Professor and Chair, Department of Obstetrics and Gynecology, Western Michigan University Homer Stryker M.D. School of Medicine, Kalamazoo
Dr. Rebar reports no financial relationships relevant to this field of study.
SYNOPSIS: The major factors leading to increased odds of cesarean delivery in all infertile women, but particularly in those who conceive following in vitro fertilization, are advanced maternal age and previous uterine surgery.
SOURCE: Stern JE, Liu C-L, Cabral HJ, et al. Factors associated with increased odds of cesarean delivery in ART pregnancies. Fertil Steril 2018;110:429-436.
To determine why the incidence of cesarean deliveries is greater in women with pregnancies resulting from in vitro fertilization (IVF) than in fertile pregnant women, Stern et al retrospectively compared singleton deliveries from primiparous women in Massachusetts between 2004 and 2010. To acquire the data, the investigators linked the Massachusetts vital and hospital records to the Society for Assisted Reproductive Technology (SART) Clinic Outcome Reporting System. During the years studied, there were six to eight clinics performing IVF in Massachusetts, and all reported their outcome data to SART. Of the 173,130 deliveries in Massachusetts, 5,768 followed IVF, 2,657 occurred in infertile women who did not undergo IVF, and 164,705 occurred in fertile pregnancies. Of the deliveries, 117,743 were vaginal and 55,387 were by cesarean delivery. The rates of cesarean delivery were 45.7%, 43.3%, and 31.1% in the IVF-treated women, infertile women not undergoing IVF, and fertile women, respectively. The women undergoing IVF were older, more often white and non-Hispanic, and more apt to have private insurance, prior uterine surgery, gestational diabetes, hypertension during the pregnancy, bleeding, and placental abnormalities than fertile women. The same was true for the infertile women who did not undergo IVF. The unadjusted odds ratios (ORs) compared with fertile women were 1.84 (95% confidence interval [CI], 1.75-1.94) for IVF-treated and 1.68 (95% CI, 1.55-1.81) for infertile women who did not undergo IVF. After adjustment for demographics, underlying medical factors, previous uterine surgery,
and placental and delivery complications, the adjusted odds ratios (aORs) compared with fertile women were 1.27 (95% CI, 1.19-1.36) for IVF-treated and 1.15 (95% CI, 1.04-1.27) for infertile women not undergoing IVF. The strongest confounders for odds of cesarean delivery were age and previous uterine surgery.
It is clear that the odds of cesarean delivery is higher among infertile women and those undergoing IVF.1-3 It also is known that infertile women and especially those undergoing IVF have an increased risk of both maternal and fetal morbidity.3,4 This study adds to our understanding of why.
Not surprisingly, infertile women who conceive either with or without IVF are older. Consequently, they are much more apt to have chronic disorders such as diabetes, hypertension, and obesity. Moreover, they are more apt to have undergone abdominal or uterine surgery, especially myomectomy, conization, operative hysteroscopy, and endometriosis. It is not surprising that the strongest confounders in this study predisposing to cesarean delivery were age and previous uterine surgery. The increased odds for cesarean delivery also probably are the result of infertile women asking for elective cesarean delivery.5 Some women choose this route of delivery despite being advised that cesarean delivery is associated with increased maternal morbidity5,6 and possible negative effects on the infant.7 It may well be that women with pregnancies resulting from IVF and their physicians elect cesarean delivery because of the much greater investment of time and money in achieving pregnancy. It may be that physicians feel more comfortable ensuring an optimal outcome by recommending elective cesarean delivery or elect to proceed with cesarean delivery at the first hint of any problem during labor. It also is known that advanced maternal age is associated with increased stillbirths and is a risk factor for cesarean delivery.6 In any case, it is certainly true from this study that the rates of cesarean delivery were higher among infertile women.
It is also interesting to note that cesarean delivery rates were significantly higher in all infertile women, regardless of whether they underwent IVF to achieve pregnancy. In fact, although cesarean deliveries were significantly more frequent after IVF than in other infertile women, the major increase was observed in infertile women regardless of how they conceived. In retrospect, this too should be obvious if advanced age and prior uterine surgery are the major risk factors in all infertile women. So why did I choose to highlight this particular study? It is simply because all healthcare providers caring for these women should be aware that infertile women are at increased risk during their pregnancies and should be monitored closely. I think that is a lesson well worth remembering.
- Kallen B, Finnstrom O, Nygren KG, et al. In vitro fertilization in Sweden: obstetric characteristics, maternal morbidity and mortality. Br J Obset Gynaecol 2005;112;1529-1535.
- Sullivan EA, Chapman MG, Wang YA, Adamson GD. Population-based study of cesarean section after in vitro fertilization in Australia. Birth 2010;3:184-191.
- Luke B, Gopal D, Cabral H, et al. Pregnancy, birth, and infant outcomes by maternal fertility status: The Massachusetts outcomes study of assisted reproductive technology. Am J Obstet Gynecol 2017;217:327:e1-e14.
- Hayashi M, Nakai A, Satoh S, Matsuda Y. Adverse obstetric and perinatal outcomes of singleton pregnancies may be related to maternal factors associated with infertility rather than the type of assisted reproductive technology procedure used. Fertil Steril 2012;98:922-928.
- Ecker J. Elective cesarean delivery on maternal request. JAMA 2013;309:1930-1936.
- Mylonas I, Friese K. Indications for and risks of elective cesarean section. Dtsch Arztebl Int 2015;112;489-495.
- Cho CE, Norman M. Cesarean section and development of the immune system in the offspring. Am J Obstet Gynecol 2013;208:249-254.