# Abstract

 

## Background To investigate whether cumulus cell removal after a 3 h co-incubation of gametes can affect the outcomes of in vitro fertilization. 

## Methods A prospective randomized sibling-oocyte study was performed in which sibling oocytes obtained from each patient were randomly assigned to either a 3 h or 20 h group (cumulus cells removed at 3 h or 20 h after insemination, respectively). Same origin embryos (either 3 h or 20 h) were transferred. The study participants were patients \< 38 years old and with infertility due to tubal factors. The study outcomes included fertilization, embryo quality, and birth status. 

## Results The study enrolled 172 patients, from whom 2275 oocytes were retrieved (1139 oocytes for the 3 h group and 1136 oocytes for the 20 h group). A total of 134 patients received embryo transfers (74 patients in the 3 h group and 60 patients in the 20 h group), and there were 54 live births (32 in the 3 h group and 22 in the 20 h group). When compared with patients in the 20 h group, patients in the 3 h group produced a larger number of optimal quality embryos, but had higher rates of polyspermy and low birth weight newborns. The two groups showed no differences in their rates of normal fertilization, pregnancy, and live birth. 

## Conclusions When compared with results obtained using a traditional cumulus cell removal protocol, early cumulus cell removal has both advantages and disadvantages. Further studies, and especially long-term outcome studies on newborns, need to be performed. 

## Trial registration Current controlled trial [ChiCTR-OOC-15006878](#) # Results The study recruited 172 patients; among whom, 134 patients were analyzed (Fig. [1](#), 74 patients in the 3 h group and 60 patients in the 20 h group). The mean age of the patients was 29.7 years (30.3 ± 3.7 years in the 3 h group and 29.3 ± 2.7 years in the 20 h group). The numbers of treatment cycles in the 3 h and 20 h groups were 1.0 ± 0.2 and 1.1 ± 0.4, respectively. Thirty patients were excluded due to either cancelled cycles (3 patients) or mixed embryo transfers (27 patients). Eight patients were not included in the statistical analysis because they received early rescue ICSI. <figure> <p><img src="" /></p> <figcaption>CONSORT flow diagram</figcaption> </figure> The fertilization, embryo, and pregnancy outcomes are shown in Tables [1](#), [2](#), and [3](#). When compared with the 20 h group, the 3 h group had a significantly higher polyspermy rate and percentage of optimal embryos. An analysis on obstetric outcomes showed that low birth weight infants were more common in the 3 h group (Table [4](#)). ::::table-wrap

::: caption
Comparison of fertilization characteristics between two groups
:::

```
                                  3 h group     20 h group   *P*
```

______________________________________________________________________

Oocytes obtained, (n) 1139 1136\
Metaphase II oocytes, n (%) 1066 (93.6) 1040(91.5) 0.06
Normal fertilization (2PN), n (%) 672 (59.0) 700 (61.6) 0.20
Polyspermy rate (>2PN), n (%) 226 (19.8) 171(15.1) 0.01:::: ::::table-wrap
::: caption
Comparison of embryo characteristics between two groups
:::

```
                                 3 h group   20 h group   *P*
```

______________________________________________________________________

Cleavage rate, n (%) 988(86.7) 969(85.3) 0.32
Available embryo rate, n (%) 705(61.9) 718(63.2) 0.52
Optimal embryo rate, n (%) 524(78) 503(71.9) 0.01
Blastocyst formation rate, n (%) 323(63.7) 342(61.5) 0.46
Optimal blastocyte rate, n (%) 138(42.7) 140(40.9) 0.64
Frozen blastocyst rate, n (%) 211(65.3) 225(65.8) 0.90:::: ::::table-wrap
::: caption
Comparison of pregnancy outcomes between two groups
:::

```
                                        3 h group   20 h group   *P*
```

______________________________________________________________________

Patients recruited, (n) 74 60\
Embryos transfer, (n) 148 120\
Mean number of embryos transferred, (n) 2.0 2.0\
Implantation rate, n (%) 59(39.9) 49(40.8) 0.87
Clinical pregnancy rate, n (%) 39(52.7) 33(55) 0.07
Ongoing pregnancy rate, n (%) 35(47.3) 28(46.7) 0.90
Live birth rate, n (%) 32(43.2) 22(36.7) 0.40
Twins rate, n (%) 16(50) 7(31.8) 0.18
Premature delivery rate, n (%) 11(14.9) 5(8.3) 0.20:::: ::::table-wrap
::: caption
Comparison of obstetric outcomes between two groups
:::

```
                              3 h group   20 h group   *P*
```

______________________________________________________________________

Live birth fetuses, (n) 48 31\
Premature delivery fetus, (n) 21 8\
Gender ratio,(male/female) 1.3 0.9 0.50
Birth weight(Kg), mean ± SD 2.8 ± 0.5 2.9 ± 0.4 0.20
Low birth weight rate, n(%) 16(33.3) 4(12.9) 0.04::::


Extracted trial result:
Outcome: Birth status (binary)
Intervention: Patients in the 3h group
Comparator: Patients in the 20h group
Intervention events: 32
Intervention group size: 74
Comparator events: 22
Comparator group size: 60
Notes: Used numbers for live birth rate.