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Extremes of body mass index do not affect first-trimester pregnancy outcome in patients with infertility
Extremes of body mass index do not affect first-trimester pregnancy outcome in patients with infertility Diana Roth, MD, Richard V. Grazi, MD, and Susan M. Lobel, MD Brooklyn, NY OBJECTIVE: The study was undertaken to ascertain whether body mass index (BMI) affects first-trimester pregnancy outcome in patients with infertility. STUDY DESIGN: Records of 494 patients with a singleton gestation after treatment for infertility at a single academic center were retrospectively reviewed. Patients were classified with regard to BMI and treatment protocol. Outcomes were defined as ongoing pregnancy, spontaneous abortion, or ectopic pregnancy. RESULTS: The average rate of spontaneous abortion was 21.5% and of ongoing pregnancy 75.1%. This did not differ significantly in any of the BMI groups. When patients were further subdivided according to diagnosis or fertility treatment, the spontaneous abortion rate remained the same. CONCLUSION: The likelihood of a spontaneous abortion, ongoing pregnancy, or ectopic pregnancy in singleton gestations in the first trimester, after treatment for infertility, was not affected by BMI. (Am J Obstet Gynecol 2003;188:1169-70.)
Key words: Body mass index, obesity, miscarriage, infertility
Obesity has become a pandemic in Western society. In 1997, approximately 33% of adults were obese.1 The complications of obesity in the third trimester of pregnancy include increased risks of hypertension, gestational diabetes, postterm pregnancy, and cesarean section delivery.2 On the other extreme, poor weight gain is associated with increased risks for low-birth-weight infants and preterm delivery.3 There have been several studies on the effect of obesity on pregnancy outcome in patients with infertility, with conflicting results.4-6 This study was undertaken to investigate whether extremes of body mass index (BMI) at the time of conception are associated with an increased prevalence of adverse pregnancy outcome in the first trimester in patients treated for infertility. Material and methods Records of 494 patients who had conceived singleton pregnancies after having been treated for infertility at the Division of Reproductive Endocrinology and Infertility at Maimonides Medical Center in Brooklyn, NY, from May 1996 until June 2001 were reviewed. Patient data were analyzed according to age, parity, BMI, diagnosis (tubal factor, anatomic, polycystic ovary syndrome, endometriosis, From the Department of Obstetrics and Gynecology, Maimonides Medical Center Reprint requests: Diana Roth, MD, 4815 14th Ave, Brooklyn, NY 11219. © 2003, Mosby, Inc. All rights reserved. 0002-9378/2003 $30.00 + 0 doi:10.1067/mob.2003.285
male factor, and unexplained), treatment (clomiphene citrate, gonadotropins, in vitro fertilization, intracytoplasmic sperm injection, intrauterine sperm injection, surgery, or untreated), and outcome (spontaneous abortion, ectopic or ongoing pregnancy). BMI was calculated on the basis of height and weight measurements obtained at the time of the initial patient consultation. Ongoing pregnancy was defined as a viable singleton gestation diagnosed by transvaginal ultrasound after 6 weeks’ gestation. Spontaneous abortion included both gestational sacs passed spontaneously and missed abortion on transvaginal ultrasound requiring curettage (D&C). Ectopic pregnancy was defined by the absence of villi on endometrial sampling and/or the visualization of the ectopic pregnancy on ultrasound or laparoscopy. Multiple gestations and chemical pregnancies were excluded from the study. Patients were monitored until the end of the first trimester (13 weeks’ gestation). Results Patients were divided into three groups on the basis of BMI: underweight, BMI less than 20; normal weight, BMI 20 to 26.9; and obese, BMI 27 or greater. Fifteen percent of the patients had a BMI less than 20, 49.6% had a BMI 20 to 26.9, and 35.4% had a BMI 27 or greater. Controlling for age and parity, there were no statistically significant differences, with χ2 analysis, in the incidence of spontaneous abortion, ectopic pregnancy, or ongoing pregnancy among patients in the three different BMI categories (Table I). Patients were further subdivided according to diagnosis (Table II). With the use of χ2 1169
1170 Roth, Grazi, and Lobel
May 2003 Am J Obstet Gynecol
Table I. BMI and pregnancy outcome* BMI
Spontaneous abortion
Ectopic
Ongoing
No.
13 (17.6%) 54 (22%) 39 (22.3%) 106 (21.5%)
3 (4.1%) 7 (2.9%) 7 (4%) 17 (3.4%)
58 (78.4%) 184 (75.1%) 129 (73.3%) 371 (75.1%)
74 245 175 494
<20 20-26.9 27 Total *P = .861.
Table II. Distribution of patients by diagnosis Diagnosis Tubal factor Cervical PCO Endometriosis Male factor Unexplained Mixed Other Total
No. 69 12 125 9 77 103 72 27 494
% 14 2.4 25.3 1.8 15.6 20.9 14.5 5.5 100
PCO, Polycystic ovary syndrome.
analysis, there was no difference in outcome when analyzed according to diagnosis or BMI. Likewise, when patients were subdivided according to treatment regimens, and the incidence of spontaneous abortion, ectopic pregnancy, and ongoing pregnancy in each BMI category was analyzed, by χ2 analysis, there was no statistically significant difference in outcome when analyzed according to treatment group or BMI. Comment Our study found that the first trimester outcome of singleton gestations in patients with infertility was not influenced by BMI. This is consistent with the study of Lashen et al,6 who found that extremes of body mass did not affect the spontaneous abortion rate in patients who had
undergone in vitro fertilization. Our results suggest that patients with extremes of BMI do not need to be monitored differently during the first trimester. This is in contrast to the management of the third trimester, as a result of the known increased risks associated with extremes of BMI at the end of pregnancy. Most of the adverse effects associated with extremes of BMI, such as diabetes mellitus and hypertension, do not usually manifest themselves until the third trimester and this may be why BMI does not have an effect on first-trimester pregnancy outcome. However, larger studies are needed to confirm these findings. Our study was confined to looking at singleton gestations to minimize confounding factors. Therefore, further studies are needed to ascertain whether BMI influences first-trimester outcome in patients with multiple gestations. We thank Dr Joseph Feldman for his help with statistical analysis. REFERENCES
1. Norman, RJ. Obesity and reproductive disorders. Female Patient 2000;25:62-9. 2. Gastrointestinal disorders. In: Cunningham FG, MacDonald PC, Gant NF, Leveno KJ, Gilstrap LC, Hankins GDV, et al, editors. Williams’ obstetrics. 20th ed. Stamford (CT): Appleton & Lange; 1997. p. 1167-8. 3. Preterm birth. In: Cunningham FG, MacDonald PC, Gant NF, Leveno KJ, Gilstrap LC, Hankins GDV, et al, editors. Williams’ obstetrics. 20th ed. Stamford (CT): Appleton & Lange; 1997. p. 802. 4. Galletly C, Clark A, Tomlinson L, Blaney F. Improved pregnancy rates for obese, infertile women following a group treatment program. Gen Hosp Psychiatry 1996;18:192-5. 5. Fedorcsak P, Storeng R, Dale PO, Tanbo T, Abyholm T. Obesity is a risk factor for early pregnancy loss after IVF or ICSI. Acta Obstet Gynecol Scand 2000;79:43-8. 6. Lashen H, Ledger W, Bernal AL, Barlow D. Extremes of body mass do not adversely affect the outcome of superovulation and in-vitro fertilization. Eur Soc Hum Reprod Embryol 1999; 14:712-5.
Key words: Body mass index, obesity, miscarriage, infertility
Obesity has become a pandemic in Western society. In 1997, approximately 33% of adults were obese.1 The complications of obesity in the third trimester of pregnancy include increased risks of hypertension, gestational diabetes, postterm pregnancy, and cesarean section delivery.2 On the other extreme, poor weight gain is associated with increased risks for low-birth-weight infants and preterm delivery.3 There have been several studies on the effect of obesity on pregnancy outcome in patients with infertility, with conflicting results.4-6 This study was undertaken to investigate whether extremes of body mass index (BMI) at the time of conception are associated with an increased prevalence of adverse pregnancy outcome in the first trimester in patients treated for infertility. Material and methods Records of 494 patients who had conceived singleton pregnancies after having been treated for infertility at the Division of Reproductive Endocrinology and Infertility at Maimonides Medical Center in Brooklyn, NY, from May 1996 until June 2001 were reviewed. Patient data were analyzed according to age, parity, BMI, diagnosis (tubal factor, anatomic, polycystic ovary syndrome, endometriosis, From the Department of Obstetrics and Gynecology, Maimonides Medical Center Reprint requests: Diana Roth, MD, 4815 14th Ave, Brooklyn, NY 11219. © 2003, Mosby, Inc. All rights reserved. 0002-9378/2003 $30.00 + 0 doi:10.1067/mob.2003.285
male factor, and unexplained), treatment (clomiphene citrate, gonadotropins, in vitro fertilization, intracytoplasmic sperm injection, intrauterine sperm injection, surgery, or untreated), and outcome (spontaneous abortion, ectopic or ongoing pregnancy). BMI was calculated on the basis of height and weight measurements obtained at the time of the initial patient consultation. Ongoing pregnancy was defined as a viable singleton gestation diagnosed by transvaginal ultrasound after 6 weeks’ gestation. Spontaneous abortion included both gestational sacs passed spontaneously and missed abortion on transvaginal ultrasound requiring curettage (D&C). Ectopic pregnancy was defined by the absence of villi on endometrial sampling and/or the visualization of the ectopic pregnancy on ultrasound or laparoscopy. Multiple gestations and chemical pregnancies were excluded from the study. Patients were monitored until the end of the first trimester (13 weeks’ gestation). Results Patients were divided into three groups on the basis of BMI: underweight, BMI less than 20; normal weight, BMI 20 to 26.9; and obese, BMI 27 or greater. Fifteen percent of the patients had a BMI less than 20, 49.6% had a BMI 20 to 26.9, and 35.4% had a BMI 27 or greater. Controlling for age and parity, there were no statistically significant differences, with χ2 analysis, in the incidence of spontaneous abortion, ectopic pregnancy, or ongoing pregnancy among patients in the three different BMI categories (Table I). Patients were further subdivided according to diagnosis (Table II). With the use of χ2 1169
1170 Roth, Grazi, and Lobel
May 2003 Am J Obstet Gynecol
Table I. BMI and pregnancy outcome* BMI
Spontaneous abortion
Ectopic
Ongoing
No.
13 (17.6%) 54 (22%) 39 (22.3%) 106 (21.5%)
3 (4.1%) 7 (2.9%) 7 (4%) 17 (3.4%)
58 (78.4%) 184 (75.1%) 129 (73.3%) 371 (75.1%)
74 245 175 494
<20 20-26.9 27 Total *P = .861.
Table II. Distribution of patients by diagnosis Diagnosis Tubal factor Cervical PCO Endometriosis Male factor Unexplained Mixed Other Total
No. 69 12 125 9 77 103 72 27 494
% 14 2.4 25.3 1.8 15.6 20.9 14.5 5.5 100
PCO, Polycystic ovary syndrome.
analysis, there was no difference in outcome when analyzed according to diagnosis or BMI. Likewise, when patients were subdivided according to treatment regimens, and the incidence of spontaneous abortion, ectopic pregnancy, and ongoing pregnancy in each BMI category was analyzed, by χ2 analysis, there was no statistically significant difference in outcome when analyzed according to treatment group or BMI. Comment Our study found that the first trimester outcome of singleton gestations in patients with infertility was not influenced by BMI. This is consistent with the study of Lashen et al,6 who found that extremes of body mass did not affect the spontaneous abortion rate in patients who had
undergone in vitro fertilization. Our results suggest that patients with extremes of BMI do not need to be monitored differently during the first trimester. This is in contrast to the management of the third trimester, as a result of the known increased risks associated with extremes of BMI at the end of pregnancy. Most of the adverse effects associated with extremes of BMI, such as diabetes mellitus and hypertension, do not usually manifest themselves until the third trimester and this may be why BMI does not have an effect on first-trimester pregnancy outcome. However, larger studies are needed to confirm these findings. Our study was confined to looking at singleton gestations to minimize confounding factors. Therefore, further studies are needed to ascertain whether BMI influences first-trimester outcome in patients with multiple gestations. We thank Dr Joseph Feldman for his help with statistical analysis. REFERENCES
1. Norman, RJ. Obesity and reproductive disorders. Female Patient 2000;25:62-9. 2. Gastrointestinal disorders. In: Cunningham FG, MacDonald PC, Gant NF, Leveno KJ, Gilstrap LC, Hankins GDV, et al, editors. Williams’ obstetrics. 20th ed. Stamford (CT): Appleton & Lange; 1997. p. 1167-8. 3. Preterm birth. In: Cunningham FG, MacDonald PC, Gant NF, Leveno KJ, Gilstrap LC, Hankins GDV, et al, editors. Williams’ obstetrics. 20th ed. Stamford (CT): Appleton & Lange; 1997. p. 802. 4. Galletly C, Clark A, Tomlinson L, Blaney F. Improved pregnancy rates for obese, infertile women following a group treatment program. Gen Hosp Psychiatry 1996;18:192-5. 5. Fedorcsak P, Storeng R, Dale PO, Tanbo T, Abyholm T. Obesity is a risk factor for early pregnancy loss after IVF or ICSI. Acta Obstet Gynecol Scand 2000;79:43-8. 6. Lashen H, Ledger W, Bernal AL, Barlow D. Extremes of body mass do not adversely affect the outcome of superovulation and in-vitro fertilization. Eur Soc Hum Reprod Embryol 1999; 14:712-5.