[Predictive factors for fetal tolerance to cordocentesis: a monocentric retrospective study]

Indications for fetal blood sampling (FBS) are getting more limited. In this context, we aimed to evaluate fetal loss and morbidity associated with FBS and to precise the predictive parameters for fetal complications. More than a retrospective evaluation of our practices, the final end point of our study was to better inform the patients coming to our centre.

Retrospective monocentric cohort (Canadian Task Force classification II-2) of the 99 FBS performed between April 2004 and June 2010 on 80 fetuses, after excluding the procedures done for termination of pregnancy. The main clinical outcome was a composite outcome criteria for fetal tolerance including cesarean section for abnormal non stress test within the 24 hours, or any event responsible of a modified obstetrical management during the 14 day following FBS.

Mean maternal age at FBS was 30 years ± 5.13 SD and parity was 2.49 ± 1.38 SD. FBS was performed by an experienced operator in 86.5% of cases (CI 95%, 78-92.6); with a single insertion in 83.3% of circumstances (CI 95%, 74.4-90.2). The mean duration was 11 min ± 6.37 SD. The total rate of intrauterine death, in our series, was 7.1% (CI 95%, 2.9-14), including all reported fetal demise within the 14 days after FBS, whatever the relation with the procedure. Our study demonstrated a 9.1% occurrence of post-FBS altered CTG fetal testing (CI 95%, 4.2-16.6), half of it with spontaneous resolution. The rate of severe complications (main clinical outcome) was 11.1% (CI 95%, 5.7-19) including one fetal death liable to FBS and 10 emergency caesarean sections: 5.1% for fetal bradycardia (CI 95%, 1.7-11.4), 2% for placental abruption (CI 95%, 0.2-7.1), 2% for premature preterm rupture of membranes (CI 95%, 0.2-7.1) and 1% for significative umbilical cord bleeding (CI 95%, 0-5.5). Univariate factor analysis highlights 4 parameters for impaired fetal tolerance; a prolonged procedure, presence of low fetal platelets (<30.10(9)/L); and FBS performed for fetal anaemia during Parvovirus B19 infection or allo-immune thrombocytopenia.

FBS remains a tricky procedure with a substantial risk of fetal loss or complications especially when performed on high-risk fœtuses. The length of the procedure should be shortened as much as possible (trained operator, postponed procedure when all favourable condition are not available). Fetal thrombocytopenia is a meaningful risk factor encouraging carefulness when exploring allo-immune fetal thrombocytopenia.