Assisted reproductive technology induces different secondary sex ratio: parental and embryonic impacts

Table 4 Multinomial logistic regression analysis with SSR in twins from twin gestation

Birth^*	Variables	OR	95% CI
Female twins	Dosage of Gn (× 10³ IU/L)	0.931	0.805–1.076
	Days of Gn use (day)	1.021	0.977–1.067
	Age difference
	Older mother	0.815	0.546–1.215
	Older father	0.864	0.629–1.187
	None	1.000
	Embryo transfer stage
	Cleavage stage	0.783	0.530–1.158
	Blastocyst	1.000
	Paternal age group (year)
	≤30	1.056	0.773–1.444
	31–32	0.988	0.712–1.371
	33–35	1.072	0.794–1.448
	≥36	1.000
	Maternal BMI
	<18.5	1.129	0.770–1.654
	18.5–23.9	1.048	0.786–1.396
	≥24	1.000
	Fertilization method
	IVF	1.061	0.703–1.600
	ICSI	0.844	0.514–1.386
	FET	1.000
Boy-girl twins	Dosage of Gn (× 10³ IU/L)	0.837	0.715–0.980
	Days of Gn use (day)	1.032	0.985–1.081
	Age difference
	Older mother	0.917	0.616–1.366
	Older father	0.682	0.492–0.945
	None	1.000
	Embryo transfer stage
	Cleavage stage	1.754	1.133–2.716
	Blastocyst	1.000
	Paternal age group (year)
	≤30	0.939	0.672–1.312
	31–32	0.972	0.686–1.377
	33–35	0.995	0.719–1.377
	≥36	1.000
	Maternal BMI
	<18.5	1.340	0.892–2.012
	18.5–23.9	1.160	0.845–1.591
	≥24	1.000
	Fertilization method
	IVF	0.846	0.546–1.312
	ICSI	0.882	0.531–1.464
	FET	1.000

^*Male twins selected as the reference category
SSR Secondary sex ratio, IVF In vitro fertilization, ICSI Intracytoplasmic sperm injection, FET Frozen embryo transfer, Gn Gonadotropin, BMI Body mass index

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