ABSTRACT
The incidence of multiple births is increased after ovarian stimulation used either alone or in conjunction with in vitro fertilisation (IVF) or donor insemination (DI). National data in the United Kingdom is not collected for induction of ovulation but the outcome of all treatment cycles by IVF and DI is published by the Human Fertilisation and Embryology Authority (HFEA). The IVF singleton and multiple pregnancy rates by the number of embryos replaced is shown in Table 1. This data confirms the increased incidence of multiple pregnancies with multiple embryo replacements.
Embryos replaced
No. of cycles
Singleton
Twins
Triplets
Total
n
%
n
%
n
%
One
2309
171
95.5
7
4.0
1
0.5
179
Two
6449
1001
77.2
288
22.2
8
0.6
1297
Three
11455
1892
67.9
714
25.5
191
6.8 *
2797
Total
20212
3064
75.2
1009
24.8
200
5.0
4073
Includes 3 sets of quads
Source: Data derived from HFEA 5th Annual Report (1996)