Maternal serum markers of placental damage in uncomplicated dichorionic and monochorionic pregnancies in comparison with monochorionic pregnancies complicated by severe twin-to-twin transfusion syndrome and the response to fetoscopic laser ablation

Abstract 

Objective

Twin-to-twin transfusion syndrome (TTTS) is a morbid perinatal condition associated with abnormal placentation and is treated by fetoscopic laser ablation (FLA). We assessed basal maternal serum alphafetoprotein (MSAFP) and free β-human chorionic gonadotrophin (f-βHCG) in uncomplicated dichorionic (DC) and monochorionic (MC) twin pregnancies and a cohort of MC twin pregnancies complicated by severe TTTS. Changes in MSAFP and f-βHCG post-FLA were measured as markers of placental coagulation.

Study design

In a prospective case-cohort study, MC twins complicated by TTTS (n=23) were studied. A cohort of uncomplicated DC (n=12) and MC (n=6) twin pregnancies, which were appropriately grown for gestation with normal liquor volumes were also studied. Using solid phase, two site fluoroimmunometric assays, both MSAFP and f-βHCG from uncomplicated and complicated cohorts were measured. Samples were taken, prior to FLA then at intervals after the procedures (6h, 24h and 1 week).

Results

The median multiples of median (MoM) were not significantly different in uncomplicated DC twin pregnancies for MSAFP 1.85 (95% CI 1.62–2.34) or fβHCG 1.66 (95% CI 1.21–2.04) compared to uncomplicated MC twin pregnancies (MSAFP 1.40 (95% CI 1.16–2.58) and fβHCG 1.70 (95% CI 0.32–3.35)). However, the median MSAFP MoM in MC twin pregnancies complicated by severe TTTS was increased (MSAFP 3.10 (95% CI 2.67–4.43); p<0.05) with a more significant increase being noted in median fβHCG (MoM 5.75 (95% CI 5.22–9.12); p<0.0001) compared to uncomplicated twin pregnancies. Post-FLA, the median MSAFP increased significantly at 6h by 445% (636.65U/ml (95% CI 616–1216.9U/ml)) and remained elevated at 1 week (553.4U/ml (95% CI 203.7–3020.8U/ml; p=0.001)). No significant difference in median fβHCG was noted post-FLA (p=0.36). This rise in MSAFP appears unrelated to the number of placental anastomoses coagulated or the total energy used. Also, in the small cohort in which amniodrainage alone was performed no rise in MSAFP was noted.

Conclusions

MSAFP and fβHCG are increased in TTTS indicating an association with abnormal placentation. Post-FLA, a significant rise in MSAFP was noted for up to a week post-coagulation. This was not noted after amniodrainage.

Keywords: Maternal serum alphafetoprotein (MSAFP), Free β-human chorionic gonodotrophin (fβHCG), Twins, Twin–twin transfusion syndrome (TTTS), Fetoscopic laser ablation (FLA)