If a five foot woman and a six foot man conceive a child, it is likely that she would have a baby that is larger than if she had a baby with a smaller man. But the contribution of that extra foot is small.
No cesarean should be scheduled on the basis of pelvic assessment alone because there is more to labor than the bony pelvis. The four Ps of labor assessment must also be considered:
- "Powers," also known as maternal contractions, can be strong and capable of dilating the cervix and moving the baby down or they may be poor or dysfunctional. Sometimes these "powers" can be augmented with the use of rest, fluids, medications for pain or by oxytocin, a uterine stimulant. Another aspect of the "powers" is the maternal efforts. If a mother is frightened, exhausted or feels unsafe, she might not work as well with her body and her contractions. She may be unable to effectively push during the second stage of labor. Sometimes medications can decrease a mother's ability to work with her own body as well.
- "Passage" refers to the pelvic shape and size. It cannot stand alone as a determinant of vaginal birth unless it is congenitally misshapen or fractured without the benefit of appropriate healing. Other determinants of the "passage" are the quality of the soft tissue and muscles of the pelvic floor.
- "Passenger" refers to the baby. It is important to note that even mothers with small pelves can give birth to large babies if the other Ps are working for them. In our practice the other day, a mother had an 11 pound baby, despite being only 4 feet 11 inches tall! In a similar vein, I have seen women with large pelves who are not able to birth small babies vaginally.
- "Psyche" refers to the mother's state of confidence, as well as the support she feels from those around her. Midwives are experts at supporting the efforts of mothers during labor. They can also teach fathers and others in the birthing area how to assist the mother. Attending childbirth education classes and reading will also help to increase knowledge and confidence. Having a "doula" or woman attendant has been shown to decrease the risk of cesarean birth for this same reason.
