Elsevier

Obstetrics & Gynecology

Volume 100, Issue 3, September 2002, Pages 414-419
Obstetrics & Gynecology

Original research
Neonatal outcome in pregnancies from ovarian stimulation1

https://doi.org/10.1016/S0029-7844(02)02069-0Get rights and content

Abstract

OBJECTIVE:

To study the neonatal outcome in pregnancies after ovarian stimulation, not including in vitro fertilization. The outcomes studied were multiple birth, preterm birth, and low birth weight among singletons, congenital malformations, and infant death.

METHODS:

We identified 4029 women who delivered between 1995–1999 after ovarian stimulation alone and compared them with 438,582 women who neither had ovarian stimulation nor in vitro fertilization. We controlled for the confounding effect of year of birth, maternal age, parity, and length of subfertility before the pregnancy.

RESULTS:

The twinning rate was 5.9% in the study group and 1.2% in the control group. The triplet rate was 0.5% in the study group and 0.02% in the control group. A nearly doubling of the rate of monozygotic twinning was indicated in the study group compared with the control group. There was an excess of singleton preterm births and low birth weight infants in the study group, but this was mainly explainable by confounding of maternal age, parity, and subfertility. The rates of congenital malformations and perinatal deaths were increased, also mainly explainable by maternal characteristics. No increase in specific types of congenital malformations was seen.

CONCLUSION:

As the deviations in neonatal outcome after ovarian stimulation alone were reduced or disappeared when the confounding of maternal age, parity, and subfertility was taken into consideration, there is probably little direct effect of the stimulation procedure as such.

Section snippets

Materials and methods

The Swedish Medical Birth Register started in 1973 and contains information on nearly all births in Sweden.1 Since 1982, it is based on copies of the relevant medical documents from antenatal care clinics, delivery units, and the pediatric examination of the newborn. Since 1983, information on subfertility is included in the register, based on an interview made by the attending midwife at the first antenatal visit (usually weeks 10–12) and stated as number of years of involuntary childlessness.

Results

A total of 4029 women (1.3% of all delivered women) were identified as having a delivery after ovarian stimulation, resulting in 4307 infants born. There were 438,582 control women (no ovarian stimulation, no IVF).

The women undergoing ovarian stimulation were older and more often of parity 1 than the control women (Table 1). When the length of involuntary childlessness as a measurement of subfertility was compared between subfertile women who got ovarian stimulation and who did not, a maximum

Discussion

Early studies7, 8, 9, 10 found no increase in the total congenital malformation rate related to ovarian stimulation, but concern was raised over a possible association between the use of clomiphene citrate and neural tube defects, especially anencephaly.11 A review12 including also IVF pregnancies reached the conclusion that ovarian stimulation does not represent a risk factor for neural tube defects in the offspring. A later study13 found no association between ovarian stimulation and neural

References (18)

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1

The study was made possible by data on in vitro fertilization, collected by the Committee on In Vitro Fertilization, National Board of Health and Welfare, Stockholm. Anders Ericson at the National Board of Health and Welfare participated in the initiation of the study but died during the summer of 2001 before its completion.

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