Table 1.
Description of study groups from complete cases, before and after propensity score weighting
| Study groups before propensity score weighting | Study groups after propensity score weighting | |||||||
|---|---|---|---|---|---|---|---|---|
| Factor | Fresh transfer with AH (48,858 cycles) | Fresh transfer without AH (103,413 cycles) | P value | SMD | Fresh transfer with AH (148,723 cycles) | Fresh transfer without AH (153,114 cycles) | P value | SMD |
| Age at retrieval | < 0.001 | 0.796 | 0.201 | 0.015 | ||||
| < 35 | 15,978 (32.7) | 64,654 (62.5) | 78,955 (53.1) | 81,861 (53.5) | ||||
| 35–37 | 9445 (19.3) | 23,136 (22.4) | 31,847 (21.4) | 32,197 (21.0) | ||||
| 38–40 | 13,664 (28.0) | 11,195 (10.8) | 24,054 (16.2) | 24,361 (15.9) | ||||
| 41–42 | 6448 (13.2) | 3169 (3.1) | 9310 (6.3) | 9805 (6.4) | ||||
| ≥ 43 | 3323 (6.8) | 1259 (1.2) | 4557 (3.1) | 4890 (3.2) | ||||
| Race | < 0.001 | 0.151 | < 0.001 | 0.188 | ||||
| White | 24,679 (50.5) | 49,815 (48.2) | 78,135 (52.5) | 71,798 (46.9) | ||||
| Asian | 4942 (10.1) | 8847 (8.6) | 14,239 (9.6) | 12,660 (8.3) | ||||
| Hispanic Latino | 3257 (6.7) | 5672 (5.5) | 9671 (6.5) | 8502 (5.6) | ||||
| African American | 2993 (6.1) | 5040 (4.9) | 8346 (5.6) | 7665 (5.0) | ||||
| American Indian | 114 (0.2) | 206 (0.2) | 350 (0.2) | 307 (0.2) | ||||
| Unknown | 12,873 (26.3) | 33,833 (32.7) | 37,983 (25.5) | 52,182 (34.1) | ||||
| BMI (mean (SD)) | 26.08 (29.32) | 25.80 (29.99) | 0.082 | 0.01 | 25.94 (26.65) | 25.94 (32.98) | 0.982 | < 0.001 |
| Gravidity | < 0.001 | 0.154 | 0.36 | 0.016 | ||||
| 0 | 25,464 (52.1) | 61,032 (59.0) | 84,431 (56.8) | 86,871 (56.7) | ||||
| 1 | 11,543 (23.6) | 22,734 (22.0) | 33,819 (22.7) | 34,362 (22.4) | ||||
| 2 | 5920 (12.1) | 10,457 (10.1) | 15,847 (10.7) | 16,618 (10.9) | ||||
| 3 | 3197 (6.5) | 5103 (4.9) | 8212 (5.5) | 8296 (5.4) | ||||
| 4 | 1502 (3.1) | 2312 (2.2) | 3497 (2.4) | 3911 (2.6) | ||||
| 5 | 704 (1.4) | 1038 (1.0) | 1739 (1.2) | 1820 (1.2) | ||||
| > 5 | 528 (1.1) | 737 (0.7) | 1178 (0.8) | 1237 (0.8) | ||||
| Parity | < 0.001 | 0.085 | < 0.001 | 0.04 | ||||
| 0 | 12,266 (38.4) | 25,801 (42.5) | 35,423 (39.5) | 38,748 (41.4) | ||||
| ≥ 1 | 19,706 (61.6) | 34,881 (57.5) | 54,345 (60.5) | 54,818 (58.6) | ||||
| Infertility diagnosis | < 0.001 | 0.354 | 0.004 | 0.031 | ||||
| Diminished ovarian reserve | 9663 (19.8) | 8754 (8.5) | 18,554 (12.5) | 19,268 (12.6) | ||||
| Endometriosis | 3832 (7.8) | 7941 (7.7) | 11,853 (8.0) | 11,991 (7.8) | ||||
| Male factor | 17,642 (36.1) | 41,654 (40.3) | 57,439 (38.6) | 59,331 (38.7) | ||||
| PCOS | 3508 (7.2) | 11,688 (11.3) | 15,059 (10.1) | 15,309 (10.0) | ||||
| Tubal | 1142 (2.3) | 2677 (2.6) | 3483 (2.4) | 4051 (2.8) | ||||
| Unexplained | 6730 (13.8) | 17,622 (17.0) | 23,173 (15.6) | 23,940 (15.6) | ||||
| Uterine | 784 (1.6) | 1405 (1.4) | 2374 (1.6) | 2130 (1.4) | ||||
| Other | 5557 (11.4) | 11,672 (11.3) | 16,788 (11.3) | 17,094 (11.2) | ||||
| Maximum FSH (mean mIU/mL (SD)) | 8.45 (26.19) | 7.32 (29.99) | < 0.001 | 0.04 | 7.58 (17.07) | 7.64 (53.49) | 0.27 | 0.009 |
| Number of embryos transferred (mean (SD)) | 2.35 (0.98) | 1.90 (0.65) | < 0.001 | 0.55 | 2.05 (0.82) | 2.06 (0.80) | 0.319 | 0.007 |
| Day of transfer | < 0.001 | 0.785 | 0.027 | 0.015 | ||||
| 3 | 35,995 (73.7) | 38,630 (37.4) | 72,970 (49.1) | 74,407 (48.3) | ||||
| 5 | 12,863 (26.3) | 64,783 (62.6) | 75,753 (50.9) | 79,107 (51.7) | ||||
P value < 0.05 denotes a difference in groups; SMD, standard mean difference; SMD < 0.1 implies balance; AH, assisted hatching; BMI, body mass index; FSH, follicle-stimulating hormone; SD, standard deviation