Table 4.

The effect of excess embryos transferred and excess fetal heartbeats on length of gestation, birthweight, and birthweight Z-score

	ET-FHB groups	Singletons at birth					Twins at birth
		ET	FHB	Beta	SE	P value	ET	FHB	Beta	SE	P value
Length of gestation (days)	Excess ET	2	1	−0.20	0.14	0.14	3	2	−0.03	0.25	0.90
		≥3	1	−0.69	0.19	0.0002	≥4	2	−1.50	0.43	0.0005
	Excess ET + FHB	≥2	≥2	−2.78	0.24	<.0001	≥3	≥3	−3.53	0.46	<.0001
Birthweight (g)	Excess ET	2	1	−15.3	5.4	0.005	3	2	−7.0	7.3	0.34
		≥3	1	−36.3	7.3	<.0001	≥4	2	−47.1	12.5	0.0002
	Excess ET + FHB	≥2	≥2	−163.4	9.3	<.0001	≥3	≥3	−140.4	13.3	<.0001
Birthweight Z-score	Excess ET	2	1	−0.01	0.01	0.10	3	2	−0.04	0.02	0.016
		≥3	1	−0.03	0.01	0.011	≥4	2	−0.02	0.03	0.45
	Excess ET + FHB	≥2	≥2	−0.19	0.02	<.0001	≥3	≥3	−0.10	0.03	0.002

Models adjusted for number of embryos transferred, number of fetal heartbeats, maternal age, race and Hispanic ethnicity, pregravid BMI, diabetes (pregestational and gestational), oocyte source and embryo state, infant sex, and State and year of birth

Bolded values are significantly increased