Objective
To evaluate risks for adverse pregnancy outcomes by number of embryos transferred (ET) and fetal heart beats (FHB) in ART conceived singleton live births.
Design
Longitudinal cohort using cycles reported to the Society for Assisted Reproductive Technology Clinic Outcomes Reporting System between 2004 and 2008 among women who were treated and gave birth in Massachusetts.
Setting
Clinic-based data.
Patients
ART data on 6,073 births between 2004 and 2008 were linked to vital records and hospital data. Likelihood of ET ≥3 vs 1–2, FHB >1 vs 1, and risks of preterm birth (PTB, <37 weeks gestation), low birthweight (LBW, <2,500g), and small-for-gestational age birthweight (SGA, <10th%ile) with FHB >1 were modeled with binary logistic regression using a backward-stepping algorithm, and presented as adjusted odds ratios (AORs) and 95% confidence intervals.
Interventions
None
Main Outcome Measures
ET≥3, FHB >1, PTB, LBW, and SGA.
Results
Higher ET was significantly more likely with older maternal age, intracytoplasmic sperm injection, assisted hatching, cleavage-stage embryos, and thawed embryos. The likelihood of FHB>1 with ≥3 ET vs 1–2 ET was 2.04 (1.68–2.48). Risks of PTB and LBW with FHB>1 were 1.63 (1.27–2.09) and 1.81 (1.36– 2.39), respectively; the risk of SGA was not significant. Nulliparity was associated with higher risks of PTB (1.34, 1.12–1.59), LBW (1.48, 1.20–1.83), and SGA (2.17, 1.69–2.78).
Conclusions
Number of ETs were strongly associated with FHBs, with twice the risk of FHB>1 with ≥3 ET versus 1–2 ET. Increasing FHBs were associated with significantly greater risks for PTB and LBW outcomes.