Background
Methods
Study patients
Minimal ovarian stimulation cycle in vitro fertilisation
SVBT in natural and letrozole cycles
Study outcomes
Statistical analyses
Results
Characteristics of the study cohort
Before propensity score matching | After propensity score matching | |||||
---|---|---|---|---|---|---|
Natural | Letrozole | P-value | Natural | Letrozole | P-value | |
No. of patients, n | 12,700 | 1,911 | 1,910 | 1,910 | ||
Female age (years), (range) | 38.7 ± 0.0 a (23–49) | 36.7 ± 0.1 b (22–46) | < 0.0001 | 36.7 ± 0.1 (26–50) | 36.7 ± 0.1 (26–49) | 0.8844 |
Male age (years), (range) | 40.1 ± 0.0a (25–69) | 38.4 ± 0.1 b (26–68) | < 0.0001 | 38.4 ± 0.1 (25–62) | 38.4 ± 0.1 (26–68) | 0.5857 |
Body mass index | 20.8 ± 0.0 | 20.9 ± 0.1 | 0.1204 | 20.9 ± 0.1 | 20.9 ± 0.1 | 0.8924 |
Serum AMH level | 2.1 ± 0.0 | 2.9 ± 0.2 | < 0.0001 | 2.9 ± 0.2 | 2.9 ± 0.2 | 0.5464 |
Previous OR cycles | 1.7 ± 0.0 | 1.7 ± 0.0 | 0.8249 | 1.7 ± 0.0 | 1.7 ± 0.0 | 0.1817 |
Previous ET cycles | 0.6 ± 0.0 | 0.6 ± 0.0 | 0.0891 | 0.6 ± 0.0 | 0.6 ± 0.0 | 0.1704 |
Previous deliveries | 4,024 (31.7) | 816 (42.7) | < 0.0001 | 838 (43.9) | 816 (42.7) | 0.4725 |
Previous miscarriages | 3,363 (26.5) | 456 (23.9) | 0.0151 | 436 (22.8) | 456 (23.9) | 0.4443 |
Previous caesarean section | 887 (7.0) | 111 (5.8) | 0.0579 | 135 (7.1) | 111 (5.8) | 0.1137 |
Previous smoking | 812 (6.4) | 127 (6.7) | 0.6753 | 137 (7.2) | 127 (6.7) | 0.5235 |
Insemination methods | 0.9196 | |||||
cIVF, n (%) | 4,836 (38.1) | 694 (36.3) | 0.1386 | 691 (36.2) | 694 (36.3) | |
ICSI, n (%) | 7,864 (61.9) | 1,217 (63.7) | 1,219 (63.8) | 1,216 (63.7) | ||
Culture time to the expanded blastocyst stage (h) | 126.7 ± 0.1 | 125.4 ± 0.3 | < 0.0001 | 125.4 ± 0.3 | 125.4 ± 0.3 | 0.9238 |
Blastocyst diameter (μm) | 173.3 ± 0.4 | 176.3 ± 0.9 | 0.0043 | 180.4 ± 0.5 | 180.2 ± 0.5 | 0.1250 |
Morphological grade | ||||||
ICM Grade A, n (%) | 3,373 (26.6) | 588 (30.8) | < 0.0001 | 573 (30.0) | 587 (30.7) | 0.6913 |
Grade B, n (%) | 4,827 (38.0) | 763 (39.9) | 753 (39.4) | 763 (40.0) | ||
Grade C, n (%) | 4,500 (35.4) | 560 (29.3) | 584 (30.6) | 560 (29.3) | ||
TE Grade A, n (%) | 2,967 (23.4) | 552 (28.9) | < 0.0001 | 534 (28.0) | 552 (28.9) | 0.7410 |
Grade B, n (%) | 4,054 (31.9) | 619 (32.4) | 615 (32.2) | 618 (32.4) | ||
Grade C, n (%) | 5,678 (44.7) | 740 (38.7) | 761 (39.8) | 740 (38.7) |
Pregnancy outcomes after SVBTs in natural and letrozole cycles
Natural | Letrozole | P-value | |
---|---|---|---|
ET cycles, n | 1,910 | 1,910 | |
Oestradiol on the day of the trigger (pg/mL) | 335.7 ± 3.5 | 258.5 ± 3.0 | < 0.0001 |
Progesterone on the day of the trigger (ng/mL) | 0.5 ± 0.0 | 0.4 ± 0.0 | 0.0003 |
Luteinising hormone on the day of the trigger (mIU/mL) | 18.0 ± 0.2 | 14.1 ± 0.2 | < 0.0001 |
Oestradiol on the day of SVBT (pg/mL) | 169.5 ± 1.7 | 114.2 ± 1.5 | < 0.0001 |
Progesterone on the day of SVBT (ng/mL) | 16.6 ± 0.1 | 22.0 ± 0.2 | < 0.0001 |
Insufficient luteal function, n (%) | 258 (13.5) | 84 (4.4) | < 0.0001 |
Endometrial thickness on the day of SVBT (mm) | 10.6 ± 0.0 | 10.7 ± 0.0 | 0.0273 |
Implantation, n (%) | 1,088 (57.0) | 1,120 (58.6) | 0.2945 |
Clinical pregnancies, n (%) | 962 (50.4) | 1,035 (54.2) | 0.0180 |
Ongoing pregnancies, n (%) | 850 (44.5) | 921 (48.2) | 0.0212 |
Live birth, n (%) | 746 (39.1) | 808 (42.3) | 0.0411 |
Early pregnancy loss, n (%) | 126 (11.6) | 85 (7.8) | 0.0014 |
Miscarriages, n (%) | 214 (22.3) | 226 (21.8) | 0.8254 |
Twin pregnancies, n (%) | 10 (1.3) | 10 (1.2) | 0.8599 |
Still birth, n (%) | 2 (0.3) | 1 (0.1) | 0.5181 |
Univariate analysis | Multivariate analysis | ||||||||
---|---|---|---|---|---|---|---|---|---|
Odds ratio | 95% CI | P-value | AUC | Adjusted odds ratio | 95% CI | P-value | AUC | ||
Female age (years) | 0.876 | 0.861–0.982 | < 0.0001 | 0.642 | 0.888 | 0.868–0.909 | < 0.0001 | 0.711 | |
Male age (years) | 0.939 | 0.92–0.952 | < 0.0001 | 0.592 | 0.996 | 0.979–1.013 | 0.6814 | ||
Body mass index | 0.970 | 0.947–0.993 | 0.0128 | 0.523 | 0.988 | 0.979–1.013 | 0.3616 | ||
Culture time to the expanded blastocyst stage | 0.962 | 0.956–0.967 | < 0.0001 | 0.621 | 0.975 | 0.968–0.982 | < 0.0001 | ||
Blastocyst diameter | 1.008 | 1.005–1.011 | < 0.0001 | 0.561 | 1.007 | 1.004–1.011 | < 0.0001 | ||
Gardner’s criteria | |||||||||
ICM | Grade A | Reference | - | - | 0.615 | Reference | - | - | |
Grade B | 0.729 | 0.625–0.850 | < 0.0001 | 1.097 | 0.919–1.309 | 0.3015 | |||
Grade C | 0.315 | 0.264–0.376 | < 0.0001 | 0.746 | 0.591–0.941 | 0.0135 | |||
TE | Grade A | Reference | - | - | 0.640 | Reference | - | - | |
Grade B | 0.586 | 0.497–0.691 | < 0.0001 | 0.702 | 0.585–0.843 | 0.0002 | |||
Grade C | 0.273 | 0.231–0.322 | < 0.0001 | 0.492 | 0.394–0.615 | < 0.0001 | |||
Endometrial preparation | |||||||||
Natural | Reference | - | - | Reference | - | - | |||
Letrozole | 1.144 | 1.005–1.301 | 0.0412 | 0.516 | 1.156 | 1.006–1.329 | 0.0397 |
Perinatal outcomes after SVBTs in natural and letrozole-induced cycles
Natural | Letrozole | P-value | |
---|---|---|---|
Live birth, n | 746 | 808 | |
Female age | 35.5 ± 0.1 | 35.6 ± 0.1 | 0.6882 |
Male age | 37.8 ± 0.2 | 37.5 ± 0.2 | 0.2048 |
Body mass index | 20.6 ± 0.1 | 20.8 ± 0.1 | 0.1734 |
Pregnancy complications, n (%) | 37 (5.0) | 52 (6.4) | 0.2110 |
Hypertensive disorders of pregnancy, n (%) | 8 (1.1) | 3 (0.4) | 0.0996 |
Gestational diabetes mellitus, n (%) | 4 (0.5) | 7 (0.9) | 0.4380 |
HELLP syndrome, n (%) | 0 (0) | 1 (0.1) | 0.3365 |
Preterm premature rupture of membrane, n (%) | 1 (0.1) | 4 (0.5) | 0.2093 |
Low-lying placenta, n (%) | 4 (0.5) | 4 (0.5) | 0.9099 |
Placenta previa, n (%) | 9 (1.2) | 10 (1.2) | 0.9554 |
Placental abruption, n (%) | 1 (0.1) | 2 (0.3) | 0.6107 |
Others, n (%) | 1 (0.1) | 2 (0.3) | 0.6107 |
Caesarean section rate, n (%) | 220 (29.5) | 216 (26.7) | 0.2267 |
Gestational age, weeks | 39.0 ± 0.1 | 39.0 ± 0.1 | 0.6539 |
Preterm delivery (< 37 weeks), n (%) | 40 (5.4) | 45 (5.6) | 0.8575 |
Birth length (cm) | 49.1 ± 0.1 | 49.0 ± 0.1 | 0.7309 |
Birth weight (g) | 3,031 ± 16 | 3,017 ± 15 | 0.5208 |
Low birth weight (< 2,500 g), n (%) | 66 (8.9) | 72 (8.9) | 0.9648 |
Small for gestational age | 31 (4.2) | 34 (4.2) | 0.9589 |
Large for gestational age | 126 (16.9) | 116 (14.4) | 0.1688 |
Infant sex | 0.9515 | ||
Male, n (%) | 388 (52.0) | 419 (51.9) | |
Female, n (%) | 358 (48.0) | 389 (48.1) | |
Birth defect, n (%) | 31 (4.2) | 36 (4.5) | 0.7755 |
Outcomes | Adjusted odds ratio | 95% CI | P-value |
---|---|---|---|
Pregnancy complications a | 1.304 | 0.844–2.015 | 0.2313 |
Hypertensive disorders of pregnancy a | 0.341 | 0.089–1.304 | 0.1162 |
Gestational diabetes mellitus a | 1.403 | 0.400–4.910 | 0.5960 |
Preterm premature rupture of membrane a | 3.314 | 0.366–29.984 | 0.2863 |
Low-lying placenta a | 0.885 | 0.219–3.568 | 0.8642 |
Placenta previa a | 1.036 | 0.418–2.565 | 0.9383 |
Placental abruption a | 1.857 | 0.167–20.557 | 0.6137 |
Caesarean section b | 0.884 | 0.690–1.133 | 0.3321 |
Preterm delivery (< 37 weeks) c | 1.058 | 0.669–1.676 | 0.8069 |
Low birth weight (< 2,500 g) d | 1.023 | 0.711–1.473 | 0.8995 |
Small for gestational age e | 1.026 | 0.623–1.689 | 0.9178 |
Large for gestational age f | 0.800 | 0.606–1.056 | 0.1163 |
Birth defect g | 1.061 | 0.649–1.735 | 0.8113 |