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Table 1 The characteristics of 1210 patients included the sex ratio among singleton births following the first single blastocyst frozen embryo transfer (FET) cycles performed from January 2015 to February 2019

From: Does the sex ratio of singleton births after frozen single blastocyst transfer differ in relation to blastocyst development?

Characteristic Description
Number of cycles 1210
Mean maternal age (years±SD) 30.5 ± 4.5
Mean paternal age (years±SD) 31.6 ± 5.4
Mean maternal BMI (kg/m2) 23.6 ± 3.2
Mean duration of infertility (years±SD) 3.3 ± 2.6
Type of infertility (%)
 Primary 541 (44.7%)
 Secondary 669 (55.3%)
Main infertility cause (%)
 Female factor 661 (54.6%)
 Male factor 307 (25.4%)
 Mixed factor 193 (16%)
 Unexplained infertility* 49 (4%)
Type of fertilization (%)
 IVF 855 (70.7%)
 ICSI 355 (29.3%)
Day of embryo transfer (%)
 D5 783 (64.7%)
 D6 427 (35.3%)
Blastocyst quality of transfer (%)
 Good 638 (52.7%)
 Poor 572 (47.3%)
Singleton livebirths (%)
 Male 667 (55.1%)
 Female 543 (44.9%)
  1. Note: Data are presented as the mean ± SD and proportion (%). BMI = body mass index; D = day; IVF = in vitro fertilization; ICSI = intracytoplasmic sperm injection; *Unexplained infertility is rarely used as a diagnostic indicator for IVF in China because it is a controversial diagnosis