Aim of the study :The major aim is to evaluate the effectiveness of the induction of labor in case of fetal macrosomia on the reduction of neonatal traumatism risk. The secondary aims are to evaluate maternal morbidity and the risk of Caesarean in case of induction of labor, compared to a spontaneous labor.

A clinical trial multicentric randomized controlled will be organized. A total of 1000 women will be recruited between 36 and 38 weeks of amenorrhoea (GW) if the pregnancy is single, in cephalic presentation and the fetus is estimated macrosomic for the gestational age (> 90e percentile clinically and >95° percentile sonographically).All agreeing patients will be randomized in one of the two following groups: - 1. Induction of labor between 37+0 and 38+6 GW and within 3 day after the randomization. - 2. Expectancy until the spontaneous beginning of labor or up to 41 GW.The measurement of principal exit is the neonatal traumatism (criterion composite associating: dystocia of the shoulders, fractures osseous, paralysis/paresis of the plexus brachial or intracerebral haemorrhage).The secondary criteria are neonatal asphyxiation (arterial pH < 7.10 or Apgar < 7 to 5 minutes), the maternal traumatism (tear of 3rd or 4th degree) and the Caesarean. The long-term after-effects for the mother and her child will be also evaluated

Inclusion Criteria:

• Agreed women Sonographic estimation of begin of pregnancy <20GW Single pregnancy in cephalic presentation Macrosomic fetus :
• clinical estimation : 36GW : ≥3350g or 34cm 37GW : ≥3550gor34cm 38GW : ≥3750g or 35cm
• sonographic estimation : 36GW : ≥ 3500g 37GW : ≥ 3700g 38GW : ≥ 3900g

Exclusion Criteria:

• Typical diabetes I or typifies II or diabetes gestational treated by insulin.
• Antecedents of tear of the anal sphincter or severe urinary or faecal presence of an incontinence.
• Antecedent of dystocia of the shoulders or neonatal traumatism.
• Antecedents of caesarian or uterine scar.
• contraindication in the release of the work or in the childbirth by low way.