Pelvic floor morbidity is present in more than 50% of patients with history of vaginal deliveries.
However, there are some other factors that could worsen the effect of the vaginal delivery in pelvic floor morbidity, such as macrosomia or instrumental deliveries. Vaginal delivery of infants>4000g has long been recognised as major risk factor for subsequent pelvic floor morbidity, due to an overdistension of the perineal muscles; the most important, the levator ani muscle. Injuries in this muscle have been strongly related with pelvic floor morbidity. Perineal pain and dyspareunia, urinary and anal incontinence are the most frequent complaints at short and long term following childbirth.  

The increasing concern for pelvic floor morbidity and the recovery of the pelvic musculature in the postpartum, has resulted in an increase in consciousness for the prevention of pelvic floor injuries among professionals attending labor.

This study aimed to determine the association between macrosomia and urinary incontinence (UI), anal incontinence (AI), and dyspareunia in postpartum period.

A retrospective consecutive cohort study was carried out. The study group was formed of macrosomia; control group: primiparous women after spontaneous vaginal childbirth with intact perineum or first degree perineal injury (infant˂4000g). Telephone survey was performed where data from symptomatology was collected. We used the following questionnaires: ICIQ for urinary incontinence, St Mark questionnaire for anal incontinence and presence of dyspareunia one year after childbirth.

93 patients agreed to participate in the study; 60 in control group and 30 in the study group.  Patients in the study group were older than controls (average age of 33.6 vs 29.2), and had higher BMI (26.5 vs 22.6).
Regarding urinary symptoms, vaginal delivery of fetus>4000g is associated to a higher risk of developing UI at one year after delivery [OR=15 (CI95% 3,9 – 59,9)].  Whent ICIQ test was performed, results showed an average result of 0.21 in control group versus 4.4 in the study group, statistically significant.
The same happened with results from dyspareunia, appearing to be an association between pain during sexual intercourse and history of vaginal delivery of a macrosoma fetus [OR=13 (CI 95% 2,6 – 65,4)]. 
Anal incontinence could not be studied because of insufficient data in control group.

Within the study group (macrosomia) no differences were found in Wexner, St. Mark or ICIQ tests results, when regarding the perineal injury (2n degree perineal tear vs 1st degree or no injury). However, risk for dyspareunia seemed to be increased in cases of macrosomia and 2nd degree perineal tear OR 8.8 (CI95% 0,9 – 83,3).

As other factors, vaginal deliveries of fetus>4000g cause an important impact in patient’s pelvic floor. As shown in results of this study, the overdistension of muscles caused by the fetus can result in greater predisposition for developing urinary incontinence or dyspareunia in the future.

When talking about dyspareunia, macrosoma deliveries seems to be also a risk factor for developing dyspareunia in future sexual intercourses. Nevertheless, results showed also a relation between the apparition of dyspareunia and the presence of 2n degree perineal tear. An interesting approach in this field would be to determine whether the major risk factor is the vaginal delivery of a macrosoma fetus or the perineal injury.

Macrosomia has been shown in this study as a risk factor for developing UI at short and long term following childbirth, regardless perineal tear degree. Using this information, as fetal weight is not a modifiable variable, obstetric management could focus on the prevention of pelvic floor morbidity, when the estimated fetal weight is> 4000g. 
Macrosomia is also associated to an increase of dyspareunia after delivery, although it seems to be at the expense of perineal injury degree. Futher studies in this field would be necessary to distinguish any confusional factors. 
A greater sample would be necessary to study this question and AI.