Female obesity increases the risk of preterm birth of single frozen-thawed euploid embryos: a retrospective cohort study

Figures & data

Table 1. Baseline characteristics and IVF treatment.

BMI	<18.5 (n = 81)	18.5–25 (n = 637)	25–30 (n = 108)	≥30 (n = 25)	p-value
Female age (y)	30.67 ± 4.08	31.06 ± 3.78	31.69 ± 4.07	29.96 ± 4.26	.123
Infertility duration (y)	2.25 ± 2.01	2.07 ± 2.18	2.81 ± 2.53	3.02 ± 2.06	.003
No. of oocyte retrieved	14.58 ± 8.71	13.56 ± 6.81	12.00 ± 6.53	12.28 ± 6.77	.065
Endometrial thickness (mm)	9.71 ± 1.34	10.05 ± 1.72	10.44 ± 1.93	10.78 ± 1.54	.006
Infertility type					.002
Primary infertility	32 (41.03%)	196 (31.16%)	33 (30.84%)	16 (64.00%)
Secondary infertility	46 (58.97%)	433 (68.84%)	74 (69.16%)	9 (36.00%)
Protocol in fresh cycle					.031
Agonist	43 (53.09%)	285 (44.74%)	50 (46.30%)	17 (68.00%)
Antagonist	29 (35.80%)	315 (49.45%)	48 (44.44%)	8 (32.00%)
Other	9 (11.11%)	37 (5.81%)	10 (9.26%)	0 (0.00%)
Endometrial preparation protocol					.358
Natural cycle	9 (11.25%)	107 (16.96%)	15 (13.89%)	1 (4.00%)
HRT	52 (65.00%)	419 (66.40%)	73 (67.59%)	19 (76.00%)
GnRHa + HRT	19 (23.75%)	105 (16.64%)	20 (18.52%)	5 (20.00%)

Table 3. Logistic regression analysis of live birth rate.

Model effect/value	OR (95%CI)	p-value
BMI (kg/m^2)
Continuous	0.01 (−0.04, 0.06)	.574
<18.5 vs 18.5–25	0.77 (0.42, 1.42)	.408
25-30 vs 18.5–25	1.04 (0.65, 1.66)	.870
≥30 vs 18.5–25	1.19 (0.45, 3.15)	.723
Infertility duration (y)	0.99 (0.92, 1.07)	.839
Endometrial thickness (mm)	1.16 (1.05, 1.28)	.003
Infertility type
Primary infertility vs secondary infertility	0.99 (0.67, 1.45)	.943
Protocol in fresh cycle
Agonist vs antagonist	0.91 (0.65, 1.27)	.576
Agonist vs other	0.81 (0.38, 0.92)	.131
Biopsied blastocysts	0.98 (0.92, 1.03)	.426
No result embryos	0.91 (0.53, 1.57)	.735

Note: As covariables we included infertility duration, endometrial thickness, infertility type (primary infertility vs secondary infertility), protocol in fresh cycle (agonist, antagonist, other), biopsied blastocysts, no result embryos.

Figure 1. Clinical outcomes in different BMI groups (A) Percentage of clinical pregnancy rate, live birth rate, and miscarriage rate per transfer after PGT-A. (B) Percentage of preterm birth rate after euploid embryo transfer. Statistically significant for total preterm birth rate.

Table 2. Clinical outcomes of different BMI categories of WHO category.

BMI	<18.5 (n = 81)	18.5–25 (n = 637)	25–30 (n = 108)	≥30 (n = 25)	p-value
Biopsied blastocysts	5.28 ± 4.00	4.54 ± 2.65	3.84 ± 2.34	4.55 ± 3.29	.007
Euploid embryos	2.35 ± 2.36	2.06 ± 1.60	1.79 ± 1.31	1.68 ± 1.36	.090
No result embryos	0.65 ± 1.85	0.19 ± 0.69	0.06 ± 0.28	0.68 ± 2.06	<.001
Mosaic embryos	0.24 ± 0.72	0.16 ± 0.46	0.09 ± 0.29	0.32 ± 0.78	.094
Euploid rate (%)	51.35 ± 31.01	51.04 ± 29.84	51.62 ± 30.45	44.97 ± 35.56	.817
Mosaicism rate (%)	2.54 ± 7.74	3.06 ± 9.56	3.77 ± 14.05	5.83 ± 13.61	.524
Clinical pregnancy	47/81 (58.02%)	425/637 (68.66%)	76/108 (72.38%)	21/25 (84.00%)	.054
Miscarriage	5/47 (10.64%)	58/425 (13.65%)	11/76 (14.47%)	4/21 (19.05%)	.821
Ectopic pregnancy	1/81 (1.23%)	2/637 (0.31%)	1/108 (0.93%)	0/25 (0.00%)	.585
Pregnancy complication					.476
No	62 (93.94%)	497 (93.60%)	85 (88.54%)	20 (83.33%)	.649*
Placenta previa	0 (0.00%)	3 (0.56%)	1 (1.04%)	0 (0.00%)	.456*
PIH	1 (1.52%)	11 (2.07%)	6 (6.25%)	1 (4.17%)	.028*
Gestational diabetes	2 (3.03%)	17 (3.20%)	4 (4.17%)	3 (12.50%)	.526*
Premature rupture of membranes	1 (1.52%)	1 (0.19%)	0 (0.00%)	0 (0.00%)	.106*
Placental abruption	0 (0.00%)	1 (0.19%)	0 (0.00%)	0 (0.00%)	.597*
Heart disease	0 (0.00%)	1 (0.19%)	0 (0.00%)	0 (0.00%)	.597*
Preterm birth	2/81 (2.47%)	17/637 (2.67%)	9/108 (8.33%)	1/25 (4.00%)	.026
Preterm birth categories					.109
Extremely preterm (<28w)	0 (0.00%)	1 (5.88%)	1 (11.11%)	1 (100.00%)
Very preterm (28–32w)	0 (0.00%)	4 (23.53%)	1 (11.11%)	0 (0.00%)
Moderate to late preterm (32–37w)	2 (100.00%)	12 (70.59%)	7 (77.78%)	0 (0.00%)
Type of delivery					.231
Vaginal	3 (10.34%)	70 (25.09%)	9 (17.31%)	3 (21.43%)
Cesarean section	26 (89.66%)	209 (74.91%)	43 (82.69%)	11 (78.57%)
Live birth	29 (43.94%)	279 (52.25%)	52 (54.17%)	14 (58.33%)	.513
Birth weight (g)	2884.79 ± 1380.73	2600.90 ± 1459.10	2624.33 ± 1602.18	2697.61 ± 1230.57	.756
Fetal gender					.890
Female	17/29 (58.62%)	144/279 (51.61%)	26/52 (50.00%)	7/14 (50.00%)
Male	12/29 (41.38%)	135/279 (48.39%)	26/52 (50.00%)	7/14 (50.00%)

Note: *p-value is considered to be significant when <.007 (Bonferroni correction (.05/7)).

Table 4. Relationship between BMI and preterm birth in different models.

Outcome	Crude Model^a		Adjusted Model^b
	OR (95%CI)	p-value	OR (95%CI)	p-value
BMI (kg/m^2)
<18.5 vs 18.5–25	0.92 (0.21, 4.06)	.914	1.32 (0.28, 6.18)	.728
25–30 vs 18.5–25	3.31 (1.44, 7.63)	.005	3.18 (1.29, 7.80)	.012
≥30 vs 18.5–25	1.52 (1.09, 10.88)	.041	1.49 (1.03, 12.78)	.027

Note: ^aWe did not adjust other covariates.

^b Adjusted for infertility duration, endometrial thickness, infertility type (primary infertility vs secondary infertility), protocol in fresh cycle (agonist, antagonist, other), biopsied blastocysts, no result embryos, endometrial preparation.

Table 5. Clinical outcomes of different BMI categories of Asian classification.

BMI	<18.5 (n = 81)	18.5–22.9 (n = 486)	23–24.9 (n = 151)	≥25 (n = 133)	p-value
Clinical pregnancy	47/81 (58.02%)	322/486 (68.51%)	103/151 (69.13%)	97/133 (74.62%)	.094
Miscarriage	5/47 (10.64%)	49/322 (15.22%)	9/103 (8.74%)	15/97 (15.46%)	.334
Preterm birth	2/81 (2.47%)	14/486 (2.86%)	3/151 (2.04%)	10/133 (7.52%)	.040
Live birth	29 (43.94%)	208 (51.87%)	71 (53.38%)	66 (55.00%)	.521